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Factors affecting th local distribution of blue grouse on a breeding range Elliott, Peter Wayne 1965

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FACTORS AFFECTING THE LOCAL DISTRIBUTION OF BLUE GROUSE ON A BREEDING RANGE by Peter Wayne E l l i o t t ( B . S c , U n i v e r s i t y of B r i t i s h Columbia, 1958) A THESIS SUBMITTED IN PARTIAL FOR THE DEGREE OF i n DEPARTMENT FULFILMENT OF THE REQUIREMENTS MASTER OF SCIENCE the OF ZOOLOGY We accept t h i s t h e s i s as conforming to the re q u i r e d standard: THE UNIVERSITY OF BRITISH COLUMBIA December, 1965 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 r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree t h a t 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 s t u d y . I f u r t h e r agree t h a t p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head of my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i 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 a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of Zoology The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada F e b r u a r y 1 1 , 1966 i ABSTRACT The d i s p e r s i o n of a population of blue grouse was analyzed using data from a breeding range on east-central Vancouver Island. During the summers of 1959-1962, the lo c a t i o n s , densities,- »ega*»fe4ve preferences, and behaviour of grouse were studied using several habitats with varying den s i t i e s of vegetation. A removal experiment was performed i n d i f f e r e n t habitats to tes t the e f f e c t of i n t e r a c t i o n and s e l e c t i o n of habitat on the d i s p e r s i o n of males. A l l adult males and a few y e a r l i n g males were t e r r i t o r i a l , and t e r r i t o r i e s were spaced i n a near-uniform pattern. Within a given season, males removed from t h e i r t e r r i t o r i e s were seldom replaced by other adults, suggesting that no surplus of n o n - t e r r i t o r i a l adults was present. About h a l f of the y e a r l i n g males were prevented from e s t a b l i s h i n g t e r r i t o r y by the presence of adults, and these y e a r l i n g s were att r a c t e d to the v i c i n i t y of t e r r i t o r i a l males. The l o c a t i o n of t e r r i t o r i e s by newly-adult males di d not depend s i g n i f i c a n t l y on the number of t e r r i t o r i e s already present, even though the tendency toward uniform spacing was preserved. Comparison with other studies indicated that t e r r i t o r y s i z e and po s s i b l y the f r a c t i o n of y e a r l i n g males i n the population were inv e r s e l y r e l a t e d to the density of males. Females r e s t r i c t e d t h e i r movements while on the breeding range but were not t e r r i t o r i a l . No pair-bonds were observed but females stayed near t e r r i t o r i a l males p r i o r to nesting. A f t e r the hatch, the locations of females and broods bore no r e l a t i o n to each other or to the positions of males. Int e r a c t i o n apparently had no e f f e c t on breeding numbers. A l l b irds preferred sparse vegetation to dense. When compared to randomly-chosen points, t e r r i t o r i e s were found more often i n areas with i i sparse vegetation, elevated points, and patches of open ground. Within open habitats, nests were usually located where cover by logs, stumps, and ground-level vegetation was high, and cover by dead plants and l i t t e r was low. Broods were associated with moist areas and other areas having heavy cover by vegetation at the ground level. Chicks apparently dispersed widely between their f i r s t and second summers. In their third summer, males usually returned within one-half mile of the positions they used as yearlings. Once territories were established, the owners returned to them in succeeding summers. Females one year and older showed a f a i r l y accurate return to their previous locations. The dispersion was described somewhat theoretically by considering the summer population to be grouped into two types of aggregations. The f i r s t , found in the earlier half of the summer, was caused by the attraction of yearling males and lone females to t e r r i t o r i a l males. Later, hens with their broods were the dominant groupings. The spacing, movements, and habitat preferences seemed to be adaptations allowing such populations to rapidly exploit new habitats. 