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Contributions to nesting ecology of forest birds. Horvath, Otto 1963

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CONTRIBUTIONS TO NESTING ECOLOGY OF FOREST BIRDS  by  Otto Horvath B.S.F.(S), U n i v e r s i t y of B r i t i s h Columbia, 1959  A THESIS SUBMITTED.IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY i n the Faculty of Forestry  We accept t h i s t h e s i s as conforming t o the required standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1963  I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements  f o r an advanced degree at the U n i v e r s i t y of  B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study.  I f u r t h e r agree that per-  m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may  be granted by the Head of my Department or by  h i s r e p r e s e n t a t i v e s . I t i s understood  that copying, of  publi-  c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n .  Department of  'Forestry  The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date  May  7,19.63  . <  Ii  . ABSTRACT An approximately 228 acres large f o r e s t e d area near Hope, B.C., has "been i n v e s t i g a t e d i n the mahonietosum subassociation of PseudotsugetoGaultherietum mesic a s s o c i a t i o n of the Coastal D o u g l a s - f i r Zone. B o t a n i c a l , survey and b i r d census work by the nest (or t e r r i t o r y ) mapping method were c a r r i e d out during two summer seasons.  Fifteen" ecosystem types are  described and t h e i r b i r d population, expressed.in average d e n s i t i e s per area u n i t as w e l l as by average biomass i s tabulated. P h y s i c a l environmental c o n d i t i o n s , e s p e c i a l l y p e r t a i n i n g t o microclimate, were measured a t 55 nests of the eight most common passerine species, and nest p l a c i n g and c o n s t r u c t i o n has been considered at 167 nests of the same species.  I t has been found that the nesting of these species  i n t h e i r h a b i t a t s i s the f u n c t i o n of the present vegetation, p h y s i c a l environment and.the adaptive range of the species.  I n c e r t a i n species the  b i r d s apparently chose nest s i t e s with.equable microclimate. . I n others i t was found t h a t the i n s u l a t i o n of the nest v a r i e s according t o the needs i n d i c a t e d by the extremes of the microclimate; again i n others the nest .material chosen provided the best a v a i l a b l e r e s i s t a n c e t o mechanical stresses. While other e s s e n t i a l environmental requirements were not studied the r e s u l t s point toward an assumption that microclimate strongly i n f l u e n c e s the s i t e , height p o s i t i o n , and.material of the nests, and u l t i m a t e l y , the s e l e c t i o n of n e s t i n g h a b i t a t of the b i r d s studied.  viii  ACKNOWLEDGMENTS The author i s g r a t e f u l t o Dr. I . McT. Cowan, Head of the Department, f o r o f f e r i n g help and c r i t i c i s m . i n a l l phases of the work.  The author  wishes t o express sincere thanks t o Dr. M.D.F. Udvardy f o r h i s generous c o u n c i l i n the study,.for h i s assistance i n the organization o f the p r o j e c t and f o r h i s guidance i n the research work. Thanks are extended t o Mr. L. O r l o c i f o r h i s . a s s i s t a n c e i n the i d e n t i f i c a t i o n of c e r t a i n plants and d e s c r i p t i o n of the f o r e s t types, to Mr. G. Lesko f o r h i s help i n i d e n t i f y i n g the major s o i l groups.in the f i e l d , t o Mr. A. Kozak f o r h i s help i n s t a t i s t i c a l c a l c u l a t i o n s , f o r Mr. P. Grant f o r supervising the E n g l i s h of the manuscript,.and f o r Mr. G. Van Eerten f o r manyfold t e c h n i c a l assistance i n p r o v i d i n g the f a c i l i t i e s f o r the research.  iii  TABLE OF COIWENTS page INTRODUCTION  1  GENERAL DESCRIPTION OF THE STUDY AREA  . . . .  5 8  TECHNIQUES ECOSYSTEM TYPES AND BIRD POPULATION  10  .  Danthonia s p i c a t a Secondary t h i c k e t of Corylus, Acer, and other shrub . . Pachystima - G a u l t h e r i a - P e l t i g e r a Gaultheria - Cladonai - Rhacomitrium G a u l t h e r i a - Mahonia Eurhynchium - Mahonia Polystichum . . . . . . . . . Thuja - Lysichitum - Oenanthe Spiraea d o u g l a s i i . : Carex r e t r o t s a Nuphar polysepalum Typha l a t i f o l i a Glycera - Carex Spiraea • S a l i x - L y s i c h i t u m - Oenanthe . . Populus t r i c h o c a r p a The q u a n t i t a t i v e structure of the b i r d population i n the study area RELATION OF THE NESTING AVIFAUNA AND FOREST TYPES STUDIED. . . Rufous hummingbird Winter wren Robin Varied thrush Swainson's thrush Solitary vireo Red-eyed v i r e o Oregon junco ANNOTATED CHECK LIST OF THE AVIFAUNA  -  •  11 . 1 2 13 18 20 27 3^ 41 44 46 46 46 46 47 47 48 48 55 6l 70 86 112 . 117 123 146 150  . . I58.  SUMMARY  177  BIBLIOGRAPHY  179  APPENDIX  iv  TABLES Table 1 2  page Monthly and annual mean temperature of Hope, B.C. f o r the year i 9 6 0 , and averages f o r an 18 year p e r i o d  6  Monthly and annual t o t a l p r e c i p i t a t i o n of Hope, B.C. f o r the year i 9 6 0 , winter snowfall 1 9 5 9 - 6 0 , and average f o r 18 years  3a The biomass value of ecosystem types  6 49  .....  3b The biomass values.of the tree n e s t i n g and ground n e s t i n g 50  b i r d s i n d i f f e r e n t ecosystem types 4  Comparison of the biomass of b i r d s i n the ecosystem types . 51  5  L i s t of the avifauna, i n d i c a t i n g the r o l e of each species i n the ecosystem types  52  6  U t i l i z a t i o n of l i g h t energy by d i f f e r e n t s o i l s  59  7  Comparison of l i g h t . i n t e n s i t i e s of Hummingbird nests. . . .  65  8 9  Comparison of l i g h t i n t e n s i t i e s of Winter wren nests. . . . Ecotopic and stand s t r u c t u r a l c h a r a c t e r i s t i c s of Eyrhyncfaium Mahonia f o r e s t p l o t s containing Winter wren breeding t e r r i t o r i e s  73  10  F i e l d data of Robin nests  11  Comparison of l i g h t i n t e n s i t i e s of Robin nests.  12  Ecotopic and stand s t r u c t u r a l c h a r a c t e r i s t i c s of f o r e s t p l o t s containing Robin breeding t e r r i t o r i e s  85 107 88 110  13  A n a l y s i s of Robin nest m a t e r i a l  14  Comparison o f . l i g h t , i n t e n s i t i e s of Varied thrush nests. . . 114  15  Comparison of l i g h t . i n t e n s i t i e s of Swainson's thrush nests. 119  16  M a t e r i a l of Swainson's thrush nests i n $ of nest weight . . 121  17  Comparison of l i g h t ..intensities of S o l i t a r y v i r e o nests . . 125  18  A n a l y s i s of S o l i t a r y v i r e o nest m a t e r i a l  19  Data of S o l i t a r y v i r e o nests  I l l  Appendix 145  V  Table  page  20  Comparison of l i g h t i n t e n s i t i e s of Red-eyed v i r e o nests. . 147  21  A n a l y s i s of Red-eyed v i r e o nest m a t e r i a l  150  22  Comparison of l i g h t i n t e n s i t i e s of Junco nests  153  vi  FIGURES Figure  page  1  Vegetation p r o f i l e s . o f the f o r e s t ecosystem types  2  Diagrammatic  3  A i r movement i n the opening around nests a) and b ) . . '. . . .  63  k  The p o s i t i o n of Rufous hummingbird's nests. .  71.  5  L i g h t curves.of Rufous hummingbird  II  6  L i g h t curves of Winter wren  7  Temperature curves of Winter wren nests  8  R e l a t i v e temperature curves of Winter wren  9  L i g h t curves of Robin n e s t s . i n Eurhynchium-Mahonia f o r e s t type  10 11  I 6l  cross s e c t i o n of a t r e e crown  . . .  I l l IV V VI  L i g h t curves of Robin nests on the ecotone of -Polystichum and Spiraea f o r e s t type L i g h t curves,of Robin i n G a u l t h e r i a - Claddmia Rhacomitrium f o r e s t type  VII . . VIII  12 . L i g h t curves of Robin i n Thuja - Lysichitum - Qenanthe f o r e s t type 13  The p o s i t i o n of Robin's nests  Ik  The b a s i c Robin's nest form d i f f e r e n t ecosystem types of the Thacker E c o l o g i c a l Research Reservation of U n i v e r s i t y of B r i t i s h Columbia, Hope, B.C.  15 .Light curves of V a r i e d -thrush nests . . . .  IX X  XI  '  XII  l 6 . L i g h t curves of Swainson's thrush nests 17  L i g h t curves of S o l i t a r y v i r e o nests  18  S o l i t a r y v i r e o nests  XIII XIV XV  19 . L o c a t i o n of nest, i  XVI  20  Four sides of nest i  21  The s i t u a t i o n of S o l i t a r y v i r e o nests  22  D i s t r u b u t i o n of nest .materials i n S o l i t a r y v i r e o nests. . . .  XVII XVIII XIX  vii Figure  page  23  Light curves of Red-eyed v i r e o nests  24  R e l a t i o n of Junco and Towhee d e n s i t i e s t o coverage of ground by shrubs  155  L i g h t curves,of Oregon junco nests  XXI  25  XX  INTRODUCTION The b i o c o e n o l o g i c a l study of f o r e s t "bird populations i s a r e l a t i v e l y new'branch.of ornithology. Based upon a holocoenotic approach t h i s d i s c i p l i n e studies the i n t e r r e l a t i o n s h i p s between b i r d populations and t h e i r b i o t i c and p h y s i c a l environment. O r n i t h o l o g i c a l biocoenology, which may be c a l l e d ayicoenology o r i g i n a t e d i n F i n l a n d w i t h the a c t i v i t y of Palmgren who studied b i r d communities w i t h i n the framework ..of Cajander's f o r e s t types. ;  I n h i s remarkable work ( 1 9 2 8 , 1 9 3 0 ) ,  Palmgren introduced the biomass c o n c e p t . i n d i c a t i n g the c a r r y i n g capacity f o r b i r d s of the f o r e s t types.  The biomass values of the d i f f e r e n t forests vary  f o r the d i f f e r e n t bird.populations i n agreement with.the p r o d u c t i v i t y of the .soil. Turcek ( 1 9 5 6 ) studied the b i r d communities of a number of f o r e s t types i n Czechoslovakia; he determined the biomass values of b i r d s f o r the d i f f e r e n t f o r e s t types.  There are a number of European e c o l o g i s t s who are working  along s i m i l a r l i n e s e.g. Ferry ( 1 9 6 1 ) i n France, Bruns ( 1 9 6 1 ) i n Germany, and Yapp ( 1 9 5 0 ) i n England. In North American e c o l o g i c a l studies of b i r d populations were i n i t i a t e d by the I l l i n o i s school of e c o l o g i s t s ; Shelford ( 1 9 1 5 ) n d Kendeigh ( 1 9 3 ^ , a  >kk, '1+5, ' 4 6 , ' 4 7 etc.),.then Odum ( 1 9 5 0 ) and Johnston and Odum ( 1 9 5 6 ) . Temperature adaptations of nesting b i r d s were i n t e n s i v e l y studied by Kendeigh ( 1 9 3 4 , 1 9 4 8 ) , Baldwin and Kendeigh ( 1 9 3 2 ) ; Udvardy ( 1 9 5 1 ) pointed out the d i f f e r e n c e i n microclimate of nests w i t h i n the same major h a b i t a t . • I n t h i s present study an attempt has been made t o show, the adaptations of b i r d s whereby t h e i r nests w i t h i n the nesting h a b i t a t are placed i n t o m i c r o c l i m a t i c a l l y advantageous s i t e s , which vary with.season, stand, succession etc.  as i t s h a l l be shown.  Subsequent t o the termination of the f i e l d work  I  Secondary t h i c k e t t  A - A  Pachystima - G a u l t h e r i a Peltigera  4 1 A.  G a u l t h e r i a - Cladonia' Rhacomitriura  Eurhynchium - Mahonia  Thuja - Lysichitum - Oenanthe  - G a u l t h e r i a - Mahonia  ^ Polystichum  Spiraea douglasii.  Figure 1. Vegetation p r o f i l e s of the f o r e s t ecosystem types. (The symbols are s e l f - e x p l a n a t o r y , a n d the p r o f i l e s . sould be viewed while reading the d e s c r i p t i o n of •"' the ecosystems). • '.  -2on which,the thesis..is based more, data have accumulated which, however s h a l l form the.basis of a l a t e r p u b l i c a t i o n . Regarding the study of the b i r d h a b i t a t s , i . e . of the f o r e s t , the author employed a holocoenotic approach which was used also by K r a j i n a  (i960),  Lesko ( 1 9 6 1 ) and O r l o c i ( 1 9 6 1 ) i n the ecosystem c l a s s i f i c a t i o n of f o r e s t s i n the P a c i f i c Northwest.  This approach,includes the combined study of the  biotope and ecotope ( c f . Sukachev, 19^7) with the purpose of e s t a b l i s h i n g ecosystem u n i t s which provide a.basic framework i n the study of b i r d communit i e s (avicoenoses) and t h e i r responses t o the impact of t h e i r environment. The purpose of the i n v e s t i g a t i o n was (a) d e s c r i p t i v e study-of the avicoenoses w i t h i n the f o r e s t ecosystems i n the Thacker E c o l o g i c a l Research Reserve of the U n i v e r s i t y of B r i t i s h Columbia, Hope, B.C., (b) study of the ecology of nest s i t e s of c e r t a i n f o r e s t b i r d s i n order t o understand why d i f f e r e n t b i r d s s e l e c t d i f f e r e n t habitats or occur with d i f f e r e n t density v a l u e s , i n each ecosystem. The study was based on the assumptions that d i f f e r e n t b i r d s have d i s t i n c t c a p a c i t i e s of nest.placing and nest b u i l d i n g techniques which vary i n the d i f f e r e n t ecosystem types.in order t o s e l e c t conditions.best  f i t f o r hatching  and f o r the p r o t e c t i o n of t h e i r young which have no a b i l i t i e s t o protect themselves from the extreme impact of t h e i r b i o t i c and p h y s i c a l environment. The t h e o r e t i c a l b a s i s , i s explained i n more d e t a i l s i n Part I I of the study (see p. 5 5 ) . The i n v e s t i g a t i o n s t a r t e d i n the e a r l y summer of i 9 6 0 and continued i n t o 1961.  I n i 9 6 0 the period of May 14 t o J u l y 15 has been spent.in assessing  the habitat and with census work; i n 1 9 6 1 , May 2 t o J u l y l,.when the f o r e s t f i r e s i n t e r r u p t e d the study. M i c r o c l i m a t i c work was resumed J u l y 12 and  -k-  Map 1.  Ecosystem types of the Thacker E c o l o g i c a l Research Reservation and surroundings.  -5-  GEMRAL DESCRIPTION OF THE STUDY AREA  The study area belongs to the Coastal D o u g l a s - f i r Zone ( K r a j i n a , 1959)  near the east border of the Coast F o r e s t - B i o t i c Region (Munro and-"-'  Cowan, I 9 4 7 ) Hope.  I t composes the Thacker E c o l o g i c a l Research Reserve near  The area,is located between 121°24' to 1 2 1 ° 2 6 ' longitudes and 4 9 ° 2 3 '  l a t i t u d e s i n the southwestern p o r t i o n of British.Columbia, Canada. a l t i t u d e l i m i t s are 49 m.  The  (lowest) and 2 l 6 m ( h i g h e s t ) .  The a r e a - i s on a h i l l , with steep slopes oriented toward .South, East and West.  Large open rock flows are numerous.  The surface materials are  g r a n i t e , p h y l l i t e and hornblende andensite which form a c i d s o i l s . f o l l o w i n g s o i l subgroups are. important i n the area of study:  The  ( l ) orthic.:..  concretionaryreddish brown, ( 2 ) gleyed concretionary reddish brown, ( 3 ) l i t h o s o l i c , (4)  g l e y s o l and ( 5 ) organic  ClimateAccording  soils.  to Chapman ( 1 9 5 6 ) the main c l i m a t i c features-of..  the study area i n d i c a t e an oceanic c o a s t a l climate.  I t i s i d e n t i c a l with  .Koppen's Cfb climate, that r e f e r s to a warm temperature r a i n y climate without d i s t i n c t dry season and with cool summer. But. the temperature conditions are somewhat more extreme than i n the Cfb climate which i s c l e a r l y an. i n d i cation of the t r a n s i t i o n a l c o n d i t i o n f o r the c o a s t a l climate to the c o n t i n e n t a l i n t e r i o r Dfb  climate.  The c l i m a t i c v a r i a t i o n s of the study area are i n d i c a t e d by the c l i m a t i c . records of Hope, B.C..(see Climate of B r i t i s h Columbia, report f o r i 9 6 0 ) . The present state of the f o r e s t stands i n the study area could be ,. characterized b r i e f l y by the f o l l o w i n g f a c t s : between 1 9 4 5 - 1 9 5 1 '  about 80 per cent was  logged  The remaining p a r t . i s mature timber of mainly Douglas-  Monthly and annual mean temperatures of Hope, B.C. f o r the year i 9 6 0 , and averages f o r an 18 year period:  Month  I  II  III  IV  V  VI  VII  i960.  32  39  42  50  5U  60  Average  32  37  h2  49  56  60  Table 1  VIII  IX  X  XI  XII  An.  67  , 64  60  53  ho  35  50  65  65  6l  51  hi  35  49  Monthly and annual t o t a l p r e c i p i t a t i o n of Hope, B.C. f o r the year i 9 6 0 , winter snowfall 1 9 5 9 - 6 0 / and average f o r 18 years., Table 2 .  Jan. Feb. Mar. Apr. May  June J u l y Aug. Sept. Oct. Nov. Dec. Ann- Snowual  i960  6.66  6.60 6.08 4.19  4.74  2 . 0 2 Tr.  3.6O 3.78  7-31  fall  8 . 9 3 4 . 9 8 5889  .68.6  Average 8 . 7 8 6 . 6 2 5 - 9 9 4 - 3 8 2 . 8 2 2 . 2 3 1 ^ 1 1*50 3-^6 6 . 9 3 7 - 9 0 9 - 7 3 6174  51.5  -7-  fir.  The area has a bad f i r e h i s t o r y .  More r e c e n t l y i t was burned over i n  1951;.the f i r e claimed nearly 80 per cent of the area.  In 1958 and.in 196l  nearly 30 per cent of the stands burned again. The c h a r a c t e r i s t i c combination of species f o r the D o u g l a s - f i r Zone i s as f o l l o w s : Pseudotsuga m e n z i e s i i Saultheria shallon Lonicera c i l i o s a Mahonia nervosa Holodiscus d i s c o l o r Rosa gymnocarpa Corylus c a l i f o r n i c a Arctostaphylos uva-ursi Pachystima m y r s i n i t e s Achlys t r i p h y l l a Apocynum androsaemifolium Eurhynchium oreganum  TECHNIQUES 1.  C l a s s i f i c a t i o n of the study area.  The ecosystem type i s the b a s i c u n i t i n the c l a s s i f i c a t i o n of the study area.  This method of c l a s s i f y i n g f o r e s t s has been employed.in our region  r e c e n t l y by K r a j i n e ( l 9 5 3 > i 9 6 0 ) .  Since we have no previous knowledge of  the synecological r e l a t i o n s of birds, i n these f o r e s t communities, i t seems the best way t o d i s t i n g u i s h the f o r e s t ecosystem types and to.: i n v e s t i g a t e how the avifauna f i t s i n t o t h i s c l a s s i f i c a t i o n . Some ecosystem types were previously described by K r a j i n a and S p i l s b u r y , 1953*  The others, however, are new, prepared •with.help of Mr. G.L. Lesko  and.Mr. L. O r l o c i . The mesophytic a s s o c i a t i o n (vegetation type) of the whole study area i s the Pseudotsugeto-Gaultherietum represented by the Mahonia nervosa suba s s o c i a t i o n , called' mahonietosum ( K r a j i n a and O r l o c i 1 9 6 1 ) . 2.  The study of b i r d population.  Census of b i r d s was made by the mapping method.  Each observed b i r d or  nest was marked on f i e l d maps of the part areas, and the number of i n d i v i d u a l s (nesters and a c c i d e n t a l s separately) summed on the b a s i s of 5 t o t a l surveys throughout the n e s t i n g season, between May 1 (both years) and J u l y 15 ( i 9 6 0 ) and J u l y 1  (1961).  The methods of biomass c a l c u l a t i o n s are discussed on p. kQ, and the sources of weight data on p. hQ.  Nests were grouped by ecosystem types, and some t y p i c a l nests were selected f o r d e t a i l e d examination.  These included the comparative  study of  nest m a t e r i a l s , nest b u i l d i n g techniques of b i r d s and the l i g h t r e l a t i o n s of i n d i v i d u a l nests.  D e t a i l e d data of a l l nests were noted on B.C. Nest  Record Scheme cards and are deposited with the Scheme (Department of Zoology, U n i v e r s i t y of B r i t i s h Columbia,  Vancouver).  Since i n d i v i d u a l study of each n e s t i n g p a i r of the species under s c r u t i n y was impossible, the categories " f i r s t nest" and, "second nest" were d e l i m i t e d l by a .chosen calendar data f o r each species corresponding to o b s e r v a t i o n a l data. The l i g h t . i n t e n s i t i e s i n the surroundings of the nests were measured with,"Sixtomat X 3" l i g h t meter. - I n each case, data were obtained as an average of 8 measurements: two readings were made.  i n each compass d i r e c t i o n (N./W., S. and E.),  Nest . i l l u m i n a t i o n values were measured simultane-  ously with.those i n the nearest open,.unshaded a r e a Temperature measurements were made w i t h .normal mercury thermometers. • I n order t o analyze the nest m a t e r i a l s the nests were d r i e d out. i n d r y i n g chamber at 65°C i n the case of s o l i t a r y and red-eyed v i r e o nests and a t 8o°C f o r the r o b i n and Swainson's .thrush nests.  For s o l i t a r y and  red-eyed v i r e o nests lower temperature was used t o avoid burning of s i l k . The d e t a i l s of the measuring procedures w i l l be described and discussed.in the presentation of the data.  -10-  ECOSYSTEM TYPES AND BIRD POPULATION The b i r d . p o p u l a t i o n s were i n v e s t i g a t e d i n d e t a i l i n ten ecosystem types of the study area.  Most of these communities are a l s o present,in  areas adjacent to the Thacker f o r e s t .  The b i r d population of these adjacent  f o r e s t areas and the adjacent marsh area were i n v e s t i g a t e d a l s o f o r comparison. B i r d populations were studied i n the f o l l o w i n g ecosystem types: 1.  Danthonia s p i c a t a (Oat-Grass).  Marked with D.  2.  Secondary t h i c k e t of Corylus, Acer and other shrub species.  3-  Pachystima - G a u l t h e r i a - P e l t i g e r a . (False-box--Salal-Lichen).  if.  Gaultheria-Cladonia-Rhacomitrium ( S a l a l - L i c h e n ) . G--CTR  5-  Gaultheria-Mahonis (Salal-Oregon grape) G-M  6.  Eurhynchium-Mahonia (moss-Oregon grape) E-M  7-  Polystichum (Sword-fern). P  8.  Thuja-Lysichitum-Oenanthe  9-  Spiraea d o u g l a s i i (Spiraea). S  (Red.cedar-Skunk-cabbage--Water parsley).T-L-0  10.  Carex r e t r o s a (Retrorse sedge). C  n.  Nuphar polysepalum  12--  Typha l a t i f o l i a ( C a t - t a i l ) . T  !3-  Glyceria-Carex (Manna grass-Sedge).  ik.  Salix-Lysichitum-Oenanthe  15-  Populus t r i c h o c a r p a (Black cottonwood).  (Water l i l y ) . . N  G-C  (Willow-Skunk-cabbage--Water p a r s l e y ) .  of the study area (Map l )  s i z e i s given on p. 48.  C h a r a c t e r i s t i c species:  S-L-0  P  The extent of these types i s marked on the. map and t h e i r approximate  P-G-P  Species of t h i s category do not n e s t . i n any  other ecosystem type and t h e i r presence i s independent from the  secondary  -11-  succession of the plant community. Dominant species:  Species of t h i s category may n e s t . i n several eco~  system types, ..but are most abundant i n the general area occupied by the c h a r a c t e r i s t i c species.  An ecosystem type may have d i f f e r e n t  combinations  of dominant species i n the d i f f e r e n t faces of the secondary succession. Accessoric species:  Species of t h i s category are only o c c a s i o n a l  v i s i t o r s from other ecosystem types, or r e l a t i v e l y - infrequent nesters. 1.  Danthonia s p i c a t a ecosystem type (Oat-grass).  This i s an open rock outcrop slope with mostly brown l i t h o s o l (an embryonic Av. C s o i l ) .  This a s s o c i a t i o n forms complexes with other p r i m i -  t i v e l i c h e n and b r y o p h i t i c communities.  The p r e v a i l i n g plants are:  Cladonia g r a c i l i s C. impexa , C. r a n g i f e r i n a Cryptogramma c r i s p a Danthonia s p i c a t a VFestuca o c c i d e n t a l i s Polytrichum commune P-. juniperinum P. p i l i f e r u m Rhacomitrium canescens Sel.'taginella w a l l a c e i Saxifraga f e r r u g i n e a B i r d o c c u r r i n g i n t h i s ecosystem type:  Junco oreganus  Wo. of individual per 100 acres  Average ..weight of individual ••• gm.  Biomass of species population gm.  ko  18  720  This community i s one of the nesting habitat of the Oregon junco.  The  In t h i s , and the f o l l o w i n g tables the biomass value are c a l c u l a t e d from the average weight.of the i n d i v i d u a l m u l t i p l i e d by the number of individuals per 100 acres. They thus r e f e r t o nesting adult population c a l c u l a t e d from two seasons census work, therefore they represent approximate values only.  -12-  n e s t . i s placed i n t o small ground c a v i t i e s which provide e f f e c t i v e p r o t e c t i o n f o r the nest against the extremes of the ecoclimate. A c l o s e l y r e l a t e d dry edaphic h a b i t a t , the rock flow on extremely steep slopes i s ' o n l y mentioned here, since i t was not s t u d i e d , i n s u f f i c i e n t d e t a i l s w i t h respect of v e g e t a t i o n a l s t r u c t u r e and since i t has no nesting b i r d species. 2.  Secondary t h i c k e t s of Corylus . c a l i f o r n i c a , Acer c i r c i n a t u m , Coenotus  sanquineum and other shrub species. This secondary community develops on steep slopes f o l l o w i n g f i r e i n place of higher f o r e s t communities.  This i s ecosystematically heterogeneous,  however, i t must be recognized because i t covers considerable part of the study area.  Despite i t s heterogenity i n o v e r a l l composition, as a .dense  thicket,, i t : i s quite uniform .in i t s b i r d fauna. This type occurs as a b e l t . i n the middle p a r t of the south slope i n the study area.  During.two summers,, a number of observations were.made f o r . t h e  presence of spotted towhee,. M a c G i l l i v r a y s warbler and Oregon junco.' 1  In the summer of I96I, a few weak flyers(towhee and M a c G i l l i v r a y s 1  warbler)were  seen here, but there i s no evidence of. t h e i r n e s t i n g though  the major part.of t h e i r t e r r i t o r i e s were i n t h i s type. B i r d s occuring i n t h i s ecosystem type: No. of individual per 100 acres 0poro nis t o l m i e i P i p i l o maculatus r  20 20  Average, weight of individual 11  ko  Biomass of species population gm. 220 800 1020  -14-  L i s t of plants  Species s i gnificance  Apocynum adrosaemifolium Asplenium trichomanes Cryptogramma c r i s p a Festuca o c c i d e n t a l i s Galium t r i f l o r u m Heuchera glabra Hieracium a l b i f l o r u m Lathyrus n u t t a l l i i Pteridium aquilinum Trientalis l a t i f o l i a D  A n t i t r i c h i a .curtipendula Claopodium sp. Dicranum scoparium Hyloconium splendens P e l t i g e r a canina P o l y t r i c h i a juniperinum Rhacomitrium canescens R. heterostichum  Sociability  mm  1 1 2  -  _  2  3 3 5 3  3 5 3 2  1 1 2  k  3  5  -  if  -  5 2  If •5 3  if  Vigor of species  '3 2 2 .2 2  -  if  -  5 5  if. 3 6  4 3  -  3 3 3 3 3 3 3 3  Despite i t s occurrence i n a r e l a t i v e l y l a r g e p a r t . i n study area (30%), the b i r d population i s poor i n t h i s ecosystem type. This ecosystem type i s present i n two successional stages, (a) mature stands and (b) young . stands.  Because both t h e i r composition and b i r d  population were d i f f e r e n t , these stages were separately t r e a t e d . Mature stand.occurred i n the east and southeast part of the study area. v a r i e s from 30° t o ^ 5 ° ' of D o u g l a s - f i r .  Sloping  The t r e e canopy i s composed of a loose crown l a y e r  The understory was destroyed by the heavy f i r e of 1951*  hence the shrub l a y e r i s i n i t s developing s t a t e . occupied by rock outcrops.  A l l stand openings are  The poor b i r d population i s due to the extremely  simple stand structure and the extreme ecoclimate.  -15-  B i r d s occurring i n t h i s ecosystem type: No. of. individuals 100 acres A  C h a r a c t e r i s t i c species  B  Dominant species Falco sparverius Colaptes cafer Dendrocopos w i l l o s u s Cyanocitta s t e l l e r i Parus rufescens S i t t a canadensis Regulus satrapa R. calendula Dendroica townsendi D. auduboni Piranga l u d o v i c i a n a Spinus pinus Carpodacus purpureus  Average weight of individual  Biomass of species population gm.  none  8 16 8 16 16  ko  20  k.  1056 2688 640 1982 128  132 168 80  124 8 10 6 6  400 120  24  8 72  ll ll  1+8  29 10  88 792 1372 •80  23  184  .8 8  .  Accessoric species Accipiter gentilis Buteo jamaicensis Bonasa umbellus Bubo v i r g i n i a n u s Chordeiles minor Selasphorus rufus Sphyrapicus v a r i u s Nuttallornis borealis Contopus sordidulus Corvus brachyrhynchos Parus a t r i c a p i l l u s Parus gambeli Turdus migratorius Ixoreus naeyius Myadestes townsendi Dendroica nigrescens Oporornis t o l m i e i Hesperiphona vespertina P i p i l o maculatus Junco oreganus Melospiza melodia  2  680  1360  8  35  280  24  11  26^  16 kO  ko 18  6k0 720 :.13036'  C h a r a c t e r i s t i c and dominant species are nesters. The nesters among the accessoric species are distinguished-by the census values.  -16-  The bird, population of Pachystima - G a u l t h e r i a • - P e l t i g e r a .ecosystem-type i s separated i n t o three subpopulations. 1.  Species of the crown l a y e r .  Species which are f i d e l e t o mature  Douglas-fir belong here, generally only a low number of i n d i v i d u a l s are present. Both,Kinglet species are present, but the number of golden-crowned kinglet,may be higher than that of the ruby-crowned k i n g l e t .  The  stratum  i n which they are a c t i v e i:s the crown canopy. A number of Audobon's warblers were present during the n e s t i n g .season, but l a t e r they disappeared and only a.few i n d i v i d u a l s were seen i n t h i s ecosystem type.  I t i s suggested, that t h e i r absence was caused by food  shortage f o r they stayed.in the general area. Townsend's warbler. the n e s t i n g season.  There were only a few observations made during  On other occassions i t was often seen i n t h i s type.  In general,. Pine s i s k i n and Purple f i n c h are rare during the n e s t i n g season,.but e a r l y May and l a t e summer t h e i r f l o c k s were often seen i n t h i s type.  A l l other species which.belong  t o t h i s group are rare one, passage  v i s i t o r s or vagrants. 2.  Species of. the trunk stratum,.three species only were present. Red-  shafted f l i c k e r nested .in both years; Hairy woodpecker was often seen. Although the Red-breasted nuthatch i s an abundant species of the mature Douglas-fir stands i n the study a r e a , . i t i s present i n low numbers here. 3.  Species i n the lower l a y e r s .  M a c G i l l i v r a y s warbler occurred.in 1  openings -of the ecotone of the Eurhynchium-Mahonia and Pachystima - G a u l t h e r i a P e l t i g e r i a ecosystem types Oregon junco and Towhee l i v e around the roadsides. Song sparrow l i v e s i n the dense shrubs near the water.  -17-  The young stand occurred on southern and western slopes of the study area; the s l o p i n g v a r i e s from 35° "to 45°.  The stand was harvested 1958  and  .in the previous years. • Only a few economically worthless Douglas-firs were l e f t standing. and 1959.  The .shrub l a y e r was destroyed by the f o r e s t f i r e s of  1951  There are a.number of large open rock flows on the upper and  middle slopes.  A closed shrub l a y e r occupies: the lower part of the slope.  The b i r d population i s l i m i t e d t o a narrow b e l t around the border, while the middle part i s f r e e from any b i r d l i f e .  The b i r d population i s poor  becuase of l a c k of food and the very extreme ecoclimate.  The temperature  ,0  of the south slopes often exceeds 40 C during the warmer summer days. B i r d s occurring i n the. immature stand of t h i s ecosystem type Average Biomass No. of weight of individual of species individual per population gm. 100 acres gmA  C h a r a c t e r i s t i c species none  B  Dominant species Bombycilla cedrorum Oporornis t o l m i e i P i p i l o maculatus Junco oreganus S p i z e l l a passerina  C  Accessoric species Falco sparverius Bonasa umbellus Selasphorus rufus Dendrocopos w i l l o s u s .Asyndesmus lewiS Tyrannus tyrannus Nuttallornis borealis Empidonax t r a i l l i i Corvus brachyrhynchos Turdus migratorius Myadestes townsendi  6 24 12 1+2 6  37 11 40 18 13  222 264 480 756 78  -18-  No. of individual per 100 acres  Average weight of individual gm.  Biomass of species population gm.  Dendroica petechia Geothlypis t r i c h a s Piranga l u d o v i c i a n a Carpodacus purpureus Spinus t r i s t i s Spinus pinus Z o n o t r i c h i a leucophrys Melospiza melodia 1800  The d i s t r i b u t i o n of the b i r d population i n t h i s young stand,is not d e t a i l e d here, because the b i r d population i s l i m i t e d t o a narrow-belt around the border, mostly i n the lower part of slope, near t o the marsh. CONCLUSION The b i r d population of Pachystima - G a u l t h e r i a - P e l t i g e r a ecosystem t y p e i s poor g e n e r a l l y , presumably due to the l a c k of adaquate food and the :  presence of an extreme ecoclimate. Although several species were present, t h e i r number was extremely low. In the case of mature stand, b i r d s present i n t h i s f o r e s t type are those which are f a i t h f u l to mature Douglas-fir stands i n general. Most.of those species which are included i n t h i s l i s t are accessoric.  They d i f f e r i n t h e i r  requirements considerably. In the case of young stands the b i r d l i f e i s l i m i t e d to a narrow b e l t around.the border zone. k.  Gaultheria-Cladonia-Rhacomitrium ecosystem type ( S a l a l - L i c h e n ) .  On l o c a l h i l l t o p s w i t h shallow g l a c i a l t i l l substrata, the dryness of which, i s only comparable w i t h the ecotope of the Pachystima -GaultheriaP e l t i g e r i a ecosystem type, a l i c h e n community of low p r o d u c t i v i t y , c a l l e d the Gaultheria-Cladonia-Rhac omi trium ecosystem type, develops.  The vege-  -19-  t a t i o n a l composition i s a mixture of apparently o r i g i n a l p l a n t s , such as Pseudotsuga m e n z i e s i i , G a u l t h e r i a s h a l l o n , Mahonia aquifolium, Arctostaphylosu v a - u r s i , Holodiscus d i s c o l o r and s e v e r a l Cladonia and Rhacomitrium species and i n t r u d e r s . o f shrubs, grasses, bryophytes and l i c h e n s . This i s one of the d r i e s t ecostystem types of study area.  I t s stand  only c o n s i s t s of a.few poorly developed D o u g l a s - f i r trees which are branched from . the grounds. B i r d s occurring i n t h i s ecosystem type are as f o l l o w s : No. of individual per 100 acres Turdus migratorius Junco oreganus  Average weight of individual gm.  160 80  Biomass 'gm.  85 18  13600 1440 15040  The very poor b i r d population of t h i s ecosystem type i s due t o i t s extreme: ecoclimate. type.  Only two species were found to nest, i n t h i s  Robin uses t h i s type f o r i t s second nest only.  ecostystem  I t places i t s nest  i n the densest part of the crown of D o u g l a s - f i r . This provides p r o t e c t i o n of the nest from the extreme of the ecoclimate.  effective  Oregon junco  places i t s n e s t , i n t o the small ground c a v i t i e s on the slope, or underneath the dense l e s s e r vegetation. A l l other species which were seen sometimes w i t h i n t h i s type, such as Ruffed grouse and,Cedar waxwing, are not t i e d w i t h . t h i s type. The b i r d population of t h i s ecosystem type gained i t s food m a t e r i a l from the adjacent ^ecosystem types.  -20-  5-  Gaultheria-Mahonia ecosystem type (Salal-Oregon grape).  This i s a .mesophytic community.  I t i s widely d i s t r i b u t e d on moderate  slopes w i t h medium deep mesic concretionary reddish brown s o i l s . p r o d u c t i v i t y i s medium. study area.  This ecosystem type covered about 7 0 acres of the  E l e v a t i o n v a r i e s from 1 9 0 t o 2 3 0 m.  1951 and i n the previous years.  Stands were logged i n  Only a few economically worthless Douglas-  f i r and maple were l e f t standing i n the east p a r t of the area. p a r t , a l l trees were removed.  touched the western part a l s o .  I n the west  The logging was followed by a .heavy f i r e . i n  1951 which destroyed the remainding lower l a y e r s completely.  of secondary  Stand  In.1961,  fire  Now t h i s ecosystem type i s i n e a r l y stages,  succession varying from .logged and burned areas, t o p a r t i a l l y  recovered loose stands.  Therefore, the d e s c r i p t i o n of two p l o t s would give  (marked p l o t 1 and 2 ) the exact d e s c r i p t i o n of t h i s stand.  The b i r d pop-  u l a t i o n i s d i f f e r e n t enough t o j u s t i f y the separation of these two stages. About.20 per cent of t h i s f o r e s t type ( 1 5 acres) i s f r e e from birds,.because t h i s p a r t . i s covered by a very dense l a y e r of Pteridium aquilinum which hindered the nesting of ground nesters.  Vegetational s t r u c t u r e and com-  p o s i t i o n based on May and-August surveys on l / l O acre large representative p l o t s i s as f o l l o w s : P l o t 1. Layering  A  B,  1  80  L i s t of p l a n t s  A  Pseudotsuga m e n z i e s i i Acer macrophyllum  B  C  2  20  D, h  90  Species significance  Sociability  Vigor of species 3 2  -21-  Species significance B.  Acer glabrum Amelanchier f l o r i d a Betula p a p y r i f e r a Coenotus sanguineus Holodiscus d i s c o l o r Pinus contorta Populus t r i c h o c a r p a Pseudotsuga m e n z i e s i i Prunus emarginatus Rosa sp. S a l i x sp. Spiraea l u c i d a Symphoricarpus r i v u l a r i s Vaccinium p a r v i f o l i u m Mahonia aquifolium M. nervosa Rubus p a r v i f l o r u s R. v i t i f o l i u s Achlys t r i p h y l l a A g r o s t i s alba .Anaphalis margaritacea .Acetium lappa Apotinum androsaemifolium Disporum oreganum Festuca sp. Senecio sp. Lathyrus n u t t a l l i i Pteridium aquilinum Rumex a c e t o s e l l a  D,h  Sociability  Vigor of species  5  7 5 8  3  7 6  3 3 3 3 3 3 2  5 3  7 6  3  7 5 6  3  5  3 2  if 3 5 3  5 ,5 6 6  2 2 2 3  3 3 3  if if  2 3 3 2  5  5 5  if  if  2  8  10  3 3 2 2 2  3 2 3 3 2 2 3  .Polytrichum juniperinum Plot 2 Layering  L i s t of plants Pseudotsuga m e n z i e s i i  A  B1  B2  C  D  60  30  80  1  100  Species significance 7  h  Sociability 8  Vigor of species  -22-  Species significance B  ^  B  Acer circinatum Amelanchier f l o r i d a Cornus n u t t a l l i i Corylus c a l i f o r n i c a Holidiscus discolor Lonicera c i l i o s a Rosa sp. Gaultheria s h a l l o n Mahonia nervosa Rubus p a r v i f l o r u s R. v i t i f o l i u s Achlys t r i p h y l l a Lathyrus n u t t a l l i i  Vigor of species  7 5 7 7 5  2 3 3 2 2 3 2  8  10 8  1  5  2 2 2 2  5 5 3 2  2  Sociability  5  2  l  2  2  Pteridium aquilinum Dicranum scoparium Eurhynchium oreganum Hylocomium splendens Rhytidiadelphus t r i q u e t r u s A l e c t o r i a sp. C e t r a r i a sp. Cladonia subsquamosa Dicranum fuscescens Parmelia sp. Usnea sp.  9 2  2 9  2 3 3 3  3 3  3 3 3 3 3 3  h k  l  3 3 3  B i r d s occurring i n t h i s ecosystem type: No. of individual 100  acres  Average weight of individual gm.  Biomass of species population gm.  C h a r a c t e r i s t i c species none B  Dominant species Falco sparverius Dendragapus obscurus Bonasa umbellus Chordeiles minor Selasphorus rufus Stellula calliope Colaptes cafer  3 5 37 8 10 5 10  132 1000 750 63 3 3 168  396 5000 27750 504 • 30 15 1680  -23-  No. of individual per 100 acres Dendrocopos w i l l o s u s Nuttallornis borealis Empidonax d i f f i c i l i s Cyanacitta s t e l l e r i Parus a t r i c a p i l l u s S i t t a canadensis Turdus migratorius Regulus satrapa R. calendula Bombycilia cedrorum Vermivora c e l a t a Oporornis t o l m i e i Dendroica auduboni ,D. townsendi ,Piranga l u d o v i c i a n a Spinus pinus P i p i l o maculatus Junco oreganus C  8 5 3 3 5 28 8 8 •3 18 10  24. 13 3 13 5  Average weight of individual gm. 80 35  11 124  8  10  85 6 6 37  11 11 11 11  3k k2  29 13 50 18  5 3 3  23 27 20  Biomass of species population gm. 640 175 33 372  40  280 680  48  18 666 110  264 143  33 377 65 1360 756  Accessoric species Accipiter gentilis Buteo jamaicensis Bubo v i r g i n i a n u s Glaucidium gnoma Columba f a s c i a t a Sphyrapicus v a r i u s Corvus brachyrhynchos Ixoreus naevius Hylocichla ustaluta . S i a l i a currocoides Myadestes townsendi Pheucticus melanocephalus Hesperiphona vespertina Carpodacus pupureus Z o n o t r i c h i a leucophrys Melospiza.melodia  115 81 60 41691  Due to the r e l a t i v e l y r i c h f l o r i s t i c composition and the mesic ecotope, i t s b i r d fauna.is very v a r i a b l e .  This ecosystem.is c h a r a c t e r i z e d by a strong  b i r d population of the lower vegetation l a y e r as compared to that of the other l a y e r s .  -2k1.  Species of crown l a y e r .  Most.of the o c c u r r i n g species which belong  to t h i s group show a strong f i d e l i t y t o D o u g l a s - f i r .  This i s not a constant  group, only a.few species and i n d i v i d u a l s are present during the n e s t i n g season.  But. they are abundant enough, i n other times.  The most common  species are S t e l l e r ' s j a y , Western tanager, O l i v e - s i d e d f l y c a t c h e r and Audob on's warbler. I t must be emphasized, that the Black-capped chickadee i s present i n t h i s ecosystem type,,but apparently i t s requirements are so d i f f e r e n t that one cannot r e g a r d . i t as a f a i t h f u l member of t h i s community a l t h o u g h , i t occurs i n t h i s f o r e s t type frequently.  Most of the o l d logging roads are  covered by young red a l d e r , w i l l o w and b i r c h . t r e e s , or these trees are present along the road sides.  Black-capped chickadees favour these roads  and never go f a r from them provided a s u i t a b l e stub, i s present f o r t h e i r nesting. . I t seems that the population ibf Townsend's warbler changes y e a r l y .  In  the summer of i 9 6 0 , t h i s species was i n abundance i n t h i s ecosystem type. In 1961, the r e l a t i v e l y abundant spring population disappeared by the middle of May and the f i r s t group of i t was again seen by e a r l y August.  Between  these periods i t was seen only f i v e times i n t h i s f o r e s t type. The Rufous hummingbird occurred only i n the ecotone of the GaultheriaMahonia ecosystem type and a spiraea swamp, while the C a l l i o p e hummingbird occurred i n the drier-most part of the Gaulther ia-Mahonia. 2.  Species of the trunk, the Hairy woodpecker i s more abundant.in t h i s  ecosystem type than i n the others of the study area.  T h e r e f o r e , . i t . i s be-  l i e v e d , that the open and semi-open f o r e s t .is the favoured habitat of the h a i r y woodpecker.  I t s nests were found.in t h i s ecosystem type only.  -25The Red-breasted sapsucker i s a rare v i s i t o r i n t h i s ecosystem type, only a.few observations i n d i c a t e d i t s occurrence, but most of them were seen a f t e r the breeding season. The population of the Red-breasted nuthatch i s r e l a t i v e l y high compared to the scarceness of the D o u g l a s - f i r .  I t , i s suggested that t h i s population.is  a remainder of the o r i g i n a l b i r d population, which could not r e - e s t a b l i s h , i t s e l f completely a f t e r the logging.  The b i r d species which remained here are able  to adapt themselves to the a l t e r e d conditions.  The Red-breasted nuthatch  was o f t e n observed searching f o r food on the branches of the deciduous t r e e s , thus e x h i b i t i n g i t s a b i l i t y t o adapt.to d i f f e r e n t kinds of woods. 3-  Species occurring i n the lower layers c o n s t i t u t e the major group  of the b i r d population i n t h i s f o r e s t type. The Robin and Cedar waxwing a l s o belong to t h i s group. The Ruffed grouse i s an abundant and.most evenly d i s t r i b u t e d b i r d . i n t h i s ecosystem type (except f o r the dense Fteridium p a r t s ) .  Seemingly, the  circumstances are very good f o r the Ruffed grouse, while the Blue grouse i s one of the rare species. The Orange-crowned warbler occupied those parts of t h i s ecosystem type which are covered by a l a y e r of shrubs.  The M a c G i l l i v r a y ' s warbler i s a  b i r d of the densest parts near the road-side, or around openings which had a closed dense shrub l a y e r . The Oregon junco i s the most abundant, i n places where mature Douglasf i r trees are present and the ground.is covered with an open shrub l a y e r . I have the impression that there i s a good c o r r e l a t i o n between the s i z e of population of junco and the successional stage of the f o r e s t .  I t s population  -26-  is  highest  low  on  those  situation early  where  places  of  the  of  7  after  years  optimum  the  this  The  forest  Song  sparrow  The  already constant  no  that  when The both  junco  a  its  near  closed.  Its  .Junco a n d  placing for  nests  were  the  not  to  on  own  the  located an  about is  5  the  to  the  however,  i n  succession  swamp.  Therefore,,  sparrow  rocky  colon-  i t  population.  places  of  this  trees. layer  places  always  The  type  Spiraea  song  open  active  at  the  The  close  i n  is  present.in  occur,  junco  i t  cover.  formations.  has.its  and  abundant.  They  to  other  the  found  may b e  this  is  begins  the  Douglas-fir  under  road.  method  i t  is  Towhee.  f i d e l i t y  found  old  the  are  layer  replace  swamp  only  nests  nests  shrub  Towhees  few  the  layer  complete  where the  Spiraea were  provides  shrub  because  with  nests  open  Gaultheria-Mahonia ecosystem  stages.  each  an  reversed,  connections  waxwing  optimum h a b i t a t  is  with  layer  strong  Cedar  nest  shrub  indicated  places  located  covered  forest  for  surrounded by  Robin  were The  an  has  Nighthawk  type  of  starts  habitat  type.  it  the  logging.  forest  supposed  The  nests  the  is  towhee  stage  successional  Apparently may b e  where  towhee  nesting  different  ground  Spotted  successional  ization  of  the  where  near  indication  of  the that  a  vegetation.  A l l  young  is  road. this  forest  This  very  forest  type  is  species. CONCLUSION  The study  Gaultheria-Mahonia ecosystem  area.  eastern  part  It a  is  now  i n  the  (economically  early  type  stage  worthless)  was of  logged  secondary  loose  stand  of  and burned  i n  succession. Douglas-fir  the In  the  is  present. The  b i r d  population  i n  the  crown  layer  is  poor.  Apparently,  this  pop-  not  -27-  u l a t i o n depends on the adjacent f o r e s t types and. i t was believed- that most b i r d s are only temporarily present  here.  The Rufous hummingbird and the Black-capped chickadee do not belong c l o s e l y t o t h i s community. The trunk species are quite abundant, i n s p i t e of the poor Douglasf i r stand.  The population of red-breasted nuthatch, i s p a r t i c u l a r ] / abundant.  The major part of the b i r d population of t h i s f o r e s t type i s the group of the lower l a y e r s .  Seemingly there i s a good c o r r e l a t i o n between the  succession of t h i s f o r e s t type and the ehanges i n the b i r d population, e.g.the Junco disappears when the shrub l a y e r begins to be closed a t about 5 t o 7 years of age. Then, the population of the Towhee increases. The Huffed grouse appeared t o be r e l a t i v e l y , c h a r a c t e r i s t i c f o r t h i s f o r e s t type w i t h . i t s . high f i d e l i t y . 6.  Eurhynchium-Mahonia ecosystem type (MosS-Oregon -grape).  This ecosystem type i s a moist edaphic community w i t h mostly  gleyed  concretionary reddish brown s o i l s and temporary or permanent seepage, on concave lower slopes... Forest stand p r o d u c t i v i t y i s high.  Floristical  composition i n d i c a t e s a i'rrch f l o r a . Layering  Aj_  Ag  20  60  L i s t of plants A-,  Pseudotsuga m e n z i e s i i  B 50  Species significance 6.-  1  40  B  2  60  C  Dfc  20  50  Sociability  Vigor of species 3  -28-  L i s t of plants .  Species significance  Sociability  .6 7  -  .5 8  9  2 2 2 3  Abies grandis Acer circinatum ;Acer glabrum A. macrophyllum Betula papyriphera Cornus n u t t a l l i i Corylus c a l i f o r n i c a Tsuga .heterophylla  6 3 3 3 5  7 5 5 .5 ,5 6 7  3 3 2 2 2 2 2 3  Abies grandis Lonicera c i l i o s a Mahonia aquifolium M. nervosa Rubus v i t i f o l i u s  2 8 2  5 9 5  3 3 3 3 3  Achlys t r i p h y l l a Clintonia uniflora Disporum .oreganum Goodyera o b l o u g i f o l i a Pteridium aquilinum Lactuca muralis Lathyrus n u t t a l l i i Trientalis l a t i f o l i a  6 5 1 .2 1 -  A n t i t r i c h i a curtipendula Eurhynchium oreganum Hylocomium splendens Mnium insigne M. m e n z i e s i i M. spinulosum M. venustum Neckera douglassi N. menziessi Porella navicularis P. p l a t y p h y l l a Pseudisothecium stoloniferum Rhytidiadelphus t r i q u e t r u s R. torenus  4 5 2 3 2  Acer macrophyllum Alnus rubra B e t u l a papyriphera Thuja p l i c a t a Tsuga heterophylla Acer macrophyllum Betula p a p y r i f e r a Thuja p l i c a t a Tsuga heterophylla  .  4  7 5 5 -  6  Vigor of species  8  6  .  6  5 7 4 3 2 3 3 3 2 3 .5. k  1  3 2 3 3 3  3 3 3 3 2 2 2 2 3 3 3 3 3 3 .3 3 3 3 3 3 3 2  -29-  The Eurhynchium-Mahonia ecosystem type i s the most extensive community i n the study area.  The richness of the b i r d fauna of t h i s ecosystem type i s  due t o the h i g h l y s t r a t i f i e d stand s t r u c t u r e , the presence of a large number of plant species and eventually i t s favourable edaphic and c l i m a t i c conditions.  The w e l l s t r a t i f i e d f o r e s t stand can provide nesting places f o r many  kinds of b i r d species which d i f f e r i n t h e i r n e s t i n g h a b i t .  Moreover,  because the stand.of the Eurhynchium-Mahonia ecosystem t y p e . i s composed of many tree species, i t can accommodate b i r d s adapted t o deciduous,  conifer-  ous and mixed f o r e s t s . B i r d s occurring i n t h i s ecosystem type: No. of individual per 100 acres  Average weight of individual gm.  Biomass of species population gm.  C h a r a c t e r i s t i c species Troglodytes troglodytes Vireo s o l i t a r i u s Ixoreus naevius  80 130 60  6  480  17 90  2210 5400  180 27 3 170  7200 270  Dominant species Columba.fasciata Glaucidium gnoma Selasphorus rufus Dryocopus p i l e a t u s Sphyrapicus v a r i u s Empidonax t r a i l l i i E. d i f f i c i l i s Cyanocitta s t e l l e r i Parus a t r i c a p i l l u s P. rufescens S i t t a canadensis Certhia f a m i l i a r i s Turdus migratorius Hylocichla ustaluta Regulus satrapa R. calendula Dendroica auduboni D. nigrescens D. townsendi  40 10 50  10 30  10 20 20 30  10 30 130 ' 60  20 10 60 50  . 10  46 11 11  124 8 8  150 1700 .1380  110 220 2kQ0 240  10  80 300  85  11050  6 6 11 11 11  60 660 550  44  2640 120  110  -30-  No. of individual  Average weight of individual  100 acres Piranga l u d o v i c i a n a Hesperiphona vespertina Carpodacus purpureus Spinus pinus  Biomass of species population gm.  50 20 10 20  29 45 23 13  1450 900 230 260  10  80  800  20  14  280  20 10 30 30 10 10 30  ll ll ll  18  220 110 330 300 120 400 540  10  25  250  Accessoric species Accipiter gentilis Falco sparverius Bonasa umbellus Zenaidura macroura Colaptes cafer Dendrocopos w i l l o s u s Nuttallornis borealis Contopus sordidulus Corvus corax C. brachyrhynchos Certhia f a m i l i a r i s Myadestes townsendi Vireo alovaceus Vermivora , c e l a t a Dendroica petechia Oporornis t o l m i e i Wilsonia p u s i l l a Spinus t r i s t i s P i p i l o maculatus Junco oreganus Melospiza melodia Zonotrichia a t r i c a p i l l a  10 12  40  43600  The b i r d community of the Eurhynchium-Mahonia  ecosystem type i s  separated.into three' subcommunitie s. 1.  Species of the crown l a y e r .  They play important maintenance of  the biocoenosis. Rob i n .  I t s f i d e l i t y t o the community of t h i s ecosystem type i s strong  That the conditions seem t o be e x c e l l e n t f o r the Robin i s i n d i c a t e d by i t s aggressiveness, toward other kinds of b i r d s having s i m i l a r demands f o r the supplies of the environment.  These b i r d s have.to s e t t l e i n the other  -31-  parts of the f o r e s t which are l e s s favored by the Robin.  We s h a l l return  l a t e r t o t h i s phenomenon. The Robin population i s concentrated i n places where the r e l a t i v e l i g h t . i n t e n s i t y i s between kO t o 50 per cent of the open l i g h t .  These places  of f o r e s t are i n d i c a t e d w i t h a w e l l s t r a t i f i e d crown l a y e r , poorly developed shrub and.herb l a y e r s , and the absence of bryophytes i n general.  /  The V a r i e d thrush occupied .those areas where the l i g h t ranges are between kO and k-3 per cent of the l i g h t i n the open and the ground i s covered w i t h a.heavy bryophytic l a y e r . The Swainson's thrush • i s adapted to the nesting l i g h t range of Robin, . i t l i v e s i n those places which are completely or almost completely devoid of Robins. • In these p l a c e s , . w e l l developed s~hrub and moss layers are found;, these l o c a l i t i e s are a d j o i n i n g the optimal habitat of the Robin. The l i g h t range, i n which robins and s o l i t a r y v i r e o s nest i s the same but they d i f f e r i n nesting and feeding.habits.  Robins feed mostly on the  ground, while the s o l i t a r y v i r e o c o l l e c t s , i t s f o o d . i n the crown. The S o l i t a r y v i r e o and Black-throated gray warbler l a r g e l y complement one another i n t h e i r habitat demands.  The a c t i v e l a y e r of both b i r d s i s the  same, the suppressed or co-dominant crown l a y e r .  The former uses the crown  of broadleaf maple and dogwood, the l a t t e r c o l l e c t s i t s food i n the crown l a y e r of b i r c h only, according to my observations which,.however, were not quantitative. The Black-throated gray warbler and Black-capped chickadee show a similar relation.  The favoured tree species..of both.birds i s b i r c h , but  t h e i r a c t i v e l a y e r i s d i f f e r e n t ; the former  occurs :in the higher part of the  crown, the l a t t e r uses the suppressed parts of b i r c h .  In places where the  -32-  crown of the b i r c h i s high above the ground, the Black-capped  chickadee  always remained i n the lower parts and c o l l e c t e d i t s food on red a l d e r , w i l l o w and other decidious t r e e s .  The nesting places of these b i r d s are  different also. Apparently, the two chickadee species are so d i f f e r e n t . i n t h e i r r e quirements that one cannot regard them as sharing the same niche although they may occur i n the same f o r e s t stand.  The Chestnut-backed chickadee  shows a strong f i d e l i t y t o the crown l a y e r of o l d D o u g l a s - f i r . At places of t h i s f o r e s t type where Douglas-far i s scarce chestnut-backed was often observed on vine maple.  Black-capped  chickadee  chickadee have never been  seen on t h i s tree during the observation period of two summers. The two k i n g l e t (Ruby and Golden-crowned-) and two warbler species (Townsend's and Audubon's) are permenent members of t h i s . f o r e s t type during the breeding season. fir.  These species show strong f i d e l i t y t o the o l d Douglas-  The two warbler species c o l l e c t t h e i r food and place t h e i r nests on  the lower part of the crown of o l d D o u g l a s - f i r s . A number of observations .indicated that the complementary t r e e species f o r Audubon's warbler i s the g r a n d - f i r , on which i t feeds and nests. -  Townsend's warbler was  observed  sometimes on deciduous t r e e s , such as birch.and red.alder. Because the D o u g l a s - f i r crown i s high above ground (25 to kO m.)  in  t h i s f o r e s t type, and because the two k i n g l e t species carry out t h e i r a c t i v i t i e s i n the higher parts of crown l a y e r , i t i s hard to d i s t i n g u i s h them and t o separate t h e i r a c t i v e l a y e r s i n t h i s dense f o r e s t stand without s p e c i a l observation time devoted t o these b i r d s only. 2.  Species of the trunks  The F i l e a t e d woodpecker was observed occurring only i n the Eurhynchium  -33-  Mahonia ecosystem type i n the study area.  They were only, seen on cedar  trunks but K. K e l l e h e r working on the same area i n 196I-62 n o t e d . i t a few times feeding on the other stumps too.  No nest has been located here or  elsewhere on the study area. The Red-breasted sapsucker occurs on trunks of deciduous t r e e s , mostly of broad-leaved maple, but i t was often seen on the coniferous tree trunks a l s o . A number of observations i n d i c a t e s that the Red-breasted nuthatch uses both coniferous and deciduous trees w i t h equal frequency i n t h i s community. Brown creeper was observed on maple trees only, but because of the s c a r c i t y of observations t h i s occurrence has no s i g n i f i c a n c e . 3.  Species occurring i n the lower l a y e r s .  Song sparrows occupy f o r e s t edges adjacent t o dense Spiraea t h i c k e t s . The Golden-crowned sparrow occurs i n the dense brush.of the warm f o r e s t edge, which, i s covered.mostly by maple and dogwood. l i v e s i n the wetter parts of t h i s f o r e s t type.  The P i l e a t e d warbler "  In general, these places  are adjacent to the Salix-Lysichitum-Oenanthe f o r e s t type.  MacGillivray's  warbler i s the b i r d of the dense bushy f o r e s t edges located at the higher parts of t h i s f o r e s t type, mostly along road sides, rockflow and steep rock walls. The Oregon junco and Spotted towhee occur i n t h i s f o r e s t type i n i t s young stage.  They nest, i n the openings i n the higher parts of t h i s type.  They have s p e c i a l nesting h a b i t s , which exclude them from mature, stands of the Eurhynchium-Mahonia ecosystem type. Winter wren occurs i n those parts of t h i s ecosystem type where the ground i s covered w i t h a heavy l a y e r of bryophytes and a number of decaying  -34-  trunks.  These p l a c e s a r e i n t h e deeper,  hemlock-cedar  dense p a r t s o f t h e s t a n d  around  groups.  CONCLUSIONS  I n t h e Eurhynchium-Mahonia ecosystem r i c h f l o r a and the moderately -rich,bird The (l)  type the highly  stratified  stand,  moist h a b i t a t f a v o r s t h e development o f a  community. b i r d community o f t h i s t y p e i s s e p a r a t e d . i n t o t h r e e  crown l a y e r  subcommunity.  subcommunities:  T h i s group i s c h a r a c t e r i z e d w i t h t h e presence  o f a p e r m a n e n t l a r g e number o f s p e c i e s a n d i n d i v i d u a l s f o r m i n g a d e f i n i a t e assemblance and by t h e i r system  type.  (2)  strong,fidelity  t o t h e Eurhynchium-Mahonia  I n t h e t r e e t r u n k subcommunity, P i l e a t e d woodpecker and  Brown c r e e p e r were f a i t h f u l t o t h i s t y p e a n d t h e y were r a r e l y other forest types.  eco-  (3)  The l o w e r l a y e r  seen  i n the  subcommunity o c c u r s . i n t h e young  b u s h y s t a n d s o f t h e Eurhynchium-Mahonia e c o s y s t e m  type only.  The change  of e c o l o g i c a l c o n d i t i o n s i n the mature s t a t e o f t h e f o r e s t  stand.inhibits  them, a n d t h e n t h e y c a n o c c u r i n f o r e s t edges and o p e n i n g s  only.  The  W i n t e r wren i s present, i n t h i s ecosystem  covered'by  a heavy l a y e r o f b r i o p h y t e s .  t y p e where ground i s  The W i n t e r w r e n i s i n d e p e n d e n t  from the s u c c e s s i o n a l stage o f t h i s type of f o r e s t from  other communities.  T h e r e f o r e t h e w i n t e r wren can be c o n s i d e r e d as t h e  most c h a r a c t e r i e s t i c b i r d i n t h e ecosystem The  stands, and i t i s absent  o f t h e E u r h y n c h i u m - M a h o n i a type,  s o l i t a r y v i r e o and v a r i e d t h r u s h a r e a l s o c h a r a c t e r i s t i c  7.  P o l y s t i c h u m ecosystem  This ecosystem than those  type  birds.  (; S w o r d - f e r n ) .  type o c c u r s on lower concave s l o p e s , s l i g h t l y  o f t h e Eurhynchium-Mahonia ecosystem  type.  wetter  Seepage i s permanent  -35-  and the s o i l subgroup i s frequently  a c i d dark brown f o r e s t s o i l .  ecosystem type has the highest p r o d u c t i v i t y i n the area. composition i s w e l l i n d i c a t e d  B 70  L i s t of plants (secondary) Acer macrophyllum Alnus rubra Betula papyrifera Acer circinatum Cornus n u t t a l l i i C. o c c i d e n t a l i s Corylus c a l i f o r n i c a Holodiscus d i s c o l o r Rubus p a r v i f l o r u s R. v i t i f o l i u s Achlys t r i p h y l l a Adenocaulon b i c o l o r Athyrium f i l i x - f e m i n a Circaea a l p i n a Dicentra formosa Disporum oreganum Galium t r i f l o r u m Polystichum munitum Pyrola a s a r i f o l i a Smilacina s t e l l a t a Tiarella trifoliata T. u n i f o l i a t a T r i l i u m ovatum Trientalis l a t i f o l i a D  Its floristical  by the f o l l o w i n g l i s t of species:  Layering  B  This  A n t i t r i c h i a curtipendula Cladonia subsquamosa Claopodium c r i s p i f o l i u m Heterocladium sp. Mnium insigne M'. venustum Neckera d o u g l a s i i Pore11a n a v i c u l a r i s Pseudisothecium stoloniferum  D  60  20  10  Sociability  Vigor of species  .7  -  8  2 2 .2  5  7  -  - •  3 2 2  -  5 5 9 5  3 3 3 3  6  .8  3 6 2  -  3 3 3 3 3 3 3 3 3 ' 3 3 33 2  Species significance  -  -  -  -  8  •7 3  -  3 3 2 •5 2  3  -  '  .5 3 6  -  .2  k  -  -  -  -  -  -  2  -  5  l  2 3 3 2 3 2 3  3 3 3 3 3 3 .3 3 2  -36-  A f t e r  i s  q u i t e  f i r e  o r  o n l y  mature  e x t e n t  about  15  i n  e a r l y  s t a t e  b o r d e r i n g  t h e  v e s t i g a t e d  a r e  s t a n d  a c r e s .  study  o f  B u t  o f  t h i s  t h i s  s e c o n d a r y  a r e a .  . i n d e t a i l  t h e  crown  Some  the  A l n u s  r u b r a - B e t u l a  o f  l a y e r  h i g h e r  w h i c h  case  t h e  The  o f  i s  ecosystem  a n d t h e  type  ecosystem  type  s u c c e s s i o n s  i n  T h e b i r d  i n d i c a t e  p a r t s  b i r d  s p e c i e s  a r e  p o p u l a t i o n  h i n d e r s  mature  f o l l o w i n g  t h e  o f  a r e  a  i s  a . f e w  t h e  stands  a v e r a g e  v e r y  a  p o o r  here  s p e c i e s  t h i s  e v e n ,  .dense  c o l o n i z a t i o n  o f  age  d i s t r i b u t e d  c o v e r e d . b y  c a n accommodate  The  c o n s o c i a t i o n  t h e  study  a r e a  more  e x t e n s i v e l y  t h e  Y a l e  I n d i a n  o f  b o t h  stands  t h a t  o f  t h e i r  m a i n l y  l a y e r  due  t o  o n l y .  b y  o f  t h e  T h e  t h e  e c o s y s t e m  b i r d  h a d a n  R e s e r v a t i o n  were  i n -  p o p u l a t i o n s  100  C h a r a c t e r i s t i c  V i r e o  Rubus  v e r y  y e a r s .  a l d e r  a n d  d e p r e s s i o n s ,  b i r c h .  w h i l e  p a r v i f l o r u s .  even  l a y e r  s t a n d  o f  s t r u c t u r e  Rubus  n e s t i n g . b i r d s .  i n h a b i t e d  b y  t h e  o f  Columba  o f  i n d i v i d u a l  Biomass o f  s p e c i e s  p o p u l a t i o n  gm.  gm.  1+8  17  8l6  24  180  4320  36  108 264 168  s p e c i e s  f a s c i a t a  t r a i l l i i  24  3 11  s o r d i d u l u s  12  14  S e l a s p h o r u s Empidonax Contopus  a c r e s  Average w e i g h t  s p e c i e s  o l i v a c e u s  Dominant  r u f u s  a t r i c a p i l l u s m i g r a t o r i u s  H y l o c i c h l a D e n d r o i c a S p i n u s  t h e  o f  6l  s p e c i e s :  p e r  T u r d u s  i n  dense  a r e  s t a n d . i s  l a y e r  g r o u n d  type  No.  P a r u s  t h e  l o o s e  i n d i v i d u a l  B  i n  o c c u r r e d  p o p u l a t i o n s  r e s u l t s ,  o u r a r e a ,  composed  shrub  p a r v i f l o r u s  A  p a p y r i f e r a  d i f f e r e n t .  I n  The  t h e  common.  The  i t s  l o g g i n g  u s t u l a t a n i g r e s c e n s  t r i s t i s  1+8  85  4080  72 84 12  . kk 11 12  3168 92k 144  -37No. of individual 100 acres C  Average weight of. individual gm.  Biomass of species population gm.  Accessoric species Bonasa umbellus Zenaidura macroura Dendrocopos w i l l o s u s Sphyrapicus v a r i u s Empidonax d i f f i c i l i s Cyanocitta s t e l l e r i S i t t a canadensis Certhia .familiaris Ixoreus naevius Regulus satrapa Vireo s o l i t a r i u s Dendoica petechia D. audoboni D. townsendi Opornis t o l m i e i Piranga l u d o v i c i a n a Pheucticus melanocephalus Hesperiphona vespertina Carpodacus.purpureus P i p i l o maculatus Junco oreganus Melospiza melodia  12  45"  540  14,820 A general c h a r a c t e r i s t i c of the b i r d population of t h i s Alnus-Betula consociation of the Polystichum type i s that only those species are present i n the crown l a y e r which can feed on deciduous trees during the summer season.  But during the migration p e r i o d . i n spring and autumn, a number of  Townsend's and Audubon's warblers, k i n g l e t s and-Purple f i n c h f l o c k s are present a l s o . 1.  The population of the trunk and lower l a y e r s . i s poor.  Species of crown l a y e r :  The Red-eyed y i r e o i s a c h a r a c t e r i s t i c  species i n the mature stands of the Alnus-Betula consociation.  I t favours  birch' and.maple f o r feeding, and places i t s nests i n the bushy depressions. Although.it has strong l i m i t a t i o n s regarding nest s i t e s , i t uses a r e l a t i v e l y large feeding area.  -38-  Those densest.parts of t h i s ecosystem type where the ground.is covered by a stong l a y e r of shrubs from the f a v o r i t e h a b i t a t of Swainson's thrush. Apparently the Swainson's thrush does not occur i n places where the l i g h t ranges are above 60 per cent and the ground.is covered by a dense l a y e r of Rubus p a r v i f l o r u s .  The lower parts of the crown and the shrub l a y e r are,  besides the ground, the layers i n which the b i r d c a r r i e s out i t s a c t i v i t i e s . Due to the abundance.of b i r c h , t h i s ecosystem type i s the favoured h a b i t a t .of the Black-throated gray warbler and Black-capped chickadee. The former species occurs i n thoseplaces where the crown of b i r c h . i s high above the ground, while t h e . l a t t e r species occurs mostly along the edge of the f o r e s t , roadsides and f o r e s t openings where the crown of the b i r c h i s lower.  Both species nest and are present.in a r e l a t i v e l y high number i n  t h i s f o r e s t type during the nesting season. Robin nests are present i n the Spiraea ecotone and l i k e w i s e Rufous hummingbird nests here. Band-tailed pigeon nests, and small groups of up t o nine i n d i v i d u a l s were observed f r e q u e n t l y . 2.  The species of the trunk are not too numerous i n t h i s ecosystem type.  Probably the deciduous f o r e s t . i s not a f a v o u r i t e h a b i t a t f o r them. breasted sapsucker was seen most often here.  The  However, no evidence was  Redfound  f o r i t s n e s t i n g . Only a.few observations i n d i c a t e d the occurrence of Hairy woodpecker.  The Red-breasted nuthatch was seen at the edges only.  In the  summer of i 9 6 0 , a.pair of Brown creeper was present i n t h i s f o r e s t type. 3.  Species o c c u r r i n g i n the lower l a y e r s .  This group was represented  by only a few species;, according to t h e i r p a r t i c u l a r l o c a l i t i e s one  cannot  suggest t h a t they are regulair i n h a b i t a n t s of t h i s ecosystem type i n i t s  -39-  present successional stage. only.  Song sparrow occurred i n the spiraea swamp  The Junco and M a c G i l l i v r a y ' s warbler occurred i n the edge of t h i s  ecosystem type. The b i r d population of the Polystichum ecosystem type was s t u d i e d . i n young secondary stands a l s o .  The f l o r i s t i c composition of t h i s young stand  .is s i m i l a r t o the mature stand. B i r d s occurring i n t h i s young stand are as f o l l o w s : No. of individual per 100 acres A  60  45  2700  10  180  1800  10 10 10 20 50 10 20  11 8 ' 8 5  110 80 850 880 1850 180  10 20 10 10 20 10  11 11 11 45  Dominant species Columba f a s c i a t a Zenaidura macroura Empidonax.traillii •Parus a t r i c a p i l l u s Turdus migratorius Hylocichla ustulata Bombycilla cedi'orum Vireo olivaceus Spinus t r i s t i s  C  Biomass of species 'population gm.  .Characteristic species Pheucticus melanocephalus  B  Average weight of individual gm.  44  37 18 12  240  Accessoric species Bonasa umbellus Selasphorus rufus H y l o c i c h l a guttata Dendroica petechia Wilsonia p u s i l l a Oporornis t o l m i e i Hesperiphona vespertina P i p i l o maculatus Junco oreganus  40  18  110 220 •110 450 800 180  5870  -40The b i r d population of the; young stage of t h i s ecosystem type includes those species mostly which l i v e i n the lower vegetation l a y e r s ; only a few species of the crown l a y e r occurred here. The Black-headed  grosbeak i s a c h a r a c t e r i s t i c species o c c u r r i n g only  i n the young stands of t h i s ecosystem type. i z e the whole area of t h i s type.  The adult b i r d does not colon-  A l l known nests were placed i n the upper  one-third, p a r t . i n the crown of young alder trees along streamlets. might i n d i c a t e that the black-headed  This  grosbeak has a r e l a t i v e l y narrow range  of adaptation i n t h i s type. The Cedar waxwing i s an abundant species i n t h i s stand.  I t places  i t s nest s i m i l a r l y as in' the Gaultheria-Mahonia ecosystem type. i t s p r e f e r r e d h a b i t a t . i s a l s o here i n the edge of the stand. nests were l o c a t e d on the roadside.  As there,  Most of the  The p r e f e r r e d h a b i t a t of Swainson's  thrush and the Eed-eyed v i r e o c o n s i s t s of the depressions,.the stand of which i s dense and r e l a t i v e l y o l d with a shrub l a y e r .  A l l three nests of  Swainson's thrush i n t h i s area.were found i n depressions.  Several i n d i v i -  duals of Hermit thrush were seen only i n springs in" t h i s ecosystem type. Band-tailed pigeon i s an abundant species here at l e a s t with respect to i t s feeding.  The Morning dove sometimes occurred here as a v i s i t o r from  the o l d stands along the bank of the Fraser River where t h i s species i s abundant. Only a.few observations.indicated the presence of the Robin.  Two  nests were found along the streamlets. The P i l e a t e d and Yellow warblers and the American gold f i n c h were often seen i n the wet openings.  On those places where dense bushy parts occurred  mostly i n the depressions, Song sparrows are always present, while i n dense,  -lHd r i e r places, M a c G i l l i v r a y ' s warbler commonly occurs. CONCLUSIONS Generally speaking, the b i r d population of the Polystichum ecosystem type i s poor i n both mature and young stages.  In the case of the mature  stand i t s poorly s t r a t i f i e d s t r u c t u r e i n h i b i t s the development of an abundant b i r d population and only a.few species occur which can adapt to the crown l a y e r of Alnus rubra and B e t u l a p a p y r i f e r a .  The dense layer of Rubus  p a r v i f l o r u s hindered the occurrence of ground feeders and ground nesting species.  The observed b i r d s of trunks and of lower l a y e r s i n d i c a t e d very  weak populations i n these s t r a t e s .  Judging from the rare occurrence of  i n d i v i d u a l s .in both groups one cannot regard those species as regular members i n the Polystichum ecosystem type.  One may regard them as oc-  c a s i o n a l u t i l i z e r s of t h i s type. The mature stand of the Polystichum ecosystem type has a . r e l a t i v e l y a c t i v e b i r d l i f e during,the migration season.  An 8 t o 12 years o l d dense  young stand of the Polystichum ecosystem type can accommodate a few species only. 8.  Thuja-Lysichitum-Oenanthe  ecosystem type (Red cedar-Skunk-cabbage-  Water p a r s l e y ) . In depressions where seepage i s at.the s o i l surface and i t s movement i s very slow, or along small streamlets, the Lysichitum-Oenanthe develops.  The s o i l i s " poorly aerated, g l e y s o l .  The vegetaional composi-  t i o n i s quite s p e c i f i c f o r t h i s h a b i t a t . Layering  A  1  20  A  g  50  B  1  15  B  2  15  swamp  C  D  100  80  h  -42-  L i s t of plants  Species significance  Sociability  Vigor of species 2(on the edge of depression)  Pseudotsuga m e n z i e s i i  Thuja p l i c a t a  5  8  2  Alnus rubra Thuja p l i c a t a  6 4  8 7  .2 2  5 6  .2 2  -  3 2  Acer circinatum Alnus rubra Rhamnus purshiana Thuja p l i c a t a Alnus rubra Betula papyrifera Rubus s p e c t a b i l i s Sambucus pubens Sorbus s i t c h e n s i s Thuja p l i c a t a Athyrium f i l i x - f e m i n a Dryopteris a u s t r i a c a Epilobium adenocaulon Galium t r i f l o r u m Glyceria pauciflora Lysichitum americanum Physocarpus capitatus Polystichum munitum Veronica americana Viola glabella V. p a l u s t r i s Eurhynchium oreganum E. s t o k e s s i Hylocomium splendens Mnium insigne M. punctatum P e l t i g e r a rufescens Rhytidiadelphus t r i q u e t r u s A n t i t r i c h i a curtipendula C e t r a r i a sp. Dicranoweisia c i r r h a t a Frullania nisquallensis Neckera .douglasii Parmelia sp. Pseudisothecium stoloniferum  _  -  4  7  _  _  -  -  5  6  -  -  -  8 2 1 2 4 4  -  2  -  6 4 3 3  -  2  -  -  10 4 4  3 6 5  2 2 3 2 2 2 3 3 3 3 3 2  -  3  3 3 3  3 3 3  3 7 5 .5 4  2 3 3 3 3 3 3  -  -  5 4 2 1 3 3 2 5  l  3 3 3 •3 3 3 3  -43-  This i s the wettest ecosystem type i n the study area.  In general,,  t h i s type i s flooded a l l year round, or at l e a s t f o r 9 to 10 months i n a year.  A very dense l a y e r of herbs develops i n t h i s type which excludes  the ground feeders and n e s t i n g species completely.  Because of the even  stand s t r u c t u r e and the strong e f f e c t of the edaphic f a c t o r s , a high degree of adaptation i s required of the b i r d s , hence the b i r d population i s poor i n t h i s ecosystem typ. B i r d s occurring i n t h i s ecosystem type: No. of individual per 100 acres A  Average weight of individual gm.  Biomass of species population •  SB*  C h a r a c t e r i s t i c species none  B  Dominant species Parus a t r i c a p i l l u s S i t t a canadensis Turdus migratorius Wilsonia p u s i l l a Spinus t r i s t i s Melospiza melodia  C  Accessoric species Columba f a s c i a t a .Zenaidura macroufa Selasphorus rufus Sphyrapicus v a r i u s Dendrocopos w i l l o s u s Tyrannus tyrannus Empidonax t r a i l l i i Corvus brachyrhynchos Cyanocitta s t e l l e r i Ixoerus naevius Hylocichla ustalata H y l o c i c h l a gutta Sturnus v u l g a r i s Dendroica petechia D. nigrescens Geothlypis t r i c h a s  40  8  120  85 11 12 20  40 40 80  320 .10200  440 480  1600  -kk Ho. of individual 100 acres  Average weight of individual gm.  Biomass of species population gn.  Carpodacus purpureus Agelaius phoeniceus Euphagus cyanocephalus Molothrus ater Hesperiphona vespertina P i p i l o maculatus Zonotrichia a t r i c a p i l l a The b i r d population i s represented by those species which are f a i t h f u l to the crown l a y e r .  The Robin shows a high adaptation i n t h i s type  considering i t s n e s t . b u i l d i n g and nest p l a c i n g method. f i r s t nest i s b u i l t above the open water.  In general, the  The second n e s t , i s placed  s i m i l a r l y to the f i r s t . i f the f l o o d water i s s t i l l present, b u t . i n case of dry surface the second nest w i l l be placed .into the ecotone of t h i s type and the adjacent types.  Robins cannot use t h i s type f o r feeding, because  of the dense l a y e r of ground vegetation. The Black-capped type.  chickadee i s not .influenced by the extremes of t h i s  I t c a r r i e s , o u t a l l of i t s a c t i v i t i e s on red a l d e r t r e e s .  Apparently  the population of t h i s s p e c i e s . i s always numerous i n t h i s ecosystem type which,indicates that the circumstances of l i f e are favourable f o r i t . Swainson' thrush was seen o f t e n here,, but no evidence was found f o r i t s n e s t i n g i n t h i s type of area. Song sparrow and P i l e a t e d warbler occurred i n the dense edges of 'this type. A l l other b i r d species which were mentioned i n the l i s t are accessoric species only. 9.  Spiraea douglasii"ecosystem type (Spiraea).  This i s a .thicket formation developed on low moors as an advanced stage i n the succession of l a k e s . I t i s f l o r i s t i c a l l y poor, c h a r a c t e r i s t i c a l l y ,  -45-  d i f f e r e n t from the other ecosystem types discussed e a r l i e r i n the t e x t .  This  community i s dominated "by Spiraea d o u g l a s i i , Carex r e t r o r s a , Lycopus u n i f l o r u s Veronica americana and some other species are s p o r a d i c a l l y present.  This  habitat .is mainly floodedfor a t l e a s t nine months of the year, except J u l y , August and September. B i r d s occurring i n t h i s ecosystem type: No. of individual per 100 acres Bonasa umbellus Selasphorus rufus Empidonax t r a i l l i i Turdus migratorius Hylocichla ustalata Bombycilla .cedrorum Wilsonia p u s i l l a Agelaius phoeniceus Spinus t r i s t i s Melospiza melodia  52 26 26 338  Average weight of individual gm.  11 65 12 20  Biomass of species population gm.  572 1690 312 6760 9334"  The c h a r a c t e r i s t i c species of t h i s type i s the Song sparrow i n our area.  Apparently each Spiraea swamp h a s . i t s own Song sparrow population.  The red-winged b l a c k b i r d . i s present only i n the large Spiraea swamp i n the study area.  I t c a r r i e s out a l l i t s a c i t v i t i e s w i t h i n t h i s ecosystem type.  Whether those species which may b u i l d t h e i r nests i n the ecotone of Spiraea swamp are i n .feeding r e l a t i o n s w i t h t h i s type, or they place t h e i r nests here f o r i t s s u i t a b l e ecoclimate only, has not yet been evidenced with f i e l d data.  During the second nesting p e r i o d , Robins were often  observed as feeding on the dry ground of t h i s type.  -k6-  10.  Carex r e t r o r s a ecosystem type (Retrorse sedge).  This i s a low moor, w i t h dominating Carex r e t r o r s a . flooded a l l through.the year.  The surface i s  I t occurs i n zonal or fregmental complex  with the Spiraea t h i c k e t or w i t h the f l o o d i n g community of Nuphar. This ecosystem type i s always connected t o the previous type having the same "bird population. Eutroph,Lake. 1.  Nuphar polysepalum ecosystem type (Water  lily).  Nuphar polysepalum dominates.in the 0.3,to 1.5 m. deep water.  This  zone adjoins the Typha l a t i f o l i a stands on the shallower side and communit i e s of water weeds on the deeper side. This type i s the feeding ground f o r a number of waterfowl species. Four of them - M a l l a r d , American golden-eye,.Buffle-head and Wood duck were present during the summer.  Evidence of n e s t i n g were found, i n the cases  of the M a l l a r d (on the lake) and wood duck (adjoining f o r e s t ) only. The large l e a f of Nuphar harbours a r i c h invertebrate fauna p r o v i d ing an important food source f o r the Red-winged b l a c k b i r d . 2.  Typha l a t i f o l i a ecosystem type ( C a t - t a i l ) .  This type colonizes waters shallower than approximately 2 f e e t .  Its  companions are Comarum p a l u s t r e , A n g e l i c a genuflexa, Galium t r i f i d i u m and s e v e r a l Carex species. C h a r a c t e r i s t i c species of t h i s t y p e - i s the B i t t e r n .  I t shows such a  strong f i d e l i t y t o the community of t h i s ecosystem type that only a few occurrences were noted.in the adjacent types.  Red-winged b l a c k b i r d s a l s o  favoured t h i s h a b i t a t . 3.  Glyceria-Carex ecosystem type (Manna grass-sedge)  In shallower waters, l e s s than one f oot,, G l y c e r i a p a u c i f l o r a , C-. e'lata  -kl-  •and.G. s t r i a t a form a s s o c i a t i o n w i t h s e v e r a l Carex species and plants from .the adjacent communities. The pure stand of Carex occurs as a b e l t around the spiraea.type. I t i s d i f f i c u l t t o d i s t i n g u i s h a separate b i r d population f o r t h i s type.  The  most often observed species are the b i t t e r n , the yellow-throat and.the song sparrow. k.  Spiraea d o u g l a s i i ecosystem type (Spiraea).  Already described on page kk.  B i r d s , o c c u r r i n g i n t h i s ecosystem type  are as f o l l o w s : Selasphorus rufus Tyrannus tyrannus Dendroica petechia Geothlypis t r i c h a s Wilsonia p u s i l l a Aegelaius phoeniceus Melospiza vmelodia The c h a r a c t e r i s t i c species of t h i s type are the yellow-throated and red-winged b l a c k b i r d . The song sparrow a l s o shows f i d e l i t y t o t h i s type. !  5«  Salix-Lysichitum-Oenanthe  ecosystem type (Willow-Skunk-cabbage-  Water p a r s l e y ) . This community develops on the h a b i t a t above the l e v e l of permanent f l o o d i n g on g l e y s o l i c s o i l s .  The dominating  species are S a l i x s i t c h e n s i s ,  Alnus rubra,, Spiraea .douglasii, Oenanthe sarmentosa, Cinna l a t i f o l i a , Lysichitum americanum, Typha l a t i f o l i a , Solanum nigrum, Lonicera i n v o l u c r a t a , Athyrium f i l i x - f e m i n a and G l y c e r i a p a u c i f l o r a . This ecosystem type covered a r e l a t i v e large part of the swamp... I t seems that t h i s . t y p e i s the most valuable ecosystem of the swamp area i n regard t o the avifauna.  During the migration period a number of large  f l o c k s of d i f f e r e n t species such as Audobon's warbler,.purple f i n c h , pine s i s k i n e t c . , were observed here.  I n the l a t e summer t h i s type i s the  r e s t i n g place f o r b l a c k b i r d s , cowbird and s t a r l i n g .  -U8-  The species which were found to n e s t . i n t h i s ecosystem type are as .follows: Tyrannus tyrannus . Parus a t r i c a p i l l u s Turdus migratorius Bombycilla.cedrorum Dendroica petechia Wilsonia p u s i l l a Spinus t r i s t i s P a r t i c u l a r l y the 'black-capped chickadee has a r i c h population i n t h i s type.  I t seems that the dense young stand of w i l l o w and alder i s godd  h a b i t a t . o f t h i s species.  The P i l e a t e d .warbler shows also strong f i d e l i t y  to t h i s community. 6.  Populus t r i c h o c a r p a ecosystem type.  This type develops on higher grounds along the drainage channels of the l a k e .  Flooding i s p e r i o d i c a l and ceases only f o r short .periods once  or twice a year.  Dominating plants are Populus t r i c h o c a r p a , Lonicera  i n v o l u c r a t a , Rubus s p e c t a b i l i s and Symphoricarpos r i v u l a r i s . occupies a.small area, t h e r e f o r e , , i t . i s r e l a t i v e l y  This type  unimportant.  This ecosystem type cannot be used, i n the e v o l u t i o n of the true features of i t s b i r d population, because of i t s small extent.  The Crow  shows a strong f i d e l i t y t o t h i s type. The q u a n t i t i a t i v e s t r u c t u r e of the b i r d p o p u l a t i o n s . i n the study area. The species of each ecosystem type are given by the numbers of i n d i v i d u a l s per 100 acres.  These numbers r e f e r to the nesting p a i r s only.  Occasional v i s i t o r s and rare species are n o t . i n c l u d e d . i n t h i s chapter.  The  b a s i c weights used.in the" c a l c u l a t i o n of biomass were obtained from Mr. Witt by o r a l communication and from Stegeman (1955) and from Nqrris and Johnson (1958).  We are aware, as has been pointed out by Z e d l i t z (l926),Nice (1938),  and others, of the d i u r n a l , seasonal and r e g i o n a l v a r i a t i o n s of weight; t h e r e f o r e , the weight averages, and the biomass calculations.based upon them, are considered t e n t a t i v e and approximative only.  The biomass of Eurhynchium-  Mahonia ecosystem type was considered as the b a s i c value i n the comparisons. The d i f f e r e n c e s of the biomasses of the ecosystem types are expressed as percentages of the biomass i n the Eurhynchium-Mahonia ecosystem type which i s taken as 1 0 0 .  The differences.are given.in Table 1 .  The biomass value of ecosystem types. Ecosystem type  Dantonia.spicata Secondary t h i c k e t s of Corylus, Acer e t c . Pachystima-GaultheriaPeltigera(mature stand) (immature stand) Gaultheria-CladoniaRhacomitrium Gaultheria-Mahonia Eurhynchium-Mahonia Polystichum (mature stand) (immature stand) Thuj a-Lys i chiturn-Oenanthe Spiraea and Carex v  Size of total study area acres 5  20  Table 3&  No. of individual per 100 acres  Biomass (JSE)  per' 100 acres :  7 2 0  . 1 . 6 5  1+0  1020  2 . 2 9  . 2 9 . 8 3  3 7 6  1 3 0 0 6  3 0  9 0  1 8 0 0  5  1 5  20 10 8  •If.13  240  ll+21+O  3 2 . 6 0  3 1 1  I+I69I  9 5 - 6 2  1 5 0  1+3600  i+08  14820  3 3 . 9 9  5 8 7 O  1 3 . 3 9  2 8 0 3 2 0 -  .•type.  1+0  2 5  70 20  Biomass i n ft of b a s i c  1+42  •  1 0 0 . 0 0  13040 9334  2 9 . 9 0  21.1+0  The a p p l i c a t i o n of the.biomass v a l u e s , i s u s e f u l i n the case of b i r d .census and, i n the comparison of the d i f f e r e n t ecosystem types. wants t o propose t o express the biomass values by l a y e r s .  The author  I n t h i s case  the biomass i s a good expression of the present conditions of f o r e s t stands. For instance, the Gaultheria-Mahonia ecosystem t y p e . i s represented.in the  The studied areas cover more acreage than the l i m i t s of the Thacker Ecol o g i c a l Research Researve,.for i n many instances census e t c . work was extended i n t o neighbouring f o r e s t s .  -50-  study-area by e a r l y secondary successional stages. (The b i r d population of t h i s f o r e s t type i s very poor, but because grouse i s present and t h i s has high body weight the biomass of t h i s type i s considerably increased .up t o 95* 39 P r cent .'if Eurhynchium-Mahonia e  ecosystem type i s taken as 1 0 0 .  I f grouse was not counted t h i s type would lose a large part of i t s biomass). I f the biomass i s separated i n t o two l a y e r s . i t gives a more comprehensive' p i c t u r e as seen i n Table 4 . The biomass values of the tree nesting and ground nesting b i r d s i n d i f f e r e n t ecosystem types. Table 3 b . Ecosystem type  Dantonia s p i c a t a Secondary t h i c k t e t s of Corylus, Acer e t c . •Pachystima-GaultheriaP e l t i g e r a (mature stand) (immature stand) Gaultheria-CladoniaPhacomitrium Gaultheria-Mahonia Eurhynchium-Mahonia Polystichum (mature stand) (immature stand) Thuja-Lysichitum-Oenanthe Spiraea and Carex  Biomass (gm) per 100 acres 720  Biomass o f tree l a y e r nesting species i n fo :  0  Biomass of ground nesting species in% '  100.00  1020  78.44  21..56  13006 1800  89.55 31.34  10.45 68.66  14240  89.89 16.18 96.93 100.00 83.22 100.00 100.00  10.11 83.82 3.07 0 . 16.78 0 0  41691 43600 14820 5870 13040 9334  Comparison o f the biomass o f b i r d s i n the ecosystem t y p e s . T a b l e 4 -p OJ  o •H-  2  2  H  o> e  1  1  -P cd PS cd -P • g w o ( L v 5 1 PL,  O ' J 1  PH 3 Cl 1 -P cd c5 t« -P 1 e  Eurhynchium-Mahonia  0  Gaultheria-Mahonia  95-62  0  Polystichum  33-99  35-54  32.66.  3 4 . 1 5 96-68  0  Oenanthe  29.90  3 1 - 2 7 87.76  91-57 0  Pachystima-GaultheriaS p i r a e a and Carex P e l t i g e r a (mature)  2 2 91- 8- 33 4 2321- 3- 91 9 68 72 .. 79 68  96 51- -5 43 3 79 91- -7 45 8 701 - 7 6  Polystichum  1 3 - 3 9 14-01  If 1 . 0 1  (mature)  'd ce  2 cd  -P -P cd co S "  f^SS  1  3  OO-P '  cd  w.  .i>> .  -.'•>> M H u  o.  .  . cu . o. o.  0  Gaultheria-cladoniaRhacomitrium Thuja-Lysichitum-  (young)  I  39-40  44-78  44-90  0 62.56  M  0  Pachystima-GaultheriaPeltigera  (young)  4 . 1 3 > - 3 2 12.14 1 2 . 6 4 1 3 . 8 0 1 3 - 8 3  1 9 - 2 8 30-82  0  Secondary t h i c k e t o f Corylus, Acer e t c .  2.29  2.44  6 . 8 8.7.16 7 - 8 2  7 - 8 4 1 0 - 9 3 .17-38  56-66  . 0  Danthonia s p i c a t a  I.65  .1-73  4.86 5-05 5-52  5-54 7-71 12-27  40.00  70-59  L i s t of the avifauna i n d i c a t i n g the r o l e of each species i n the ecosystem type Table 5 Explanation of symbols: 10 1  •'10 -J-10 10 Species  —  -p <u M V  •H Si  -P O  <u  CQ  Great blue heron American b i t t e r n Goshawk R e d - t a i l e d hawk Osprey Golden eagle Bald eagle Marsh hawk Peregrine f a l c o n Sparrow hawk Blue grouse Ruffed grouse Band-tailed pigeon Mourning dove Great horned owl  U -P  ai S  -—y  CM  censused number of individuals/lOO acres species not present a c c i d e n t a l ; vagrant from other areas accessoric: breeds i n some stand dominant, often seen suspected breeder dominant, regular breeder c h a r a c t e r i s t i c species, r e s t r i c t e d t o one community  y  fl  o  CD  u  >> CM  O 1  1  CM  CM  -p S  K  o o •  i  x— bO fl  o >>  I  CMI.  CM  I  I  !  EH  CQ  I  o  l-H  C5  CO  i  CM  I  ro i  •3  - -5  O  oi  -37  '  I  !  I  -40 -24 -10 -10  u w> 2 fl +> o 3  -p OJ  ^o a-p  Rufous hummingbird C a l l i o p e hummingbird Belted kingfisher Red-shafter f l i c k e r P i l e a t e d woodpecker Lewis' woodpecker Red-breasted sapsucker Hairy woodpecker Downy woodpecker Eastern k i n g b i r d Western k i n g b i r d T r a i l l ' s flycatcher Western f l y c a t c h e r Olive-side f l y c a t c h e r V i o l e t green swallow Rough-winged swallow Barn swallow Tree swallow C l i f f swallow Purple martin Canada jay Steller's jay Common raven Common crow Black-capped chickadee Chestnut-backed chickadee Mountain chickadee Red-breasted nuthatch Brown creeper  C  £  £  PM  PM  Q  P  M  a « -p - 3 g  «  P  *  M  C  -  -16  -  _ -  _  _  1  _  '1  ••_  _ _ 8  „^  OJ .  Cfl  S  O  W  P  _  M  P  _  _ > -30 • < _ _ 8 ' i o '  9  O  -io -50 -36 __ _ _ -10 ' _  _  :  M  E  ' _ -  ' _ -  _  _  -  •  ? H  -10 - 1 0 -2k -10 -3 - 2 0 ' -5 ' -  -16  -3  -20  I  -16 -ko  -5 -28  -30 -10  -  -28 - 3 0 4  - 1 0 -ko  C  *  A  O  -  - .' -  &  E  _  H  _  _ • _  -  O  C  O  P  M  _  ' 1  l  _  _  _  -  I 00  I  x!-P  Q  8  PH O o <OQ u P PHhH C C  >>  PH O 1H p PH  PH | O Ot O  3 O  -P cd J  ^  p  H  P  H  _O  O E  H  C  Q  Dipeer Winter wren - 80 - Robin -. ' ' -160 -8 -130 -48 -10 -120 Varied thrush - - - - - 6 6 - thrush - - - - ' -60 -72 -20 Hermit thrush - - - - - - - Golden-crowned k i n g l e t - -20 - -8 -20 Ruby-crowned k i n g l e t - -h -3 -10 - Cedar waxwing - -6 ' -18 - -50 Starling Solitary vireo _ _ _ _ _ _ -130 - Redy-eyed v i r e o — — —— — — — — **-8 -10 Orange-crowned warbler ' -10 20 Yellow warbler -' ' - - - 1 0 ' Audubon warbler - -72 - -13 -60 Townsend's warbler - -8 - -3 -10 ' - Black-throated gray warb. - - ' - - -50 -Qk ' M a c G i l l i v r a y ' s warbler - -20 '24 -24 - -24 '30 ' -10 Yellowthroat _ _ _ ' . . _ _ _ _ _ _ _ House sparrow Red-winged b l a c k b i r d _ _ _ _ _ _ _ _ _ + . -26 Brewer's b l a c k b i r d - - - - - - - - - Brown-headed cowbird _ _ _ _ _ _ ' ' _ ' _ Western tanager - -48 ' - -13 -50 ' Black-headed grosbeak _ _ _ _ _ ' _ ' 6 0 - Evening grosbeak _ _ • _ _ ' _20 '12-10 Purple f i n c h - -8 ' - '5 -10 * Pine s i s k i n - -8 ' - -5 -20 - American goldfinch ' - '10 -12 -20 -40-26 'Spotted towhee - -20 'l6 -12 - -34 '10 ' '20 ' Oregon junco -40 - '40 -42 -80 -42 '30 ' '10 Chipping sparrow White crowned sparrow ' Golden crowned sparrow - ' 10 - •' Song sparrow ' - '3 ' ' ' -80 338 1  1  1  1  1  O  f  e  E  H  O  t  n  O  i  -55-  RELATION OF THE NESTING AVIFAUNA AND FOREST TYPES STUDIED Forests are ecosystems, the components of which are p l a n t s , animals and the p h y s i c a l h a b i t a t ships with one another.  These components are i n close mutual r e l a t i o n -  Tansley (1935) remarked that "changes i n one com-  ponent are r e f l e c t e d i n the e n t i r e system, and the consequences w i l l continue t o be f e l t u n t i l dynamic e q u i l i b r i u m has again been reached . -Besides the members of the non-ayian fauna (and these r e l a t i o n s were outside the scope of t h i s study), b i r d s as members of t h i s ecosystem complex are c l o s e l y i n t e r r e l a t e d with the p l a n t s , s o i l and climate. The study of c e r t a i n such r e l a t i o n s h i p s was based on the assumptions .that: 1.  A l l nests must provide conditions which can ensure s u c c e s s f u l  hatching and development of young w i t h i n the t o l e r a n c e . l i m i t s of the species. 2.  A given species nests i n an ecosystem type i f t h i s can provide  favourable conditions f o r that species i n the c r i t i c a l period.of r e a r i n g young possessing.but l i m i t e d c a p a c i t i e s of adaptation to the constantly f l u c t u a t i n g i n f l u e n c e s of the surrounding. P a r t i c u l a r adaptations of the breeding ecology, ranked i n order of importance, concern the f o l l o w i n g aspects: A.  P l a c i n g the nest .into the r i g h t microclimate (by h a b i t a t and nest  site selection). B.  Mechanical measures.to adapt the nest t o the p r e v a i l i n g c l i m a t i c  f a c t o r s . ( i n s u l a t i o n of nest, s t a b i l i z i n g i t against wind, e t c . ) .  -56C.  Behavioural responses toward c r i t i c a l extremes of the environment -  (brooding, shading, e t c . ) . While the l a s t aspect was not considered, the b a s i c purpose of t h i s study was t o answer questions p e r t a i n i n g t o A. and B., i . e . , how a b i r d can adapt t o the f o r e s t environment and how i t can maintain t h i s adaptation during the n e s t i n g season.  The presence of t h i s adaptation of the species  i s the b a s i s of v i s n e s t i n g success.  Only a f t e r s u c c e s s f u l adaptation to  the microclimate of the nesting grounds can other l i m i t i n g f a c t o r s , e.g. food supply, be considered.  The.importance of food supply, predation,  proper nest m a t e r i a l a n d ' s i m i l a r e s s e n t i a l f a c t o r s i s not denied hereby;-it i s merely t h a t the focus of t h i s study was only one of the s e v e r a l e s s e n t i a l (or e x i s t e n t i a l ) f a c t o r s :  microclimate.  - In general, the e c o l o g i c a l conditions i n a w e l l s t r a t i f i e d f o r e s t stand change continuously i n time and space.  The amplitudes of these changes  determine which species of b i r d s w i l l o c c u r - i n the f o r e s t .  Therefore, the  a s c e r t a i n i n g of the magnitude of these changes i s a b a s i c question i n the e c o l o g i c a l study of f o r e s t b i r d s . Now regarding.the c l i m a t i c aspect of the environment. The i l l u m i n a t i o n curve was introduced to measure the changes of ecol o g i c a l f a c t o r s i n the nest surroundings.  L i g h t curves are good indlc&brsr.s  i n f o r e s t b i r d s t u d i e s . A l l meteorological elements, as w e l l as the presence of p l a n t s , animals and the q u a l i t y of the s o i l around the nest, are subs t a n t i a l l y i n f l u e n c e d by the l i g h t conditions and temperature  i n the stand.  The l a t t e r obviously l i m i t s the s u r v i v a l of the young i n a b i r d population, or i n f l u e n c e s the adaptive features of the nesting cycle that serve t o counteract adverse temperature  effects.  -57The r e l a t i o n between the i l l u m i n a t i o n of a given place and i t s temperature could be explained with,three b a s i c laws (Geiger, 1959 1956)  and Di G l e r i a ,  which are as f o l l o w s : The warming up of the a i r i s caused by the absorbed l i g h t , energy on the  surface.  The s o i l surface transforms the short wave length energy ( l i g h t ) to  that form of long wave length energy (heat) which r a d i a t e s t o the a i r and causes the warming up of the a i r (Wien law). Ait any given-wave length and temperature the quotient of the r a d i a t i n g and absorbing capacity of a l l materials i s constant ( K i r h o f f ' s law). Thus, £ = E a Where "e" i s the r a d i a t i n g capacity,,"a" i s the absorbing capacity of a given m a t e r i a l and' "E" i s a .constant number. The r a d i a t i n g capacity of the m a t e r i a l i s e = aE The increase of the amount of the l i g h t energy which.is absorbed by the materials w i l l increase the r a d i a t i n g energy i n a d i r e c t r e c i l i n e a r proportion.  Thus,  s o i l surface which absorbs more l i g h t energy w i l l  r a d i a t e more heat energy. The. i n t e n s i t y of"the r a d i a t i o n depends on the temperature of r a d i a t i n g materials and.it i s p r o p o r t i o n a l t o the f o u r t h power of the absolute temperature of the r a d i a t i n g materials (Stefan-Boltzmann law).  e = o(t-273)^ Where "e" i s r a d i a t i o n energy i n cal/sq.cm/min., " t " i s temperature of the r a d i a t i n g m a t e r i a l , and " 0 " i s constant ^with .a value of 8.26  x lO"-^-.  The r a d i a t i o n from.the s o i l surface i s not a constant value, but depends upon the temperature of the s o i l surface; t h e r e f o r e , the energy r a d i a t i n g from  -58-  the s o i l surface i s smaller where the ground, i s covered by a dense l a y e r of ( i n s u l a t i n g ) vegetation than where i t , i s f r e e . I f the l i g h t and the temperature conditions of a place are known, and the l i g h t conditions i n another,, i t s temperature conditions can be c a l c u l a t e d . We can presume that those places which.have nearly the same i l l u m i n a t i o n , composition, density and s i z e of vegetation l a y e r s , as w e l l as s i m i l a r s o i l texture,.the l i g h t r e f l e c t i o n s and evapo-transpiration are also s i m i l a r .  If  there are no s i g n i f i c a n t differences' i n the surroundings of a number of nests, but the i l l u m i n a t i o n l e v e l s are d i f f e r e n t ,in each place,,the m i c r o c l i m a t i c ranges w i l l p a r a l l e l the i l l u m i n a t i o n .  I f the i l l u m i n a t i o n of "A" l o c a l i t y  i s higher than that of "B" l o c a l i t y , but the ground i s covered with a dense l a y e r of vegetation the temperature range may be lower than that of "B", because the energy surplus received an "A" l o c a l i t y w i l l be lost.through more i n t e n s i v e evapo-transpiration, and the higher r e f l e c t i o n from the denser green l a y e r . . L i g h t energy penetrating more deeply i n t o the water a f f e c t s a . r e l a t i v e l y l a r g e r volume than i n s o l i d media.  Because water has higher s p e c i f i c heat  and heat of transformation during evaporation a higher l i g h t . i n t e n s i t y i s required to obtain a c e r t a i n degree of heating.  Wet s o i l requires a l a r g e r  amount 4>f l i g h t energy t o obtain the same temperature range as dry s o i l . 1.  Hence i t i s important t o emphasize the d i f f e r e n t heat economies of  the d i f f e r e n t kinds of s o i l .  In t h i s study, the f i n d i n g s of Botvay (195*0,  Geiger ( 1 9 5 9 ) and Di G l e r i a ( 1 9 5 & ) are accepted as general p r i n c i p l e s .  In  d i f f e r e n t s o i l types, d i f f e r e n t q u a n t i t i e s of l i g h t energy are required f o r r a i s i n g the s o i l temperature because of d i f f e r e n c e s i n energy l o s s from r e f l e c t i o n and evaporation as. i n d i c a t e d i n Table 6. of Botvay I.e. and Di G l e r i a I . e . ) .  (Composed from data  -59-  Irradiated l i g h t energy unit  Loss f o r reflection \  Loss f o r evaporation \  Available f o r temperature increase fo  Granite  100  50  0  50  Sand  100  50  25  25  Clay  100  40-50  30-40  10-20  .100  37  54  9  Bog  The s p e c i f i c heat.and temperature  c o n d u c t i v i t y of a c e r t a i n k i n d of  s o i l s t r o n g l y modifies i t s temperature. 2.  With increase i n a i r temperature, the r e l a t i v e humidity  3-  There.is a . r e l a t i o n between the l i g h t range of a place and i t s wind  conditions.  The i l l u m i n a t i o n of a.place depends on the d e n s i t y of the  f o r e s t stand.  The range of l i g h t . i n t e n s i t y i s narrow and wind v e l o c i t y i s  low i n dense stands. are higher.  decreases.  I n more open stands wind v e l o c i t y and l i g h t . i n t e n s i t y  Therefore,, increase i n the l i g h t i n t e n s i t i e s i s . i n d i r e c t  p r o p o r t i o n t o increase of wind v e l o c i t i e s . The l i g h t curve gives a number of advantages f o r the study of f o r e s t b i r d ecology: 1.  In measuring the e c o l o g i c a l requirements  of a species at. i t s nest.  I f one e s t a b l i s h e d a number of l i g h t i n t e n s i t y curves f o r nests of a species that w i l l i n d i c a t e the range of e c o l o g i c a l tolerances of that species.  This  l i g h t range i s c h a r a c t e r i s t i c f o r that species i n a given f o r e s t type. Those curves which are near the center of the range i n d i c a t e optimal circumstances f o r the b i r d (provided that our m a t e r i a l includes a s u f f i c i e n t number of nests).  The maximum and minimum curves, i n d i c a t e the extremes.in tolerance  f o r the f a c t o r s i n f l u e n c i n g l i g h t curves. 2.  I n comparisons of the demands of d i f f e r e n t species.  A comparison  of the l i g h t ranges of the d i f f e r e n t species w i t h i n a given f o r e s t type,  -60-  d i s c l o s e s the d i f f e r e n c e s . i n t h e i r demands. 3-  Comparison of d i f f e r e n t microhabitats w i t h i n a stand.  Because the  l i g h t curve expresses the e c o l o g i c a l conditions of a given place w i t h i n the stand, a comparison of the l i g h t curves of d i f f e r e n t places .points out their ecological differences. k.  Comparison of d i f f e r e n t h a b i t a t s used by the species. Because most  b i r d species express t h e i r capacity of c l i m a t i c adaptation i n the nest p l a c i n g and nest building.techniques, a comparison of l i g h t I n t e n s i t i e s at the n e s t s . i n d i f f e r e n t geographic areas reveals the degree of adaptation i n these d i f f e r e n t l o c a l i t i e s . In t h i s t h e s i s the main purpose of the use of l i g h t curves i s the des c r i p t i o n of the m i c r o c l i m a t i c circumstances of a given place f o r the p e r i o d of day-time hours.  L i g h t . i n t e n s i t i e s were measure i n l u x u n i t s at the nest  and simultaneously i n the open. minutes.  The l i g h t values were recorded every 30  The measurements at the nest were expressed as percentages of  l i g h t . i n t e n s i t i e s measured simultaneously i n the open. The measurements were c a r r i e d out, i n empty nests at the end of the breeding season.  The l i g h t  values there were comparable with those i n the  e a r l y summer when incubation and hatching of the f i r s t clutches took place. For each species s t u d i e d , i n respect to l i g h t curves, one nest was selected as the c o n t r o l nest f o r comparison.  The c o n t r o l nest was the one  of the simplest structure as compared t o the other of the species. c o n t r o l nest hatching and development of young were successful.  In the  The d i f f e r -  ences of i n c i d i e n t l i g h t energies at each nest are expressed as percentages of l i g h t . i n t e n s i t y r e l a t i v e t o the " c o n t r o l " nest, which i s taken as  100.  The measured t o t a l l i g h t energies were used .for comparisons of simul-  - 6 1 -  taneous measurements.  When the t o t a l l i g h t energies of a day could not be  obtained f o r a nest the l i g h t amplitudes were used f o r comparisons with the l i g h t amplitude of the c o n t r o l nest. Terminology: " l " to "6" p a r t ,  The crown o f the tree was d i v i d e d i n t o  three l e v e l s and each l e v e l i n t o two parts. of a l l s i x p a r t s .  Figure 2 shows the l o c a t i o n  I n the f o l l o w i n g parts " l " t o "6" w i l l r e f e r t o l o c a t i o n s  of nests i n the corresponding sector of t r e e crown.  I t i s b e l i e v e d that.the  e f f e c t s of the surroundings are d i f f e r e n t i n each p a r t .  Figure 2 .  Diagrammatic cros s section of a tree crown RUFOUS HUMMINGBIRD (Selasphorus rufus Gmelin)  During.the summers of  i 9 6 0  and I96I the Hummingbird was observed .in  d i f f e r e n t f o r e s t types on the area.  The d i s t r i b u t i o n of the Hummingbird pop-  u l a t i o n was not uniform w i t h i n the f o r e s t but concentrated at c e r t a i n places, i n p a r t i c u l a r i n those t r e e s which were l o c a t e d near roadsides, flooded spiraea t h i c k e t s , e t c . Within the area of study, the i n v e s t i g a t i o n covered f i v e sample p l o t s which were separated from each other by a distance of 0 . 2 t o 2 . 0 miles.  -62-  The nests can be arranged i n the three groups according.to t h e i r p o s i t i o n , as f o l l o w s : Group  Location of nests  No. of nests  1  Near the end of the long branches of coniferous or deciduous trees  5  2  Inside the coniferous crown, on the t h i c k branches  5  3  Under the a c t i v e surface of ground vegetation  2  Seven nests were studied i n d e t a i l and f o r t h e i r l i g h t values and f i v e for' t h e i r l o c a t i o n and p l a c i n g only. The purpose was t o answer the f o l l o w i n g questions: 1.  What r e l a t i o n s h i p . i s t h e r e between the Hummingbird and the plant  community of the f o r e s t ? 2. Why were two nests, located near one another, placed t o d i f f e r e n t parts of the. tree? 3.  I s there a  c o r r e l a t i o n between the n e s t i n g places and the feeding  ground of the Hummingbird? 4.  Why do Hummingbirds occur simultaneously i n ecosystem types which  d i f f e r markedly i n the e c o l o g i c a l sense? Sample p l o t . I .  The e c o l o g i c a l f a c t o r s were i n v e s t i g a t e d i n two nests  i n the Eurhynchium-Mahonia ecosystem type.  These nests were placed on the  f i r s t t r e e s at a.roadside. Nest a ( F i g . k) was found 2.70 m. h i g h , i n a cedar t r e e .  The nest was  located i n part 5 of crown (at 23 cm. from.the end of a ,2.10 m. long branch which was bending over the road).  The branch was swayed by a i r movement  throughout the observation period. Nest b was found 4.2 m. high .inside a cedar crown on a strong branch ;  i n part 6 of the crown, 1.2 m. from the trunk and 1.5 m. from the end of the  -6 3  branch.  This n e s t . i s considered as a standard.in the comparison throughout  t h i s chapter, because i t d i d not show any s p e c i a l adaptations t o i t s surroundings, and the l i g h t energies of each of the other nests are expressed as percentages of l i g h t . i n t e n s i t y measured i n t h i s nest w h i c h i s taken as 100. :  Figure  3.  A i r movement i n t h e o p e n i n g  a r o u n d n e s t s a and b.  According t o the meaning of the K i r h o f f and Stefan-Boltzmann  lawa  (see p. 57) the higher i n c i d e n t l i g h t energy at nest a (8$ over nest b) increases the temperature  of the surroundings.  This heat surplus does not  influence the temperature  of the nest, f o r the f o l l o w i n g reason:  the main  cour se of a i r movement i n a f o r e s t opening i n r e l a t i o n t o the upper winds i s channelled.in the center of the opening (road cut) with decreasing v e l o c i t y toward the edges ( f i g . 3 ) .  The nest a was placed on the end of a 2 . 1 m. long  branch bending over t o the middle part of the road where the current of the a i r was at i t s maximum.  The heat surplus was thereby eliminated. At the  nest b, however,.this c o o l i n g e f f e c t was not observed, because i t was located  Sk-  at the q u i e t e r edge, beyond the path, of the main a i r current. S i m i l a r i n v e s t i g a t i o n has been done i n two sample p l o t s ( I I and I I I ) of the Folystichum f o r e s t type. 300  The distance between these two p l o t s i s  m. In sample p l o t . I l l , l i g h t i n t e n s i t i e s of nest c were studied. This  nest was found 2 . 1 m .  above the ground, i n a broadleaf maple t r e e .  The  nest was l o c a t e d i n part.5 of the crown ( 2 . 7 m. from the trunk and.1.2 m. -from the end of the branch).  The ground was covered by a t h i c k l a y e r of herbs.  This nest was i n a small'forest.opening, the north, south and east sides of which c o n s i s t e d of closed dense stands.  At the western side,.the opening  was adjacent t o a small Spiraea swamp. The l i g h t i n t e n s i t y of nest c i s iQ.^kfy lower than of nest b• The reason why the Hummingbird p l a c e d . i t s nest w i t h i n a lower l i g h t range can be explained.by the e c o l o g i c a l circumstances i n the v i c i n i t y of a Spiraea swamp.  The l i g h t r e l a t i o n s of t h i s swamp were determined by three measured  l i g h t curves, the-amplitudes of which were 9 - 3 l x i n nest c and 9 - 7 l x ( t o t a l 2 1 3 . 3 0 l x ) and 1 0 . 5 l x ( t o t a l 2 1 3 . 3 5 l x ) i n the two Robin nests. I f one compares the amplitudes of these nests one w i l l see t h a t the Hummingb i r d placed i t s nest on t h a t part of the swamp shore which had the most even microclimate. In sample p l o t  I I I the l i g h t . i n t e n s i t i e s were s t u d i e d . i n nest d,  which was found 0 . 6 m. above the ground under the a c t i v e l a y e r of Rubus p a r y i f l o r u s t h i c k e t (see F i g . k).  This nest a l s o shows a considerable  d i f f e r e n c e from nest .b ( 1 8 . 6 9 $ ) , but the d i f f e r e n c e between nests c and d i s very small, only 0 . 0 6 per cent, i n measured l i g h t . w i l l be given l a t e r , on p. 6 7 .  The reason f o r t h i s  -6 5  Sample p l o t . I V .  The e c o l o g i c a l f a c t o r s were i n v e s t i g a t e d . i n a s i m i l a r  p a i r of nests mentioned i n p l o t I i n the Gaultheria-Mahonia ecosystem type. Nest e was found 2 - 7 m. above the ground i n young D o u g l a s - f i r (see F i g . k).  The nest was located i n part 6 of crown ( 0 . 5 m. from the trunk and  0 . 9 ni. from end. of the branch'). spiraea swamp.  This tree was 5 - 5 - from .the shore of a m  The ground was covered by a w e l l developed l a y e r of herbs.  Nest f was placed .7-5 ' above the ground i n a,birch. m  located on a long, slender branch.  The nest was  Under the nest there was about 0.3.m-  of water and a dense Sprtaea d o u g l a s i i t h i c k e t . The distance between nests e and f was about 3 0 m. Nest f received 7 per cent higher light,energy than nest e, which was responsible f o r i t s higher temperature.  But t h i s heat s u r p l u s , i s e l i m i n a t e d  the same way as i n the case of p l o t . I , , i . e . by convection. Comparison of l i g h t i n t e n s i t i e s of Hummingbird nests. Table 7 Nests  Measured light i n l x  a b c d e f  278.48 258.33 209.93 210.07 278.93 298.43  Mean l i g h t intensity 2&  Amplitudes.in % of l i g h t i n open  75-69 70.11 58.99 59'-15 74.66 80.13  88.75 86.76 69.69 74.01 82.83 92.01  Light i n t e n s i t i e s of nest of nest b 107.90 ,100.00 81.26 81.31 107.97 H5.52  The sample p l o t V was located i n the ecotone of Gaultheria-Mahonia type and the slough area.  The only nest which was found i n p l o t V was not  studied f o r l i g h t data,.because i t s surrounding was d i s t u r b e d by the f o r e s t f i r e of J u l y 2 , 1 9 6 1 . Nest g ( F i g . 4 ) was found on the branch of a pear tree (Malus sp.) p r a c t i c a l l y covered under the " a c t i v e " surface of a 1 . 0 5 ni. high grass l a y e r . The nest was a t 67 cm. above ground l e v e l .  -66DISCUSSION The i n v e s t i g a t i o n was based on the assumptions that ( l ) the newly hatched young Hummingbird cannot a d a p t . i t s e l f t o the e f f e c t s of i t s e n v i r onment, (2) Hummingbirds cannot p r o t e c t t h e i r h a t c h l i n g s during a good part of the day, because they spend a considerable time c o l l e c t i n g food. •An example:  The Hummingbird of nest f departed and returned lh times  during the observed three hour p e r i o d . minutes, and was away 157 minutes.  (She sat on the nest a l t o g e h t e r 23  The young of t h i s nest were f o u r days  o l d (June 22). I t i s suggested that an evenly changing microclimate i n the nest plays an important r o l e i n the p r o t e c t i o n of the young). I t has been mentioned already that those nests which are located near the end of a branch are b e t t e r i l l u m i n a t e d than those i n s i d e the tree crown. Yet the warming e f f e c t i s nearly equal i n both cases, because excess heat ..is d i s s i p a t e d by a i r movement. i n the immediate surroundings of the nest. This i s apparently the case in' both a - b and e - f nest p a i r s . A .comparison of the d i f f e r e n c e s between l i g h t i n t e n s i t i e s . i n the two nesting places i n p l o t I and I I , shows that the d i f f e r e n c e between a and b nests  i s 7-9 pei" cent i n Eurhynchium-Mahonia ecosystem type, nearly the same  as that between e and f nests (6.99 per cent) i n the Gaultheria-Mahonia ecosystem type.  S i m i l a r l y the d i f f e r e n c e between a and f nests (9-3 P ^ cent)  i s nearly the same as that between b and e nests (8.0 per cent).  e  The  general e c o l o g i c a l circumstances of these two f o r e s t types, however,.are very d i f f e r e n t (20. pp. 27). The f a c t that these s i m i l a r i t i e s e x i s t between the nests of the two f o r e s t types i n d i c a t e s that the microclimates of the nests are influenced but not l i m i t e d by the f o r e s t types.  -67-  Comparing the surroundings of the nests i n the two f o r e s t types, one may f i n d a number of s i m i l a r i t i e s . In the Eurhynchium-Mahonia ecosystem type: ( 1 ) the a and b nests are about 60 m. from Kawkawa Lake.  Therefore  they are s t r o n g l y i n f l u e n c e d by i t s compensating e f f e c t s of temperature  and  a i r humidity. (2) The crown, extending over a road s t r i p , may reduce  r a d i a t i o n l o s s of  heat from the ground at night to a c e r t a i n extent. (3) During the day, the a i r l a y e r near the ground becomes heated over the road s t r i p , but remains r e l a t i v e l y c o o l i n the f o r e s t ; the cooler a i r flows out i n t o the road s t r i p and thus dampens the temperature  variation.  In the Gaultheria-Mahonia f o r e s t type: Nest e and f were l o c a t e d on the shore of 0.2 acre Spiraea swamp.  The  water surface was covered w i t h a dense l a y e r of a 1.5 m. high Spiraea douglasii thicket.  The water,in the pond was 0.4 m. deep during the f i r s t  week of May; and was gone completely before the l a s t week of J u l y . Therefore, i t i s supposed that the l i g h t surpluses measured i n e and f nests were used up.in i n t e n s i v e t r a n s p i r a t i o n and evaporation, and the e and f nest thus may have been under c o o l i n g e f f e c t of a high evapo-transpiration, due to the dense l a y e r of Spiraea d o u g l a s s i i and the presence of a water body. Thus we may assume that the e c o l o g i c a l circumstances of the nests are not s i m i l a r to those of the f o r e s t type, because of t h e i r d i f f e r e n t microc l i m a t i c conditions as o u t l i n e d above. The reason why the Hummingbird placed i t s nest d i f f e r e n t l y i n the Polystichum f o r e s t type needs to be answered.  I t has been mentioned already  that the s i t e near the swamp of nest c had the most even m i c r o c l i m a t i c con-  -68-  ditions.  Moreover, the nest was l o c a t e d i n an opening - hence the e c o l o g i c a l  circumstances of t h i s nest were d i f f e r e n t from the other parts of the f o r e s t , because the a i r moisture of the opening, i s about 5 "to 7 per cent higher than the other parts of the f o r e s t stand and i t s temperature i s more compensated (Botvay, 1954). The f a c t that d and c nests were d i f f e r e n t l y placed may be explained by the circumstances i n the surroundings of nest d, where there i s a loose crown l a y e r of alder and b i r c h while the ground i s covered by Rubus p a r v i f l o r u s .  '  I t i s l i k e l y that the microclimate of p l o t .III was more extreme than that of p l o t , I I because of the loose stand which could not hinder a i r motion, r a d i a t i o n , etc.  By.placing i t s , nest under the dense " a c t i v e " l a y e r of Rubus p a r v i f l o r u s  the Hummingbird protected i t from the extremes of the microclimate i n t h i s thinned stand:  the conditions then w i l l be about the same as those of nest c.  The s i t u a t i o n i s the same i n respect to nest g which was l o c a t e d under an a c t i v e l a y e r , a good p r o t e c t i o n against the extremes of the climate. The  light  conditions of nest g may nearly equal thoseof nest f , but there i s a d i f f e r e n c e between t h e i r h a b i t a t s . The problem of c h i l l i n g or overheating was not present here because the nest was placed under the a c t i v e l a y e r of grass.  Most  mechanisms which can modify the microclimate were u t i l i z e d by the Hummingbird i n order t o . g a i n p r o t e c t i o n against overheating.  The most e f f e c t i v e mechan-  isms were the evapa-transpiration of a dense grass l a y e r and the wet ground. In order t o t e s t t h i s t h e o r e t i c a l reasoning, I made the f o l l o w i n g crude experiment:  On May 23, I96l, when the young were .5 days o l d , I t i e d up the  nest branch so that the nest was above the surface of an a c t i v e l a y e r of girass, the young d i e d / w i t h i n k8 hours, i n s p i t e of increased brooding of the female.  -69-  Hence, i t i s b e l i e v e d that the deaths were caused by the m i c r o c l i m a t i c extremes. CONCLUSIONS The study of twelve nests proved that the Hummingbird r e q u i r e d f o r i t s c l u t c h an even ecoclimate which cannot be found w i t h i n stands of any of the f o r e s t types of the study area-  Therefore Hummingbirds placed t h e i r nests  always i n ecotones, p a r t i c u l a r l y of two f o r e s t types, or of the EurhynchiumMahonia f o r e s t type and open h a b i t a t ; whereby the c o o l a i r of the dense f o r e s t , meeting the hot a i r of the road s t r i p , develops an even microclimate f o r the nest. By p l a c i n g i t s nest c i n the f o r e s t opening, the Hummingbird gained p r o t e c t i o n against the extermely humid and cold ecoclimate i n the loose stand of the Polystichum f o r e s t type. I f the edaphotope i s not extremely wet the Hummingbird-places i t s nest under an a c t i v e l a y e r of p l a n t s as i n the case of d_and g nests. A number of observations i n d i c a t e d that the Hummingbird i s t i e d . t o c e r t a i n parts of the study area, i r r e s p e c t i v e of a n y - p a r t i c u l a r plant community. The observations i n d i c a t e d a l s o that a number of Hummingbirds were present i n an adjacent swamp i n l a t e A p r i l , but the f i r s t Hummingbird occurred .in the f o r e s t stand only a t the time of nest b u i l d i n g .  A f t e r the nesting season  passed, a number of Hummingbirds were seen again i n the swamp area.  I n general,  during the nesting season the swamp area was free from female Hummingbirds. The male Hummingbird was present i n the nest surroundings during the courtship and the nest b u i l d i n g time only.  When the female s t a r t e d l a y i n g ,  the male l e f t the nesting area but was seen often around.the swamps. Thus while the. n e s t i n g female showed preference f o r c e r t a i n f o r e s t  -70-  communities as discussed above, the feeding ground.in many instances was- i n a different habitat. The only plants t o whose presence the Hummingbird nests could be r e l a t e d i n the study area were Populus tremuloides and P. t r i c h o c a r p a . Their achene seeds w i t h pappas are used i n the l a t e nests of hummingbirds:  nearly 5 0 - 6 0  per cent of the m a t e r i a l of these nests i s composed of these achenes.  Cotton-  wood or aspen was never f a r t h e r than a few hundred meters from the Hummingbird nests. The m i c r o c l i m a t i c r e l a t i o n s of Hummingbird nests were f u r t h e r observed during the season of I962. reparoted here.  The evidence then found corroborates the f i n d i n g s  The m i c r o c l i m a t i c and height r e l a t i o n are discussed.in a  separate paper (Horvath, 1 9 6 3 ) This d i s c u s s i o n answers the four questions r a i s e d at the beginning of t h i s chapter. WINTER WREN (Troglodytes troglodytes hiemalis V i e i l l o t ) According t o observations made during the summers of i 9 6 0 and 1 9 6 1 , the winter wren was found only i n the Eurhynchium-Mahonia ecosystem type.  The  s o i l of t h i s f o r e s t type has a r e l a t i v e l y high.humus content and a good cruiribly s t r u c t u r e .  The crown canopy i s w e l l s t r a t i f i e d (see a l s o p. 2 7 ) -  Winter wren population i s not evenly d i s t r i b u t e d w i t h i n t h i s f o r e s t type, but i t . i s concentrated at c e r t a i n places where the ground i s covered by a heavy l a y e r of bryophytes. Within t h i s community the i n v e s t i g a t i o n covered f i v e sample p l o t s which are separated from each,other by a distance of 0 . 7 t o 3 - 0 miles.  I n these  f i v e / p l a c e s a t o t a l of 15 Winter wren nests were found during the two seasons, and i n v e s t i g a t e d as a b a s i c part of the study.  -71-  Figure k.  The position of Eufous hummingbird's nests  Under the active surface of ground vegetation nest d  nest g  -72-  These nests can be arranged i n the four groups according t o t h e i r p o s i t i o n as f o l l o w s : Group  Location of nests  No. of nests  Light measurement  1  c a v i t y i n ground  1  1  2  tree hole  5  3  3  branch  8  h  k  under bark of tree trunk  1  1  Nine mests were studied i n d e t a i l i n c l u d i n g l i g h t curves.  The remaining  s i x were studied f o r t h e i r composition only. The purpose was t o answer the f o l l o w i n g questions: 1. What.is the reason f o r the Winter wren occurring i n the community of Eurhynchium-Mahonia ecosystem types i n the study area? 2.  What are those f a c t o r s which exclude the Winter wren from the stands  of nine other ecosystem t y p e s . i n the study area? 3. What i s the reason f o r the Winter wren using four d i f f e r e n t nest p l a c i n g methods w i t h i n the Eurhynchium-Mahonia community? The f i r s t part of the study of the Winter wren nests involved,the measurement of the i r r a d i a t e d l i g h t of each nest (Table 8 and F i g . 6). Sample p l o t I . The e c o l o g i c a l f a c t o r s were i n v e s t i g a t e d i n four nests and included the study of l i g h t curves. Nest a. This nest was l o c a t e d 1.5 m. above road l e v e l on a road cut i n a hole.  The nest was shaded permanently by an extension of the roots and  top s o i l above i t .  The nest c a v i t y was s h e l t e r e d by a,kO mm. t h i c k l a y e r of  undisturbed dry earth.  At the end of the nesting period, the nest was dug up  and measured f o r the thickness of the entrance w a l l which was found t o be 30 mm. and the side w a l l s more than 5 mm. i n each d i r e c t i o n .  -73-  Nest b was found i n the hole of a dead b i r c h t r e e , 4.2 m. above ground leval. . Nest c was found under the bark of a dead b i r c h tree 1-5 m. above ground level.  This nest was apparently s i m i l a r t o normal nests of the Winter wren  which are b u i l t on tree branches.  I t seems that the bark gave s t a b i l i t y t o  the nest, and d i d not play a r o l e i n the i n s u l a t i o n . Nest d was b u i l t on a hemlock branch 0 . 7 m., above ground l e v e l .  The nest  was l o c a t e d a t a distance of 1-5 m. from the end of the branch, and 3 - 3 from the trunk.  This type of nest p l a c i n g method i s considered a b a s i c type,  because ( l ) i t was b u i l t i n an o r i g i n a l , mature stand f r e e from apparent human i n t e r f e r e n c e , except f o r l i g h t f i r e s which might have been caused by man and because (2) i n the summer of i 9 6 0 a nest s i m i l a r t o nest d was found i n the place of nest d. The l i g h t energies of each nests are expressed as percentage of the l i g h t i n t e n s i t y measured i n the nest d which i s taken as 1 0 0 . Comparison of L i g h t I n t e n s i t i e s of Winter wren nests Measurements c a r r i e d out between J u l y 17 and 21, 1961. Table 8 Nests  a* b* c d e*. f g* h i  Measured light, i n l x .  Mean l i g h t intensity \  275.09 176.03 154.83 154.42 258.03 '162.27 188.70 -  74.78 47.04 41.02 40.79 71.80 46.29 58.99 -  Amplitudes i n jo of l i g h t i n open 93-12 68.94 68.04 58.79 86.46 61.66 70.89 53.10 45.72  Light.intensities of nests % of nest d 178.14 113.99 100.26 100.00 I67.IO 105.10 122.20 86.06** 79.28**  *•* This comparison was done using the amplitudes of. the l i g h t curves, because t h e i r l i g h t measurements were c a r r i e d out f o r shorter periods than i n nest d. * Nest i n tree or ground hole.  -74-  The average amplitude  of hole nest .is 7 9 - 8 5 , that of the nest, i n the  "jo  open i s 57-42, which values are s i g n i f i c a n t l y d i f f e r e n t at 0.02 p, df 7According to meaning of the K i r h o f f and Stefan-Boltzmann  law,  (see p. 57)  whitb, increased amount of i r r a d i a t e d l i g h t energy on a given place, the amount of r a d i a t e d energy of t h i s place i s increased d i r e c t l y .  Those ground surfaces  that absorbed more l i g h t energy w i l l r a d i a t e more energy. , Therefore, the changes.in the m i c r o c l i m a t i c f a c t o r s of the i n d i v i d u a l nests are d i r e c t l y p r o p o r t i o n a l to the amount of i r r a d i a t e d l i g h t energy at the nest.  There-  f o r e , the v a r i a t i o n of l i g h t : i n t e n s i t i e s as found i n nests a,.b and c, compared with that of nest d, i n d i c a t e s the v a r i a t i o n s of the m i c r o c l i m a t i c condit i o n s from those of nest d.  .This l a t t e r nest, as we r e c a l l , , was considered  as the b a s i s of the m i c r o c l i m a t i c comparison, because i t was b u i l t i n a closed f o r e s t stand and thus received the l e a s t amount of i r r a d i a t e d l i g h t . Because there i s no d i f f e r e n c e between the l i g h t / i n t e n s i t i e s of nest d and of nest c, i t may be presumed t h a t the e c o l o g i c a l circumstances of these two nests are near i d e n t i c a l . The sample p l o t . I I was l o c a t e d .in the Fraser R i v e r bank where the ecol o g i c a l f a c t o r s of nests h and _i_ were i n v e s t i g a t e d . i n a small f o r e s t opening of the dense cedar stand.  These nests were l o c a t e d I f the l i g h t curves of  these nests are studied,, i t w i l l be seen that these show a r i s e of the curves, suddenly t o the maximum point which i s f o l l o w e d by an undulating p o r t i o n of the curve terminated by an almost l e v e l s e c t i o n .  These two Winter wren placed  t h e i r nests onto the surface of the crown of the dedars. nest i was 4.2 m. above the ground.  Nest h was 4 . 8  m.,  This n e s t . p l a c i n g method could be ex-  p l a i n e d on the b a s i s of the m i c r o c l i m a t i c study of f o r e s t openings (Geiger, 1959,  Botvay, 1 9 4 8 ) .  In a small f o r e s t opening the l i g h t cannot reach the  ground surface,. because the crown of t r e e s , which are branched from the ground  -75-  up, hinder i t . Therefore,. the a i r i n that f o r e s t opening cannot warm up s u f f i c i e n t l y a t ground l e v e l .  This species i s an e a r l y nester and c o l d can  presumably a c t as a l i m i t i n g f a c t o r .  This might be an explanation why these  two Winter wren b u i l t t h e i r nests on the crown surface high above ground. Sample p l o t , I I I .  Two nests were i n v e s t i g a t e d . i n d e t a i l .  One of these  nests was a male nest b u i l t by the male but not used f o r breeding (nest e ) . The other (nest f ) was a breeding nest. Nest f was found 1.1 m. above the ground on the branches of a shrub i n the deeper part of a dense group of shrubs, adjacent t o a large piece of decaying l o g . mosses.  The surface of t h i s decaying l o g was densely covered with  I n other d i r e c t i o n s , . the l o c a l i t y was covered with a dense t h i c k e t  .of Rubus p a r v i f l o r u s ;  Although the crown canopy i s missing, nest f has a  l i g h t curve s i m i l a r t o that of nest d. Considering nests d, f , h, and i_ which are b u i l t on the tree branches, the r e s u l t i n d i c a t e s that the Winter wren places i t s nests on the tree branches i n the range of low l i g h t . i n t e n s i t i e s . Sample p l o t . I V . I n t h i s p l o t one of the two nests was examined f o r the v a r i a t i o n of the l i g h t curves. Nest g was l o c a t e d . i n the hole of a.red-.alder 3*3 ni. high above ground. One wren nest from.the previous year (I960) was found i n a .hole of that same branch 6.9 m. above nest g. Thus data measured i n nest g may be a p p l i e d t o the second nest as w e l l . Sample p l o t V.  The only nest which was found here has not been studied  as i n t e n s i v e l y as the r e s t , therefore i t i s used only f o r comparison.  This  nest was found 3*4 m. above the ground, i n a hole of the dead b i r c h ..tree. At t h i s nest, 10 l i g h t measurements were completed a t d i f f e r e n t times i n 2 days. The measured data, of t h i s nest were 2 t o 9 P  e r  cent higher (average 5*3 per  -76-  cent) than those of nest b which were measured a t nearly the same time.  The  conditions of t h i s nest apparently were intermediate between those of nest b and g,. One of the two observed nests on sample p l o t I I I i s nest e. was.located i n the hole of a dead b i r c h t r e e , 3-3.ni. above ground.  This nest This  n e s t . i s not considered as a.true nest, because i t was not used f o r breeding. Probably i t served only as p r o t e c t i o n t o a male b i r d a t night and on r a i n y days.  Nevertheless i t s e c o l o g i c a l conditions were a l s o examined.  The aim  of t h i s examination was t o recognize d i f f e r e n c e s of the e c o l o g i c a l conditions i n these two kinds of nests. Above o b s e r v a t i o n s . i n d i c a t e that the l i g h t curves of nests l o c a t e d i n holes are higher than those of nests b u i l t on the tree branches, and the ground hole had the highest l i g h t value. T h e r e f o r e , , i t can be s a i d that the Winter wren places i t s nest on branches.in the case of a dense stand.  The n e s t . i s b u i l t i n the t r e e holes at  lower stand d e n s i t i e s , while i t . i s l i k e l y t h a t . i t i s b u i l t i n the ground c a v i t y a t high,illuminations,.though only one ground nest was studied. The second part of the wren study i s intended t o e x p l a i n the temperature i m p l i c a t i o n s . i n regard t o the n e s t i n g habits of the Winter wren. The i n v e s t i g a t i o n was based on the assumptions that ( l ) the heat production of a Winter wren i s s m a l l , because of i t s small body; (2) that part of the Winter wren's.body which covers the eggs I s r e l a t i v e l y very small compared with the surface of i t s s i x eggs.  Namely,, i n b i r d s w i t h . i n c r e a s i n g body  s i z e the r e l a t i v e s i z e of eggs decreases and v i c e versa (Stresemann, 1927-3^). Therefore,, i t i s admissible that the microclimate of the nest plays an important r o l e i n the hatching and the p r o t e c t i o n of the young f o r which a very w e l l i n s u l a t i n g nest w a l l i s r e q u i r e d and the thickness of the w a l l must.increase  -77-  proportionately with the increase of the temperature amplitude of the surrounding of the nest.  The m a t e r i a l of the nest w a l l and the s i z e of the  w a l l were constant.in the cases.of a l l nests w i t h i n each nest type (see page 72' f o r the d i f f e r e n t nest t y p e s ) . The temperature f l u c t u a t i o n s were measured.in nests a, b, d and e f o r a p e r i o d of 24 hours.  The temperature was recorded once i n every 30 minutes.  The curves which were obtained are u s e f u l f o r the comparison of the e c o l o g i c a l conditions with the v a r i a t i o n of temperature i n the d i f f e r e n t nests.  Tempera-  ture change was supposed t o be d i r e c t l y p r o p o r t i o n a l with the two readings, i . e . one reading at the beginning of the 30 minutes p e r i o d , and the other at the end of the; p e r i o d ( i . e . no extreme deviations went unrecorded between the reading times). I t must be'emphasized .that t h i s temperature study was mainly aimed at establishanlg the i n s u l a t i n g c a p a b i l i t y of the d i f f e r e n t nest w a l l s . One thermometer was p l a c e d . i n nest a, and another thermometer outside nest a t o r e g i s t e r temperature changes. Inside (a^) as wellas outside ( a ) the nest.. Q  A s i m i l a r p a i r of thermometers was placed at nest d f o r measurement of the outside ( d ) and.inside (d-j_) temperature changes. Q  Only one thermometer was used.in nest b; and one i n the nest e.  Because  of the d i f f i c u l t i e s encountered to reach nest e i t was brought beside nest b f r o m . i t s o r i g i n a l place. The measured data are given i n Figure 7 ' Temperature measurement of nest a. Amplitudes a'o  Difference of amplitudes  C.  in 11.0  -  28.2  17.2  17.0  -  I9.6  2.6  14.6  Light Curves of Selosphorus rufus Nests on UBC Forest near Hope B.C.  -78j  The i n s u l a t i n g capacity of the w a l l of nest a ( s o i l - nest w a l l ) i s given by the d i f f e r e n c e of a o  and a. (14.6 °C). .1  The w a l l of nest a  reduced the temperature amplitude 6 . 6 times ( t h i s c o e f f i c i e n t . . i s c a l l e d . i n t h i s study as. i n s u l a t i n g c a p a c i t y ) . Temperature measurement of nest d Temperature range i n °C. d  Q  d_ j  Amplitudes i n C. W  11.6  - 23.0  11.4  13.5  - 20.0  6.5  Difference i n oc. 4.9  The i n s u l a t i n g capacity i s 1 . 7 5 . i n t h i s case. Temperature measurements of nest b Temperature range b  15.7  i  - 19-5  Amplitude i n °C. 3-8  The outside temperature of nest b was not measured f o r l a c k of s u i t a b l e thermometers.  The l i g h t r e l a t i o n s of nest b are known, therefore the outside  temperature of the nest can be c a l c u l a t e d with.the same accuracy on the b a s i s of K i r h o f f s law. 1  According the l i g h t . c u r v e s , nest b r e c e i v e d 114$ of the  l i g h t r e c e i v e d by d nest.  Because the composition, density and s i z e of the  herb and b r i o p h y t i c l a y e r as w e l l as s o i l texture are nearly the same i n both nests, and hence the l i g h t r e f l e c t i o n and evapo-transpiration are presumably s i m i l a r i n both nests a l s o , the use of K i r h o f f ' s law seems j u s t i f i e d .  The  c a l c u l a t i o n i n d i c a t e s that the outside temperature of nest b was approximately 13.O  °C.  R e l y i n g on t h i s f i g u r e , the i n s u l a t i n g capacity of nest b i s 3 ' 4 .  Temperature measurement of nest e Temperature range i n °C. 12.4 - 21.6 e. 1 The i n s u l a t i n g capacity of nest e i s 1.4  Amplitudes i n °C. 9.2  -79-  One can see from the above data that nest a, which.is b u i l t i n the ground c a v i t y , has the most even microclimate; hence the r a p i d change of outside temperature cannot a f f e c t i t .  The microclimate of nest b i s s l i g h t l y compen-  sated, whereas the nest which was b u i l t on the tree branch (nest d) has the most uneven microclimate. . I t was already mentioned that the Winter wren presumably requires a f a i r l y constant microclimate f o r incubation and nesting period which we  now  can suppose.is t o be the same.in a l l nests due to the e f f e c t of the surroundings and t o the i n s u l a t i n g capacity of materials used.in the nest w a l l , as j u s t shown. The question of the d i f f e r e n t nest p l a c i n g habits of the Winter wren can a l s o be answered.by the r e l a t i v e temperature curves.  The r e l a t i v e temperature  curves express the r e l a t i o n between the outside and i n s i d e temperature, as w e l l as the i n s u l a t i o n of the nests ( F i g . 8).  The a  Q  l i n e represents the tempera-  ture, of ambient a i r and. i s taken as the b a s i s of camparison, and.its given a  -  value (lOO) at any one time; the temperatures of a^ (ground h o l e ) , dj_ ( i n s i d e nest.d) which, i s a nest b u i l t on a.branch, d  Q  ( j u s t outside nest d) are expres-  sed by t h e i r * p e r c e n t a l d e v i a t i o n from the a c t u a l temperature of the ambient a i r , and p l o t t e d on the time scale.  The a^ and d^ curves are  close to each other and.indicate that both nests have s i m i l a r thermomicroclimate. i n the middle of the day, although t h e i r w a l l s have d i f f e r e n t i n s u l a t i n g c a p" a c i t i e s .  The r e l a t i v e curve of d o i s between a^o and d.. 1  .that thermoclimate of nest .d has two components.  This i n d i c a t e s  One i s the  i n s u l a t i n g capacity of the n e s t . w a l l ( d - d^), the other i s the p r o t e c t i o n of Q  f o r e s t stand ( a  Q  - d ) which minimizes temperature extremes. Q  The temperature  d i f f e r e n c e s at n i g h t . i n d i c a t e that the ground hole conserved more heat than  -80the w a l l of the nest i n the open. Comparing the temperature amplitudes, of•"a " ( 1 7 - 2  °C) and."d " 0  (11.4  °C) a decrease of 5'8°C i s observed due t o the temperature compensating e f f e c t of the environment of the nest ( i e . the f o r e s t stand). Thus to obtain a . s i m i l a r nest temperature i n d i f f e r e n t e c o l o g i c a l c i r cumstances, the q u a l i t y of nest w a l l and the .position of nest must be a l t e r e d . In view of the former,, the Winter wren must place i t s nest on the tree branches i n " d " l o c a l i t y , t o keep the i n s i d e temperature amplitude of the 0  nest w i t h i n reasonable l i m i t s which would not be disadvantageous f o r the n e s t l i n g s on colder or warmer days. The s i t u a t i o n was s i m i l a r i n the case of nest a. high on the slope of a road cut.  This nest was located  I t was surrounded by dry s o i l , the granular  structure of which was f i l l e d w i t h a i r and so increased the i n s u l a t i n g capac i t y of the s o i l .  The Winter wren could not place a nest i n a ground c a v i t y  i n "d" l o c a l i t y , because there was a t h i c k humus and high water content.in the  s o i l , thus the amount of l i g h t  (5670  of that reaching.the ground around  nest a) would not be able.to maintain a temperature of 1 7 - 0 to 19«6 °C i n s i d e the nest as observed.in the case of "a" l o c a l i t y . The s i t u a t i o n i s the same i n the case of a n e s t . i n a.tree hole.  The  Winter wren cannot place" i t s nest i n a tree hole i n a completely closed stand because of the low l i g h t range and because of the high temperature compensating e f f e c t of the f o r e s t stand. The temperature i n s i d e the nest would be too low on c o l d days.  On the other hand,.if the Winter wren placed i t s nest, i n the  tree hole i n the completely open "a" l o c a l i t y , the hatching and development of o f f s p r i n g could not be successful because the temperature compensating e f f e c t of the f o r e s t stand i s absent and the i n s i d e temperature would.be too high.  -81-  The e c o l o g i c a l circumstances i n the male nests are not so important as .in the breeding nests, because the adult b i r d can withstand the extremes of weather b e t t e r than eggs, or young.  The r o l e of t h i s nest i s apparently  p h y s i c a l s h e l t e r i n g f o r the adult .bird. In accordance with the above mentioned f a c t s , one can say that there i s d e f i n i t i v e c o r r e l a t i o n between the e c o l o g i c a l circumstances of the environment and the nesting'place f o r the Winter wren.  The coincidence of these  two f a c t o r s enables the Winter wren to e s t a b l i s h an even microclimate i n i t s nest, independent,of the surrounding c l i m a t i c f a c t o r s . One might venture t o say that the Winter wren could nest i n other f o r e s t types as w e l l .  The l i g h t curves of the hole nests (breeding nests b and g)  t y p i c a l l y i n d i c a t e those of the l i g h t circumstances i n the Polystichum ecosystem type, while the l i g h t curve of ground nest (a) i s s i m i l a r t o t h a t of the Gaultheria-Mahonia ecosystem type. these f o r e s t types.  Yet the Winter wren was not found.in  Therefore,, i n the t h i r d part of t h i s study I am t r y i n g  .to e x p l a i n the f i d e l i t y of Winter wren to the Eurhynchium-Mahonia f o r e s t type The e c o l o g i c a l circumstances of the Winter wren were s t u d i e d . i n a logged area.of the Eurhynchium-Mahonia f o r e s t type. moved, i n 1959  and .in previous years.  The stand of the p l o t was r e -  A f t e r the logging a few small economic  c a l l y worthless cedar and maple trees were l e f t standing.  The s i z e of t h i s  area was about 2 acres with an e a s t e r l y o r i e n t e d slope of 2 5 ° .  The ground  was covered with poorly developed shrubs and an abundant l a y e r of herbs. In t h i s , p l o t (sample p l o t I I I ) the nests of Winter wren were observed .in both i 9 6 0 and 1961 and f ) .  summers.  Two nests were i n v e s t i g a t e d . i n d e t a i l (see nest  In the case of nest f , the wren gained the temperature  compensating  e f f e c t from the dense t h i c k e t and from the high evapo-transpiration, a c o o l i n  -82-  e f f e c t due t o the denseRobus p a r v i f l o r u s l a y e r . The f a c t that the wren remained on t h i s p l o t a f t e r the logging, shows that the enormous.change of e c o l o g i c a l circumstances caused by the logging did not e f f e c t the Winter wrens of the l o c a l i t y . Winter wren i s independent of the tree l a y e r .  T h i s . i n d i c a t e s that the  In the case of a given p h y s i c a l  environment the presence of an i n d i v i d u a l i s dependent upon the supplies ofthe b i o t i c environment.  Since the wren is.independent of the successional  state of the tree l a y e r , i t . i s supposed that.those f a c t o r s of EurhynchiumMahonia ecosystem type which are e s s e n t i a l f o r the niche of the Winter wren, were present i n the shrub, herb and bryophite l a y e r that remained a f t e r logging. I t was found that the bryophyte l a y e r i s not evenly d i s t r i b u t e d w i t h i n the Eurhynchium-Mahonia ecosystem type, and limited.mainly t o c e r t a i n l o c a l i t i e s under a denser canopy.  In a few places, however, a heavy moss layer-  may occur which replaces the sparce c o r t i c o l o u s , or l i g n i c o l o u s herb l a y e r , on the f a l l e n logs or stumps.  These two kinds of mossy areas, i . e . mossy  patches of the ground and mossy stamps and l o g s , play the most important r o l e i n the l i f e of the Wren. The b i r d s were observed to occupy these p l a c e s , f l y i n g from trunk t o trunk and r e g u l a r l y c o l l e c t i n g f o o d . i n the l a y e r of c o r t i c o l o u s and l i g n i colous mosses.  In general, the wren does not v i s i t places where such l y i n g  trunks are absent.  Many observations proved that the Winter wren i s attached  to the f a l l e n trees which are covered with a heavy moss l a y e r . The Winter wren was a l s o seen sometimes on the o l d l i v i n g remnants of mostly maple.  The lower trunks of these trees are covered withibryophytes.  It.may be suggested that these moss-covered o l d trees may play a r o l e i n a t t r a c t i n g Winter wrens t o the l o c a l i t y .  The broad-leaved maple i s a " f i d e l "  -83-  species i n Eurhynchium-Mahonia ecosystem type.  The occurrance of the Wren i s  r e l a t e d here with the presence of l y i n g , moss-covered l o g s . The l a r g e s t part of the bryophytes l a y e r i s missing on the ground i n "sample p l o t I I I " due to the r a p i d changes i n e c o l o g i c a l circumstances which were caused by the logging (vehicles tore up the ground).  Mosses occurred  mainly on f e l l e d trunks i n greater q u a n t i t i e s and these supported the wrens. A s i m i l a r s i t u a t i o n has been found i n "sample p l o t . I V " . A number of observations i n d i c a t e that the Winter wren i s t i e d -with Eurhynchium-Mahonia ecosystem type, because of the s p e c i a l moss cover which i s an e c o l o g i c a l c h a r a c t e r i s t i c of t h i s f o r e s t type, and i s m i s s i n g . i n a l l other f o r e s t communities of the area. CONCLUSIONS The Winter wren i n d i c a t e d a strong attachment to the community of Eurhynchium-Mahonia ecosystem type.  A simple i n v e s t i g a t i o n of the e c o l o g i c a l  conditions revealed that the Eurhynchium-Mahonia ecosystem type was  controlled  mainly by the edaphic f a c t o r s (see page 27). The f a c t that (a) no nesting on the area occurs i n other ecosystem types, and (b) wrens nested.in t h i s h a b i t a t even a f t e r the f o r e s t was logged out, seems to prove t h a t t h i s ecosystem .provides favourable feeding h a b i t a t by , i t s mossy ground stratum; the nesting conditions of the b i r d are a l s o met, but by d i f f e r e n t adaptations of nest s i t e s e l e c t i o n i n dense, l i g h t and open areas w i t h i n the feeding h a b i t a t . The well-developed moss l a y e r s are dependent on the edaphic f a c t o r s . e.g. logging.  They may remain present even a f t e r severe disturbances,  Hence the successional status of crown canopy i s not l i m i t i n g  f o r the Winter wren.  A f t e r logging, the Winter wren remains i n the same place.  The e f f e c t of the d i f f e r e n t secondary successional stages of EurhynchiumMahonia f o r e s t type, i n young, middle age and mature stands on the changes i n  -8kWinter wren population was not i n v e s t i g a t e d . On the b a s i s of the observed .15 nest s i t e s the f o l l o w i n g groups can be made:  ( l ) nest i n a ground c a v i t y , (2) nest i n a tree hole, and (3) nest  on t r e e branches. The i r r a d i a t e d l i g h t was measured i n the surrounding of the nests and the r e s u l t s were expressed i n percentages of l i g h t i n the open.  Graphs were  constructed which were used to compare the e c o l o g i c a l circumstances of the nests. . I t was concluded that the Winter wren placed i t s nests on the t r e e branches i n dense f o r e s t s where the l i g h t i n t e n s i t i e s are between kO to 45 per cent of the i r r a d i a t e d light.measured i n the open.  The tree hole was used  by the.Winter wren f o r nesting i n more open stands w i t h an i r r a d i a t e d l i g h t .range of 45 to 65 per cent.  The ground c a v i t y was used where i l l u m i n a t i o n was  heavy and more than 70 per cent of the open l i g h t , but only one such n e s t i n g was  observed. The reason f o r these p e c u l i a r types of nest p l a c i n g i s explained by the  study of the i n s u l a t i o n of the nest, which, i s determined by two f a c t o r s : ( l ) the p r o t e c t i v e f u n c t i o n of the f o r e s t stand, (2) the i n s u l a t i n g capacity of of the nest w a l l .  Comparing nest a and d, the r e d u c t i o n of the  temperature  amplitudes i n nest d was 5-8 °C outside the nest, due to the denser stand .in "d" l o c a l i t y .  The i n s u l a t i n g capacity v a r i e d w i t h the d i f f e r e n t nest types.  I t was 6.6.in the round c a v i t y , 3-4 i n the t r e e hole and 1.75  o n  the branch.  Combining these c o e f f i c i e n t s w i t h the p r o t e c t i v e capacity of the f o r e s t stand: the value represents the i n s u l a t i n g capacity of the nest w a l l alone i n the case of nest a ( i . e . 6.6) because i t was not. protected by a . f o r e s t stand considerably of nest d.  5.0 (3.4-I.6) i n case of nest b; and 3.7.5  (1.75-2.0) i n the case  These values i n d i c a t e that the t o t a l i n s u l a t i n g capacity i s  best i n the ground c a v i t y , intermediate i n the t r e e hole and worst on the  -8kWinter wren population was not i n v e s t i g a t e d . On the b a s i s of the observed .15 nest s i t e s the f o l l o w i n g groups can be made:  ( l ) nest i n a ground c a v i t y , (2) nest i n a tree hole, and (3) nest  on tree branches. The i r r a d i a t e d l i g h t was measured i n the surrounding of the nests and the r e s u l t s were expressed i n percentages of l i g h t i n the open.  Graphs were  constructed which were used to compare the e c o l o g i c a l circumstances of the nests. . I t was concluded that the Winter wren placed i t s nests on the tree branches i n dense f o r e s t s where the l i g h t i n t e n s i t i e s are between 40 to 45 per cent of the i r r a d i a t e d light,measured i n the open.  The tree hole was  used  by the Winter wren f o r nesting i n more open stands w i t h an i r r a d i a t e d l i g h t .range of 45 t o 65 per cent.  The ground c a v i t y was used where i l l u m i n a t i o n was  heavy and more than 70 per cent of the open l i g h t , but only one such n e s t i n g was  observed. The reason fDr these p e c u l i a r types of nest p l a c i n g i s explained by the  study of the i n s u l a t i o n of the nest, which,is determined by two f a c t o r s : ( l ) the p r o t e c t i v e f u n c t i o n of the f o r e s t stand, (2) the i n s u l a t i n g capacity of of the nest w a l l .  Comparing nest a and d, the reduction of the temperature  amplitudes- i n nest d was 5.8 "d" l o c a l i t y .  °C outside the nest, due to the denser stand i n  The i n s u l a t i n g capacity v a r i e d w i t h the d i f f e r e n t nest types.  . I t was 6 . 6 . i n the round c a v i t y , 3.4 i n the tree hole and .1.75  on the branch.  Combining these c o e f f i c i e n t s w i t h the p r o t e c t i v e capacity of the f o r e s t stand: the value represents the i n s u l a t i n g capacity of the nest w a l l alone i n the case of nest a ( i . e . 6.6) because i t was not protected by a f o r e s t stand cons i d e r a b l y ; ,5.0 ( 3 . 4 - 1 . 6 ) i n case of nest b; and 3-75 of nest d.  ( l . 7 5 - 2 . 0 ) i n the case  These values i n d i c a t e that the t o t a l i n s u l a t i n g capacity i s  best i n the ground c a v i t y , intermediate i n the tree hole and worst on the  -85-  branches.  The d i f f e r e n c e s between these values and those at the time periods  c r i t i c a l i n r e a r i n g the young must be balanced by the b i r d i t s e l f .  The  high value of nest a i s a necessity since the heat c o n d u c t i v i t y of the s o i l i s high, and supposing t h a t t h e t o t a l i n s u l a t i n g capacity was lower, the b i r d t  could not keep an even temperature i n the c r i t i c a l nesting period.  I n the  case of nest c, although the i n s u l a t i n g capacity i s l e s s , t h i s does not i n t e r fere with the wren since the a i r and nest w a l l are of poor heat c o n d u c t i v i t y . One may state that the e c o l o g i c a l circumstances i n the nest l o c a l i t y of the Winter wren are i n a d e f i n i t e r e l a t i o n s h i p with.the l i f e functions of the b i r d during t h i s season.  These conditions must be w i t h i n d e f i n i t e l i m i t s  so that the v a r i a t i o n s of the m i c r o c l i m a t i c f a c t o r s can be balanced t o a steady l e v e l by the Winter wren i t s e l f .  I t i s b e l i e v e d that t h i s b r i e f study  pointed out some of these limits;,more extensive work i n the future w i l l undoubtedly sharpen the l i m i t s of microclimate, nest s i t e and nest i n s u l a t i o n which have been surmized on the.basis of .my l i m i t e d m a t e r i a l . Ecotopic. and stand s t r u c t u r a l c h a r a c t e r i s t i c s of .Eurhynchium-Mahonia .forest p l o t s containing W.w. breeding t e r r i t o r i e s Table 9 P l o t exposure I  II  III  eastern  Sloping  Elevation feet  5-8  200-300  0  0  25  350-400  Stand Well s t r a t i f i e d crown canopy (A,,Ag,A~). R e l a t i v e l y weak shrub and herb layer and a heavy l a y e r of bryophytes. Size 5 acres.  Logged area. The stand was removed i n 1959 > and i n previous years. A f t e r the logging a few small economically worthl e s s cedar and maple trees were l e f t standing. Ground i s covered with a poorly developed shrub l a y e r and an abundant l a y e r of herbs. Size 2 acres.  -86-  P l o t exposure  Sloping  Elevation feet  Stand  IV eastern  10  625-675  The density of the stand i s , low. The ground.is covered w i t h a dense layer of Rubus p a r v i f l o r u s . Size 10 acres.  V western  20  300  Well s t r a t i f i e d crown canopy (A ,A A^)Shrub l a y e r i s not present, herb layer i s r e l a t i v e l y weak. The bryophyte l a y e r i s w e l l developed. Size k acres. 1  2>  ROBIN (Turdus mi'gratorius Linnaeus) During the summers of i960 and I 9 6 I , 97 Robin nests were i n v e s t i g a t e d (Table 10). The i n v e s t i g a t i o n covered 8 sample p l o t s which were separated from each other by a.distance of 0.1 t o 3'0 m i l e s .  The s i z e of the area i n v e s t i g a t e d  i s about k square m i l e s . The i n v e s t i g a t i o n included the comparison of nest m a t e r i a l s , t h e i r environmental r e l a t i o n s , and the feeding habits of the species. I t was found that the r o b i n nests i n s i x ecosystem types i n the study area, the e c o l o g i c a l conditions of which show marked d i f f e r e n c e s .  The nests were  grouped by ecosystem types, and t y p i c a l nests were s e l e c t e d f o r d e t a i l e d examination.  Fresh nests, empty by the beginning of June, were considered f i r s t  nest, June-July nests as second nest. The purpose was t o answer the f o l l o w i n g questions: 1.  Which ecosystem type i s the optimum f o r the Robin on t h i s area?  2.  How f a i t h f u l i s the Robin t o the d i f f e r e n t ecosystem types?  3-  What i s the r e l a t i o n s h i p of the Robin and the b i r d community of the  d i f f e r e n t ecosystem types? k.  How do c e r t a i n nesting h a b i t s of the Robin vary i n the d i f f e r e n t eco-  system types? 5-  What i s the e c o l o g i c a l niche of the Robin i n the d i f f e r e n t ecosystem  -87-  types? Altogether, e c o l o g i c a l conditions were studied i n s i x ecosystem types f o r the Robin. Ecosystem types  No. of nests found  No. of nests studied  Eurhynchium-Mahonia  52  5  Polystichum  15  k  Thuj a-Ly s i chiturn-Oenanthe  12  3  Gaultheria-Mahonia  8  Gaultheria-Cladonia-Rhacomitrium  9  Pachystima-Gaultheria-Peltigera  1  A). Eurhynchium-Mahonia ecosystem type This ecosystem type was considered t o the optimal h a b i t a t f o r the Robin, f o r the f i d e l i t y of the Robin t o t h i s type i s higher than i n any other ecosystem type i n the area of study, and the Robin c a r r i e s out, during the nesting season, a l l i t s s i g n i f i c a n t a c t i v i t i e s w i t h i n t h i s ecosystem type. We must remark t h a t , as shown on p. 19 and p. 2 9 , the biomass value of the r o b i n i s higher i n the Gaultheria-Cladonia-Rhacomitrium than i n the EurhynchiumMahonia type.  The Gaultheria-Cladonia-Rhacomitrium, however, obtained t h e i r  highest density by second clutches of paiis that nested i n the spring, and f e d during a l l summer elsewhere. 3  2 1 nests were found i n t h i s ecosystem type during the summer of i 9 6 0 ,  and 31 i n 1 9 6 1 . ' Within t h i s type the i n v e s t i g a t i o n covered 2 sample p l o t s which are separated from each other by a .distance of 3 . m i l e s .  I n these two  areas a t o t a l of 5 nests were s t u d i e d . i n d e t a i l , the remainder f o r t h e i r composition only.  -88-  Sample plot. I .  Four nests were•investigated from which nest a and b  are nests of the same b i r d (a. i s the f i r s t , b the second n e s t ) .  Nest a i s  considered as the b a s i c nest, and the l i g h t .energies ,of nests of each ecosystem type are expressed as percentages of the l i g h t i n t e n s i t i e s measured i n nest a which i s taken as 100. We assume that the i n v e s t i g a t e d four nests from the i n t e r i o r of the stand are representative of t h e i r h a b i t a t a n d . l o c a l i t i e s , and they w i l l i n d i c a t e the c l e a r influence of t h i s ecosystem type on nest s i t e and construction. nests are l o c a t e d near the center o f the sample p l o t .  These  Here the influence- of  the adjacent types are negligable and the measured data are free from any k i n d of d i s t u r b i n g f a c t o r s . Nest a was found 4.3 m. above the ground.in the part 6 of the crown of a young D o u g l a s - f i r . Nest b was b u i l t 3*0 m. above the ground i n the part .6 of the crown of a young vine maple (see Fig.. 13). . Nest c was l o c a t e d l6.5 m. above the ground i n the part 5 of the crown of an o l d broadleaf maple. Nest d was found.2.7 m. above the' ground,in the part 6 of the crown of a vine maple. Comparison of l i g h t i n t e n s i t i e s of Robin n e s t s . 1  Nest a* b* c d* e* f* g* h*  • Measured light, in lx. 163.13 156.36 167.38 169.84 208.64 207.87 213.20  .  Mean l i g h t intensity 43.55 41.59 44.59 47.24 52.17 56.06 59.94  Amplitudes i n % of l i g h t i n 57.41 58.51 75.90 60.74 56.05 65.09 70.82 72.01  Table 11 Light i n t e n s i t i e s of nests jo of 100.0 95-5 102.6 103.8 98.9 ** 127-8 127-4 130.6  6  10  8  F i g u r e 6.  12  E x p l a n a t i o n i n the t e x t (p.  II  16  73)  18  £0  Hours  Temperature Curves of Troglodytes troglodytes Nests in Eurhynchium - Mahonia Forest Type on UBC Forest near Hope BC  ~ i  6  i  r  "  " i  i  i  i  12  F i g u r e 7-  i  i  i  i  1  1 18  1  1  ,  i  i  ,  E x p l a n a t i o n i n the t e x t (p. 77J  r  —  i  24  1  1—  i  " " " i  1  1— 6 Hours  Relative Temperature Curves of Troglodytes troglodytes Nests in Eurhynchium - Mahonia Forest Type on UBC Forest near Hope BC.  40  -  20  -  "1 6  1  1  I  1 I Figure 8.  I I I I "I I 1 1 1 'Explanation i n the textia(p. 79)  1  I  I  1 24  1  1  I  I  I  1  ~  6 Hours  -89-  Nest i j .k 1 m* n o  .Measured l i g h t .in l x .  Mean l i g h t .intensity  213.35 180.28 168.66 167.80 232.74 . 220.71 230.75  61.62 53-97 50.36 50.37 61.88 58.07 62.14  Amplitudes.in $ of l i g h t i n  Light.intensities of nests % of  78.70 60.00 62.03 62.40 87.90 72.11 78.32  130.7 110.3 103.2 102.8 142.7 135-3 141.1  The measurements were c a r r i e d out between J u l y 15 and August . 5 ,  1961.  **The comparison has been done by the amplitudes of the l i g h t curves,. because its•light.measurement was c a r r i e d out f o r a.shorter p e r i o d than i n the nest a. F i r s t nests are marked with  second nests are unmarked.  • I f one compares the values of these nests, one w i l l see t h a t the d i f ferences between them are r e l a t i v e l y s m a l l . the two extreme cases.  I t i s only 8 . 3 per c e n t . i n  This i n d i c a t e s that the robins choose nest s i t e s of  nearly the same ecoclimate. The question i s , how the Robin s e l e c t s these almost i d e n t i c a l spots i n the l i g h t range.  I t seems,.that the Robin uses f o r n e s t i n g the most uniform  parts of the f o r e s t type.  E.g. the area of an Eurhynchium-Mahonia f o r e s t  .on which p l o t . I was l o c a t e d i s about 12 acres.  Roughly one-third.of t h i s area  , i s covered w i t h a dense young ( 8 t o 12 years old) f o r e s t , , i n which only 2 of the 29 nests were found.  The other t h i r d was an o l d stand with a.heavy l a y e r  of mosses w h i c h i n h i b i t s feeding. :  There was no Robin nest found.in t h i s p a r t .  In the r e m a i n i n g . t h i r d of the area, the moss l a y e r was l e s s developed and.27 nests were found here.  (For the d e s c r i p t i o n of the areas consult .Table  12).  The nests i n t h i s sample p l o t then f a l l i n t o two aggregations, and w i t h i n each a stable nest height was  observed.  The nests i n the f i r s t group are l o c a t e d 2 . 7 t o 4 . 2 m. above the ground. A l l nests were b u i l t i n crown part 6 .  In the second group, a l l nests are  -90-  b u i l t higher than 10 m. above the ground and a l l nests are l o c a t e d . i n crown part 5-  The reason of t h i s i s that the density of the crown.layer (A-j_,Ag)  f o r the f i r s t group of n e s t s - i s r e l a t i v e l y - l o o s e , . b u t a w e l l developed A^ l a y e r - i s present.  A l l nests are l o c a t e d . i n t h i s A^ l a y e r .  In the second  group, the large Douglas-fir grees give a r e l a t i v e l y w e l l closed crown l a y e r (Aj)  and the lowest crown l a y e r ( A 3 ) i s weak.  w e l l developed Ag l a y e r .  A l l nests are l o c a t e d . i n the  The l i g h t . i n t e n s i t i e s of the A^ l a y e r i n the f i r s t  group and of the Ag l a y e r i n the second group i s very s i m i l a r .  Therefore,, i t  i s b e l i e v e d that t h i s i s one reason why Robins p l a c e d , t h e i r nest i n those l a y e r s . Sample plot.. I I .  Only one of the eight nests found i n t h i s : area was  studied f o r - i t s l i g h t r e l a t i o n s . Nest e was located on an elder shrub, 1 . 8 m. above the ground,, i n a small opening of the dense cedar stand.  This nest was found i n the most dense part  of the e n t i r e f o r e s t accommodating a . t o t a l of 97 nests.  I f one studies the  l i g h t r e l a t i o n s one w i l l see that t h i s l i g h t curve i s located as  intermediate  between the curves of the other nests s t u d i e d . i n t h i s f o r e s t type.  Table .11  shows that the d i f f e r e n c e between t h i s nest and nest a i s small, ( l . l $) practically negligible. •It one compared the temperature compensating e f f e c t of the f o r e s t stand at the places of nest e and a, t h i s d i f f e r e n c e would be n e g l i g i b l e a l s o , as i s shown i n the f o l l o w i n g t a b l e : (The temperature measurement of nest e was c a r r i e d out from 10 t o 16 hours on J u l y 2 3 ,  196l).  -91-  The measured highest temperature i n open in C  Nests  U  The measured highest temperature i n places of nest i n C ~  Differences  u  e  30-9  27.5  3A  a  34.1  31.  3-1  Because nest e was found i n the densest part of the f o r e s t i n a small f o r e s t opening, therefore i t . i s supposed that nest e represents the lowest l i g h t range where the Robin would e s t a b l i s h a n e s t . i n t h i s ecosystem type. The data obtained from the l i g h t curves i n d i c a t e s that this.opening i n the f o r e s t stand has apparently the same ecoclimate range as that of nest a. Apparently the Robin receives a l l of i t s food i n the Eurhynchium-Mahonia ecosystem type.  The major part of i t s food comes from the ground, therefore,  the Robin occupies a l l such places which are f r e e from heavy l a y e r of herbs and mosses.  This seems to be the case i n p l o t I , the ground of which i s f r e e  from a bryophytic l a y e r and only a poorly developed herb l a y e r i s present. Hence, almost a l l Robins occupy t h i s part of the f o r e s t type.  One of the ad-  jacent parts as we have seen has a s i m i l a r stand s t r u c t u r e , but i t s ground i s covered with a heavy l a y e r of bryophytes which hinders the r o b i n i n obtaining i t s food.  Supplementary food from f r u i t i n g plants i s not present here, there-  fore t h i s part of the f o r e s t type excludes  the s e t t l i n g of the r o b i n .  I t was considered that the Eurhynchium-Mahonia ecosystem type i s optimal for  the r o b i n , because of the following.reasons: 1.  A number of observations proved that there i s a strong a s s o c i a t i o n  between the Robin and the Eurhynchium-Mahonia ecosystem type, and that Robin i n d i v i d u a l s observed i n t h i s f o r e s t type perform p r a c t i c a l l y a l l of t h e i r l i f e functions with t h i s f o r e s t . t y p e . 2.  The nest has.the most simple s t r u c t u r e i n t h i s f o r e s t type compared  -92-  with.the Robin nests i n the other f o r e s t types, and the nests are exposed which circumstance stays i n contrast w i t h the p o s i t i o n of Robin nests i n the other f o r e s t types. 3-  I n general, the young remain w i t h i n the l i m i t s of the Eurhynchium-  Mahonia ecosystem type, whereas they depart from the other f o r e s t type soon 9  a f t e r feeding. The Robin cannot come i n t o such close r e l a t i o n s h i p w i t h the other communities of the study area. '. I t may use two or sometimes three d i f f e r e n t communities.in the course of the breeding season, one f o r n e s t i n g and one or two f o r feeding. Those i n d i v i d u a l s which l i v e outside the Eurhynchium-Mahonia ecosystem type show a high degree of a d a p t a b i l i t y i n that they adjust t h e i r nests t o the o p p o r t u n i t i e s given by the e c o l o g i c a l conditions of the h a b i t a t concerned. This i s i n d i c a t e d by the f o l l o w i n g f a c t s : 1.  The Robin can p r o t e c t . i t s nest against the extremes of f o r e s t eco-  climate by a p a r t i c l a r nest p l a c i n g method.  I t s nest i s placed e i t h e r i n the  ecotone of two f o r e s t types as i n cases of the hydrophytic f o r e s t types (such as: Polystichum and Thuja-Lysichitum-Oenanthe  ecosystem types) or i f the nest  i s . l o c a t e d w i t h i n the xerophytic Rhacomjtrium and mesophytic Gaultheria-Mahonia ecosystem types,.then i t . i s placed under an a c t i v e l a y e r . 2.  The Robin uses d i f f e r e n t m a t e r i a l s f o r i t s nest i n the d i f f e r e n t  f o r e s t types. 3>  The second nests of a season are frequently placed i n t o another f o r e s t  type,. because a s i n g l e f o r e s t type may not :be s u i t a b l e i n both periods. k.  A number of observations.indicated .that the feeding and nesting places  •in these f o r e s t types often are separated from each other by a distance of 0.1  -93to 0.2 m i l e s . B).  Polystichum ecosystem type  In general, t h i s f o r e s t type i s characterized.by a .poorly s t r a t i f i e d stand s t r u c t u r e , an even crown l a y e r of Alnus rubra and B e t u l a p a p y r i f e r a . The shrub.layer i s dense Rubus p a r v i f l o r u s . The d i s t r i b u t i o n of the Robin population i s not even w i t h i n t h i s f o r e s t type, b u t . i s concentrated on the edge of the type, mostly i n the ecotone of the Polystichum- and Spiraea types.  In general, the e c o l o g i c a l  circumstances  of these places are s u i t a b l e f o r f i r s t nests but the second nests w i l l often be placed i n t o another type. Within t h i s f o r e s t type the i n v e s t i g a t i o n covered t r e e sample p l o t s which were l o c a t e d 0.3 to 0.6.miles apart. Sample p l o t I I I .  West f was b u i l t on a red a l d e r 3-6 m. above the  ground.in part 6 of the crown (see F i g . 13). 1-5 m. high dense l a y e r of Spiraea d o u g l a s i i .  The ground was covered with The second nest of t h i s same  b i r d , i s nest j . Sample p l o t , I V .  One of the two nests examined.in d e t a i l , West g, was  b u i l t on a.red alder 4.2 m. high above the ground.in part 6 of the crown. The ground was covered with about 0.4 m. deep water under the nest. I t should be emphasized that the l i g h t surpluses of these ne sts(Table l l ) did not r a i s e the temperature of the surroundings of these two nests cons i d e r a b l y , presumably because a c e r t a i n part of i t , i s l o s t as heat f o r evapotranspiration.  Therefore, the high value of l i g h t surplus i s a necessity  since the r e f l e c t i o n i n the case of both water and the vegetation surface i s high and consequently more l i g h t energy i s needed f o r the heating of the water. Supposing.that the t o t a l i r r a d i a t e d l i g h t was the same a s . i n nest a the b i r d s could not nest here f o r the strong c o o l i n g e f f e c t of evapo-transpiration, and  -94-  of the water. Robins f and g were able t o breed, i n these surroundings during the f i r s t n e s t i n g p e r i o d when the presence of 0.4 m. deep water and h i g h , i r r a d i a t e d l i g h t energies gave a.well compensated ecoclimate f o r both nests.  During the  second n e s t i n g p e r i o d , hoever, the water was l o s t by a r t i f i c i a l drainage. The high l e v e l of [ i r r a d i a t e d l i g h t energies and the extreme heat r e t a i n i n g capacity of the dry b l a c k swamp s o i l provided f o r an extreme ecoclimate f o r the nests which may have been disadvatageous  f o r nesting on days of extreme temperatures.  Because the high water content of s o i l and the undeveloped stage of surrounding vegetation, Robins could n o t . c o l l e c t t h e i r food i n the Polystichum plot.  They found, i n the adjacent Gaultheria-Mahonia ecosystem type during  t h i s nesting period. Sample p l o t V.  The e c o l o g i c a l f a c t o r s were i n v e s t i g a t e d i n the f i r s t (h)  and the second (i_) nests of a .pair of Robins. Nest h was found.in-the f o r k of a dead a l d e r tree;2.7 m. high above the ground a t the southern shore of the swamp. The water of the swamp was 0.3 m. deep. N e s t . i was placed i n part.5.of the crown of a b i r c h t r e e 4.2 m. high above ;the ground at the northern shore of the swamp. dense l a y e r of Spiraea d o u g l a s i i .  The ground was covered with a  Water was not present on the ground.  The  distance between these nests was 40 m. There i s p r a c t i c a l l y no d i f f e r e n c e between the l i g h t i n t e n s i t i e s of nest h and.i (Table l l ) . Here the r o b i n received p r o t e c t i o n against surplus heating by a.high evapo-transpiration due t o the presence of water on the ground surface i n the case of nest h, and the dense Spiraea l a y e r of nest i . Why d i d t h i s Robin place i t s second nest,on the northern shore of t h e  -95swamp when there i s no s i g n i f i c a n t d i f f e r e n c e between l i g h t . i n t e n s i t i e s at the  f i r s and the second nests?  The l i g h t . i n t e n s i t y of the swamp i s appar-  e n t l y even, hence t h e o r e t i c a l l y a Robin could place i t s nest anywhere on t h i s swamp shore. Since the pond d r i e s out during the summer, the ecoclimate becomes extremely dry, hence t h i s was no longer s u i t a b l e f o r the r o b i n .  The second  nest had t o be b u i l t t o the northern shore, of the pond, where the presence of the high, evapo-transpiration of the Spiraea l a y e r could dampen the temperature extremes. This Robin p a i r h and i l i v e d i s o l a t e d from .other r o b i n s , i n the centre of a 15 acre f o r e s t p l o t .  They gathered t h e i r food.mainly from the f o r e s t  i n t e r i o r which was f r e e from dense herb l a y e r during the f i r s t nesting period.  At the time of the second nesting t h e i r food was mainly b e r r i e s of  Rubus p a r v i f l o r u s . The young i n the case of a l l the four nests discussed l e f t t h i s habitat immediately a f t e r t h e i r f u l l development. C).  Gaultheria-Cladonia-Rhacomitrium ecosystem type  This i s the d r i e s t f o r e s t type i n the area of study. Robins cannot l i v e too  w e l l i n t h i s community, because the f o r e s t stand.is poorly developed,  c o n s i s t i n g of only a few D o u g l a s - f i r t r e e s . ground.  These are branched from.the  Robins use t h i s f o r e s t type e x c l u s i v e l y f o r t h e i r second nests.  In general, the f i r s t nests observed were i n the v i c i n i t y of the Polystichum ecosystem and Spiraea swamp ecotone. Sample p l o t VI.  Three of the four nests were i n v e s t i g a t e d i n detail'.  Nest j i s the second nest of a r o b i n , the f i r s t nest of which was studied i n the Polystichum ecosystem type (p. 93)• I t was b u i l t i n the dense crown of a D o u g l a s - f i r 2.0 m. above the ground,, i n part 6 of the crown (Fig. 13).  -96-  Nest k was found i n a dense D o u g l a s - f i r crown 1 . 7 m .  above the ground,  i n part 5 of the crown. Nest i was found i n the fork, of a .Douglas-fir 1-3 m. above the ground, i n the part 6 of the crown. Comparing the l i g h t i n t e n s i t i e s of the f i r s t nest ( f ) and the second of an i n d i v i d u a l Robin, we see that the f i r s t nest received 1 5 - 7 $  nest  more l i g h t than the second nest.  This l i g h t surplus at the time of the  f i r s t nest was l o s t as heat f o r evapo-transpiration and.in r e f l e c t i o n from the surface of the dense vegetaion.  This Robin p l a c e d . i t s second nest i n  the dense crown of a D o u g l a s - f i r which provided e f f e c t i v e p r o t e c t i o n from •the extremes of the stand ecoclimate. Temperature f l u c t u a t i o n s measured i n these nests (on J u l y 1 9 ,  1962),  p a r e l l e l e d the measurements i n an open area f o r a p e r i o d of 15 hours (the temperature was recorded once i n every 30 minutes). Nests  L i g h t range i n jo of i n t e n s i t y of open l i g h t  Amplitudes of temp, i n °C open  nests  Temperature decreasing e f f . of nests surroundings l  j  53-97  k  50.36  1 a-  n  1°  21.1  19.0  11.1  21.1  18.0  17.1  50.37  21.1  18.7  12.8  43.55  20.2  16.0  26.3  •  Considering.that.the nest trees a l l were s i n g l e t r e e s . i n the open meadow, yet  they compensated the nest by  ikfo  l e s s temperature extremes on the average  then,.in the open, i t seams that the temperature compensating e f f e c t of a .tree which i s branched from the ground i s r e l a t i v e l y high. This f o r e s t type does not produce food, and the Robin must c o l l e c t . i t  -97-  from the community of i t s f i r s t nest.. A f t e r the water d r i e d up, an a c t i v e animal l i f e developed around the swamp shore.  This may have "been r e l a t e d  with.the new sources of food provided i n form of thimbleberry f r u i t s . A l l young l e f t t h i s f o r e s t type immediately a f t e r t h e i r f u l l development. D).  Gaultheria-Mahonia .ecosystem type  The stand of t h i s f o r e s t type was logged during and before 1 9 5 1 ' Following the l o g g i n g , a few small economically worthless D o u g l a s - f i r trees were l e f t standing.  The shrub l a y e r was completely destroyed .in the f i r e of  1951 and again i n 1 9 6 1 . L i t t l e information was gained concerning the Robin.  Three nests ( l f i r s t  and 2 second broods) were found.in the summer of i 9 6 0 , f i v e ( 3 f i r s t and 2 second broods) i n 1 9 6 1 .  I n both years a l l f i r s t nests were placed i n dense  maple bushes t o 0 . 5 t o 1 . 0 m. above the ground, while a l l the second nests were placed.in part h of the crown of small D o u g l a s - f i r s , which., were branched from the ground.  These small t r e e s were surrounded by a 1 . 0 t o 1 . 5 m. h i g h dense  l a y e r of shrubs ( F i g . 1 2 ) . The e c o l o g i c a l circumstances of the nests of t h i s f o r e s t types were not s t u d i e d . i n d e t a i l w i t h regard t o l i g h t . c u r v e s , because a l l the nests were hidden under the dense l a y e r of vegetation 1 . 0 t o 1 . 5 m. high.  One could  not have reached the nests without destroying the surrounding vegetation. The Robin c o l l e c t e d . i t s food e n t i r e l y w i t h i n the community of t h i s f o r e s t type during both nesting periods. At.the time of f i r s t nesting, i t s food came mainly from the ground, wet road sides and the deeper part of the forest.  I n the second nesting p e r i o d the Robin f e d on thimbleberry f r u i t .  I t is-probably the Robins take an a c t i v e p a r t . i n the community of t h i s f o r e s t type i n the mature stands only. be provided by young stands.  Such favourable conditions may not  -98-  E) . Pachystima-Gaultheria-Peltigera ecosystem type Robins do not favour t h i s h a b i t a t as only one single Robin nest  was  found there. This f o r e s t type i s l a y i n g on steep extremely dry slopes (the slope i s up t o 40°).  Stones compose about 95 P ^ cent of the s o i l c o n s i s t i n g of e  mainly boulders.  The aspect of the slope i s always warm oriented.  Due t o  t h i s extreme ecotype, the b i r d fauna,is r e l a t i v e l y poor. F) . Thuja-Lysichitum-Oenanthe ecosystem type This i s the wettest f o r e s t h a b i t a t . i n the study area. Sample p l o t V I I .  In t h i s sample plot,.two of the f i v e observed  were examined f o r the v a r i a t i o n s of the l i g h t curves. longed to a.single Robin p a i r .  nests  These two nests be-  Nest m was i t s f i r s t nest and n the second  nest. Nest m was. l o c a t e d on a red alder trunk 1.5 m. above the ground. nest received a small amount of shade only.  The  The water was about 0.6 m. deep  under the nest. Nest n was placed on a hemlock tree which was s l i g h t l y f a r t h e r from the edge edge of the swamp. bryophytes.  Decaying logs were covered here by a strong l a y e r of  The nest was b u i l t k.2 m. above the ground, i n part 6 of the  crown. Nest m received 5-4 "per cent higher i l l u m i n a t i o n that that of nest n. This l i g h t surplus was necessary, because the nest was placed above an open water surface, therefore a considerable part of i t was required to warm up the water which has higher s p e c i f i c heat than the s o i l .  At the time of  second nesting t h i s water was drained and t h i s h i g h . i l l u m i n a t i o n with bog s o i l represented an extreme microclimate f o r the nest, t h e r e f o r e , i t was s u i t a b l e f o r the second nest.  not  In the case of the second nest, nest n, a more  -99s u i t a b l e microclimate was present w i t h lower l i g h t .  This may.be considered  to be too c o l d f o r the f i r s t n e s t . i n the time of hatching. Sample p l o t V I I I .  This p l o t . i s adjacent t o Kawkawa Lake with 0.2-0.4 m.  i n deep water throughout the year.  The permanent presence of water can  insure the favourable microclimate f o r the f i r s t was w e l l as the second nests of the r o b i n .  The e c o l o g i c a l f a c t o r s were studied only i n one of the two  nests. Nest o was found on a red a l d e r 4.8 m. above the water,, i n part 6 of the crown.  According .to Table 11, t h i s nest r e c e i v e d 41.45  i l l u m i n a t i o n t h a t that of nest a.  per cent higher  This l i g h t surplus i s advantageous f o r  Robin, which was already discussed e a r l i e r . In the Thuja-Lysichitum-Oenanthe ecosystem type water i s always at the s o i l surface causing the development of a.high, dense l a y e r of herbs and shrubs which hinders the food c o l l e c t i n g of the r o b i n .  Thus, the Robin cannot  adapt i t s e l f completely t o the conditions of t h i s h a b i t a t due to the l a c k of food.  However, t h i s type i s always favourable f o r the f i r s t n e s t i n g , and  sometimes f o r the second nesting as w e l l . The young immediately leave t h i s f o r e s t type a f t e r they are s u f f i c i e n t l y developed. I f we now compare the average l i g h t amplitudes at the nests i n the d i f f e r e n t h a b i t a t s , an i n t e r e s t i n g c o r r e l a t i o n seems to emerge. Ecosystem types Eurhynchium-Mahonia -Galtheria-CladoniaRhacomitrium Polystichum •Thuja-Lysichitum-Oenanthe  Measured average in l x . 7-90 8.25 9.60 10.50  L i g h t amplitudes in % 100.00 .104-5 121-5 133-0  One can see that t h e . i l l u m i n a t i o n of the nests s i t e s increases i n d i r e c t  -100proportion with increase of the wetness of the ecosystem type.  I f one c a l -  culated the amount of l i g h t energy which was needed t o warm up the surroundings of the nests on the b a s i s of Table 6 (p. 59) > one w i l l get nearly equal values f o r each ecosystem type. Eurhynchium-Mahonia respect.  and the Thuja-Lysichitum-Oenanthe ecosystem t y p e s , i n t h i s  According to Table 6, i n the case of c i a y s o i l , an average of 15$  and i n the bog s o i l 9$> roundings.  To give an example,. I am comparing now.the  of i r r a d i a t e d l i g h t i s used f o r heating up the sur-  In the former type l.l8.1x. ( c a l c u l a t e d the average l i g h t ampli-  tude), and.in the l a t t e r 0.9^5  l x . i s used f o r t h i s purpose.  The high l i g h t value of the Thuja-Lysichitum-Oenanthe ecosystem type i s a necessity since more than h a l f of i t i s l o s t as heat f o r the evapotranspiration.  Supposing that the l i g h t i n t e n s i t y was lower, the Robin could  not place i t s nest there, because of the disadvantageous microclimate during incubation, or f o r the n e s t l i n g s on a,colder day.  In the case of the Eurhyn-  chium-Mahonia ecosystem type, although the l i g h t . i n t e n s i t y i s l e s s , t h i s does n o t . i n t e r f e r e with.the Robin, since the clay s o i l uses up smaller heat than the  peat s o i l f o r evaporation. One may state that the m i c r o c l i m a t i c conditions  of nests i n each eco*-  system f o r e s t type are nearly the same, because the v a r i a t i o n s of the microc l i m a t i c f a c t o r s can be balanced on a .certain l e v e a l by the r o b i n i t s e l f . • I t was shown that the r o b i n can take part, i n the community l i f e of d i f f e r e n t ecosystem types. This i s due to i t s high a d a p t a b i l i t y .  I f necessary  the Robin p l a c e s , i t s nest under an a c t i v e l a y e r of vegetation to p r o t e c t . i t from the e c o c l i m a t i c extremes, or nests i n the ecotone of two f o r e s t types where the n e s t . i s under m i l d c l i m a t i c conditions compared with that i n the open o r - i n the stands. Robins showed a high degree of adaptation to the  -101-  d i f f e r e n t f o r e s t types by the change of t h e i r nest b u i l d i n g technique a l s o . Generally speaking,. i f one studies the nest of the Robin regarding the m a t e r i a l used and the technique of nest b u i l d i n g , one w i l l f i n d that a l l r o b i n nests can be c o r r e l a t e d with.the e c o l o g i c a l impact of t h e i r surroundings. The second part of Robin study i s intended t o elaborate upon the r e l a t i o n ship between the f o r e s t .types and the nest b u i l d i n g techniques of the Robin. A'O . Eurhynchium-Mahonia . ecosystem type The t y p i c a l feature of the r o b i n nest i n t h i s h a b i t a t i s the l a r g e and loose moss and l i c h e n mass.  I n volume, about 60 t o 70 per cent of the nest  consists of moss or l i c h e n s , only a.few per cent of twigs, grasses,.decaying leaves and r e l a t i v e l y very l i t t l e mud (average 22.h% of weight) i s used .compared t o nests'built..in the other ecosystem types (Table 13). There, i s a.difference between the m a t e r i a l of the f i r s t and second nest. In the f i r s t nest, the moss.is always p r e s e n t . i n high percentage of the nest w a l l (av. 31*8$ of weight). Lichen i s l a c k i n g , or present, i n a low proportion. In the second nest a high,percentage of l i c h e n (av. present.  of wieght) i s  The high per cent of mosses of the f i r s t nest, i s due t o the c o l d  environment of t h i s ecosystem type i n May. 27.670)  38.^70  The amount of mud.is' more (av.  i n the f i r s t nest", l e s s (av. 17-2$) i n the second..  The higher pro-  p o r t i o n of mud is.necessary-in. the case of the f i r s t nest t o cement the short fragmented mass of m a t e r i a l .  Mud does not.play an important r o l e i n the  second nest,. because of the long l i c h e n m a t e r i a l t h a t can w e l l be bound,. without strengthening i t w i t h mud. The h i g h l y s t r a t i f i e d ' stand structure of t h i s ecosystem type i s able t o give a good p r o t e c t i o n to' the nest against the mechanical e f f e c t s of environment (wind.,> r a i n , e t c . ) .  Therefore,.a strong nest such as r e q u i r e d by the  -102-  other.. ecosystem types i s not necessary here. temperature  This f o r e s t type has the highest  lowering e f f e c t i n the study area, e s p e c i a l l y during the f i r s t  nesting season, t h e r e f o r e , the high i n s u l a t i n g e f f e c t of nest w a l l i s a h i g h l y necessary requirement, which i s given by the high proportion of mosses, or l i c h e n s . Nest e was considered as a s p e c i a l l y adapted nest.  The structure of t h i s  nest shows that i t was b u i l t against the high mechanical s t r e s s exerted upon i t b y . i t s environment.  This nest was placed among the branches of the'fork  of an elder bush i n a f o r e s t opening of a.dense middle aged cedar stand; The wind could penetrate i n t o the opening and.itrcaused the branches of the nest holding t r e e t o v i b r a t e .  Consequently,.the  nest had t o be f l e x i b l e t o  withstand deformation and r e g a i n i t s o r i g i n a l shape during a,windy period. I t could r e s i s t t h i s time a f t e r time with i t s r e l a t i v e l y high content of very f i n e long r o o t l e t s (19-6$ of weight') and by i t s s p e c i a l l o c a t i o n .  The high  moss content (38-3$ of weight) provides f o r a good p r o t e c t i o n against the c o l d environment. B).  Polystichum ecosystem type  In t h i s h a b i t a t the secondary a l d e r - b i r c h canopy provided a t h i n l a y e r which cannot protect the Robin's .nest.  This i s exposed t o strong mechanical  e f f e c t s , . t h e r e f o r e , a h e a v i l y b u i l t n e s t . i s necessary here, the s t a b i l i t y of which.is given by high percentage of twigs (av. 13-8$) i n the nest .material or by the f o r k of the t r e e .  I n t h i s l a t t e r case the nest contained a low  proportion of twigs (av. 3'Ofo), because the branches of the f o r k already provided good s t a b i l i t y against mechanical f o r c e s . f i r s t n e s t . i s always' high.  The moss component i n the  I n the second nest, i t i s very low, or absent.  -103-  C) . Gaultheria-Cladonia-Rhacomitrium ecosystem type The Robin protected i t s nest from the e c o c l i m a t i c extremes i n t h i s f o r e s t type by s p e c i a l nest p l a c i n g methods, i . e . the w e l l closed crown surface which p r a c t i c a l l y extends down t o the ground protects the nest against any mechanical.impacts.  The nest i s b u i l t of. r e l a t i v e l y small amounts of  grass (av. 33-3$) and of a high p r o p o r t i o n of mud m a t e r i a l s (av. 47.1$). The mud w a l l of the n e s t , i s very strong.  Twigs are found only i n the bottom of  the nest s e r v i n g as supports of the nest on the branches.. D) . Gaultheria-Mahonia ecosystem, type Here again the Robin protected i t s nests from the e f f e c t s of ecoclimate by a . s p e c i a l nest p l a c i n g method.  The dense surface of maple brush, or the  dense l a y e r of herbs which surrounded the young .Douglas-fir, protected the nest against any k i n d of mechanical e f f e c t s . M a t e r i a l s of the nest are high i n mud (av. 45-7$)•  T n e  nest does not  have twigs, or i n very low p r o p o r t i o n . The s i z e of the r o b i n n e s t . i s l e a s t .in t h i s f o r e s t type (Fig..14).  The second n e s t . i s always l o c a t e d i n part 4  of the crown where the r e l a t i v e small branches can give support t o a small nest only. E) . Thuja-Lysichitum-Oenanthe  ecosystem type  In general the nest, i s " located..in the open without any cover on the crooked trunks o r - i n the f o r k s of a l d e r t r e e s . q u a n t i t i e s i n these nests (av. 37•5$)-  Mud.is not used.in large  The surrounding a i r i s h i g h l y humid,  therefore mud could not provide enough s t a b i l i t y f o r the nest.  The nest, how-  ever, withstands severe mechanical effects,.because i t , i s strong, t h i c k l y w a l l e d , mainly b u i l t of t i n y , long.tree roots (av. 22-5$ of weight). general i t does not contain t w i g s , or only a n e g l i g i b l e amount.  In  The twigs  Figure 14.  The b a s i c forms of Robin's nests from d i f f e r e n t ecosystem types on the Hope, B.C. study area  -104play a r o l e only i n the supporting of the nest from below. The f i r s t and second nests do not d i f f e r from one another i f both are l o c a t e d w i t h i n t h i s f o r e s t type.  Of course, those second nests which- are  placed.into the ecotone show s l i g h t d i f f e r e n c e from the f i r s t nest f o r they contained more mud and r e l a t i v e l y small amounts of tree r o o t s . The r e l a t i o n of Robin to the other members of the community The Robin shows the strongest f i d e l i t y t o those places where the , l i g h t ranges between 40 to, 50 per cent of the l i g h t i n t e n s i t y i n the open and which.have w e l l s t r a t i f i e d crown l a y e r s and poorly developed shrub and,moss layers.  The surface of the s o i l i s r e l a t i v e l y c l e a r with high humus content  -  and a good crumby structure< The Robin-is a strong competitor and does not t o l e r a t e other species i n i t s t e r r i t o r y . i n those h a b i t a t which provide i t with optimal  environmental  conditions. The strongest competition i s between the r o b i n and v a r i e d .thrush.in the Eurhynchium-Mahonia type as the f o l l o w i n g example shows: 1961,  In the spring of  a v a r i e d thrush nest (nest a) was found.in the sample p l o t . I at the  l i g h t range of 42.99 per cent.  Subsequently,  a Robin (nest a) p l a c e d . i t s  nest about.13 m. from the nest of the Varied thrush at the l i g h t range of 43-55 per cent.  The male Robin sat on a branch of a hemlock tree which was  nearest to the nest of the Varied thrush and repeatedly attacked the Varied •thrush p a i r .  At the l a s t the Varied thrush p a i r was f o r c i b l y pushed out.of t h e i r  original territory.  Near t o t h i s same place, another Varied thrush nest  (nest c) was found.in the l i g h t range of 39-76 per cent and.the ground was covered with a heavy l a y e r of bryophytes.  No struggle was observed here,  because the h a b i t a t conditions were not optimal f o r Robin. The Swainson's thrush .uses the same l i g h t range as the Robin i n the  Eurhynchium-Mahonia f o r e s t type; hence the Robin forces  Swainson s.thrush !  i n t o those parts of t h i s f o r e s t where a.well developed shrub l a y e r i s present" thus being unsuitable f o r the Robin.  I n the Polystichum ecosystem type'. no  competition e x i s t s between these two b i r d s , because Robins do not favour t h i s place f o r i t s e c o l o g i c a l p o t e n t i a l s . The Robin shows a.close a s s o c i a t i o n with.the S o l i t a r y v i r e o .  Both  species b u i l d t h e i r nests on broadleaf maple and t h e i r nesting l i g h t ranges are the same, but the Robin b u i l d s . i t s nest on the stronger branches while the S o l i t a r y v i r e o nests on branches w i t h diameters smaller than .10 mm.  More-  over t h e i r feeding, places are d i f f e r e n t , hence there i s no competition between them. Robins can protect t h e i r nest against the S t e l l e r ' s jay quite well.. Only four of the 97 r o b i n nests were found destroyed by S t e l l e r ' s j a y . A number of observations not d e t a i l e d here.indicated that the Robin i s the dominant member of the b i r d community i n the Eurhynchium-Mahonia ecosystem type a n d . i t s stays i n a .direct, or i n d i r e c t r e l a t i o n s with.most of the members of the b i r d community i n t h i s type.  But i n the other-ecosystem  types  of the study area .Robins cannot dominate i n the b i r d communit ies because of t h e i r unfavourable h a b i t a t c o n d i t i o n s . The B i o l o g i c a l value of the Robin i n the b i o t i c communities of f o r e s t types The Robin i s the most a c t i v e member of the b i r d community i n the Eurhynchium-Mahonia ecosystem type, and i t ; : i s quite unimportant. i n the other f o r e s t types.  I n the Eurhynchium-Mahonia ecosystem type, the Robin contributes  to the community with.various functions such as:  d i s t r i b u t i n g of seeds,  preparation and .cultivation of the s o i l , c o n t r o l of damagers on c e r t a i n plants and helping m i n e r a l i z a t i o n of plant parts and feeding on seeds.  -106-  During the summers of i960 and I96I, nearly one hundred Robin nests were i n v e s t i g a t e d . The Eurhynchium-Mahonia ecosystem type was considered t o provide optimal conditions f o r the Robin, which i n d i c a t e d i t s strongest f i d e l i t y t o t h i s f o r e s t type.  Apparently, the r o b i n plays the most .important r o l e i n  the b i r d community of the Eurhynchium-Mahonia ecosystem type.  This f o r e s t  type i s s u i t a b l e f o r a l l the a c t i v i t i e s of a nesting Robin population. In the other f o r e s t types,,the Robin showed a good adaptation t o the community, I n h a b i t i n g the ecotone as i n the Polystichum ecosystem type or often i n the Thuja-Lysichitum-Oenanthe  ecosystem type.  With i t s wide s e l e c t -  i v i t y regarding the nest s i t e , . i t can p r o t e c t . i t s nests from the extremes of the ecoclimates. The Robin i n d i c a t e d . i t s strong capacity of a d a p t a b i l i t y when p l a c i n g i t s f i r s t and second-nests  i n t o d i f f e r e n t f o r e s t types, or when both nests  are ..placed w i t h i n a s i n g l e f o r e s t type, each b i n g i n d i f f e r e n t e c o l o g i c a l strata.  Considering the seasonal c l i m a t i c d i f f e r e n c e s a t the time of the f i r s t  and second n e s t i n g , the a l t e r a t i o n of nesting p l a c e . i s necessity f o r nesting success.  I f the Robin cannot j o i n i n the community of a .forest type, then  i t s n e s t . i s i n one, a n d . i t s feeding ground i n another f o r e s t type.  I n such  a.case the young leave the f o r e s t type of the nest as soon as they fledge. The density of the Robin p o p u l a t i o n . i s h i g h e s t . i n the mature EurhynchiumMahonia ecosystem .type.  In other f o r e s t types, the population density v a r i e s  with ..the ecoclimate, and the degree of food supply, but i t i s always very low as compared w i t h the Eurhynchium-Mahonia ecosystem type.  I n area of p l o t .I  eight Robin p a i r s nest and feed on an about k t o 5 acre land.  In Gaultheria-  Mahonia ecosystem type, i t was found that the nest and feeding places are  -107-  s e p a r a t e d from each o t h e r hy a d i s t a n c e o f 0 . 1 t o 0 . 2 m i l e s , thus a p a i r o f r o b i n s used 1 0 a c r e s o f l a n d . The i n v e s t i g a t i o n i n d i c a t e d .that the R o b i n p l a c e s i t s n e s t s i n t o n e a r l y the  same m i c r o c l i m a t i c range independent from the e c o c l i m a t e  types.  of the f o r e s t  I t i s a b l e t o do so, because i t can compensate f o r t h e d i f f e r e n t  l o g i c a l circumstances  w i t h . i t s p e c u l i a r n e s t p l a c i n g methods and t e c h n i q u e s .  The n e s t m a t e r i a l and t h e n e s t b u i l d i n g t e c h n i q u e s  o f t h e Robin showed a  d e f i n i t e r e l a t i o n s h i p w i t h t h e m e c h a n i c a l impacts o f t h e f o r e s t types the n e s t .  eco-  With i n c r e a s i n g t h e m e c h a n i c a l e f f e c t t h e s t a b i l i t y  upon  o f n e s t s must  be i n c r e a s e d as w e l l i n d i r e c t p r o p o r t i o n i n t h e i n t e r e s t o f s u r v i v a l .  F i e l d data of Robin nests. Table  Nests  T r e e .species  Nest height m.  Location of nest i n part o f crown  Eurhynchium-Mahonia ecosystem type, 1* 2* 3* 4* 5* 6* 7* 8* 9* 10 11 12 13 14 •15 16 17 18 19 20 21  Vine maple Vine.maple Hemlock Vine maple Douglas-fir Douglas-fir Hazel-nut B r o a d l . maple Willow B r o a d l . maple Birch B r o a d l . maple B r o a d l . maple Red a l d e r Birch Vine maple B r o a d l . maple Douglas-fir Vine maple Hazel-nut B r o a d l . maple  10  Number o f eggs laid hatched  No. o f young fledged  i960 6 6  3-2 2.7 1.2 3-6 1.8 2-7 .2.8 3.6 2.4 5-4 12.0 11.5 4.8 0.6 14.0 3-6 13'.0  4 4 4 4 4  4 ? 4 4 0 0 4 4 4 4  7  ?  1 4 4 1  5 6  4 1 4 4 4 4  1 4 4 9 4 1 i 4 4 4  5  4  4  5 6 6 6 6 6 6 6 5 5 6 •5 5 6 5 5 6  6.5 2.4 1.8 4.1  4 q h 4  4  .  •  4 • 3 0 4 0 0 4 4 4 4 1 1 4 4 1 4 1 4 4 4 4  1961 22*  B r o a d l . maple  3.2  4  -108-  Nests  23*  24* 25* 26* 27* 28* 29* 30* 31* 32* 33*  34* 35* 36* 37* 38*  39  40 41 42 43  44 45 46 47 48 4950 51 52  Tree species  Nest height m.  Location of nest i n part of crown  Vine maple 2-5 (a)Douglas-fir 4.3 6.0 Broadl. maple Vine maple 1-7 Douglas-fir 0-9 (d)Vine maple 2.7 9.0 Birch 2.1 Cedar 2.6 Vine maple Red alder 3.1 .1.8 (e) Elder 1.6 Red alder Douglas-fir ' " .1.10 Elder 1.6 1.4 Hazel-nut Broadl. maple 3-1 2.6 Red alder 2.0 Elder 4.0 Douglas f i r (b )Vine maple 3-0 (c )Broadl.maple 16.5 •15.0 Douglas-fir Vine maple 3-1 3-0 Hemlock 10.0 Broadl.maple Grand f i r 1.7 Broadl. maple 0.7 Douglas-fir 1.3 2.2 Douglas-f i r i _ Birch 7-5  6 6 5 6 6 6 6 5 6 6 6 6 6  Number of • eggs laid hatched 3  4  No. of young fledged 3  3  . 4  U  7  7  7  4  h  4  4  4 2 4  7  7  7  7  3  3  3  4 4  4 4  4 if  3 3  3 3  3 3 .3  5 6  .4  4 7  • 3  5 6 6 6 5 5 6  4 4  4 4  if if  4  4  4  7 7.  4  7 7.  4  7 7  1+  5 5 6 6 6  7 7  7 7  3  4  4  3  .3  4 1  .6  7  7 7 ?  4  7  7  7  .  2 4  7  7  5 6  3  7  0 0 7  0 0 7  6 6 6 6 6 6  4 4  4 4  4 4  4  4  i  4 4 4  If 4 4  4 4 4  7 7  7 7  7 •7  2.7  6 6 6 6 6 6  4  4 if  8.0 3.2  5 5 6  4 4  Polystichum ecosystem type, i960 1* 2* 3*  4* 5 6  Red alder Red alder Birch Elder Red a l d e r Red alder  2.8 1.7 k.O 1-7  If.8 3-3  7 7 7  7 7 7  7  2 7  I96I 7* 8* 9*  .10*  11* 12* 13 ;:  14 15  Red a l d e r (f)Red alder (g)Red alder Birch Birch (h)Red alder (i)Birch Broadl. maple Red alder  2.0 3-6  4.2 9.0  , 14.0 4.2  7  7  7  4  4  k  -109-  Nest  Tree species  Nest height m.  Location of n e s t . i n part of crown  Number of eggs laid hatched  No. of young fledged  Gaultheria-Cladonia-Rhacomitrium ecosystem type, i 9 6 0 1* 2 .3 4 5  Douglas-fir Douglas-fir Douglas-fir Douglas-fir Douglas-fir  6 6 6 6 6  4  4  4  7  9  4  4  7  1  4  4  3 4 2 4  2.0  6  4  4  4  1-7 1.3 1.5  5 6 6  3 4  3 4  .3 4  7  l  6 6 6  3 4 4  3 4 4  3 4 4  6 6 6 6 6  3 3 4 4 .2  3 3 4 4  3 •3 4 4  l  l  .2  7  7  .4  4  7 7  1.3 1.9 1-5 2.2 2.3 1961  6 7  8 9  ( j )Douglas-fir (k)Douglas-fir (l)Douglas-fir Douglas-fir  Gaultheria-Mahonia .ecosystem type, i 9 6 0 •1* 2 3  Vine maple Douglas-fir._ Douglas-fir  1.2 0.9 1.4 1961  4* 5* 6* 7  8  Broadl. maple Vine maple Vine maple Douglas-fir Broadl. maple  1.6 1-3 1.0 1-3 1.1  Pachystima-Gaultheria-Peltigera 1*  Vine maple  .ecosystem type, i 9 6 0 6  1.4  Thuja-Lysichitum-Oenanthe ecosystem type, i 9 6 0 .1* 2* 3* .4* -.5  Cedar Red a l d e r Red alder Hemlock Red•alder  2.0  6  7-5 1.2 3-5 9.0  •5 5 5 6  7  7  4  4  7  7 7  .  4 2  7  1961 6* 7*  8*  9 10 11 12  (m)Red a l d e r Red a l d e r Red alder (n)Hemlock Red alder Red alder (6)Red alder  F i r s t .nests *  1-5 4.9 2.0  k.2 7-5 3-4 4.8  6 6 6 6 6 6 6  4  4  7  7  4  7  4 .4 ?  4 4  4  1  7 7,  4  4  .7 . 7 7 7  -110-  Ecotopic and stand s t r u c t u r a l c h a r a c t e r i s t i c s of f o r e s t p l o t s containing Robin breeding t e r r i t o r i e s . Plot  I  Exposure  eastern  Sloping £  5-8  Elevation feet  200-300  250  Table 12 Stand  Well s t r a t i f i e d crown canopy, r e l a t i v e l y weak shrub and herb.layers. No bryophyte l a y e r .  II  Well s t r a t i f i e d crown canopy. The shrub and herb.layers are l e s s w e l l developed. The bryophyte l a y e r i s r e l a t i v e l y abundant.  III  Ecotone of Polystichum ecosystem type and spiraea swamp. 15 m. high dense Spiraea d o u g l a s s i i l a y e r - i s present.  IV  -  Eastern  -  5  700  625  Ecotone of Polystichum ecosystem type and spiraea swamp. 0 . 6 m. deep water under the nest. The water was free from p l a n t s . Ecotone of - Polystichum ecosystem type and Spiraea swamp. 0.4 m. deep water under the f i r s t nest. I n the second nest a.dense spiraea l a y e r i s present without water.  v  -  -  . 650  VI  -  -  700  Stand i s poorly developed. The trees are branched from the ground. The density of stand i s very loose.  -  -  350  Poorly developed stand of Thuja-Lysichitum-Oenanthe ecosystem type. 0 . 6 m. deep water under the f i r s t nest. The second nest was l o c a t e d on the ecotone so ground was covered with a strong l a y e r of bryophytes.  -  200  VII  VIII  -  Poorly developed stand of Thuja-Lysichitum-Oenanthe ecosystem type, with 0 . 3 . t o 0.4 m. deep water throughout the year. :  -IllAnalysis  Nests  Weight of  nest  of Robin nest material.  Moss gm./yo  .Lichen  Tree  Twigs  Root  Soil  Herbs  gm./yo  leaf  gm./yo  gm./$>  gm./yo  gm./yo  38.1 21.0 16.2 17.1 21.7 17.3 19.8  48.1  gm.  gm./yo  Eurhynchium-Mahonia ecosystem a*  I85.5  55.8 30.1  9^-9  -  c  125-6  3.8  d*  1 0 0 . If  e*  146.3  b  Average  130.5  180.0  -  28.7 19.6  19.7 50.5 34.5  18.4 .14.1  5-5 4.2  21.5 16.5  6.6 5-0  29.2 22.4  20.8 10.-  6.4 3-5 7-1 4.5  • 0.5 .0.2 28.6 18.4  59-7 33-0 3-8 2.4 4.2 2.4 23.5 16.2  5-5 3.2 5.7 3-7 5.2 3-0 3-3 2.3  63.7 35-2 60.1 38.5 82.9 47.0 51.7 35.4  30.2 16.7 34.9 22.4 38.2 21.8 29.9 20.5  22.8 13.8  4.8 2.9  64.6 39-4  33-3 20.2  79.8 52.7 52.0 48.3 67.0 50.0  41-5 27.4 60.6 34.6 37.8 28.4  66.2  46.6  -  '  9-7 5-1 8.6  9.0 4.3 3-5 4.1 4.0  -  14.9  25.6 .17.5  19.3 11. T  9-7 5-9  10.0  Gaultheria-Cladonia-Rhacomitrium  ecosystem  156.2  h*  176.0  .i  Average  j  145.9.  164.5  151.4 —t  -  k  135.9  1  133.5  -  140.2  _  Average  -  25.8  11.4 12.0 21.9 17.5 14.4 14.3  ."8.2 5.6  type  8.2 16.0 10.2 39-6 22.4 6..8 4.6  g*  1.8 1.0 1.2 1-3 1.4 1.1  28.5 15.2 .24.4 25.7 19.5 15.6 31.8 31.8 2.9 2.0  33-1 3^.9 52.6 41.9 3.0 3-0  3~l 27.3 27/2 56.0 38.3 .28.5 21.8  type 3-5 1.8  -  Polystichum ecosystem f*  T a b l e 13  -  -  -  • 5-9 3.4 5-1 3-5  6.1  type  10.8 7.2 7-2 5.3 13.7 10.3  2.4 1.8  19.3 12.7 16.1 11.8 12.6 9.5  10.6  0.8  16.0  -  -  -  -  -112-  Nests  Weight. of nest gm.  Moss gm./$  Lichen  Tree leaf gm./$  Twigs gm./$  Root gm./f*  Soil gm./$  27.6 29.4 22.9 22.7  23.4 24.9 35-0 34.7 66.9  Herbi  m-l\  Thuja-Lysichitum-Oenanthe ecosystem type m*  94.1  n*  100.8  d  139-4  Average  lll.U  Gaultheria-Mahonia P  61.2  q. r* Average  8.7 9.2 6.2 6.2  1.8  3.1 2.2  1.9 4.3 4.3 2.0 1.4  6.0 5-4  2.7 2.4  0. 8 0.8 C  -  -  0.3 0.3  .2.0 .2.1 9.2 9.1 5-6 4.1  .5.6 5.0  .25.1 18.0  29.8 31". 7 23.2 23.0 36.7 26.3  48.0  .25.2 22.5  4l.7  3.8 6.2  .28.0  •-  37.2 44.6 38.8  37.5  ' 29.9 26.9  ecosystem type _  3-2 5-3 1.8 2.4  -  -  -  75-5  -  2.8  91.2  -  -  -  3.7 8.3 9.1  3-4 3.7  7.1 7.8  3.7 4.8  1.1 1.4  4.0 5-3  75.9 -  -  •  34.7 45.7  4o.o  5  -7  . : 2.6 2.8 2.1 2.8  42.5  26.2 42.9 33.7 49.3 31.0 34.1  4 .0  .  30.3  F i r s t nests * VARIED THRUSH (ixoreus naevius Gmelin) According t o observations made i n the summers of i 9 6 0 and 1 9 6 1 , the V a r i e d thrush was found only i n the Eurhynchium-Mahonia ecosystem type. I t was not observed outside t h i s community during the breeding season.  After  the nesting season, although the Varied thrush remains i n contact w i t h " t h i s type, i t was often observed.in other hydrophyiic ecosystem types .also. The Varied thrush population i s not evenly d i s t r i b u t e d w i t h i n t h i s community.  I t i n d i c a t e d a very r e s t r i c t e d h a b i t a t , apparently occupying the"  t r a n s i t i o n a l zone between the "habitat of the Robin and of the Winter wren. The nesting h a b i t a t of the Varied thrush was.investigated on two p l o t s  Light and Temperature Curves of Turdus migratorius Nests in Eurhynchium- Mahonia Forest Type on UBC Forest near Hope B.C.  Light Curves of Turdus migrotorius Nests on the Ecotone of Polystichum and Spiraea Forest Types on UBC Forest near Hope B.C.  Light and Temperature Curves of Turdus migrotorius Nests in Gaultheria - Cladonia - Rhacomitrium Forest Type on UBC Forest near Hope B.C.  Figure 11.  Explanation i n the text (p.  89)  Light Curves of Turdus migrotorius Nests in Thuja - Lysichitum - Oenanthe Forest Type on UBC Forest near Hope B.C. 100  -i  90 -J  Hours  Figure  12.  Explanation i n the text (p.  89)  X Figure 13.  The position of Robin's nests  In Gaultheria-CladoniaRhacomitrium ecosystem type nest j  In Gaultheria-Mahonia ecosystem type  -113which are separated from each other by a distance of 0.8 m i l e s .  S i x nests  were found, three of which were on the two p l o t s mentioned.  These three  nests were studied..in d e t a i l i n c l u d i n g the l i g h t . i n t e n s i t y .  The remaining  three nests were used f o r comparison only. The  purpose of t h i s study was t o answer the f o l l o w i n g questions:  1.  What i s the reason f o r the Varied thrush occuring only i n the  Eurhynchium-Mahonia community of the study area? 2.  What are the e c o l o g i c a l d i f f e r e n c e s between the h a b i t a t of the Varied  thrush and those of the r o b i n and the Swainson's thrush? 3«  What are the f a c t o r s which exclude the Varied thrush from the  communities of other ecosystem types i n the study area. The f i r s t part of t h i s study, i n v o l v e d the measurement of the i r r a d i a t e d l i g h t e n e r g i e s . i n the nests. P l o t I has a w e l l s t r a t i f i e d crown l a y e r ( a l l the sublayers are present). The ground i s covered -by r e l a t i v e l y weak shrub and herb l a y e r .  The moss  l a y e r v a r i e s step by step. West a was placed 2.9 m. h i g h . i n the crown of a young D o u g l a s - f i r ( i n the part k of the crown).  The s o i l had a r e l a t i v e l y high humus content and a  good crumbly s t r u c t u r e and was covered by a very weak l a y e r of A c h y l i s tripholia.  Shrubs and moss were not present.  This nest i s considered as the  b a s i s f o r comparison of the three nests, and the l i g h t energies of the nests are expressed as percentages of the l i g h t i n t e n s i t i e s measured.in t h i s nest which are taken as 100. West b was found 2-7,m. high above the ground i n the crown of a young D o u g l a s - f i r ( i n part k of the crown). layer of bryophytes.  The ground was covered w i t h an abundant  The distance between nest a and b was 35 m.  -114-  P l o t I I was l o c a t e d i n the f o r e s t adjacent t o the Thacker E c o l o g i c a l Reserve.  The f o r e s t had a w e l l s t r a t i f i e d crown l a y e r ; weak moss and herb  l a y e r s were present, but there was no shrub l a y e r .  The only nest which was  found here was placed 3-70 m. high i n the crown of a young D o u g l a s - f i r ( i n part 4 of the crpwn). Comparison of l i g h t i n t e n s i t i e s of Varied thrush nests. Table 14 Nests  Measured light, i n lx.  Mean l i g h t . intensity  Amplitudes.in jo of l i g h t i n open  Light intensity of nests yo of nest a  A  163.56  42.99  62.22  100.0  B  149.79  39-76  60.29  91-5  c  147.90  40.50  57.03  90.5  The lower l i g h t energy of nest b i s not f u l l y u t i l i z e d f o r an abundant moss l a y e r i s present on the ground and therefore i t s microclimate may be considerably colder than t h a t of nest a. The nest c a l s o has a colder microc l i m a t i c c o n d i t i o n as i n d i c a t e d by i t s low i l l u m i n a t i o n compared with.the b a s i c nest (Fig.15). The second part of t h i s study.intends t o e x p l a i n what e c o l o g i c a l d i f ferences e x i s t between the h a b i t a t of the Varied thrush and those of the Robin and the Swainson's thrush. The i n v e s t i g a t i o n of two summers i n d i c a t e d that the p r e f e r r e d h a b i t a t of the Varied thrush i s the dense dark f o r e s t .  I t was a l s o observed t h a t . i t f e d  on the open ground where the s o i l had a high humus content and a good crumbly s t r u c t u r e , and one my surmize that t h i s s o i l c h a r a c t e r i s t i c provided optimal conditions f o r i t s i n v e r t e b r a t e food on our area.  Where the ground i s covered  by dense l a y e r s of brush, herb, or mosses, these keep the Varied.thrush away, since they hinder i t s ground feeding.  The Varied thrush i n h a b i t s the darkest  -115parts of the f o r e s t among the three thrush species.  The l i g h t i n t e n s i t y  at i t s n e s t . i s approaching, the l i g h t i n t e n s i t y of the Winter wrenl  This  low  l i g h t range, requirement l i m i t s the l o c a l d i s t r i b u t i o n of the Varied t h r u s h . i n the Eurhynchium-Mahonia f o r e s t because t h i s community i s mainly c o n t r o l l e d by edaphic f a c t o r s (seepage), hence the. l e s s i l l u m i n a t e d places become covered by an abundant l a y e r of mosses which i s i n v i t i n g as feeding ground f o r the Varied thrush.  The spots where the ground i s s u i t a b l e f o r feeding obtain  between 40 to 50 per cent r e l a t i v e l i g h t . i n t e n s i t y . are a l s o optimal f o r the.Robin.  These places,.however,  Because the Varied t h r u s h . i s an e a r l y nester  i t i s able to nest in.the areas around the lower l i m i t .of the Robin's l i g h t range, before the Robin e s t a b l i s h e s i t s t e r r i t o r y .  By the time the Robin  begins to b u i l d i t s nest the Varied thrush eggs are already hatched, or at l e a s t h e a v i l y incubated. young on May May 2, 1961.  3, 19&1,  For instance, the Varied t h r u s h . i n nest a hatched i t s  while the Robin of nest a began to b u i l d . i t s ' nest on  The Robin may.be a . t e r r i t o r i a l competitor, considering both  nest s i t e and feeding area,'for i n an observed case i t d i d not t o l e r a t e the v a r i e d thrush as we have discussed e a r l i e r on page 104. I t seems that the high population of Robins the s u i t a b l e nesting h a b i t a t f o r the Varied thrush i s guaranteed .'only by i t s e a r l i e r nesting i n the study area.  The b i r d of nest b was a l a t e nester when i t began to b u i l d i t s  nest on May 11 (the young i n nest a were hatched May  5)'  By t h i s time a l l  s u i t a b l e t e r r i t o r i e s were already occupied by Robins and t h i s p a i r seemed to have been forced out to an area covered by a heavy moss l a y e r .  The  Varied  thrush i s i n no competition with Swainson's thrush, because t h e i r h a b i t a t demands are so d i f f e r e n t . Varied thrushes•indicated the most r e s t r i c t e d nesting h a b i t a t among the thrush species.  Even w i t h i n t h i s h a b i t a t the.-nests were placed very uniformly  -116-  .  a l l s i x nests studied having been i n part k of the crown of young Douglas-fir trees.' The nest height v a r i e d between 2.7 and 3>8 ' m  This uniform l o c a t i o n  of the nests i s i n c o r r e l a t i o n with t h e i r s i m i l a r l y uniform s t r u c t u r e . A l l were moss nests interwoven with small s t i c k s .  I t seems that the branches of  a dense young crown give s t a b i l i t y to the nest, moreover the dense crown protects i t against the mechanical e f f e c t s of the weather.  These conditions  might be found s i g n i f i c a n t with more observations i n the f u t u r e . The Varied thrush was found only i n the Eurhynchium-Mahonia ecosystem type.  While the f o l l o w i n g conclusions were based on a small evidence, there-  fore we have t o take them with caution-.  The f a c t o r s which excluded-this b i r d  from the other communities of the study area.might be the f o l l o w i n g : 1.  Conditions of the ground.  communities.is  The ground surface of a l l the other  covered with dense l a y e r s of herbs and shrubs, thus they are  not s u i t a b l e f o r the feeding of the Varied thrush. 2.  Lack of the p r o t e c t i v e e f f e c t of the stands.  The few Varied thrush  nests studied were a large moss structure without strong b i n d i n g m a t e r i a l (mud). They were t i e d only w i t h small twigs, therefore they could not r e s i s t the strong mechanical forces of the wind p r e v a i l i n g i n the other more open communities. CONCLUSION Six Varied thrush nests were found i n the mature stands of EurhynchiumMahonia ecosystem type during two summers and no Varied .thrush were observed i n other communities of the study area. among a l l the other thrushes.  I t required the densest f o r e s t stand  I t i n d i c a t e d a very r e s t r i c t e d nesting h a b i t a t ,  p l a c i n g i t s nest on the dense crown of small D o u g l a s - f i r around the relative light intensity. a cool microclimate range.  kQPJo of  Here the stand p r o t e c t i o n e f f e c t . i s high expressing This species seems to compensate f o r the low  Light Curves of Ixoreus naevious Nests in Eurhvnchium - Mohonia Forest Type on UBC Forest near Hope BC.  -117temperature by the high i n s u l a t i n g capacity of the t h i c k moss w a l l of i t s nest as we a l s o have seen i n the case of the.Winter wren (p. 78). One can t h i n k a . r e l a t i o n s h i p may e x i s t between the r e s t r i c t e d n e s t i n g h a b i t a t and the large moss nest of the v a r i e d thrush.  Because the v a r i e d  thrush does not use mud.in the nest, the.large mass of the moss i s steadied by small twigs; t h e r e f o r e , the dense crown of the nest bearing young tree and the high p r o t e c t i v e e f f e c t of the nest s i t e seem t o be necessary.  The  loose, poorly s t r a t i f i e d stands of the other communities seem not t o provide the even c o n d i t i o n and the necessary p r o t e c t i o n f o r the nest of the Varied thrush.. SWAINSON'S THRUSH (Hylocichla ustalata Nuttail) According t o observations made during the summers of i960 and 1961, Swainson's thrush was found only i n the hydrophytic communities, EurhynchiumMahonia, . Polystichum and Thuja-Lysichitum-Oenanthe,  the e c o l o g i c a l circum-  stances of which are near t o each other. Swainson's t h r u s h , i s not an e v e n l y . d i s t r i b u t e d b i r d w i t h i n these communit i e s , but i t i s concentrated at places where the stands are w e l l s t r a t i f i e d with dense understory.  Swainson's thrush, i s one bf the b i r d s which require  the most dense h a b i t a t . The e c o l o g i c a l conditions of seven nests of the nine found were i n v e s t i gated on f i v e sample p l o t s which are separated from one another by a distance of 0.5 t o 3.0 m i l e s . Ecosystem types  No. of t e r r i t o r i e s found  No. of nests found studied  Polystichum  lk  h  3  Ecotone of Thuja-LysichitumOenanthe and Polystichum  ,2  2  1  Eurhynchium-Mahonia  10  3  -3  -118-  The purpose was t o answer the f o l l o w i n g questions: 1.  Which.ecosystem t y p e . i s the optimum f o r Swainson's thrush?  2.  What are the e c o l o g i c a l d i f f e r e n c e s between the h a b i t a t s of the  Swainson's thrush and Robin, Varied thrush? 3.  How does the n e s t i n g h a b i t a t of the Swainson's thrush vary i n the  d i f f e r e n t ecosystem types. A). •Polystichum ecosystem type The deciduous stand.of t h i s ecosystem type was considered t o be the optimal type f o r Swainson's thrush because i t s nest has the most simple structure i n t h i s h a b i t a t compared with.the nests i n the other ecosystem types. In the mature stand, Swainson's thrush occupies the most dense part of t h i s community where a w e l l s t r a t i f i e d crown l a y e r and an abundant l a y e r of brushes are present.  In the young stand of t h i s community,, t h i s thrush occurs  i n the v a l l e y , along the streamlets where the young trees are r e l a t i v e l y densest and l a r g e s t .  Elevan t e r r i t o r i e s and two nests were found, i n the  mature stand of t h i s community and three t e r r i t o r i e s and two nests i n the young stand. The i n v e s t i g a t i o n covered two p l o t s which are separated from each other by a distance of 0.8 m i l e s . P l o t I.  The only nest, nest a, was•investigated here which was placed  2.1 m. high above the ground on a red a l d e r trunk.  The nest was shaded by  a w e l l s t r a t i f i e d l a y e r of red a l d e r , broadleaf maple and trembling aspen group.  This nest i s considered as the b a s i c nest, because i t s s t r u c t u r e i s  the most simple, and the l i g h t energies of the nests are expressed as percentages of the l i g h t . i n t e n s i t i e s measured.in t h i s nest, which are taken as  100.  •"• - 1 1 9 -  Comparison of l i g h t i n t e n s i t i e s of Swainson's thrush nests. Nests  Measured ' light i n lx.  a b c  181.51 198.37 193-28 142.58 i50.ll 168.48  a  e f g  -  Mean l i g h t intensity  Table 15  Amplitudes i n $> of l i g h t . i n open  i 57-68 65.85 62.88 57-28  49.41 53.36 52.44 40.12 42.12  63.35 61.17 51.20  47-93  -  Light i n t e n s i t i e s of nests % of nest a 100.00 109.29 106.48 • 78.55 82.70 92.82 93.50 *  The measurements .were c a r r i e d out between J u l y 15 and August 5> 1 9 6 l *The comparison has been done by the amplitudes of the l i g h t curves, because i t s l i g h t measurement.was c a r r i e d out shorter p e r i o d as i n nest a. P l o t I I . This p l o t was l o c a t e d .in one of the young Polystichum stands of the Yale Indian Reservation.  Two nests were i n v e s t i g a t e d here.  Nest b was found 1 . 8 m. high above the ground.in the dense crown of a small broadleaf maple. Nest c was found 1 . 0 m. high above the ground i n a.branch.of the young ;broadleaf maple , 1 . 1 m. from the trunk.  The ground was f r e e from vegetation . 1  under both nests. The higher l i g h t . i n t e n s i t i e s of nest b and £ (Table 1 5 , F i g . 1 6 ) could not.increase the temperature, because the nests are surrounded by dense crowns o f the young deciduous B).  trees.  Ecotone of "Thuja-Lysichitum-Oenanthe  and.Polystichum ecosystem types  P l o t I I I , was l o c a t e d i n the adjacent p r i v a t e f o r e s t where two nests were found, one of them was•investigated more thoroughly. Nest d was found 0 . 9 ni. high above the ground,in a small hemlock which was shaded by a dense maple group.  The ground i s covered w i t h an abundant  -120l a y e r of mosses. Nest d was found i n the most dense part of the f o r e s t accommodating a t o t a l of 9 nests (Table 15).  Because the loose stands of the ecotone  cannot  guarantee s a t i s f a c t o r y p r o t e c t i o n , the b i r d p l a c e d . i t s nest underneath a dense maple which provided the r e q u i r e d p r o t e c t i o n f o r the nest. C).  Eurhynchium-Mahonia ecosystem type  In t h i s community of the study area ten t e r r i t o r i e s and two nests were found.  Moreover, one nest was found on the bank of the Fraser R i v e r . A l l  the three nests were i n v e s t i g a t e d i n the two p l o t s which were separated by a distance of 3-0 miles." P l o t IV - two nests were i n v e s t i g a t e d here. Nest e was placed 1.0 m. high above the ground on a cedar branch .and 1.3.m. from .the trunk.  The ground was f r e e from any k i n d of vegetation.  Sloping was .15°• Nest f was found.2.3.m. high above the ground on a grand f i r branch, 1.9 m. from.the trunk.  The ground was covered w i t h weak layers of herbs, and  mosses. P l o t V.  This p l o t was l o c a t e d on the bank of the Fraser R i v e r .  was i n v e s t i g a t e d here.  Nest g  I t was found.in a f o r e s t opening 0.6 m. above the  ground on a.thimbleberry bush. Comparison of the l i g h t . i n t e n s i t y of nest g with nest a by the amplitudes of t h e i r l i g h t curves. The low l i g h t ranges of the nests i n the ecosystem type i n d i c a t e that these nests are l o c a t e d i n a.lower temperature range than that of nest a (Table 15). The second part, of t h i s study intended to e l u c i d a t e the r e l a t i o n s h i p between the f o r e s t types and the nest b u i l d i n g techniques of the Swainson's  -121-  thrush. When the nest b u i l d i n g techniques of.Swainson's thrush and the ecol o g i c a l conditions of t h e i r h a b i t a t were studied i t was found that a close r e l a t i o n s h i p e x i s t s between them.  I f the mechanical e f f e c t s of the nest  surroundings increase the s t a b i l i t y of the nest a l s o increases. The structure of the Swainson's thrush nest d i f f e r s from that of the r o b i n nest.  The  s t a b i l i t y of the n e s t . i s given by a very strong, 5-7 ni. t h i c k , middle layer of i t s w a l l which i s b u i l t from decaying wood.  This wood, i s broken i n t o small  pieces and stuck i n t o a strong i n s i d e w a l l of the nest which.can r e s i s t the impact of water,.wind e t c . does not contain mud,  In the normal s i t u a t i o n , Swainson's thrush nest  a l l i t s s t a b i l i t y i s given by t h i s strong nest w a l l .  M a t e r i a l of Swainson's thrush nests i n $ of.nest weight. Nests  a  Table l 6 b  d  e  Nest weight i n gr.  44-7  49-0  51-5  46.5  Mean l i g h t . i n t e n s i t y  49.41  53-36  40.12  42.12  Deciduous tree l e a f Herb Moss Lichen Twigs Decaying wood Soil Phloem Root  34-8 I9.6 2.2 6.8 36.4 -  24.2 4.1 36.7 10.2 18.4 6.1  3.9 23.1 34.0 35.0 3.9  2.2  '  -  34.4 2.1 9.7 28.0 I9.3 4.3  In the mature stand of the Polystichum f o r e s t , nest a was w e l l protected against the impact of the environment by i t s dense surrounding, t h e r e f o r e , there are no s p e c i a l m a t e r i a l s present which serve the s t a b i l i t y and i n s u l a t i o n capacity of the nest.  The s t a b i l i t y of the nest was served s o l e l y by a r i g i d  -122-  w a l l b u i l t ocf decaying wood. . In the immature stand of the Polystichum type, nest b was placed.in the upper t h i r d part of the crown of a young maple t r e e , therefore i t was exposed t o strong mechanical e f f e c t s .  The s t a b i l i t y of the nest, i s given  by the high percentage of phloem, s o i l and root,.but there are no twigs present, because.the branches of the f o r k on which i t was b u i l t already provided good s t a b i l i t y against mechanical f o r c e s . In the Thuja-Lysichitum-Oenanthe  type, nest d received good p r o t e c t i o n  by i t s immediate surroundings, t h e r e f o r e , there are no high s t a b i l i t y m a t e r i a l s i n the nest.  The high,moss content provided a good p r o t e c t i o n against the  c o l d environment. In the Eurhynchium-Mahonia type the w a l l of nest e i s the l i g h t e s t among the mentioned nests- i n d i c a t i n g that the mechanical stresses are not too strong i n the nest surroundings.  For the coldest environment the high percentage of  moss i s required. What are the e c o l o g i c a l d i f f e r e n c e s between the h a b i t a t of Swainson's thrush, of the Robin and of the Varied thrush? The observations i n d i c a t e d that the Swainson's thrush p r e f e r s s i t u a t i o n s w i t h i n the Eurhynchium-Mahonia community where the light, range i s between 40 t o  5O70  of the l i g h t . i n the open, i . e . equal t o the l i g h t ranges p r e f e r r e d  by the r o b i n and v a r i e d thrush.  Nevertheless, there are remarkable d i f f e r e n c e s  between t h e i r h a b i t a t demands. Within t h i s l i g h t range the r o b i n and v a r i e d ' thrush.use s i t e s where the s o i l surface i s f r e e or weakly covered by herbs or moss l a y e r s , , w h i l e the Swainson's thrush has no close connection w i t h the s o i l surface, b e c a u s e . i t , i s not an e x c l u s i v e ground feeder and does a l l the a c t i v i t i e s on those places where a dense w e l l developed understory i s present.  Light Curves of Hylocichla ustulata Nests on UBC Forest near Hope B.C.  -123-  CONCLUSION Twenty-six t e r r i t o r i e s and nine nests were found,in the stands of hydrophitic communities of the study area.  Seven nests were s t u d i e d , i n more  d e t a i l and. it', was'found .that the l i g h t range of these nests was between 4 0 . 1 2 and 5 3 - 3 6 per cent of the l i g h t i n the open.  The h a b i t a t demands of the Swainson's thrush d i f f e r from those of the r o b i n and the v a r i e d thrush.  The Swainson's t h r u s h , i n h a b i t s s i t e s covered  with a dense, w e l l developed understory. SOLITARY VIREO (Vireo s o l i t a r i u s Wilson) According t o observations made i n the summer of i 9 6 0 and I 9 6 I the S o l i t a r y v i r e o i n d i c a t e s strong f i d e l i t y t o the community of EurhynchiumMahonia ecosystem type.  I t was not observed outside t h i s community during  the n e s t i n g season. Apparently the population of S o l i t a r y v i r e o s i s evenly d i s t r i b u t e d i n the Eurhynchium-Mahonia ecosystem type.  Within t h i s community, the i n v e s t i -  gation covered seven sample p l o t s which are separated from each other by a distance of 0 . 3 t o 1 . 5 m i l e s .  Nine of the s i x t e e n S o l i t a r y v i r e o nests were  s t u d i e d . i n d e t a i l , . i n c l u d i n g l i g h t measurement.  The remaining seven nests  were studied f o r t h e i r p o s i t i o n only. The purpose was t o answer the f o l l o w i n g questions: 1.  What i s the reason f o r the S o l i t a r y v i r e o occurring o n l y , i n the  Eurhynchium-Mahonia ecosystem type i n the study area? 2.  What e f f e c t do the e c o l o g i c a l f a c t o r s of the Eurhynchium-Mahonia  community have on the nest b u i l d i n g technique of the S o l i t a r y • v i r e o ? 3.  How do the d i f f e r e n t successional stages of the Eurhynchium-Mahonia  ecosystem type i n f l u e n c e the development of the S o l i t a r y v i r e o population?  -124h.  What are those f a c t o r s which exclude the S o l i t a r y v i r e o from the  communities of other ecosystem types of the study area? The e c o l o g i c a l i n v e s t i g a t i o n of the S o l i t a r y v i r e o was done i n two parts:  ( l ) The nest s i t e s were examined f o r the v a r i a t i o n of the l i g h t i n -  t e n s i t y (see F i g . 17)' (2) I n v e s t i g a t i o n of nests and the c o n s i d e r a t i o n of the e c o l o g i c a l e f f e c t s on nest, nest m a t e r i a l s and nest "building techniques. Sample p l o t I . Three of the f i v e nests were i n v e s t i g a t e d here. Nest a was found 1.8 m. high above the ground, i n part 5 of "the crown of a vine maple.  The d e n s i t y of the crown l a y e r was about 50$. There was a  w e l l developed .bush l a y e r and the ground was covered w i t h poorly developed layers of herbs and mosses.  Sloping was 15°.  The nest was considered•as  a .basic nest,.because i t shows the most simple structure ( F i g . 18), and the l i g h t energies of each nest are expressed as percentages of the l i g h t i n t e n s i t i e s measured i n t h i s nest, which were taken as 100 (see Table 17). Nest b was located 5«4 m. high above the ground i n part 5, of the crown i n a dogwood.  The crown of the nest holding tree was closed on four sides.  The crown l a y e r was w e l l s t r a t i f i e d , but the herbs and moss layers were poorly developed. Nest c was found 10 m. high above the ground i n p a r t 5 of the crown of a broadleaf maple. sides.  The crown of the nest holding tree was closed only two  There was no bush l a y e r .  A weak herb l a y e r and an abundant moss  l a y e r were present. The remaining two nests of t h i s p l o t i n which no r e g u l a r l i g h t curves were obtained, are used only f o r comparison and t h e i r measured data though not enough f o r drawing a graph, were two t o three per cent higher than those of nest a with which they were measured at nearly the same time.  Figure 19•  Location of nest i  XVII  Figure 20.  Four sides of nest i  Nest f F i g u r e 21.  Nest h  The s i t u a t i o n o f S o l i t a r y v i r e o n e s t s . Nest f p l a c e d i n a dense "bush f o r a weak crown l a y e r of i t s s i t e . Nest h p l a c e d on a s m a l l t r e e , q u i t e open, under t h e w e l l s t r a t i f i e d crown l a y e r .  XIX  % of nest material  silk 1 — moss and lichen  70-,  ———-  short phloem  —  long phloem  —  large surface material  50  60  Mean light intensity % Figure 22.  D i s t r i b u t i o n of nest material i n S o l i t a r y vireo nests  -125-  Comparison of l i g h t i n t e n s i t i e s of S o l i t a r y v i r e o nests Table 17 Nests  Measured light in l x .  a b c d . e f g h i  Mean l i g h t intensity 50.06  174.36  47.34 50.92 56.56 .57.49 52.17 .54.07 40.44  197.63 147.96 243.87  Light intensities of nests fo of nest a  i  I83.29 185.52 .207.20 207.76 I9O.56  Amplitudes.-,in jo of l i g h t i n open 70.96 58.90  100.0 95-2 101.1 112.8  64.24 68.49 73.82  103.8  78.35 68.27 55-09 81.20  67.IO  .  II3.I 107.7 80.7 130.2  The measurements were c a r r i e d out between J u l y 12 and August 1,  1961.  A l l the measured nests were l o c a t e d near the center of p l o t . I .  There-  f o r e , the obtained r e s u l t s show the c l e a r e c o l o g i c a l circumstances of the S o l i t a r y v i r e o nests i n t h i s stand.  One can see that there are only i n -  s i g n i f i c a n t d i f f e r e n c e s between t h e i r l i g h t data; nevertheless, there are remarkable d i f f e r e n c e s . i n the p o s i t i o n of the nests above the ground. (This s i t u a t i o n was already mentioned.in the case of Robin nests, see p. 9 0 ) .  The  S o l i t a r y v i r e o of nest a p l a c e d . i t s nest i n the 5 0 . 0 6 $ l i g h t range which was given around the 1 . 8 m. height above the ground, because the crown canopy i s r e l a t i v e l y open.  The b i r d of nest c placed .its nest 10.D  m. high above  the ground; i t could obtain nearly the same l i g h t range (50.9270) i n that p o s i t i o n only (the measurement was c a r r i e d out, i n the n e s t ) . Regarding the e c o l o g i c a l c o n d i t i o n s , p l o t I i s considered as the b a s i c h a b i t a t of the S o l i t a r y vireo,.and one of the aims of t h i s study i s t o e s t a b l i s h the f a c t o r s which exclude the S o l i t a r y v i r e o from the community of the other f o r e s t t y p e s . i n the study area.  F o r t u n a t e l y , nests were found near ;  the ecotone of Eurhynchium-Mahonia and the four most important ecosystem  -126-  types.  The nests were subject t o conditions approaching those of the  Eurhynchium-Mahonia community.  Since.the nest of a .bird must always be  balanced against the,impact of i t s surroundings i t was.thought that the f a c t o r s which excluded.the S o l i t a r y v i r e o from other ecosystem types might be revealed by the i n v e s t i g a t i o n of the environment of the nest and the .nest b u i l d i n g technique of the b i r d at these l o c a t i o n s . P l o t . I I was located on the ecotone of Eurhynchium-Mahonia and ThujaLy s i c h i turn-Oenanthe ecosystem types. The only nest i n v e s t i g a t e d f o r l i g h t . i n t e s n s i t y (nest d) was found 2.7 high above the ground, i n part 5 of the crown of a broadleaf maple.  m.  The  o ground.is covered w i t h abundant bushes and herbs.  Sloping i s 30 •  Here, the l i g h t energy, which was absorbed by the ground surface (Table 17),. i s lower than the measured amount because of the sloping.  Moreover,, i t  can be surmised that a . c e r t a i n part of i t i s l o s t as heat f o r evapot r a n s p i r a t i o n , , therefore nest d probably d i d not u t i l i z e more l i g h t energy than nest a. This v i r e o has never been observed outside the Eurhynchium-Mahonia ecosystem type of the ecotone area and t h i s i n d i c a t e s that there, i s no r e l a t i o n s h i p between the S o l i t a r y v i r e o and the plant associations (cottonwood, spiraea, w i l l o w and a l d e r ) that were on the border of i t s t e r r i t o r y . P l o t I I I was l o c a t e d . i n the ecotone of Eurhynchium-Mahonia and Gaultheria Mahonia ecosystem types. Nest e was found 3-0 m. high above the ground,. i n the; p a r t 5 of the crown of a broadleaf maple.  The nest was located over the wet road which gets i t s  water supply from the roadcut of the steep slope ( 2 0 ° ) .  The ground i s covered  w i t h a heavy l a y e r of herbs, therefore i t i s acceptable that a .certain part of i t s l i g h t energy (see Table 17)  i s l o s t as heat by evapo-transpiration.  -127-  The north part of t h i s p l o t i s a logged area, belonging to the GaultheriaMahonia f o r e s t type.  The stand of t h i s part was removed i n 1951-  logging a few D o u g l a s - f i r trees were l e f t standing. dense layers of shrub and herbs.  A f t e r the  The ground i s covered by  S o l i t a r y v i r e o s do not v i s i t t h i s part which  i n d i c a t e s that there was no r e l a t i o n s h i p between t h i s v i r e o and the plant a s s o c i a t i o n of Gaultheria-Mahonia ( D o u g l a s - f i r , Rubus p a r v i f l o r u s , e t c . ) . Sample plot. IV.  This p l o t i s l o c a t e d near the ecotone of Eurhynchium-  Mahonia and Gaultheria-Cladonia-Rhacomitrium ecosystem types. Nest f was found 1.2 m. high above the ground i n part 5 of the crown of a dogwood.  The crown l a y e r of the mature stand.is absent from that immediately  surrounding the nest, i n s t e a d i t was surrounded by a .dense, mixed young stand of b i r c h , maple, dogwood and h a z e l . Here t h i s nest received nearly the same i l l u m i n a t i o n as nest a (see Table 17) which i n d i c a t e s that the S o l i t a r y v i r e o possesses a-highly s e l e c t i v e nest p l a c i n g method.  Because the mature crown l a y e r i s l a c k i n g the b i r d placed  i t s nest 1.2 m. above the ground.in a dense l a y e r of the 4.5 m. high young stand, so that the nest here had approximately the same microclimate range as nest a. P l o t V i s l o c a t e d near the ecotone of EurhynchiumQMahonia- and Polystichum ecosystem types. Nest g was found 1.5 m. above the ground i n part 5 of the crown of a broadleaf maple bush.  Sloping was 1 5 ° and the ground was covered by a.well  developed.layer of herbs. The s i t u a t i o n £f nest g i s s i m i l a r t o that of nest f.  This p a r t i c u l a r  nest p o s i t i o n i s necessary, since the poorly developed l a y e r of the crown could not guarantee the s u i t a b l e l i g h t range f o r the nest.  The 7-7 per cent  -128-  l i g h t surplus does not r a i s e the temperature of the surroundings of the nest because a w e l l developed l a y e r of herbs i s present. On the b a s i s of the nests i n v e s t i g a t e d . i n p l o t s I to V . i t became p l a u s i b l e that the S o l i t a r y v i r e o can only f i t i n t o the community of Eurhynchium-Mahonia ecosystem type on the area.  Therefore the e c o l o g i c a l  amplitude of the nest of the species was studied on two sample p l o t s ( p l o t s VI and VII) w i t h i n t h i s community. Sample p l o t VI.  This p l o t . i s located w i t h i n the Eurhynchium-Mahonia  ecosystem type,.hence the measured data show the c l e a r e f f e c t of t h i s type on the nest. Nest h was found .1.8 m. above the ground i n part:.6 of the crown of a broadleaf maple.  The ground.is covered by an abundant l a y e r of moss.  The  slope i s 38°. I t must be emphasized t h a t the measured .light i n t e n s i t y (Table 17) i s not f u l l y u t i l i z e d . b y the ground surface due t o the high degree of sloping and the heavy l a y e r of bryophytes. This nest i s considered as the lowest l i m i t of the range of the adaptation of the S o l i t a r y v i r e o among the nests studied, because (l.) t h i s nest was found.in the coldest part of the study area (2) the nest s i t e and c o n s t r u c t i o n show a high degree of adaptation on the c o l d l o c a l climate (see p. 135)  (3) a l l four eggs have hatched,, but one young d i e d at the age of  four days (June 26) and another on the s i x t h day (June 2 8 ) .  I t has been  suggested that t h e i r death was caused by the low temperature of rainy days. P l o t VTII i s located on the logged area of Eurhynchium-Mahonia type. Nest. i was found 3'3.ni. above the ground i n part 5 of the crown of a dogwood ( i t was located at a distance of 4 . 3 m. from the trunk, and 0.3 m. from the end.of the branch, see F i g . 18,  19,.20).  The ground was covered w i t h  -129a heavy l a y e r of herbs. A c e r t a i n part of the l i g h t surplus of t h i s nest (Table 17)  i s . l o s t as  heat f o r the evapo-transpiration, more i s r e f l e c t e d from the surface of the dense vegetation l a y e r , but a considerable part of i t r a i s e d the temperature of the nest surroundings; t h i s heat surplus was p a r t l y eliminated by the nest p l a c i n g .method of the b i r d , p a r t l y by the immediate surroundings  of the nest.  A s i m i l a r s i t u a t i o n was found i n the case of the Hummingbird nests f o r which an explanation i s given on p.  63•  This nest i s considered as the upper l i m i t of the range of adaptation of the S o l i t a r y v i r e o , because ( l ) i t was found among the most extreme cond i t i o n s of the Eurhynchium-Mahonia ecosystem type (logged area), (2) the nest s i t u a t i o n and.its structure show a very high.degree of adaptation to the extreme climate. The second part of t h i s study intends to e x p l a i n how the e c o l o g i c a l f a c t o r s p r e v a i l i n g • i n the Eurhynchium-Mahonia ecosystem type a f f e c t the nest b u i l d i n g technique .of the S o l i t a r y v i r e o . The i n v e s t i g a t i o n was based on the assumption that ( l ) the nest must be i n e q u i l i b r i u m w i t h the mechanical and.climatic e f f e c t s of i t s surrounding. Therefore, i n the nest which receives s u f f i c i e n t p r o t e c t i o n from.its surroundings, the s t a b i l i t y of i t s m a t e r i a l may be l e s s than that of the nest which i s not w e l l protected by i t s surroundings. the surroundings  (2) Consequently i f the impact of  increases the high s t a b i l i t y materials of the nest.would  .increase i n d i r e c t proportion. I t seems that the S o l i t a r y v i r e o nest i s strongly b u i l t because i t ; i s a small compact hanging nest, exposed to a l l the mechanical e f f e c t s which are caused by the b i r d s and by the motion i n v o l v e d ..in holding the branches f u r t h e r , a i r currents, r a i n , e t c . , a l l df which act on the nest materials as forces ( p u l l i n g , . t e n s i o n , t o r s i o n , compression, shearing and bending f o r c e s . ) .  -130-  In most cases, a l l . f o r c e s may act together as a compound f o r c e .  In a small  nest, such as the S o l i t a r y v i r e o nest,, almost.each piece of m a t e r i a l has a d e f i n i t e r o l e to play i n the service of the s t a b i l i t y and e l a s t i c i t y of the nest. When the S o l i t a r y v i r e o nests were s t u d i e d . i n d e t a i l i t was found that there i s a.close connection between the nest s t r u c t u r e , i t s p o s i t i o n and.its l i g h t range.  In those places where the l i g h t range i s high, the amount of  those m a t e r i a l s which serve the s t a b i l i t y of the.nest  against.mechanical  e f f e c t s are a l s o increased. I t was already mentioned on p.59  that the l i g h t range i n d i r e c t l y , i n -  d i c a t e d the magnitude of the mechanical e f f e c t s of the ecoclimate of a given place a l s o .  Low l i g h t range i n d i c a t e s that the nest s i t e i s w e l l protected  against the e f f e c t s of the environment by i t s dense stand.  With.increasing  l i g h t range the density of the f o r e s t stand w i l l decrease i n d i r e c t proportion.  At the higher l i g h t range the stand density i s low and the wind  can penetrate i n t o the stand e i t h e r at the edge or across the crown s t r a t a , .and attack the nest d i r e c t l y b u t . i t s i n d i r e c t e f f e c t s , . s u c h as the motion of nest holding branches i n opposite d i r e c t i o n s , cause a high degree of s t r e s s . Therefore, a l l e f f e c t s as a .compound f o r c e act on the nest m a t e r i a l s simultaneously, , and one may  consider that the s t a b i l i t y , s i z e , q u a l i t y and quantity  of nest.materials were p a r t i c u l a r l y important.in the case of such a . S o l i t a r y v i r e o nest. Nine nests were i n v e s t i g a t e d i n d e t a i l and the r e l a t i o n s h i p was e s t a b l i s h e d between the.surroundings  and the nest s t r u c t u r e and p o s i t i o n .  The  nest m a t e r i a l s were dryed out at 65°C during 120 hour periods i n the drying chamber.  The data are given i n Table 18, and g r a p h i c a l l y on F i g . 22.  -131-  The nest materials could be d i v i d e d . i n t o 3 groups according to t h e i r properties. A). 1.  Strengthening m a t e r i a l s S i l k , served t o b i n d the nest materials of the S o l i t a r y v i r e o nest.  The amount of the s i l k m a t e r i a l which creates the s t a b i l i t y of the nest i s d i s t r i b u t e d i n such,a way that the maximum force r e s i s t a n c e could be obtained. As the r e s i s t a n c e i s d i r e c t l y p r o p o r t i o n a l t o the moment of i n e r t i a of the cross s e c t i o n , i t i s i n t e r e s t i n g t o note that the s i l k d i s t r i b u t i o n i s such— that the maximum amount of m a t e r i a l i s i n the outer t h i r d of the crosss e c t i o n , much l e s s i s i n the middle p a r t , and the inner part has no s i l k at all.  In t h i s way the moment of i n e r t i a , which i s i n f o u r t h power r e l a t i o n -  ship w i t h the r a d i u s , i s . increased t o the maximum p o s s i b l e . The amount of s i l k m a t e r i a l shows a tendency to increase i n d i r e c t r a t i o With, the increase of the moss content  .and of the l i g h t range.  At the high-  l i g h t . i n t e n s i t i e s the amount of s i l k m a t e r i a l may r a i s e up t o 11 or,more per cent of nest weight i n dry stage.. 2.  Moss and l i c h e n m a t e r i a l s ; t h e i r curve ( F i g . 22) i s s i n k i n g from the  l i g h t range of kO per cent>, i t s lowest value i s around 50 per cent of l i g h t , and i t shows a r a i s i n g tendency toward the high l i g h t range.  This may be.  explained on the b a s i s of the ecology of the nest surroundings.  In the low-  l i g h t range the i n s u l a t i n g capacity of moss.is necessary f o r the nest.  At  about 50 per cent of l i g h t the h i g h l y s t r a t i f i e d f o r e s t stand gives a w e l l compensated microclimate and p r o t e c t i o n f o r the nest, hence the,presence of moss i s not necessary here'.  In the high l i g h t range the high moss proportion  i s necessary, because of i t s l i g h t n e s s . i t does not increase the weight of the nest, but i t r a i s e s the s t a b i l i t y and e l a s t i c i t y of the nest considerably, and w i t h . i t s high water absorbing the water bearing capacity i t can protect the  -132-  other nest m a t e r i a l s against drying out. 3.  Phloem of Rubus p a r v i f l o r u s .  I t was supposed that the phloem, the  s i z e of which i s longer ( 1 0 to 32 cm.), plays a more important r o l e i n the s t a b i l i t y of nests than the shorter pieces.  Namely, strands of longer than  10 cm. may reach around the nest perimeter s e v e r a l times, while those shorter than 10 cm. do not reach around, and a l s o are generally t h i c k e r pieces.  Therefore, they are separated.in the t a b l e and on the graph.  The  maximum point of the occurrence of the shorter phloem i s between the l i g h t ranges of 50 to; 55 per cent, where the moss curve gives i t s lowest value. This i n d i c a t e d t h a t there i s not necessity of high s t a b i l i t y f o r the nest because the f o r e s t stand protects i t .  The curve of longer phloem shows.its  minumum occurrence at the low l i g h t range (57 per cent) and i t increases p a r a l l e l w i t h the l i g h t range up t o 57 per cent of l i g h t , a f t e r which i t decreases.  The f a l l of the curves of phloem.is necessary at the higher l i g h t  range because of the smaller weight of n e s t , . t h e i r s t a b i l i t y e f f e c t s being supplemented by moss and f i n e plant f i b r e here.  The explanation i s that nests  at high l i g h t range were exposed to higher wind s t r e s s and t h e i r weight balance was more important. k.  Fine p l a n t f i b r e .  The case of very f i n e plant f i b r e i s quite strange.  Three of the nine i n v e s t i g a t e d nests (b,& and.i nests; see F i g . 18 and Table 18) have s p e c i a l surroundings (the nest holding branch was touching on other branches ( b ) , or was exposed to strong winds ( d , i ) thus strong mechanical stress acted upon the nest w a l l ) , and the f i n e f i b r e i s p r e s e n t , i n these three nests only.  Therefore, i t i s considered that the r o l e of t h i s f i n e  f i b r e increased the s t a b i l i t y and e l a s t i c i t y of the nest without weight. 5.  Large surface m a t e r i a l s such as f i n e bark of b i r c h . t r e e s , paper,veins  of deciduous tree leaves and the w a l l of wasp nests are present i n a l l nests  -133i n varying q u a n t i t i e s .  Apparently, the S o l i t a r y v i r e o prefers these m a t e r i a l s ;  probably they plan an important r o l e i n the s t a b i l i t y , e l a s t i c i t y and i n s u l a t i n g capacity of the nest, assuming that they have an advantageous .property from the point of view of nest m a t e r i a l .  Their large surfaces make them easy  to t i e together, with change of the nest shape by mechanical e f f e c t s , they could s l i d e over each other e a s i l y , and a f t e r r e t u r n to t h e i r o r i g i n a l shape again w i t h no l o s s of s t a b i l i t y and e l a s t i c i t y . B) . Stress d i s t r i b u t i o n materials such as grass, f i n e branches, not serving the s t a b i l i t y of the nest.  They are l o c a t e d , i n s i d e the nest and  t h e i r r o l e i s to p i c k up the mechanical e f f e c t s which are caused.by the motion and weight of the b i r d s on the rim of the nest, and to pass over the load t o the entire, nest w a l l from i t s source of o r i g i n . C) ..  Stuffing materials.  A l l other m a t e r i a l s which are found i n the  nests do not serve the s t a b i l i t y of the nests.  Their r o l e i s not.important,  probably they are s t u f f i n g m a t e r i a l s only, because they are present i n high p o r t i o n i n those which were p l a c e d . i n the w e l l protected surroundings. A M u l t i p l e Regression A n a l y s i s has been completed f o r l i g h t range percentage as a dependent v a r i a b l e on the nest m a t e r i a l s of the S o l i t a r y vireo:  the r e s u l t s are given i n Table 1 9 . Moss  x  l  Silk x  2  Large Surface m. x  3  Phloem (2-10)  cm. x  4  (10-32)  Lichen . Fine Wood Fibre  cm. x  5  x  6  x  ?  x  8  Light range y  Mean  13-67  6.50  4.88  33.85  9-70  2.54  1.05  1-35  52.91  Standard Deviation  .18.10  3.31  4.76  18.68  7-17  4.07  1.68  2.24  7-37  Correlation coefficient  0.005  O.513  0-301  0.241  0-320  0.425  O.587 0 . 0 8 8  1.000  -133-  i n varying q u a n t i t i e s .  Apparently, the S o l i t a r y v i r e o prefers these m a t e r i a l s ;  probably they plan an important r o l e i n the s t a b i l i t y , e l a s t i c i t y and i n s u l a t i n g capacity of the nest, assuming that they have an advantageous .property from the point of view of nest m a t e r i a l . Their large surfaces make them easy to t i e together, with change of the nest shape by mechanical e f f e c t s , they could s l i d e over each other e a s i l y , and a f t e r r e t u r n t o t h e i r o r i g i n a l shape again w i t h no l o s s of s t a b i l i t y and e l a s t i c i t y . B) . Stress d i s t r i b u t i o n materials such as grass, f i n e branches, not serving the s t a b i l i t y of the nest.  They are l o c a t e d . i n s i d e the nest and  t h e i r r o l e i s t o p i c k up the mechanical e f f e c t s which are caused by the motion and weight of the b i r d s on the r i m of the nest, and t o pass over the load t o the e n t i r e nest w a l l from i t s source of o r i g i n . C) . S t u f f i n g m a t e r i a l s . A l l other m a t e r i a l s which are found i n the nests do not serve the s t a b i l i t y of the nests.  Their r o l e i s not.important,  probably they are s t u f f i n g materials only, because they are present.in high p o r t i o n i n those which were p l a c e d . i n the w e l l protected surroundings. A M u l t i p l e Regression A n a l y s i s has been completed f o r l i g h t range percentage as a dependent v a r i a b l e on the nest m a t e r i a l s of the S o l i t a r y v i r e o : the r e s u l t s are given i n Table 1 9 Moss  x  l  Silk x  2  Large Surface m. x  3  Phloem  Lichen  (2-10)  (10-32)  cm.  cm.  x  4  x  5  x  6  Fine Wood Fibre X  ?  Light range  XQ  J  .13.67  6.50  4.88  33.85  9.70  2.54  1.05  1.35  52.91  Standard Deviation  18.10  3.31  4.76  18.68  7-17  4.07  1.68  2.24  7.37  Correlation coefficient  0.005  0.513  0.301  0.241  0.320  0.425  0.587  0.088  1.00(  Mean  -134-  There i s a f a c t o r w i t h s i g n i f i c a n t c o r r e l a t i o n with the precent of light (x^); silk.  The f i n e f a b r i c of p l a n t s (x^) may become s i g n i f i c a n t  with longer s e r i e s of data. The r e g r e s s i o n equation expresses the r e l a t i o n of nest m a t e r i a l s and the l i g h t range of the nest.  The regression equation i s :  Y$ l i g h t = 5 0 . 0 4 - 2 . 2 2 1 x± - 1 2 - 3 0 7 X g - 4 - 9 5 x " 0 . 8 3 1 x ^ - 0 . 1 0 2 x - 6 . 1 5 8 3  5  X5-4.689 xy-8.899 x8  SE  E  = 0.1$  R = 0.999  Where SE i s the standard e r r o r of the estimate, R i s the m u l t i p l e correlation co-efficient. before.  The independent v a r i a b l e s were e l i m i n a t e d as  I t was shown by t h i s a n a l y s i s t h a t no f a c t o r can be e l i m i n a t e d , so  the complete equation should be used t o c a l c u l a t e "Y". Studying the relations'between the nest b u i l d i n g techniques of the b i r d and the mechanical and c l i m a t i c e f f e c t s of the nest environment a close connectibn between these w i l l be found.  T h i s . i n d i c a t e s that the b i r d  adapts..its nest b u i l d i n g behaviour t o the a c t u a l s i t u a t i o n . Nests a and c; t h e i r d i r e c t l y supported perimeter low,, i n the case of nest a i t was 3 1 - 0 per cent of the t o t a l perimeter, i n nest c i t was 2 7 - 8 per :  cent.  F i g . 18 and Table 19 show that the main m a t e r i a l of these two nests i s  the short phloem, and thosematerials which guarantee the s t a b i l i t y and e l a s t i c i t y of these nests are r e l a t i v e l y few. Since both nests were i n e q u i l i b r i u m with t h e i r surroundings, they r e c e i v e d only l i t t l e  mechanical  and c l i m a t i c e f f e c t s from them. Nest b was b u i l t i n a r a m i f i c a t i o n of branches, the angle of which i s small ( 3 3 ° ) , hence i t r e c e i v e d a high compound s t r e s s , the shear force from the branches moving i n the opposite d i r e c t i o n being p a r t i c u l a r l y high.  There-  -135fore i t s high, d i r e c t l y supported perimeter i s necessary.  The required high  e l a s t i c i t y i s guaranteed by the high proportion of paper and moss m a t e r i a l s . Nest d was l o c a t e d near the f o r e s t edge on a ground slope of 30°, exposed t o strong.wind. i t s surroundings.  I t received a high degree of compound stresses from  Therefore i t shows a high degree of s t a b i l i t y and e l a s t i c -  i t y i n d i c a t e d by the high proportion of s t a b i l i z i n g m a t e r i a l s and by having d i r e c t support of as high as.57-5$ of i t s perimeter by the  suspending  branches. Nest e.  Although the d i r e c t l y supported perimeter of t h i s n e s t . i s  low (47-37o) the necessary s t a b i l i t y and e l a s t i c i t y are guaranteed by i t s 61.570 of high s t a b i l i z i n g materials (IO.6870 of s i l k ) ; f o r the favourable degree of i t s r a m i f i c a t i o n ( 5 6 ° ) the shear strength could be low. Nests f and g_; t h e i r favourable degree of r a m i f i c a t i o n (50° and 5 5 ° ) and as a consequence, the d i r e c t l y supported perimeter guaranteestheir ."• necessary s t a b i l i t y ; the per cent of t h e i r high s t a b i l i z i n g m a t e r i a l s . i s low; i n nest f i t i s 2 4 . 3 9 per cent,, i n nest g, 3 7 - 5 8 Nest h; i t was.'located, i n the most dense f o r e s t stand among the h a b i t a t s of the 16 observed nests.  The high proportion of moss (47 per cent) i s pre-  sumably due t o the cold environment of the nest, and served as i n s u l a t i o n . Nest i was found i n the logged area.  The presence of the high proportion  of moss served not only the s t a b i l i t y and e l a s t i c i t y of the nest, but..it prot e c t e d the other nest materials against drying out by i t s high water absorbing and water bearing c a p a c i t i e s .  I f we compare the p i c t u r e s of nest a with  n e s t . i we w i l l see that n e s t . i i s h i g h l y adapted.to i t s environment by i t s s p e c i a l suspension s t r u c t u r e which expands from the c i r c u l a r rim of the nest along the supporting branches,, i n c r e a s i n g the s t r e s s r e s i s t a n c e of the nest.  The proportion of high strength m a t e r i a l i s the highest of a l l nests  -136-  s t u d i e d ( 6 7 . 6 6 $ ) and the amount of s t u f f i n g m a t e r i a l i s n e g l i g a b l y  low  (0.26$). I want t o emphasize t h a t a l l the above mentioned c o n s i d e r a t i o n s were b a s e d on the i n v e s t i g a t i o n of n i n e n e s t s o n l y . 18,  A l l these d a t a g i v e n i n Table  and the photographs o f most of them, are a l s o g i v e n ( F i g . 1 8 ) .  these  Of  course,  i n v e s t i g a t i o n s cannot g i v e .a 'general r u l e because o f the low number of  i n v e s t i g a t e d nests, but.they the study o f the e c o l o g y  can g i v e a u s e f u l b a s i c . i d e a and d i r e c t i v e f o r  of f o r e s t b i r d  nests.  I s h o u l d l i k e t o compare the d a t a of m a t e r i a l s of n e s t .a w i t h those nest, i , as the two  extremes of the  nest m a t e r i a l s  series.  Nest m a t e r i a l s o f n e s t a . i n % of " n e s t weight  Hest m a t e r i a l s o f n e s t i i n $ of n e s t weight  High s t a b i l i z i n g mat.  12.1957  67.6563  Low s t a b i l i z i n g mat.  ,67.4139  11.1786  S t r e s s d i s t r i b u t i o n mat.  13.0973  20-9073  7-2958  Stuffing materials.  But we  S o l i t a r y v i r e o has the c a p a c i t y df m o d i f y i n g t o a great extent  . . •  0.2572  can .see t h e i r d i f f e r e n c e s on the photograph ( F i g . 1 8 )  b u i l d i n g technique  of  the n e s t m a t e r i a l and  a l s o . The nest  so t h a t the n e s t s are i n e q u i l i b r i u m  w i t h the normal e f f e c t s of t h e i r a c t u a l environment. The  dimensional  M u l t i p l e Regression  d a t a o f S o l i t a r y v i r e o n e s t s were u t i l i z e d f o r a Analysis with respect to t h e i r r e l a t i o n to l i g h t  T h e • c o e f f i c i e n t s g i v e n below are o n l y approximative d a t a was was  not l a r g e enough f o r a c c u r a t e r e s u l t s . .  The  range.  ones s i n c e the s e r i e s of computer -"ALWAC I I I - E "  u s e d . i n the f o l l o w i n g m u l t i p l e r e g r e s s i o n a n a l y s i s f o r l i g h t percentage as  -137-  a dependent v a r i a b l e of the data (the data.in these c a l c u l a t i o n s are i n feet as measured.in the f i e l d ) . Nest height X  Means  l  11.22  Length of branch x,. 2  Degree of ramif.  7.889  49.86  6.889  4.600  18.833  10.33  1.431  1.100  0.866  11.990  7.3837  0.377  0.489  0.629  0.260  1.000  Standard deviation  8.26  3-49  Correlation coefficient  0.012  0.924  x  Diam. of branch before after ramification  3  0.372  x  l±  x  5  nest c i r - D i r e c t . L i g h t cumfer. support. range perim. x  6  X  Y  Y  49.489 52.9055  Data on Table 1 9 shows that the distance of the nest from', the trunk i s p o s i t i v e l y c o r r e l a t e d w i t h the length o f the nest supporting branch. The length of the nest supporting branch and, as j u s t shown the distance of the nest from the trunk show highly s i g n i f i c a n t c o r r e l a t i o n w i t h l i g h t range, and the nest circumferences are a l s o s i g n i f i c a n t . i n c o r r e l a t i o n w i t h the percentages of l i g h t . The r e g r e s s i o n equation expressing the r e l a t i o n w i t h percentage of l i g h t i s as f o l l o w s : Yio  l i g h t = - 9 . 3 6 6 - - . 3 0 3 XNh - 1.793 XB1 - 0.174 Lb - 2-952 BB = 3.916  NC - 0.263 #R  SE_, = 3 - 5 $ R = 0.99 The independent v a r i a b l e s were e l i m i n a t e d . i n t u r n s t a r t i n g with the most negative or l e a s t p o s i t i v e c o n t r i b u t i o n t o an explanation of the variance of S. The a n a l y s i s again showed that the branch length (and the distance of the nest from the trunk) are most.important  f a c t o r s give the equation of  Y* l i g h t = 37-474 = 19.560 XBL  SE. E  r = 0.92  -138The e c o l o g i c a l circumstances of the S o l i t a r y v i r e o were studied from a dense f o r e s t stand t o a logged area of the Eurhynchium-Mahonia community. This b i r d was not found n e s t i n g i n any other community of the study area. Therefore, the t h i r d part of t h i s study intends t o c l a r i f y why the S o l i t a r y v i r e o shows a strong preference f o r the Eurhynchium-Mahonia community. .In spring.the S o l i t a r y v i r e o has often been seen s i t t i n g on a branch and catching i n s e c t s l i f e a f l y c a t c h e r , but l a t e r i t was observed,in broadl e a f maples and dogwoods only, f l y i n g from t r e e t o t r e e and c o l l e c t i n g i t s regular d i e t . i n the crown.  In general the S o l i t a r y v i r e o does not v i s i t  places where maple and dogwood trees are absent.  Therefore i t may  be  suggested that the preference of broadleaf maples and dogwoods i s one ot the f a c t o r s which t i e d the S o l i t a r y v i r e o to the Eurhynchium-Mahonia community. The c a t e r p i l l a r which provides food f o r the b i r d and s i l k f o r the nest l i v e s on broadleaf maples mostly, which only occur i n large numbers.in the Eurhynchium-Mahonia community. The p r o t e c t i v e e f f e c t of the stand of t h i s community i s apparently the most.important  f a c t o r which c o n t r o l s t h e . d i s t r i b u t i o n of the S o l i t a r y v i r e o  w i t h i n our area.  A w e l l s t r a t i f i e d stand protects the nest adequately against  mechanical and c l i m a t i c e f f e c t s , while the poorly s t r a t i f i e d stands of' the other communities would l a c k these c a p a c i t i e s . Generally, the S o l i t a r y v i r e o i s the most evenly d i s t r i b u t e d b i r d .in the mature stand of Eurhynchium-Mahonia community. • T h i s . i n d i c a t e d t h a t , i t s r e quirements are completely guaranteed i n t h i s community.  I t d i d not n e s t . i n  any other f o r e s t community i n the area. Our nest question i s how wide the e c o l o g i c a l amplitude of the S o l i t a r y v i r e o i s w i t h i n the Eurhynchium-Mahonia community.  The nesting range i s from  -139-  40.44 t o 67.10 per cent of open l i g h t , ascertained from data on 9 nests. Apparently i t could not be wider,' because: 1.  I t i s considered t h a t nest h was l o c a t e d near the lowest l i m i t  of the e c o l o g i c a l range of the s o l i t a r y vireo,. because i t . i s probably that the death,of the two young i n the nest on June 26 and 28, I96I, was caused by m i c r o c l i m a t i c extremes.  Probably t h i s nest was unable t o balance the  impacts of the p h y s i c a l environment during r a i n y days. 2.  Apparently, the upper l i m i t of the l i g h t range was almost reached  .in n e s t . i , because, as we s h a l l see i t , the nest would not be able t o keep . i n e q u i l i b r i u m w i t h the mechanical e f f e c t s of i t s surroundings at a higher • range. The data of s i l k m a t e r i a l of nest e w i l l now be compared with that of nest.i.  I n nest e the s i l k m a t e r i a l i s 10.6813 per cent of a l l nest m a t e r i a l s  at the 57'49 per cent value of r e l a t i v e l i g h t , and.it. i s i n nest i 10.7577 per cent at the 67-10 per cent of r e l a t i v e l i g h t .  One sees that the l i g h t range  of nest . i i s increased by 9-6l per cent of the open l i g h t , while i t s s i l k m a t e r i a l increased O.O764 per cent only compared t o t h a t of nest e.  This i n -  d i c a t e d that the e c o l o g i c a l range of t h i s b i r d could not be much wider, because the b i n d i n g m a t e r i a l s do not increase i n d i r e c t p r o p o r t i o n with the l i g h t range.  I f the l i g h t range was wider there would be problems of surplus  heat, and the d r y i n g out of the nest m a t e r i a l s might cause the nest t o shrink and t o lose i t s s t a b i l i t y and e l a s t i c i t y . The S o l i t a r y v i r e o was found i n the Eurhynchium-Mahonia community only i n the study area, but one may suppose that t h i s v i r e o could nest i n the other communities as w e l l .  The l i g h t curve of n e s t . i i s s i m i l a r t o that  of the Gaultheria-Mahonia. community, while the l i g h t curve of nest e i s near to the l i g h t curcumstances  of the Polystichum community.  Yet the S o l i t a r y  -140-  v i r e o was 'not f o u n d i n t h e s e factors  which excluded the  ecosystem types  light  S o l i t a r y v i r e o from the  and.thus the  surface  moss m a t e r i a l shows a t e n d e n c y but the  to  increase  other  s t u d y - t h a t .the  g r a v i t y decreased  i n the  higher  o f t h e n e s t was r e d u c e d .  The  s i l k w h i c h g i v e s t h e b i n d i n g o f t h e moss d o e s n o t i n c r e a s e w i t h t h e  I want t o emphasize t h a t  Therefore,  i n the  f o r the nest  compound s t r e s s ;  i n p a r t i c u l a r the  toward openness  other ecosystem types  exceeds the range  Besides,  though f e e d i n g  surmized that  the r i g h t k i n d , might be  the nest receives  n e s t . i , by i t s  of the nest  studies  of our a r e a ,  a high the  structure,  a d a p t a b i l i t y of In the  environ-  bird.  have n o t b e e n c o n d u c t e d ,  the absence  (on which they mainly  would also  speak a g a i n s t - e.g.  their  of  feed settling  caterpillar silk  o r a b s e n t where b r o a d - l e a v e d t r e e s a r e  I n a d d i t o n , the extreme e c o c l i m a t e  this  w h i c h a r e much.more open  the mechanical impact of the  c e r t a i n nest materials  scarce  placing,  surroundings.  of a d a p t a b i l i t y of our  a c c o r d i n g t o my c a s u a l o b s e r v a t i o n s ) is  a r e more  s t r e p s may b e h i g h due t o  s u b s t a n t i a l number o f m a p l e a n d d o g w o o d t r e e s  It  effects.  indirect  suspending branches)  the upper l i m i t . o f  (or exposure)  than the Eurhynchium-Mahonia f o r e s t , ment l i k e l y  that  holding branches.  and e l a s t i c i t y represents  communities of  of the  shear  The a r g u m e n t h a s b e e n t a k e n t h a t stability  supposed  cannot r e s i s t .mechanical  than d i r e c t e f f e c t s , . i . e .  opposite motion of the nest  i t may b e  case of the h i g h l i g h t range the  o f w i n d ( w i n d c a u s e d movements  dangerous  there.  those  towards the h i g h l i g h t . i n t e n s i t y ,  i s an u p p e r p o i n t above w h i c h t h e n e s t  species  communities of  second p a r t of t h i s  and weight  light, intensity i n direct proportion.  effects  the question of  s t u d y area must he t a k e n up a g i a n .  s t a b i l i z i n g materials, of high s p e c i f i c ranges  there  Therefore,  I t was a l r e a d y p o i n t e d o u t . i n t h e  1. highly  of the  communities.  of the x e r o p h y t i c communities  of  scare. dries  -141out the nest m a t e r i a l s and consequently the nest would l o s e . i t s s t a b i l i t y and e l a s t i c i t y and could not r e s i s t the increased mechanical e f f e c t s . What r e l a t i o n s h i p i s there between the S o l i t a r y v i r e o and the other members of the b i r d population? Generally speaking, the tree species w i t h which the S o l i t a r y v i r e o always a s s o c i a t e d on the study area are more or less- evenly d i s t r i b u t e d here. Since most species are concentrated.in c e r t a i n parts of t h i s community, only t h e i r contacts with.the S o l i t a r y v i r e o are s l i g h t .  In a c e r t a i n part.of  t h i s f o r e s t the S o l i t a r y v i r e o and Robin t e r r i t o r i e s may overlap, f o r the n e s t i n g l i g h t range of both b i r d s i s the s a m e b u t they d i f f e r i n n e s t i n g and feeding h a b i t a t . Apparently the other species of the b i r d population are so d i f f e r e n t i n t h e i r requirements that one cannot suppose that they would have any -direct r e l a t i o n with the S o l i t a r y v i r e o (other than predator-prey r e l a t i o n ) ". . 1  How do the d i f f e r e n t successional stages of the Eurhynchium-Mahonia ecosystem type i n f l u e n c e the development of the S o l i t a r y v i r e o population? The e f f e c t of the d i f f e r e n t successional stages of the EurhynchiumMahonia ecosystem type on the change of the S o l i t a r y v i r e o population was also investigated. Logged area:  The stand of P l o t VII was removed and only a few cedar,  maple and dogwood trees were l e f t standing.  The ground was covered with poorly  developed shrubs and an abundant l a y e r of herbs.  The nest i tree stood i n a"  small v a l l e y , and the nest was l o c a t e d near the end of a .4.0 m. long brahch. There was no overheating problem, because the nest,obtained temperature compensating e f f e c t s from the high evapo-transpiration of the surroundings, and  -142-  the  heat  food the  surplus  partly  from  logging, Young  placed  its  and  was  eliminated  the  maple  partly  stand:  An  nest.in  the  than  Food  maple  trees  were  Mature nest,  and One  with  food sees  which, i t  that  the  Solitary  can  place  b u i l t . i n  more  compensated  cause in  is  i t . i s  this  and  entire  believed  yireos  food  and  the  standing  after  showed  ground  and  k'fo  only  adjacent  that  the  Solitary  protected  higher area  light.  where  from  vireo the  intensity  a .few  mature  bush i n  gives  possesses  those  the  near the  vireo of  i n  If  a  a  good  plots  good  where  microclimate the  ground,  protection  air  its  nest  and by  the  is  In so  the  nest  for  extreme,  the  the  that  placing  the  method  microclimatic  less  where  surroundings.  places  the"  of  the  Solitary  ecosystem that  active  the  insect  Chapin  and  vireo  nest  is  stand  the  microclimate  case the  of  connest is  an  extreme  cooling  effects  evapo-transpiration  of  dense  bushes.  role  community.  Solitary  i t  Solitary  the  an  dense  than  Eurhynchium-Mahonia It  its  movements  herbs is  the  the  provided by  f  the  received  from  left  its  area.  nest  near  collected  themselves.  almost.identical.  microclimate  of  stratified  birds  be  What  well  the  w i l l  of  A  for  are  layers  obtained  vireo  standing.  stand:  ditions  are  was  nest  This  trees,.whichwere  adjacent  hush,  The  movement.  dogwood  the  dense  extremes.  a.  from  air  investigation  microclimatic nest  and  hy  found  consisted  vireo  i n  the  community  of  the  type? biological  value  eacting.bird  (1925) that  animal  entirely  Solitary  and because  investigated  the  almost  of  the  matter of  i t  vireo has  stomach  was  96.32  a  is dense  high,.bepopulation  contents  of  329  per  of  the  cent  insects.  CONCLUSION The  Solitary  vireo  indicated  a  strong  association  with.the  community  of  -143the Eurhynchium-Mahonia ecosystem type. i n any other communities of the study  I t s occurrence was never OTDserved  area.  This, high f i d e l i t y i s explained on the b a s i s of i n v e s t i g a t i o n s of the nest c o n s t r u c t i o n and of the l i g h t i n t e n s i t i e s at those nests which were placed near the ecotone of the Eurhynchium-Mahonia and adjacent  communities.  I t i s concluded that the S o l i t a r y v i r e o places, i t s n e s t . i n such a way heat surplus of the immediate surroundings, i s eliminated.  that  Therefore, i t i s  supposed that the m i c r o c l i m a t i c -range does not l i m i t the d i s t r i b u t i o n of t h i s b i r d , but that the upper and lower l i m i t s of the m a t e r i a l s of the nest are the most .important f a c t o r s governing i t s l o c a l d i s t r i b u t i o n .  Those  nest m a t e r i a l s which produce high s t a b i l i t y , but are heavy, show a.tendency to increase p a r a l l e l w i t h the l i g h t curves i n d i c a t i n g i n c r e a s i n g mechanical stresses up to a c e r t a i n p o i n t , beyond which they are replaced by moss and l i c h e n m a t e r i a l s which are low i n weight and have a high s t a b i l i t y and e l a s ticity.  The curve of b i n d i n g m a t e r i a l s ( s i l k ) evens out at about 60 per'cent  of r e l a t i v e l i g h t which i n d i c a t e s that the s t a b i l i t y of the nest cannot i n crease very much above t h i s p o i n t . 1.  Therefore,, i t . i s b e l i e v e d t h a t :  The p r o t e c t i v e e f f e c t of the Eurhynchium-Mahonia community i s the  most.important f a c t o r t o which the S o l i t a r y v i r e o responds. 2.  The broadleaf maple and dogwood members of t h i s community only i n our  area a l s o paly an important r o l e by p r o v i d i n g c a t e r p i l l a r s which are taken as food; t h e i r s i l k i s used also i n the nest c o n s t r u c t i o n . 3«  The h i g h l y humid a i r of t h i s community a l s o plays an important  because i t protects the nest m a t e r i a l s against drying out, so that the s t a b i l i t y and e l a s t i c i t y of the nests are always more or l e s s the same. The l i g h t range of the S o l i t a r y v i r e o nests i s from 40.44 t o  67-10  role,  -lucent r e l a t i v e l i g h t .  The d e t a i l e d investigations show that the most simple  nest structure occurs at a l i g h t value of 50 per cent because the s t a b i l i t y and e l a s t i c i t y components of the nest are not so important here due to the high protective e f f e c t of the stand.  These nests which were investigated  near the ecotone of t h i s community indicated that the s t a b i l i t y materials i n creased p a r a l l e l with.the e f f e c t s of t h e i r surroundings up to a c e r t a i n point.  The upper.limit of the nesting range of the S o l i t a r y vireo approxi-  mates t h i s .point.  Data of S o l i t a r y v i r e o nests. Nests  a b c d e f g h i j k 1  m n o P  Tree species  Vine maple Dogwood Broadl. maple Broadl. maple Broadl. maple Dogwood Broadl• maple Broadl. maple Dogwood Broadl. maple Vine maple Broadl. maple Broadl. maple Dogwood Broadl. maple Willow  Nest height  Branch length  Nest from trunk  m.  m.  m.  1.8 5-5 10.0 3-0 3-3 1.2 1-5 1.8 3-3 2.1 3-0 2-7 3-0 4.3 2.1 •1-7  1-5 2-3 2.1 2-7 3-7 1.8 .2.4 0-7 4-3 0.9 1.8 1.8 2.4 1.9 1.4 1-3  0.9 1.2 1.4 1.8 2.7 1-5 •1-5 0-3 4.0 0.6 1.4 .1.2 1-5 1.2 0.9 1.0  Degree of ramification o  48 33 35 66 56 50 55 53 53 h9 55 57 52  48  53  84  Table 19  Diam. of branch Circum. before a f t e r of nest, ramification mm. 8.0 8.0 8-5 7-0 6.0 8.0 5.0 7-0 5-0 7-0 6.0 8.0 7-5 8.0 5-5  1-5 5-0 8.0 4.0 4.0 4.0 7-0 2-5 5.0 3-0 2-5 5-0 3-5 5-0 4.0 3-5  Suspendedpart of circum.  mm.  mm.  mm.  4.0 4.0 3-0 7-5 5-0 4.0 5-0 4.0 5-0 4.0 6-5 4.0 6.0 5-0 6.0 4.5  175 185 180 200 190 195 185 185 200  55 100 50 115 90 105 100 105 125  -  -  -  -  -  -  t 31.5 54.0 27.8 57-5 47-3 53-8 54.0 57-0 62.5  -  -  -  I  -146-  RED-EYED VIREO (Vireo olivaceus Linnaeus) According t o t h e observations made during the summers of i960 and.1961, the Red-eyed v i r e o was found o n l y . i n the Polystichum ecosystem type, a deciduous f o r e s t community. The Red-eyed v i r e o population was not evenly d i s t r i b u t e d w i t h i n the community b u t . i t was concentrated .in low p l o t s where the ground was covered by a heavy l a y e r of bushes. Within t h i s ecosystem type,,the I n v e s t i g a t i o n covered two p l o t s which are separated from each other by a,distance of 2.5 m i l e s . two of which were on the two p l o t s mentioned.  Five nests were found,  These two nests were s t u d i e d . i n  respect t o t h e i r environmental setting,, i n c l u d i n g the f a c t o r s of l i g h t i n t e n s i t y . The remaining three nests were used f o r comparison only. The purpose of t h i s study was t o answer the f o l l o w i n g questions: 1.  What are the e c o l o g i c a l d i f f e r e n c e s between the h a b i t a t s of the  s o l i t a r y and Red-eyed vireos? 2.  What are the d i f f e r e n c e s between the nest s i t e and s t r u c t u r e of these  two b i r d s ? 3- . What are the f a c t o r s which exclude the Red-eyed v i r e o from the communities of other ecosystem types i n the study area? Sample p l o t I . This p l o t i s l o c a t e d i n the center part of the study area. The only nest (nest a) found i n t h i s p l o t was on a broadleaf maple bush 1.3 m. above the ground.  The ground was covered by a weak l a y e r of herbs.  Sample p l o t . I I . . This p l o t i s l o c a t e d on a.bank of the Fraser R i v e r . Nest b was found on a.broadleaf maple bush 1.5 m. high above the ground. ground was covered by a weak l a y e r of herbs.  The  -147-  Comparlson o f l i g h t . i n t e n s i t i e s  o f Red-eyed v i r e o  nests  Table 20  Light intensity of n e s t b % o f nest a  Measured light i n lx.  a  175-47  46.80  64.81  100.0  b  178.17  47.69  67.48  101.1  The  l i g h t energy  Mean l i g h t intensity  Amplitudes i n jo o f l i g h t i n open  Nests  of nest b i s expressed as a percentage  of the light  i n t e n s i t y , measured,in nest a. .Because, t h e r e i s no d i f f e r e n c e i n t h e i l l u m i n a t i o n o f t h e e n v i r o n m e n t of and  these n e s t s a n d no d i f f e r e n c e a t c o m p o s i t i o n , d e n s i t y a n d s i z e o f shrubs herb  layers and t h e s o i l  t e x t u r e s a r e n e a r l y t h e same i n b o t h  nests,  hence t h e l i g h t r e f l e c t i o n and e v a p o - t r a n s p i r a t i o n a r e presumably s i m i l a r i n both nests. in  T h e r e f o r e , t h e r e a r e no d i f f e r e n c e s i n m i c r o - c l i m a t i c e l e m e n t s  t h e two n e s t s a c c o r d i n g t o K i r h o f f ' s l a w . The  n e s t i n g h a b i t a t o f t h e Red-eyed v i r e o i s s h a r p l y d i f f e r e n t  the S o l i t a r y v i r e o . . I f the surroundings  of five  from}:  known n e s t s a r e c o m p a r e d . i t  w i l l be found t h a t ' t h e n e s t i n g h a b i t a t s o f these f i v e b i r d s a r e s i m i l a r .  In  each casenthe  layer  of  bushes,.the  usually The  n e s t was l o c a t e d i n a l o w s p o t w h i c h  i s c o v e r e d b y a dense  l a y e r o f h e r b s b e i n g r e l a t i v e l y weak.  These s p o t s a r e  shaded b y a f e w l a r g e t r e e s . R e d - e y e d v i r e o i s o n e :of t h e f o u r s p e c i e s w h i c h  s t r i c t e d h a b i t a t i n t h e study area.  shows a v e r y r e -  Nevertheless i t uses a r e l a t i v e l y  large  f e e d i n g t e r r i t o r y ; f o r e x a m p l e , t h e f e m a l e b i r d o f n e s t a was f o l l o w e d s e v e r a l t i m e s a n d was f o u n d t o c a r r y f o o d f o r i t s y o u n g f r o m a d i s t a n c e o f 1 0 0 t o - 2 0 0 It  i sd i f f i c u l t  t o e x p l a i n why i t s n e s t i n g h a b i t a t . i s  m.  so r e s t r i c t e d .  The. P o l y s t i c h u m e c o s y s t e m t y p e . i s n o t a f a v o u r a b l e p l a c e f o r t h e R e d - e y e d v i r e o s  -148-  and apparently only the lower areas can f u l l y provide the n e c e s s i t i e s f o r ... raising a clutch.  Since the ecoclimate of the open stand of a l d e r - b i r c h , i s  too extreme, the nest cannot come i n t o e q u i l i b r i u m w i t h the strong mechanical e f f e c t s of t h i s community.  Therefore, the Red-eyed v i r e o withdrew i t s nest  from the d i r e c t e f f e c t s of the plant community by p l a c i n g i t , i n s i d e the low strata.  Communities where t h i s b i r d could nest without such s p e c i a l adapt-  a t i o n of i t s nest s i t e are now known i n the area of i n v e s t i g a t i o n .  .  The Red-eyed v i r e o a l s o nests i n the e a r l y successional stage of the stand of Polystichum ecosystem type.  Here the nests are located, i n the de-  pression (dry stream v a l l e y ) where the stand i s oldest and densest. performs a l l i t s a c t i v i t i e s i n the dense broadleaf maple.  It  A l l the young  leave t h i s immature f o r e s t immediately a f t e r f l e d g i n g . Considering the. nest.of the Red-eyed vireo,. i t was found t h a t the m a t e r i a l used by. the Red-eyed v i r e o f o r nest b u i l d i n g i s the same as that used by the S o l i t a r y v i r e o . given i n Table 21.  The m a t e r i a l s of two Red-eyed v i r e o nests are  We see t h a t there are no s i g n i f i c a n t d i f f e r e n c e s between  the amount of the nest m a t e r i a l items of nests a and b.  These s i m i l a r i t i e s  were expected from t h e i r s i m i l a r h a b i t a t s . Both nests were w e l l protected against the mechanical e f f e c t s of wind, r a i n , e t c . , by t h e i r dense surroundings.  Therefore, the amount of strong m a t e r i a l s i s r e l a t i v e l y low i n both  nests.  Low strength m a t e r i a l s could guarantee enough p r o t e c t i o n against the  mechanical stresses which were caused by the b i r d s ; environmental s t r e s s upon the nest was s l i g h t .  Apparently the s i t u a t i o n i s the same here as i n those  nests of the s o l i t a r y v i r e o which are placed i n low l i g h t ranges. The Red-eyed v i r e o was found only i n the deciduous tree covered part of the Polystichum ecosystem type.  Those f a c t o r s which excluded i t from the  -149other parts of t h i s ecosystem type and other ecosystem t y p e s - i n the study area might be the same as i n the case of the S o l i t a r y v i r e o , which are d i s cussed on p. 138 and only b r i e f l y mentioned here.  The l a c k of the p r o t e c t i o n  o f f e r e d by the stand, l a c k of the appropriate tree species f o r i t s feeding and nesting and low humidity of a i r are apparently the most important f a c t o r s . The Red-eyed v i r e o may be a competitor of the Black-throated Gray warbler.  Both b i r d s show a strong a f f i n i t y f o r the crown of mature b i r c h .  This a l l e g e d competition may e x i s t . i n the feeding behaviour only because t h e i r nest s i t e s are strongly d i f f e r e n t from each other.  In the young stand  i t c o - e x i s t s w i t h the Black-capped chickadee, .but t h i s r e l a t i o n i s not w e l l observed, and t h e i r feeding and nesting habits are d i f f e r e n t . The b i o l o g i c a l value of the Red-eyed v i r e o may be the same as that of the S o l i t a r y v i r e o .  The Red-eyed v i r e o i s a l s o an a c t i v e i n s e c t e a t i n g b i r d .  I t s a c t i v i t i e s are p r i n c i p a l l y i n the high canopy of b i r c h . CONCLUSION The Red-eyed v i r e o was found i n Polystichum ecosystem type only.  I t has  never been observed.in other ecosystem types during the nesting season, while i n spring i t has sometimes been seen in',the Eurhynchium-Mahonia ecosystem type i n low numbers.  Thus the Polystichum ecosystem type i s the best h a b i t a t  f o r the Red-eyed v i r e o i n the study area, but i t . i s not optimal, according to i t s r e s t r i c t e d nesting.  Two Red-eyed v i r e o nests were i n v e s t i g a t e d and as i t  was found that the nest m a t e r i a l s of both v i r e o s are s i m i l a r , the e f f e c t s of t h e i r surroundings,could a l s o be the same. The p r i n c i p a l tree required.by the Red-eyed v i r e o - i n i t s h a b i t a t i s the mature b i r c h tree and i t s supplementary species i s the broadleaf maple.  -150-  Analysls of Red-eyed v i r e o nest m a t e r i a l Table 2 1 Nest  a  Light range Weight of nest ( i n gr. ) High strength m a t e r i a l s : Silk Moss Lichen Phloem .from 1 0 c. B i r c h bark Paper Leaf veins -  '  b  48.4-7  47.69  8.326  8.491  w  1o  w  *  I.58O  0.101 0.033 0.668  1-9337 5.7890 1.2731 18.9766 I.2130 0.3963. 8.0230  0.184 O.695 0.033 1-359 O.038 0.057 ' 0.560  2.1670 8.1851 O.3886 16.0051 0.4475 0.6712 6.6894  2.131  37.6047  2.926  34.5539  4.762 0.109  57.1943 I.3091  4.972 O.182  58.5561 2.1434  4.871  58.5034  5.154  60.6995  0.084 0.186  1.0088 2.2339.  0.301  3.5449  0.270  3-2427  0.301  3.5449  0.l6l 0.482 0.106  Low strength m a t e r i a l s : Phloem Pupae  Stress d i s t r i b u t i o n m a t e r i a l s : Grass Twigs  Stuffing materials: Wood Coniferous leaves Feathers  -  0.054  0.6485  0.098 0.003 0.001  0.054  0.6485  0.102  .1.1541 0.0353 0.0117 •  1.2011  ( OREGON JUNCO (Junco oreganus Townsend) According t o observations made i n the two summers, the Junco was found i n 6 of the 1 0 ecosystem types studied.  Light Curves of Vireo olivaceus Nests in Polystichum Forest Type on UBC Forest near Hope B.C  90-  80-  60-  40-  30-  10-  i  r  10  Figure 23-  12  14  Explanation i n the text (p.  "T" 16  147)  "i  r  -151-  The  t y p e s ,  J u n c o  b u t  n e s t i n g .  i t  l i v e s  Where  s p e c i e s  i s  i s  where  the  not  the  e v e n l y  stafce  g r o u n d . i s  o f  c o v e r e d  d i s t r i b u t e d  the  g r o u n d  w i t h  a  w i t h i n  s u r f a c e  dense  l a y e r  t h e s e  i s  o f  ecosystem  s u i t a b l e  f o r  v e g e t a t i o n  i960, 19  and  on  t h e s e  d e t a i l , . t h r e e  t e r r i t o r i e s ,  l a t t e r  and  d u r i n g  t e r r i t o r i e s  w i t h . l i g h t . m e a s u r e m e n t  E c o s y s t e m  seven  was  1961, 34 n e s t s  t e r r i t o r i e s ,  were  s t u d i e d  were  i n  more  w e l l .  t y p e s  No.  o f  n e s t s  No.  o f  t e r r i t o r i e s  f o u n d  f o u n d  E u r h y n c h i u m - M a h o n i a  2  4  G a u l t h e r i a - M a h o n i a  2  30  G a u l t h e r i a - C l a d o n i a - R h a c o m i t r i u m  2  9  D o n t h o n i a  1  1  s p i c a t a  P a c h y s t i m a - G a u l t h e r i a - P e l t i g e r i a  0  8  P o l y s t i c h u m  0  1  The  p u r p o s e  1.  W h i c h  2.  How  f o r e s t  f i r s t  s t r a t i f i e d  wood  study  was  t y p e . i s  n e s t i n g  to  answer  the  optimum  h a b i t a t  o f  p a r t  a n d . i n  o f  t h i s  i n c l u d i n g  I.  Two  them,  n e s t  crown  50  d i f f e r e n t  d e v e l o p m e n t . o f  p l o t  c o v e r e d  about  a t i o n ,  t h e  the  f a c t o r s , .  One  mosses  do  the  Sample  p l o t .  t h i s  e c o s y s t e m  does  How  . i n f l u e n c e  l o g i c a l  o f  o f  the  the  f o l l o w i n g  h a b i t a t  J u n c o  f o r  vary,  q u e s t i o n s :  J u n c o s ?  i n  the  d i f f e r e n t  t y p e s ?  3.  The  t h i s  a b s e n t .  D u r i n g  f o u n d ,  p o p u l a t i o n  canopy  the  s u c c e s s i o n a l  the  s t u d y  l i g h t ,  n e s t s  a ,  o f  J u n c o  the  g r o u n d . i n  mm.  h i g h  above  the  f o l l o w i n g ,  o f  o f  the  the  s t a n d  t h i s  p l a c e d . i n  a n  o p e n i n g  f o r e s t .  o f  the  e c o -  n e s t . e n v i r o n m e n t .  i n  E u r h y n c h i u m - M a h o n i a  R e l a t i v e l y  the  o p e n i n g .  the  g r o u n d .  n e s t  f o r e s t  i n v e s t i g a t i o n  f o u n d  t h i s  the  p o p u l a t i o n ?  i n v o l v e d  were  was  s t a g e s  s u r r o u n d e d  weak  l a y e r s  o f  p l a c e d  on  The  n e s t  was  T h i s  n e s t  r e c e i v e d  w i l l  be  b y  c o n s i d e r e d  as  the  the  a  t y p e  w e l l  h e r b s  and  d e c a y i n g  l e a s t . i l l u m i n -  b a s i s  o f . e c o -  -152-  logical The  comparison. o t h e r n e s t , not used i n t h e l i g h t measurement s t u d i e s , was found  1.8 m. h i g h above, t h e r o a d . l e v e l on t h e edge o f t h e r o a d out. n e s t was o n l y 23.m.  Because t h i s  away from n e s t a o f t h e W i n t e r wren a l s o u s i n g t h e r o a d  c u t , t h e i l l u m i n a t i o n v a l u e s found a t t h a t n e s t would l a r g e l y be t h e same f o r t h i s Junco n e s t . Sample p l o t . I I was l o c a t e d . i n t h e Gaultheria-Mahonia-Rhacomitrium system t y p e .  eco-  Nest b was p l a c e d underneath a s m a l l dense Rubus p a r y i f l o r u s  shrub, which was shaded by young D o u g l a s - f i r t r e e s i n t h e a f t e r n o o n . Sample p l o t . I l l was s i t u a t e d . i n t h e Danthonia s p i c a t a ecosystem t y p e . The w e s t - o r i e n t e d s l o p e -here i s 35° s t e e p . .weak l a y e r o f g r a s s e s and l i c h e n s . c a v i t y (10 cm. deep),  The ground was covered w i t h a  Nest c was p l a c e d - i n t o a s m a l l ground  thus i t was shaded.  Comparison o f l i g h t . i n t e n s i t i e s of Junco n e s t s . Table 22 Nests  Measured light i n lx.  Mean l i g h t .intensity ^  Amplitudes i n % of l i g h t i n open  a  I74.6I  48.57  80.72  100.00  b  280.8V  78.33  93.18  160.83  c  333.76  88.23  95-01  .194.14  The  Light.intensity of nests % of nest a  s i t e of- n e s t a was, a c c o r d i n g t o my o b s e r v a t i o n s , one o f t h e d a r k e s t  s m a l l openings w i t h Junco t e r r i t o r i e s w h i l e n e s t c was on a wide open s l o p e . 1  T h e r e f o r e t h e i r l i g h t . i n t e n s i t y v a l u e s may l a y near t h e lower and upper l i m i t of t h e Junco's t o l e r a n c e .  T h u s . i n h y d r o p h i t i c f o r e s t t h e 48 p e r cent  , i n t e n s i t y , . and. i n extremely limits.  open areas the 78 P ^ cent •. e  light  , may r e p r e s e n t t h e  A t ' t h e h i g h e s t , l i g h t i n t e n s i t y , , however, t h e n e s t e n j o y e d t h e e x t r a  p r o t e c t i o n o f t h e ground c a v i t y dampening t h e extremes o f the m i c r o c l i m a t e . The  a d a p t i v e l i g h t , i n t e n s i t y range o f t h e Junco n e s t . i n the. open would.be  -153-  between the values f o r nests a and b. The second.part of t h i s study intends t o e x p l a i n why the Junco i s p l a c i n g i t s nest d i f f e r e n t l y i n the d i f f e r e n t ecosystem types. The f i r s t Junco nest found i n the Eurhynchium-Mahonia community i n d i cated a c a r e f u l choice of nest l o c a t i o n by the parent b i r d , located i n the opening of a dense f o r e s t stand.  ( l ) the nest was  (2) Since the s o i l of t h i s  f o r e s t type has a r e l a t i v e l y high humus and water content, and since the heat comductivity of'the s o i l i s high, i n s u l a t i o n of the n e s t . i s necessary.  If  the, nest was placed on the clear s o i l surface the b i r d would not be able to keep an even temperature i n the c r i t i c a l periods of nesting. But i t was b u i l t on decaying wood and on a layer of. dry maple leaves, 5 cm. high above s o l i d surface; moreover i n s u l a t i n g m a t e r i a l (horse h a i r ) was found i n the nest. In the other nest of t h i s p l o t the dry s o i l of the edge of ther.oad cut guaranteed the s u i t a b l e nesting s i t e , moreover,' the nest was i n s u l a t e d by b i r d feathers. In the Gaultheria-Mahonia and the Pachystima-Gaultheria-Peltigera communities the open l a y e r of shrubs gives a good p r o t e c t i o n against the extreme ecoclimate.  Because there are no c l i m a t i c and water problems, the  two known nests were b u i l t of grasses without any i n s u l a t i n g m a t e r i a l . In places where the ground i s covered by a dense l a y e r of bracken (Pteridium aquilinum), such as the middle part o f the Gaultheria-Mahonia type f o r e s t on our area, the Junco can not nest,. because of the wet, c o l d soil.  Therefore, i t placed i t s nest here i n the middle part of the road  s t r i p , the grass growing on the road s t r i p h i d i n g the nest from human s i g h t . This road was used by a number of cars each day, nevertheless a l l the four eggs were hatched(however, on J u l y , t h i s nest was destroyed by a b u l l d o z e r ) . The eastern part of t h i s . h a b i t a t type consists of a stand of 10-12  year  -154-  old,  dense f o r e s t and here the Junco placed i t s f i r s t n e s t . i n t o a small  ground-cavity (apparently the entrance of a mouse hole) on the c l e a r e d s t r i p of a transmission l i n e .  The herbaceous vegetation of the c l e a r e d s t r i p was  s t i l l ' u n d e v e l o p e d at the time the Junco was nesting ( f i r s t , part of May)  and  could not provide.much p r o t e c t i o n . Therefore the u t i l i z a t i o n of the ground hole seemed to have great p r o t e c t i o n value.  S i m i l a r l y the Danthonia s p i c a t a  community d i d not contain such a vegetation stand which could have protected the nest, therefore the Junco placed i t s -nest.into the small ground c a v i t y of the slope.  The w e l l compensated microclimate of the c a v i t y provided a  f u l l p r o t e c t i o n f o r nest c.  Although only t h i s single nest was found.in t h i s  habitat type, the same nest .placing method of the Junco seems.to be the rule, i n the Danthonia s p i c a t a community apparently to compensate f o r i t s very extreme ecoclimate.  The temperature of t h i s slope often exceeds 40 C during G  the warmer summer days, and the humidity of the a i r i s very low.  We might  assume t h a t . i f the nest was placed on the ground the high temperature would have k i l l e d the eggs (three of the four eggs hatched i n t h i s nest i n I961). The few example mentioned i n d i c a t e that the Junco possesses a good a b i l i t y to choose a nest s i t e w i t h a.balanced ecoclimate.  Where the stand  i s .closed i t s nest i s i n the opening and i n s u l a t i n g m a t e r i a l s are used. Where the p r o t e c t i o n e f f e c t of the vegetation i s l a c k i n g as we have seen i n the case of the Danthonia type,, i t p l a c e s . i t s n e s t . i n t o the ground c a v i t i e s which minimize the extremes of the ecoclimate. How do the d i f f e r e n t successional stages of the f o r e s t stands.influence the establishment of a Junco population? ' The occurrence of the Junco has never been observed i n the closed part of mature f o r e s t stands.  I n i t n e closed stands,.the Junco occupies the openings  and the edges of the stands.  The above observations of a few.nests p o i n t . t o -  -155ward an assumption,.i.e. that the s u i t a b l e l o c a l i t i e s  f o r the n e s t i n g of  the Junco are l i m i t e d by the amplitude of ecoclimate, as we have surmized.in . the case of the Eurhynchium-Mahonia community.  Here the closed stand hinders  .the warming up of the f o r e s t and the evaporation of the high water content of the s o i l .  I t i s b e l i e v e d that the f a c t o r which excluded the nesting of  the Junco i s - n o t the microclimate of the f o r e s t stand, but r a t h e r the high ' .water content of the s o i l with i t s c o o l i n g e f f e c t . In the stand.opening and edges no such problems e x i s t e d .  The water  content of the s o i l i n the opening i s much lower due t o i t s low humus content and to the high evapo-transpiratory e f f e c t s of the unblocked a i r exchange. A number of observations of the two summers i n d i c a t e d that.the Junco i s quite abundant on those logged area.where a.few o l d trees were l e f t standing, and where these t r e e s could be used f o r t e r r i t o r i a l s i n g i n g of The highest Junco population develops .2 t o 5 years a f t e r the l o g -  the males.  ging, when an abundant weedy vegetation covers the ground and the shrubs present reach such a state that they can minimize the extreme of the climate near the ground.  I n t h i s stage of the stand the Junco population may exceed  50 p a i r s per 100 acres.  When the shrub l a y e r begins to close about 5 t o 7  years a f t e r the logging the population of Juncos d e c l i n e s , apparently i t . i s not higher than 5 to 10 p a i r s per 100 acres.  150 1 rH  co  5CC 03 o ioo •H  CO  •H  O  CD  &  -  o  0 50 Figure 24. R e l a t i o n of Junco and Towhee d e n s i t i e s t o coverage of ground by shrubs  100  %  -156-  One can see these changes i n the Gaultheria-Mahonia type on the studyrarea. This ecosystem type i s i n i t s e a r l y secondary succession stages at the present time.  This type has a bad f i r e h i s t o r y , which caused great v a r i a -  t i o n s i n the features of i t s young stands, therefore r e l a t i o n s between the Junco's population and the successional stages of t h i s stand are w e l l observed.  Where the stand of t h i s type i s already closed, the Junco occupies  the edge and the road sides, as i t has been found i n the mentioned .two cases.(nest,in the transmission l i n e s t r i p and the road s t r i p ) . The absence of the p r o t e c t i v e e f f e c t of the stand does no .'affect the. Junco, as we have been seeing i n the previous chapter, where i t s u t i l i z a t i o n of ground holes was discussed. Generally speaking, the Junco does n o t . i n h a b i t the hydrophitic ecosystem types i n a normal s i t u a t i o n on our area and the reason was the high water content of the s o i l .  thought  In the case of xerophytic ecosystem types  where the ground, i s not covered by a dense l a y e r of vegetation, the Junco i s able t o nest everywhere,. because the dry, w e l l a i r i n g s o i l allows i t . The f a c t that the extreme ecosystem type (Danthonia s p i c a t a ) was inhabited by now other b i r d . b u t Junco i n d i c a t e d that the amplitude of the a d a p t a b l i t y of the Junco i s very high concerning i t s nest p l a c i n g method. Which ecosystem type i s the optimum f o r Junco? This question was already p a r t l y answerdd i n the previous discussions. Because the Junco i s a ground nesting b i r d the e c o l o g i c a l circumstances of the stand of the f o r e s t type do not e f f e c t i t s i g n i f i c a n t l y (except the dense stand which hinders the evaporation of the ground water by i t s c o l d ecoclimate). For i t s ground nest the p h y s i c a l p r o p e r t i e s of the ground are important through t h e i r impact on the microclimate. A dry and w e l l aerated s o i l i s  -157the main demand of the Junco, because such a s o i l can guarantee a dry s i t e for the nest.  Juncos do not i n h a b i t such places where the ground i s covered  by dense shrubs, herbs and mosses, because the immediate surrounding of the nest cannot warm up f o r the high evapo-transpiration of the vegetation. Moreover the high water content and the good heat c o n d u c t i v i t y of the wet s o i l are important l i m i t i n g f a c t o r s .  Therefore i t i s surmized t h a t a.major  e c o l o g i c a l f a c t o r which c o n t r o l s the d i s t r i b u t i o n of the Junco i n the study area i s the p h y s i c a l state of the s o i l .  Where the state of s o i l provides  s u i t a b l e conditions f o r n e s t i n g , only other conditions a f f e c t i n g feeding, s h e l t e r , s i n g i n g posts etc.,.would l i m i t .the establishment of t h i s b i r d . CONCLUSION During the summers of i960 and 1961 the e c o l o g i c a l conditions of seven Junco nests and f o r t y - s i x t e r r i t o r i e s were i n v e s t i g a t e d . For three of the seven nests l i g h t curves were prepared; i t was found that the nesting range of these Juncos was between 48.57 and 88.23 P  e r  cent  of the r e l a t i v e l i g h t , i n t e n s i t i e s , , i n the study area,, i t i s a very wide range. These scahtc.data i n d i c a t e t e n t a t i v e upper and lower l i m i t s of t h e i r l i g h t r e quirements which are i n d i c a t i v e of the m i c r o c l i m a t i c tolerance l i m i t s of the Junco.  The upper extremes of the microclimate seem t o be l e v e l l e d to a c e r t a i n  extent by using ground c a v i t i e s .  Toward the lower l i g h t l i m i t s , the major  problems of Junco would be the c o l d and wet soil,.because low l i g h t . i n t e n s i t y cannot warm up the surrounding due t o the high s p e c i f i c heat of the ground water and wet humus.  The s i n g l e nest studied among such circumstances was .  placed on a dry base, and.its w a l l s were a l s o b e t t e r i n s u l a t e d than those of the other two nests studied. Summing i t up, these data i n d i c a t e that the nesting of the Junco i s .  Light Curves of Junco oreganus Nests on UBC Forest near Hope B.C.  Figure 25-  Explanation i n the text (p.  152)  -158-  c o n t r o l l e d by the p h y s i c a l state of s o i l .  Where the dry and w e l l aerated  s o i l i s present, s u i t a b l e nest s i t e i s provided on open areas near a.brushyedge f o r the Junco. Because of the wide range of e c o c l i m a t i c conditions that are t o l e r a t e d i n n e s t i n g and the surmi-zed d i r e c t dependence on edaphic f a c t o r s , . t h i s ground nester i s a s u i t a b l e subject of f u t u r e . s t u d i e s on n e s t i n g ecology.  A further  point that the v a r i a t i o n of nest s i t e , and.its c o r r e l a t i o n with m i c r o c l i m a t i c and edaphic f a c t o r s , , b r i n g s up i s that e f f e c t . o f p r o t e c t i o n seems t o play no r o l e i n nest s i t e s e l e c t i o n of t h i s Junco, f o r the i n v e s t i g a t e d nest s i t e s are equally exposed to ground predators. '• ANNOTATED CHECK LIST OF' THE AVIFAUNA GREAT BLUE HERON (Ardea herodias Linnaeus").  One Great blue heron  v i s i t e d the waters (Kawkawa Lake, marsh area) both years, which are adjacent to the study area. AMERICAN BITTERN'(Botaurus l e n t i g i n o s u s Rackett).  During the summer of  i 9 6 0 a.pair of B i t t e r n s was present.in the adjacent,marsh the Typha l a t i f o l i a ecosystem type.  and they nested i n  In 1961 only one B i t t e r n was seen i n the  marsh, which stayed there u n t i l the second of June.  This B i t t e r n stayed mainly  • i n the T y p h a . l a t i f o l i a type,.sometimes i t was seen-in the Glyceria-Carex type, but was not observed i n other types of marsh. GOSHAWK ( A c c i p i t e r g e n t i l i s Linnaeus). the study area.  This species i s a v i s i t o r i n  I t has often been seen i n the loose stand D o u g l a s - f i r .  However,.there was no evidence of i t s nesting on the area. RED TAILED HAWK (Buteo jamaicensis Gmelin). species.  This i s a r e g u l a r l y v i s i t i n g  There was no evidence of i t s nesting i n the study area, although  i t has often been.seen s e v e r a l times weekly i n i 9 6 0 and  1961.  -159-  OSPREY (Pandion h a l i a e t u s Linnaeus).  One p a i r of Ospreys nests at the  Coquihalla r i v e r side on a D o u g l a s - f i r snag about 0 - 5 miles from the studyarea.  They v i s i t the water (Kawkawa Lake, marsh etc.) which are adjacent t o  the study area.  They were s u c c e s s f u l l y nesting both summers.  GOLDEN EAGLE ( A q u i l a chrysaetos Linnaeus).  I t was seen only twice on  high t r e e s i n the study area. BALD EAGLE (Haliaetus leucocephalus Linnaeus). species.  This i s a v i s i t i n g  Sometimes i t was seen on high trees near Kawkawa. Lake.  MARSH HAWK (Circus GyaneuS Linnaeus).  This species was seen f i v e times  .in the adjacent marsh area.during.the summer of i 9 6 0 and twice i n I961. PEREGRINE FALCON (Falco peregrinus T u n s t a l l ) .  One adult male was seen  several times on the study area.in the l a t e summer of I961. SPARROW HAWK (Falco sparverius Linnaeus). on the study area.  This i s a r e s i d e n t species  I n the summer of i 9 6 0 two p a i r s nested here and one of  the nests was i n the Eurhynchium-Mahonia ecosystem type, the other i n Gaultheria-Mahonia.  I n I96I one nest only was found.in the G a u l t h e r i a -  Mahonia ecosystem type. BLUE GROUSE (Dendragapus obscurus Say). This i s a rare species i n the study area.  Only two broods were found i n the summer of 1 9 6 1 , while i n i 9 6 0  t h i s species was not present i n the study area. Mrs Thacker t o l d me that Blue grouse were p r e s e n t . i n the preceding years, but according t o h i s memory the i n d i v i d u a l members were low. But Mrs. Thacker d i d not mention the name of Blue grouse i n her b i r d l i s t  (1922).  In general, the r e l a t i o n s of Blue grouse are not w e l l observed i n the study area.. The mentioned two broods l i v e d . i n the Gaultheria-Mahonia ecotype.  -160-  BAND-TAILED PIGEON...(Columba f a s c i a t a Say).  This i s a common n e s t i n g  species of the Eurhynchium-Mahonia ecosystem type of.our area.  One of the  twelve known nests was found i n the deciduous tree dominated part of the Polystichum ecosystem type. Mahonia.  A l l the. other nests were i n the Eurhynchium-  In general, the B a n d - t a i l e d pigeon shows a strong f i d e l i t y t o  these communities during the n e s t i n g season. MOURNING DOVE (Zenaidura macroura Linnaeus).  This species has been  seen i n the study area only a few t i m e s , . b u t , i t i s f a i r l y common i n the •• mixed f o r e s t along the Fraser R i v e r . GREAT HORNED OWL (Bubo y i r g i n i a n u s Gmelin).  A p a i r of Great horned  owl was present.In our area.in both summers. PYGMY OWL (Glaucidium gnoma Wagler).  One or two i n d i v i d u a l s were  o c c a s i o n a l l y seen i n the study area both summers.  I t seems that t h i s spe-  c i e s prefers the r e l a t i v e l y open stand of the Eurhynchium-Mahonia ecosystem type.  I n d i v i d u a l s were seen at d i f f e r e n t l o c a t i o n s , on one of them, t r e e  fledged young were a l s o found i n I960,, i n the logged area of the mentioned type. COMMON NIGHTHAWK (Chordeiles minor F o r s t e r ) .  I n i 9 6 0 , one nest and  three a d d i t i o n a l t e r r i t o r i e s , , i n 1 9 6 1 one nest and one t e r r i t o r y were found i n the more open part of Gaultheria-Mahonia ecosystem type.  Both  young d i e d i n the nest of i 9 6 0 and one i n 1 9 6 1 . BLACK SWIFT (Cypseloides niger Gmelin), and VAU&'S SWIFT (Chaetura vauxi Townsend) were seen almost every day over the study area.  They do  not belong t o the population of our area, but use the a i r space above i t as feeding stratum. RUFOUS HUMMINGBIRD (Selasphorus rufus Gmelin) i s the commonest Hummingbird species i n our area, therefore i t i s discussed separately.  -l6l-  RUFFED GROUSE.(Bonasa umbellus Linnaeus).  According t o the present  observations the Ruffed grouse i n d i c a t e s a strong f a i t h f u l n e s s t o the Gaultheria-Mahonia ecosystem type, because of ( l ) i t . i s the mosty evenly d i s t r i b u t e d b i r d i n t h i s f o r e s t which i n d i c a t e d that the h a b i t a t conditions are very good f o r t h i s grouse.  (2) I t d i d not nest i n any other ecosystem  types of the study area. The question, why the Ruffed grouse i s f a i t h f u l t o the G a u l t h e r i a Mahonia ecosystem type on our area i s d i f f i c u l t t o answer, because the stand of t h i s type i s present only i n i t s e a r l y secondary succession stage. I t s stand features vary from the logged and burned area,to the loose stand of Douglas-fir t r e e s .  A w e l l developed.bush l a y e r i s present.  This stand  structure can guarantee the necessary food, s h e l t e r and n e s t i n g places f o r the grouse.  Water i s present a l s o ; a number of spiraea swamp are w i t h i n  t h i s f o r e s t type.  Unfortunately, the Gaultheria-Mahonia ecosystem type i s  not present i n mature stage around. Hope,, therefore there i s no p o s s i b i l i t y at present t o compare how the d i f f e r e n t successional stages of the stand of Gaultheria-Mahonia ecosystem type a f f e c t the population of the r u f f e d grouse. When the young reached t h e i r f u l l development  the Ruffed grouse- was  seen sometimes i n the other xerophytic ecosystem types, Gaultheria-CladoniaRhacomitrium and Pachystima-Gaultheria-Peltigeria, but few observations were made i n the h y d r o p h i t i c f o r e s t s as the Eurhynchium-Mahonia, Polystichum and Thuja-Lysichitum-Oenanthe. Eleven broods were found i n i960, fourteen i n I96I on the study area, and of these, two each w i t h seven eggs, were observed during incubation and successful hatching of a l l eggs.  . Though exact count has not been made of each  of the 25 broods there were never l e s s than f i v e chicks seen.  Thus the e a r l y  -162-  stage of brood r e a r i n g seemed t o be s u c c e s s f u l during both summers. CALLIOPE HUMMINGBIRD ( S t e l l u l a c a l l i o p e Gould).  Two t e r r i t o r i e s of  t h i s species were found i n 1 9 6 1 i n the Gaultheria-Mahonia ecosystem type. One t e r r i t o r y was i n dense young D o u g l a s - f i r stand, the other i n open Douglasf i r stand, the understory of which was dense, composed of maple, white b i r c h , D o u g l a s - f i r , ocean spray e t c . species.  The d i s p l a y i n g males were present,  but n e s t i n g would not be documented and .females have not been seen. BELTED KINGFISHER (Megaceryle alc^r-on Linnaeus). l i v e d . i n the creek of Kawkawa Lake i n both years. in  One p a i r of k i n g f i s h e r s  Only one young was seen  i960.  RED-SHAFTED FLICKER (Colaptes c a f e r Gmelin).  This species i n d i c a t e s a  . f i d e l i t y t o the loose stand of the xerophytic and .mesophytic ecostytem Gaultheria-Mahonia and P a c h y s t i m a - G a u l t h e r i a - P e l t i g e r i a.  types;  Only a few obser-  vations were made i n the Eurhynchium-Mahonia and i t ; was not observed.in the other h y d r o p h i t i c f o r e s t types which.indicates t h a t . i t s favoured h a b i t a t . i s probably the loos mature stands of D o u g l a s - f i r . PILEATED WOODPECKER (Dryocopus p i l e a t u s Linneaus).  This species was  observed o c c u r r i n g i n the Eurhynchium-Mahonia ecosystem type only during the nesting season.  I t s p r e f e r r e d t r e e species seems t o be the o l d western r e d  cedar. In the summer of i 9 6 0 and 1 9 6 1 a p a i r often v i s i t e d the study area, but there was no evidence of i t s n e s t i n g here. LEWIS' WOODPECKER (Asyndesmus lew jGray). (  study a r e a . i n the summer of i 9 6 0 .  One p a i r was present, i n the  This p a i r was always seen on the few scat-  t e r e d dead D o u g l a s - f i r t r e e s of the southern slope of the area and around the adjacent marsh area.  I t has never bee.n observed .in any other places of  -163the study area.  I t might have nested here but no evidence t o t h i s was  In the summer of 1961  found.  only one b i r d was seen twice i n the same place,  therefore t h i s species seems t o be a v i s i t o r here. RED-BREASTED SAPSUCKER (Sphyrapicus.varius .Linnaeus).  This species  p r e f e r s the mixed stand.of the coniferous and deciduous t r e e s .  Their:'nests  were found only i n the•Eurhynchium-Mahonia ecosystem type of the study area ..in both years.  They were- often observed.in the deciduous t r e e groups of the  Polystichum ecosystem type, but•found no evidence of nesting there.  The  s a p s u c k e r i s rare i n the xerophytic ecosystem types; only a few observations i n d i c a t e d t h e i r occurrence, but: most.of them were seen a f t e r the breeding season. HAIRY WOODPECKER (Dendrocopos w i l l o s u s Linnaeus).  This species, i s  abundant i n the loose -stand of the xerophytic ecosystem types of the study area.  Only a few observations were made i n the hydrophytic f o r e s t types.  I t was found.that t h i s b i r d v i s i t e d more often the loose-mature D o u g l a s - f i r stand than the close stand, therefore i t . i s . b e l i e v e d - t h a t - t h e open and semi-open xerophytic ecosystem.types are i t s favoured h a b i t a t . DOWNY WOODPECKER.(Dendrocopos pubescent Linnaeus).  This species Is a  rare v i s i t o r , only a few times was i t observed on the study area. EASTERN KINGBIRD (Tyrannus.tyrannus  Linnaeus).  Two p a i r of Estern king-  b i r d s nested i n the adjacent marsh area both summers.  They have often been  seen on the top of t r e e s . i n the loose stand of the study area.  The nesting  of these p a i r s was s u c c e s s f u l i n i960 (one p a i r had two young, the.-other three) while only one young was seen.in the summer of WESTERN KINGBIRD (Tyrrannus v e r t i c a l i s Say). a l l y a v i s i t o r here.  1961.  This species i s occasion-  I t has been seen only a very few times.  -i6h-  0  TRAILL'S FLYCATCHER (Empidonax t r a i l l i i Audubon). est f l y cathcer species i n the study area.  This i s the common-  A l l the known t e r r i t o r i e s (l4)  and nests (30)were found.in the hydrophytic communities, mainly i n the Thuja-Lys i chiturn-Oenanthe type.  and i n the lowest part of Polystichum ecosystem  I t seems that t h i s species i s associated s t r o n g l y with the w i l l e w  alder t h i c k e t located.near the waters. WESTERN FLYCATCHER (Empidonax d i f f i c i l i s B a i r d ) . the dense mixed f o r e s t stands.  This species p r e f e r s  Four t e r r i t o r i e s and two nests were found i n  the Eurhynchium-Mahonia ecosystem type and.three t e r r i t o r i e s i n the ThujaLysichitum-Oenanthe . WESTERN WOOD PEWEE (Contopus sordidulus S c l a t e r ) .  This species p r e f e r s  the dense mixed f o r e s t "stands, mainly hydrophytic communities.  Apparently  i t s h a b i t a t demand, i s near the Swainson's thrush,. because four of the seven known nests were placed near the Swainson's thrush,nests where the mean l i g h t i n t e n s i t i e s were between kQ t o 53 per cent of t h a t . i n the open i n the Polystichum and Eurhynchium-Mahonia communities. OLIVE-SIDED FLYCATCHER ( N u t t a l l o r n i s b o r e a l i s Swainson).  I t s preferred  h a b i t a t . i s the more open mature stands of the mesophytic and xerophytic communities, mainly the Gaultheria-Mahonia  and.Pachystima-Gaultheria-  P e l t i g e r i a ecosystem types,, but i t was seen o c c a s i o n a l l y i n a l l open mature stands of the study area. VIOLET-GREEN SWALLOW (Tachycineta t h a l a s s i n a Swainson).  ROUGH-WINGED  SWALLOW ( S t e l g i d o p t e r y x r u f i c o l l i s V i e i l l o t ) and BARN SWALLOW (Hirundo r u s t i c a Linnaeus).  They were often seen i n the lower part of our area.  They do not  belong t o the population o f study area,, but use the a i r space above i t as feeding stratum.  - 1 6 5 -  TREE SWALLOW (Iridoprocne b i c o l o r V i e i l l o t ) and CLIFF SWALLOW (Petrochelidon pyrrhonota V i e i l l o t ) were seen over the area by K. and  Kelleher•in'1961  1 9 6 2 .  PURPLE MARTIN (Progne subis Linnaeus). above our area, i n May,  I t has been seen only twice  i 9 6 0 .  CANADA JAY (perisoreus canadensis Linnaeus). seen i n our area.  Only one i n d i v i d u a l was  But i t . i s a f a i r l y common b i r d around Hope,, l i v i n g i n  the mountains above lOOOfeet. STELLER' JAY (Cyanocitta s t e l l e r i G m i l i n ) . the study area.  Common nesting species of  I t shows a high f i d e l i t y to coniferous stands during the  nesting season, a f t e r i t has been seen everywhere i n our area.  A l l the  known t e r r i t o r i e s ( l l ) and nests ( 2 ) were found i n the coniferous stands, i n Gaultheria-Mahonia  and Pachystima-Gaultheria-Peltigera communities.  COMMON RAVEN (Corvus corax Linnaeus). area.  This i s a rare v i s i t o r i n our  I t has been seen a few times on the top of trees or f l y i n g above the  area. COMMON CROW (Corvus brachyrhynchos Brehm).  Common nesting species  i n the cottonwood groups along the Coquihalla and Fraser r i v e r s .  They are  f a i r l y common v i s i t o r s invthe study area. BLACK-CAPPED CHICKADEE (Parus a t r i c a p i l l u s Linnaeus).  This species i s  l i v i n g i n various ecosystem types of our area but i t i s concentrated to those places where deciduous trees are present.  The w i l l o w , b i r c h and red-alder  trees are i t s favoured species and thus i t s d i s t r i b u t i o n  seems t o be  governed by these t r e e s i n the study area. The Black-capped  chickadee i s a permanent member of the b i r d population  of the Eurhynchium-Mahonia and Polystichum' communities and here it.may form  -166-  an a s s o c i a t i o n w i t h the Black-throated gray warbler on the b i r c h .  The l a t t e r  uses the higher part of the crown, while the former u t i l i z e s the suppressed part of b i r c h .  During the breeding season, i t always remains i n the lower  parts of the stands and c o l l e c t s i t s food on deciduous t r e e s .  Hence, the  Black-capped chickadee occurs i n r e l a t i v e l y open parts of the mentioned ecosystem types where the younger stands are present. The Black-capped chickadee i s r e l a t i v e l y abundant b i r d i n the S a l i x Lysichitum-Oenanthe and Ainus-Lysichitum-Genanthe ecosystem types,. because the dense w i l l o w and red-alder stands of these communities again provide i t s optimal h a b i t a t . Black-capped chickai-des occur i n the Gaultheria-Mahonia ecosystem type f r e q u e n t l y , because most of the o l d logging roads are covered by young.reda l d e r , w i l l o w and .birch t r e e s ,  i t favours these roads and hardly ever pene-  t r a t e s the f o r e s t on the s i d e , except f o r a s u i t a b l e nesting c a v i t y . CHESTNUT-BACKED CHICKADEE (Parus rufescens Townsend).  The habitat of  t h i s species d i f f e r s sharply from the former one, which uses c h i e f l y the hydrophytic communities,.while the Chestnut-backed chickadee occurs w i t h i n the xerophytic ecosystem.types.  I t prefers.the dense mature stands of  Douglas-fir and.it c a r r i e s out a l l i t s a c t i v i t i e s high up i n the crown during the nesting season.  Among such circumstances.'its observation often becomes  d i f f i c u l t , because i t often associates w i t h k i n g l e t s and warbler species and they look confusingly s i m i l a r i n the great heights. The Chestnut-backed .and Black-capped" chickadees may only meet.in the Eurhynchium-Mahonia ecosystem type during the breeding season, but t h e i r a c t i v i t i e s are so f a r from each other that they do not l i k e l y t o come i n t o any contact.  The l a t t e r always remains i n the deciduous trees while the former  -167uses ..the crown of large Douglas-fires here. Chestnut-backed  chickadees are present,in low numbers i n the study, area.  Nests wer not found,but a few young were observed both years. MOUNTAIN CHICKADEE (Parus gambeli Eidgway). visitor,±n the study area.  This species i s a rare  Only twice was, i t observed i n the loose mature  stand of Pachystima-Gaultheria-Peltigera ecosystem type. RED-BREASTED NUTHATCH ( S i t t a canadensis Linnaeus). s p e c i e s . i n our area.  This was an abundant  I t s population was highest i n the open, mature stands  of xerophytic communities,, mainly i n the Gaultheria-Mahonia ecosystem type. But i s f a i r l y abundant.in the Eurhynchium-Mahonia ecosystem type a l s o , where i t used both coniferous and deciduous trees w i t h equal frequency (three of the four known nests were found here).  A f t e r the n e s t i n g season the Red-  breasted nuthatch was sometimes seen i n the unmixed deciduous tree stands, mainly on the maple tree's. BROWN CREEPER ( C e r t h i a f a m i l i a r i s Linnaeua).  This species was present  i n the study area both years,.but only one d e f i n i t e t e r r i t o r y was found .in i960, and none i n 1961. DIPPER (Cinclus mexicanus Swainson).  A f t e r the nesting season,, i t was  seen a.few times i n the waters adjacent t o the study area. WINTER WREN (Troglodytes troglodytes Linnaeua). i s t i c species of Eurhynchium Mahonia ecosystem type. ROBIN (Turdus migratorius Linnaeus). our area.  T h i s . i s a characterDiscussed separately.  One of the w e l l known b i r d s . i n  Discussed separately.  VARIED THRUSH (ixoreus naevius Gmelin).  This i s one of the character-  i s t i c species of Eurhynchium-Mahonia ecosystem type i n the study area. Discussed separately.  -168SWAINSGN S THRUSH ( H y l o c i c h l a u s t u l a N u t t a l l ) . :  species of the studycarea.  .It i s a f a i r l y abundant  Discussed separately.  HERMIT THRUSH ( H y l o c i c h l a g u t t a t a P a l l a s ) . study area only during migration.  This species v i s i t e d . t h e  I n e a r l y May of both years, a few groups  of 2Cto h b i r d s were seen i n the lower parts of our area, but they have not been found during the breeding season. WESTERN BLUEBIRD ( S i a l i a mexicanaSwainson).  Only one male i n d i v i d u a l  was seen, i n the marsh area on June 5> 19^2. MOUNTAIN BLUEBIRD (Sialia.currucoid.es Bechstein). Two p a i r s of Mountain b l u e b i r d s were often seen i n the highest,part of the study area between the May 13 t o J u l y 8, i960.  They might have nested here,, but no  evidence t o t h i s was found. TOWNSEND'S SOLITAIRE (Myadestes.townsendi  Audubon).  This species  touches the study area only during migration. A number of b i r d s were seen during the f i r s t h a l f of May of i960 and 1961. GOLDEN-CROWNED KINGLET (Regulus satrapa L i c h t e n s t e i n ) . nests i n three ecosystem t y p e s . i n the study area.  This species  I t seems t h a t . i t s  favoured h a b i t a t i s a mixed,.relative open f o r e s t stand where the deciduous t r e e s , mostly b i r c h , are present i n low proportion only. While Mrs. Thacker (1922) noted that t h i s species has been very;'plentif u l , now.it i s present but not abundant a t a l l .  Probably, a high.population  of t h i s k i n g l e t could be'present i n mature stands of the Gaultheria-Mahonia ecosystem type which i s now i n e a r l y secondary successional stage i n the study area.  This species i s present i n low numbers.in the mature stand of Pachyst'ima-  G a u l t h e r i a - P e l t i g e r a type; i t seems that the simple stand structure i s not preferred.  I n the Eurhynchium-Mahonia community the Golden-crowned k i n g l e t  -169uses the more open part of the  stand.  RUBY-CROWNED KINGLET (Regulus calendula,Linnaeua). present i n our area.in low numbers.  This species i s  I t s habitat and i t s occurrence  nearly p a r a l l e l s the- former kinglet a n d . i t . i s often d i f f i c u l t t o d i f f e r entiate the two species when they are not singing, mostly i n the EurhynchiumMahonia ecosystem type, where both species are active i n the dense crown of the o l d Douglas-fir. CEDAR WAXWING (Bombycilla cedrorum V i e i l l o t ) . nesting b i r d i n young stands i n our area.  This i s a f a i r l y abundant  I t has never been observed i n the  closed middle age or mature stands,, therefore i t i s believed that the presence of t h i s species strongly depends on the successional stage of stands. I t places i t s nest s i m i l a r l y to the Black-headed grosbeak.  A l l the  known nests were found i n the upper t h i r d part of the young deciduous trees, mainly broadleaf maple,.hazel and ocean spray (31 nests) and young Douglas-fir (3 nests).  They had great nesting losses f o r nine of the t h i r t y -  four nests were not successful (the eggs did not hatch, i n two nests, i n others the young died a f t e r hatching, moreover,several nests have been found.in which one or two young have died). I t seems that the Cedar waxwing prefers the xerophytic communities f o r nesting, because thirty-two nests were found here. STARLING (Sturnus vulgaris Linnaeus).  This i s an abundant nesting  species around Hope, most of them nesting i n the v i l l a g e .  A f t e r the breed-  ing season large f l o c k s of t h i s species used the Salix-Lysichitum-Oenanthe type of adjacent marsh f o r roosting.  At t h i s time S t a r l i n g \vere sometimes  seen i n the lower part of the study area.  -170-  SOLITARY VIREO (Vireo s o l i t a r u s Wilson). s p e c i e s . i n our area.  T h i s , i s the commonest v i r e o  Discussed separately.  BED-EYED VIREO (Vireo olivaceus Linnaeus).  This i s a c h a r a c t e r i s t i c  species of unmixed deciduous stands of the study area. ORANGE-CROWNED WARBLER (Vermivora c e l a t a Say).  Discussed separately.  This species favours the  logged-burned areas where w i l l o w , maple arid dogwood brushes are abundant. Apparently i t s population i s highest where the ground,is covered with an open bush l a y e r .  When the young f o r e s t begins t o close the Orange-crowned  warbler leaves the area. At the present time, the best h a b i t a t s f o r t h i s warbler i n the study area are the areas covered with e a r l y secondary successional stages of the Gaultheria-Mahonia type and the secondary t h i c k e t s of Corylus,.Acer and Coenotus.  I n the mature stands t h i s species occurs only i n the edges of- the  stand (roadsides, opening, e t c . ) . YELLOW WARBLER (Dendroica petechia Linnaeus).  I t seems that the  favoured h a b i t a t . o f t h i s species i s i n the wetter hydrophytic  communities,  Salix-Lysichitum-Oenanthe and the young stand of Thuja-Lysichitum-Oenanthe. The Yellow warbler i s rare i n the study area.  Only a few observations have  been made,, i n each case they have been seen along the streamlets. AUDUBON'S WARBLER (Dendroica auduboni Townsend). During the s p r i n g migration t h i s species occurs a l l over the area. f l o c k s were seen i n the marsh area. u l a t i o n got s t r o n g l y reduced. warbler i n the study area.  Moreover, a number of  About the middle of May t h i s high pop-  Apparently t h i s species i s the second most common  I t nests mainly i n t t h e xerophytic communities  (Gaultheria-Mahonia and Pachystima-Gaultheria-Peltigera). Twelve t e r r i t o r i e s and nine nests were found here. Douglas-fir.  The nests were l o c a t e d on both mature and young  The only nest which was found i n the Eurhynchium-Mahonia eco-  -171-  system type was l o c a t e d on a G r a n d - f i r tree. TOWNSEND S WARBLER 1  (Dendroica townsendi Townsend). Apparently the s i z e  of the Townsend's warbler population f l u c t u a t e s y e a r l y . During the nesting season of i960  a number of them were seen i n the loose o l d D o u g l a s - f i r  stand of Gaultheria-Mahonia, Eurhynchium-Mahonia and Pachystima-GaultheriaP e l t i g e r a ecosystem types.  I n i p 6 l , the r e l a t i v e l y abundant spring popu-  l a t i o n disappeared by the middle of May and the f i r s t group was again seen by e a r l y August. our area.  I n l a t e summer a number of small f l o c k s (15-30 b i r d s ) were i n  These f l o c k s followed the l i n e of deciduous trees along the  roads day by day.  They spend a l o t of time on the deciduous t r e e s , mainly  on red-alder and b i r c h .  Therefore i t seems that the deciduous trees fbrm an  important feeding s t a t i o n of the migratoring Townsend's warbler. BLACK-THROATED GRAY WARBLER (Dendroica nigrescens Townsend). the most common warbler species i n the study area.  This i s  I t occurs i n the hydro-  phytic communities, mostly i n the Eurhynchium-Mahonia and Polystichum ecosystem types.  I t has never been observed i n xerophytic communities during  the nesting season.  The population of Black-throated gray warbler concentrated  at places where mature b i r c h trees are present.  I n general t h i s species  i n d i c a t e s s i m i l a r h a b i t a t demands as the Black-capped chickadee,. but i t always uses the higher .part of the crown of b i r c h , therefore i t does not v i s i t the groups of young b i r c h e s . During the two summers a t o t a l of eleven nests were found, four Df them were placed.on the lower branches of o l d D o u g l a s - f i r t r e e s , k t o 8 m. above the ground.  A l l the other nests were found i n the higher part of  b i r c h crowns, u s u a l l y 15 t o 20 m. above the ground.  -172-  MacGILLIVRAY's WARBLER (Oporonis tolmiel Townsend), i s a separate species of the dense f o r e s t edge.  I n the hydrophytic communities,  i t occurs i n the  higher part of the f o r e s t along the stand edges, and the dense brush covered parts of rockflows, while i n the xerophytic communities i t occurs normally i n dense roadsides.  Nineteen t e r r i t o r i e s and two nests were found during  the two years. YELLOWTHROAT (Geothylpis t r i c h a s Linnaeua).  This species i n d i c a t e s  strong f i d e l i t y t o the dense stand of Spiraea d o u g l a s i i and S a l i x - L y s i c h i t u m Oenanthe ecosystem types. . I t i s d i f f i c u l t t o f i n d the f a c t o r or f a c t o r s which regulate the occurrence of the Yellowthroat. About 2 t o 3 .acres of the adjacent marsh area was covered with Spiraea d o u g l a s i i which adjoined the Carex stand and Salix-Lysichitum-Oenanthe ecosystem types.  In .i960, four t e r r i t o r i e s , , i n  I96I seven t e r r i t o r i e s were found here. In the study areas, about 5 "to 6 acres of land were covered with Spiraea douglasii•  The Salix-Lysichitum-Oenanthe type i s not present here.  Carex type i s r e l a t i v e l y small. two summers.  The  No Yellowthroat was observed here during.the  Therefore i t , i s surmised t h a t both the Salix-Lysichitum-Oenanthe  and the Carex types would play a,role i n the h a b i t a t s e l e c t i o n of the Yellowthroat. WILSON'S WARBLER (Wilsonia p u s i l l a Wilson).  This species normally  v i s i t e d the edges of hydrophytic communities of our area which are connected with the Salix-Lysichitum-Oenanthe ecosystem type.  I t seems t h a t . i t prefers  the dense a l d e r - w i l l o w t h i c k e t . HOUSE SPARROW (Passer domesticus Linnaeus). were seeen i n the southern part of the area. species of Hope.  Only two male i n d i v i d u a l s  This i s a common n e s t i n g  -173-  RED-WINGED BLACKBIRD (Agelaius phoenieeus Linnaeus). i n the study area .both summers. of the adjacent marsh.  One p a i r nested  But i t i s one of the common nesting species  In the summer of i960 eleven male b i r d s were counted  here, while i n 1961 fourteen males were counted. BREWER'S BLACKBIRD (Euphagus cyanocephalus Wagler).  This species nests  around Hope and a f t e r the nesting season a number of large f l o c k s use the Salix-Lysichitum-Oenanthe type of the adjacent.marsh  for roosting.  In t h i s  time a few i n d i v i d u a l s were seen i n the southern part of our area. BROWN-HEADED COWBIRD (Molothrus a t e r Boddaert). season a few i n d i v i d u a l s were seen i n the area.  During the nesting  F i v e nests were found with  cowbird eggs (two Swainson's thrush, and three S o l i t a r y v i r e o nests).  After-  the nesting season a large f l o c k of cowbirds used the marsh area f o r r o o s t i n g . WESTERN TANAGER (Piranga l u d o v i c i a n a Wilson).  A number of observations  i n d i c a t e d that the Western tanager prefers the more open f o r e s t .  The logged  areas where-a few trees.were l e f t standing were the best h a b i t a t f o r t h i s species i n our area. I t seems that the Western tanager u t i l i z e s coniferous and trees a l i k e .  deciduous  I t s population i s about the same i n the o l d scattered deciduous  stand of Xale Indian Reservation as i n the opne Douglas f i r stand of our area.  Therefore i t i s . b e l i e v e d t h a t the presence of t h i s species i s rather  more dependent on the open stand than on the species of trees that compose i t . In the study area, Western tanager occurs i n the Gaultheria-Mahonia, Pachystima-Gaultheria-Peltigeria and the open part of the Eurhynchium-Mahonia ecosystem types.  The eastern part of the Gaultheria-Mahonia type of the study  area, where a.few o l d b i r c h and D o u g l a s - f i r ' t r e e s were l e f t standing a f t e r the logging and a dense understory of maple i s present, i s apparently the best  -174-  nesting h a b i t a t , because on t h i s  about one acre area four nests were found  i n i 9 6 0 and.two i n 1 9 6 1 .  BLACK-HEADED GROSBEAK (Pheufcteicus melanocephalus Swainson). rare species.  This i s a  I t was sometimes seen only s i n g l y or i n p a i r s i n the young  deciduous stand of the study area.  But small f l o c k s of 2 - 6 i n d i v i d u a l s were  often seen i n the young deciduous stand of the Yale Indian Reservation. It. i n d i c a t e s a.strong f i d e l i t y t o the young deciduous stand (Polystichum ecosystem type) where a few o l d a l d e r , maple and poplar trees are present. Therefore i t i s b e l i e v e d that the presence of t h i s species strongly depends on the successional stage of the stand and the species of t r e e s . A l l the seven nests were found i n the upper t h i r d of young deciduous trees which were located along streamlets.  This s p e c i a l h a b i t a t and r e -  s t r i c t e d nest p l a c i n g method i n d i c a t e s that the Black-headed grosbeak has a r e l a t i v e l y narrow range of adaptation i n our area.  This r e s t r i c t e d nesting  habitat could be explained by the nest b u i l d i n g technique of t h i s species. Namely i t s b u i l d s i t nest from hundreds and hundreds of very f i n e 6 - 8 cm. long twigs without an b i n d i n g m a t e r i a l , hence the upper t h i r d part of the crown of young deciduous trees seems t o be the only place where such a nest can be placed.  The dense branches of the upper crown can give the required s t a b i l i t y  and p r o t e c t i o n f o r the nest, and the steam side h a b i t a t may be preferred f o r i t s dense vegetation. EVENING GROSBEAK (Hesperiphona  vespertina Cooper).  I n the s p r i n g ,  during the f i r s t and second weeks of May, a number of small f l o c k s of 1 0 - 2 0 b i r d s were often seen, mainly i n the Eurhynchium-Mahonia ecosystem type. Later the r e l a t i v e l y abundant spring population decreased and only a few i n d i v i d u a l s were seen during the nesting season.,  -175-  Eight t e r r i t o r i e s were found, two of them were i n our area (one i n the Eurhynchium-Mahonia ecosystem type, other i n Polystichum), a l l others i n the Eurhynchium-Mahonia type of the adjacent f o r e s t . PURPLE FINCH (Carpodacus purpureus c a l i f o r n i c u s Gmelin).  During the  spring migration, a number of Purple f i n c h f l o c k s v i s i t e d the S a l i x Lysichitum-Oenanthe  type of the adjacent marsh and the Polystichum type of  our area, but only a few i n d i v i d u a l s were seen during the nesting season. They stayed mainly i n the loose D o u g l a s - f i r stand of Gaultheria-Mahonia Pachystjma-Gaultheria-Peltigeria communities.  and  Only four t e r r i t o r i e s were  found during.the two summers. •PINE SISKIN (Spinus pinus Wilson). i n the study area. I96I.  This species i s r e l a t i v e l y abundant  F i v e breeding t e r r i t o r i e s were found i n i960, seven i n  A l l these nests were i n the Gaultheria-Mahonia ecosystem type.  Pine  s i s k i n s spend a great deal of time i n the open .areas and feed on dendelion seeds i n May and June. During e a r l y June several small groups of young Pine s i s k i n were observed i n the mentioned h a b i t a t .  In the l a t e summer r e l a t i v e l y large f l o c k s of s i s k i n  were seen i n the Polystichum and Salix-Lysichitum-Oenanthe AMERICAN GOLDFINCH (Spinus t r i s t i s Linnaeus).  communities.  This species i s one of  the common b i r d s of the young hydrophytic ecosystem types, mainly i n the Salix-Lysichitum-Oenanthe and Polystichum.  Apparently the wet open areas with  herb vegetation are i t s best feeding h a b i t a t .  They spend a great deal of  time on the dendelion heads. The g o l d f i n c h occurs on the study area i n those parts of the ecotone of Eurhynchium-Mahonia and Polystichum types which are bordering with open grassland.  -176SPOTTED TOWHEE ( P i p i l o raaculatus Linnaeus).  I t i s a f a i r l y abundant  b i r d i n the logged and burned places of our area (both xerophytic and hydrophytic communities).  I t was found that the c o l o n i z a t i o n of the Towhee s t a r t s  when the shrub l a y e r begins t o close,about 5 t o 7 years a f t e r logging. When the vegetation l a y e r i s already closed i t disappears from the stand and occupies the edge of the f o r e s t .  I t seems that the h a b i t a t demand of  t h i s species i s between that of the Junco (open shrub l a y e r ) and of the Cedar waxwing (closed young stand). OREGON JUNCO (Junco oreganus Townsend). b i r d s of our area.  This i s one of the commonest  Discussed separately.  CHIPPING SPARROW ( S p i z e l l a passerina Bechstein). i n our area.  This i s a rare species  Only one nest was found.in the loose young stand of G a u l t h e r i a -  Mahonia ecosystem type.  But i t i s abundant i n the logged and burned places  of the same f o r e s t type of adjacent p r i v a t e f o r e s t . WHITE-CROWNED SPARROW ( Z o n o t r i c h i a leucophrys F o r s t e r ) . f a i r l y abundent nester around the v i l l a g e of Hope.  This i s a  Only a few i n d i v i d u a l s  were seen i n the burned area of our f o r e s t where the shrub l a y e r i s not yet closed.GOLDEN-CROWNED SPARROW ( Z o n o t r i c h i a a t r i c a p i l l a Gmelin).  Mrs. Thacker  (1922) noted t h a t . t h i s species i n summer r e s i d e n t i n the study area. But only one f l e d g i n g young was seen i n the lower part of Eurhynchium-Mahonia ecosystem type i n the summer of i960.  I n I 9 6 I , the l a s t i n d i v i d u a l was seen  on May 30. SONG SPARROW (Melospiza melodia Wilson).  This i s the commonest sparrow  species of our area.  I t nests i n the dense roadside near the water and i n  the spiraea swamps.  Apparently, each spiraea swamp has i t s own Song sparrow  population.  -177-  SUMMARY 1.  F i f t e e n ecosystem types of the study area and of the adjacent lake  are described. 2.  Their b i r d populations were studied i n d e t a i l and these were ar-  ranged i n the f o l l o w i n g three b a s i c groups: a)  C h a r a c t e r i s t i c species,. include those b i r d s which are f a i t h f u l  to an ecosystem type t o the degree that they are not l i m i t e d by the i o n a l status of crown canopy.  They may  success-  remain present even a f t e r severe  disturbances such as logging. b)  Dominant species include those b i r d s which are numberous w i t h i n  an ecosystem type, b u t . t h e i r presence or absence may  depend upon the  successional stage of the f o r e s t stand. c)  Accessoric species are present,in small numbers only and have  no f i d e l i t y to the ecosystem type. 3-  A t t e n t i o n was paid to the d i f f e r e n c e i n b i r d populations of  s i o n a l stages i n two ecosystem types: -Polystichum ecosystem types.  Pachystima-Gaultheria-Peltigera  succesand  The census l i s t s of these successional stages  i n d i c a t e d that change i n the b i r d populations i s p r o p o r t i o n a l with the change i n the k.  stand. The r e s u l t s of the census work (done by t e r r i t o r y and nest mapping  during two breeding seasons),, i . e . the b i r d fauna of the e a r l y summer, i s expressed by biomass values; the comparison of the ecosystem types i s based on these biomass values. 5-  The i n t e r r e l a t i o n s between the ecosystem types and t h e i r b i r d popu-  l a t i o n s were studied and.it  was found that the present avifauna i s the f u n c t i o n  of the present vegetation, p h y s i c a l environment and the adaptive range (or  -178e c o l o g i c a l p l a s t i c i t y , . w h i c h i s the same) of the species. . 6.'  Eight nesting species were studied i n d e t a i l with respect to  environmental f a c t o r s i n f l u e n c i n g nest placing.and height and nest strucAltogether 1 6 7 nests were studied during the two seasons, and at 5 5  ture.  nests, f a c t o r s such as l i g h t i n t e n s i t y , temperature and mechanical s t r e s s r e s i s t a n c e were measured. 7.  I n the course of the season, and.in the d i f f e r e n t h a b i t a t s , most  of the studied b i r d s adapted the nest s i t e to s u i t a b l e , equable microclimate.  In c e r t a i n species i n s u l a t i o n of the nest v a r i e s according t o  the needs i n d i c a t e d by extremes of the microclimate.  In other species the  nest m a t e r i a l i s chosen t o provide the best a v a i l a b l e r e s i s t a n c e to mechanical s t r e s s e s . 8.  Thus v a r i a t i o n s i n nest height, and distance from the trunk i n  tree nesters, i s explained f o r seven of the studied species.  The eighth,  the ground n e s t i n g Junco evidences that the above adaptations are not due to predator pressure or other f a c t o r s , but to the ecoclimate, because t h i s species a l s o shows d i f f e r e n t adaptations to s o i l wetness and c l i m a t e , but avoidance of ground predators here i s a b s o l u t e l y out of the question.  -179-  BIBLIOGRAPHY Baldwin, S.P. and S.C. Kendeigh, 1932. Physiology of the temperature of b i r d s . S c i . Publ. Cleveland Mus. Nat. H i s t . 3 : l - l 6 l . Botvay, K., 1954. Az.altalanos meteorologia,,idojarastan es e g h a j l a t t a n a l a p j a i . Erdomernoki F o i s k o l a Tanulmanyi Osztalya. Sopron. 1 - 3 0 2 . Bruns, H., 1 9 6 1 . Die w i r t s c h a f t l i c h e Bedeutung der Vogel im Walde. Naturw. Rundschau, 14: 95-103Chapman, J.D. and D.B. Turner, 1956. B r i t i s h Columbia a t l a s of resources. B.C. Nat. Resources Conference 1 9 5 6 . F e r r y , C, i960. Recherches sur l ' e c o l o g i e des oiseaux f o r e s t i e r s en Bourgogne. L'ayifaune n i d i f i c a t r i c e d'un t a i l l i s sous f u t a i r e . Alauda 2 8 :  93-123-  Geiger, R., 1 9 5 9 . The climate near the ground. Cambridge, Massachusetts. 1-494.  Harvard U n i v e r s i t y Press  Di G l e r i a , J . , A. Kliirjes-Szmik and M. Dvoracsek, 1957T a l a j f i z i k a es t a l a j k o l l o i d i k a . Akademia Kiadop. Budapest. 1 - 7 2 8 . Horvath, 0., 1963. Seasonal d i f f e r e n c e s i n rufous .hummingbird, nest height and t h e i r r e l a t i o n t o nest climate. M.Sc. submitted f o r p u b l i c a t i o n . Johnston, D.W. and E.P. Odum, 1956. Breeding b i r d populations i n r e l a t i o n to plant succession on the Piedmont of Georgia. Ecology, 3 7 ( l ) 5 0 - 6 2 . Kendeigh, S.C,  1934.  }  14:  The r o l e of environment. i n the l i f e of b i r d s . E c o l .  299-417.  Monogr. 4:  1944.  Measurement of b i r d populations. E c o l . Monogr.  67-IO6.  1945. Community s e l e c t i o n by b i r d s on the Helderberg Plateau of New York. Auk 6 2 : 418-436. }  }  Ecol. 27:  1946.  Breeding b i r d s of the beech-maple-hemlock community.'  226-244.  1947. B i r d population studies i n the coniferous f o r e s t biome during a spruce budworm outbreak. Ontario Dept. Lands and Forest, B i o l . B u l l . 1: 1-100. }  1948. B i r d populations and b i o t i c communities i n northern Lower Michigan. E c o l . 29: 101-114. }  1954. H i s t o r y and e v a l u a t i o n of various concepts of plant and animal communities i n North America. E c o l . 35: 152-171. }  -180-  K r a j i n a , V.J., 1959* B i o c l i m a t i c Zones i n B r i t i s h Columbia. U n i v e r s i t y of B r i t i s h Columbia. Bot. Ser. No. 1 , Vancouver, B.C., pp.. 4 7 . 105:  , i960. 197-110.  Ecosystem c l a s s i f i c a t i o n o f f o r e s t s .  S i l v a Fennica.  Lesko, G.L., 1 9 6 1 . 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Quantitative Untersuchungen liber d i e Vogelfauna i n den Waldern Sudfinnlands. Acta Zool. Fenn. 7>PP« 2 1 0 . S t e e l , R.C.D., i 9 6 0 . P r i n c i p l e s and procedures o f s t a t i s t i c s . Book Company, Toronto, pp. 4 8 l .  McGraw-Hill  Stresemann, E., 1 9 2 7 - 3 4 . Aves. Kukenthal Handbuch der Zoologie., v o l . 7 pt. 2 , pp. 8 9 9 . B e r l i n . Sukachev, V.N., 1 9 4 7 - The ground of biogeocoenologic theory, I n the book of homage devoted t o the 3 0 t h Anniversary of the Great Octob. Revol. 2 , Aca. S c i . Press. M-L. Thacker, Mrs.T.L., 1 9 2 2 , L i s t o f the commoner b i r d s of the neighbourhood of Hope, B.C. Ms. deposited.in the archives of the Dept. of Zoology, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C. Tansley, A.G., 1935* The use and abuse of vegetation concepts and terms. Ecology, 16 :• 2 8 4 - 3 0 7 • Turcek, F.J., 1 9 5 4 . A c o n t r i b u t i o n t o the f u n c t i o n of f o r e s t b i r d - p o p u l a t i o n from the point-of-view of biocoenology and f o r e s t managements. Aquila 55"58:  53-72.  -l8l-  Udvardy, M.D.F., 19^7 • Methods of b i r d s o c i o l o g i c a l survey on the b a s i s of some Tihany communities i n v e s t i g a t e d . Arch. B i o l . Hung., Ser. I I , vol.  17:  61-89.  , 1951-  Heat r e s i s t a n c e i n b i r d s .  Congr. 1 9 5 0 . , pp. —.  Proc. Xth. Internat. Ornith.  595-599-  Notes on the e c o l o g i c a l concepts of h a b i t a t , biotope E c o l . kO: 725-728.  ,1959-  and niche.  Z e d l i t z , 0 . , 1926. Vogelgewichte a l s H i l f s m i t t e l f u r b i o l o g i s c h e Forschung. J o u r n a l f . Ornith. 7k: 296-308. Yapp, W.B.,  1953.  District.  The b i r d community of the F e l l Woods of the E n g l i s h Lake Nor.  We.  Nat.  2k:  .503-512.  , i960. The c o l o n i z a t i o n of coniferous p l a n t a t i o n s by b i r d s , Proc. X l l t h I n t e r . Ornith. Cong.. 8 0 1 - 8 0 3 .  APPENDIX  Analysis of Solitary vireo nest material. Table 18. a  b  c  d  e  f  S  Light range  50.06  47.34  50.92  56.56  57.49  52.17  54.07  Weight of nest  2.035  .4.948  3.270  5.030  3.801  6.613  6.279  0.080 1.5732  0.252  %  0.180 2.1765  0.429 8.5288  0.406 10.6813  0.392 5.9277  0.370 5.8926  0.353 7.8829  O.46O 10.7577  Moss  W %  0.001 0.0196  0.901 18.2093  -  0.918 18.2504  -  0.118 1.7843  • 0.004 0.0637  2.107 47.0522  1.616 37.7221  Lichen  W  -  0.097 1.9603  -  0.143 2.8429  0.487 12.8124  0.137 2.0716  -  0.137 3.2039  1.455 17.5923  0.635 12.6242  0.788 20.7313  0.116 1.7545  0.289 6.4537  0.334  0.194 3.8568  -  West  .  h  i  50.55  67.IO  4.473  4.276  High strength materials Silk  rf  5.0929  Phloem from 10 cm.  w  0.182 3.5923  0.067 1.3540  Fine phloem  iv % w  -  0.087 1.7582  -  0.019 0.3839  0.679 0.9552  0.434 8.6232  0.341 8.9713  0.242 3.6594  0.035 0.7073  0.0604  0.905  -  -  0.044 0.5320  -  0.316 8.3136  Birch bark  % Leaf veins  w -  Wasp nest wall  •it % w  Paper  %  w %  0.317 6.2340  -  _  0.974 15.5120  -  0.162 3.7885  0.855 13.6168  -  0.063 1.4733  0.161 2.4345.  •0.042 C.6688  0.017 0.3796  0.096 2.245C  0.447 6.7594  0.115 1.8315  _  •  7.8U0  0.040 0.7866  1.020 20.6143  0.408 4.9334  0.007 0.1391  -  -  -  0.620 12.1957  2.476 50.0802  2.171 26.2493  2.760 54.8696  2.338 61.5099  1.612 24.3914  2.360 37.5354  3.429 67.4139  0.899 18.1689  3.181 33.4643  0.90S 18.0318  1.108 29.1502  3.913 59.1713  -  0.267 5.3960  0.160 1.9347  0.180 3.5783  -  0.032 1.2399  3.428 67.4139  1.166 23.5649  3.341 40.3990  1.087 21.6101  1.109 29.1502  -  0.O28 0.6548  0.032 0.7146 2.798 62.4830  2.896 67.6563  Low strength materials Phloem up to 10 cm.  tf  Pupae  w %  w %  3.995 • 60.4112  2.972 45.7397  W %  -  1.108 22.3928  twigs  W t  0.666 13.0973  0.C16 0.3233  Seta  0.416 5.0302 -  tf W %  -  0.666 13.0973  ~ 1.124 22.7161  0.416 5.0302  •  0.885 17.5944  0.341 8.9713  -  _  0.885 17.5944  0.341 8.9713  -  -  2.372 45.7397  0.996 22.2420  0.478 11.1786  w  0.002 0.0393  0.030 1.6168  -  -  0.012 0.2385  0.005 0.1315  Wood  w %  0.363 7.1386  0.012 0.2425  0.042 0.5078  0.096 1.9085  -  Seeds  'll %  -  -  -  -  -  0.009 0.2367  Wings of insects  w '  -  . -  -  -  Feathers  w  -  -  --  -  -  0.075 1.5157  -  0.190 3.7773  -  -  Resin Kaple bark  %  i  -  'li  _  %  -  w  _  0.013 0.2627  -  -  2.300 27.8113  w  _  _  w  _  0.371 7.2959  0.180 3.6377  _  -  .  0.824 12.46C3  0.319 13.0434  -  0.C61 0.9714  -  0.360 8.4190  0.924 12.4603  0.38C 14.0149  0.6u 14.3144  0.397. 20.9073  _  _  0.043 0.9602  0.011 0.2572  0.008 0.1209  0.167 2.6596  -  0.139 2.1019  -  -  -  _  _  -  -  0.004 0.0604  --  _  -  2.342 28.3191  0.298 0.298  -  -  -  _  _  _  -  0.537 12.4883  -  _  -  w• %  Root  0.006 0.1179  0.641 14.3144  -  Stuffing materials Coniferous leaves  0.478 11.1786  -  Stress distribution materials Grass  0.996 22.2420  -  z  0.009 0.2367 0.023 0.6049  0.151 2.2832  0.167 2.6596  0.0*3 0.9602  0.011 0.257?  

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