1 i i i TABLE OF CONTENTS Page ABSTRACT .. .. .. .. .. .. ,, i TABLE OF CONTENTS .. .. ., .. .. .. i i i LIST OF FIGURES .. .. .. .. .. i v LIST OF TABLES .. ,. .. .. v ACKNOWLEDGEMENTS .. .. .. .. .. v i INTRODUCTION .. ., .. .. .. .. 1 DESCRIPTION OF STUDY AREA AND VEGETATION . . . . .. 2 METHODS .. .. .. ., .. ,. 10 RESULTS .. .. .. ,. .. 12 I n t e r a c t i o n between males on c o n t r o l areas ., .. 12 I n t e r a c t i o n between males on removal p l o t s .. .. 23 Comparison of c o n t r o l and experimental p l o t s ., .. 33 Hab i t a t s e l e c t i o n by males on c o n t r o l areas .. .. 38 Habit a t s e l e c t i o n by males on removal p l o t s , t .. 45 D i s p e r s a l of j u v e n i l e s and movements of y e a r l i n g males . 49 The e f f e c t of i n t e r a c t i o n on the d i s p e r s i o n of females and j u v e n i l e s .. .. .. ., .. 55 The e f f e c t of h a b i t a t s e l e c t i o n on the d i s p e r s i o n of females and j u v e n i l e s ., .. .. .. 60 DISCUSSION .. .. .. .. .. .. 67 SUMMARY AND CONCLUSIONS .. .. .. ., .. 75 LITERATURE CITED .. .. .. .. .. 78 APPENDICES .. .. .. .. .. .. .. 82 i v LIST OF FIGURES Page Figure 1. Study area, showing p l o t s , main zones of vegetation, lakes and swamps, and l i m i t s of f o r e s t f i r e s .. .. .. .. 3 Figure 2. Photograph showing Very Open vegetation, September, 1962 .. .. .. 5 Figure 3. As 2., Open vegetation .. .. .. 5 Figure 4. As 2., Dense vegetation .. .. 6 Figure 5. As 2., Very Dense vegetation ». *. 6 Figure 6. Diagram showing an average l i n e - t r a n s e c t for each major type of habitat, spring aspect, 1962 .. .. .. 9 Figure 7. Areas used by males on main control p l o t s .. 14 Figure 8. Graph showing r e l a t i o n s h i p between number of observations and s i z e of t e r r i t o r y for males on main control plots .. .. .. 17 Figure 9. Favoured areas used for analysis of removal and repopulation on experimental plots .. 26 Figure 10. Total numbers of resident males found on con t r o l plots over four summers .. 35 V LIST OF TABLES Table I. Table II. Table III. Table IV. Table ' V. Table VI. Table VII. Table VIII. Table IX. Description of vegetative and other cover on four main habitats from line-intercepts and quadrats measured in September, 1962 .. Males found on removal plots, 1959-1962 .. Use of specific areas on the removal plots by males from 1959 to 1962 .. .. .. Comparison of numbers of new males on control and experimental plots .. .. .. Comparison of vegetation at vacated territories and use of these territories in succeeding years Movements of males from point of banding as yearlings to point of recovery as adults .. Number of females sighted on removal plots and main control plots, as compared' to type of vegetation and presence of males .. .. Comparison of cover at nest-sites with cover in Very Open and Open habitats .. .. Approximate classification of habitat at 244 broodsites .. .. .. .. .. Page 7 24 27* 36 40 53 58 62 64 v i ACKNOWLEDGEMENTS This thesis could not have been completed without the assistance of a number of people. I would particularly like to mention the large amount of help I have received from Dr. James F. Bendell, who supervised the thesis project, instigated many long discussions, advanced criticisms and suggestions, and allowed me to use many data collected in the f i e l d by him and other observers. I would also like to thank Drs. Ian McT. Cowan, Dennis H. Chitty, and Miklos D. F. Udvardy, who served on my thesis committee and helped me in many ways. Other persons whose assistance I greatly appreciated are Dr. F. C. Zwickel, who c r i t i c i z e d an early manuscript and served as a sounding-board for ideas in the f i e l d ; Dr. E. M. Hag#meier who read and corrected an early manuscript; and B. R. Simard and R. D. Jakimchuk, who took part in useful discussions and worked with me in the f i e l d . My wife's assistance made the analyses of vegetation much faster and easier. This project was supported by funds from the National Research Council, Canadian Industries Limited, the Fish and Game Branch of the Department of Recreation and Conservation (Province of B.C.) and the University of British Columbia. 1 INTRODUCTION This t h e s i s attempts to d e s c r i b e and e x p l a i n d i s p e r s i o n , or l o c a l d i s t r i b u t i o n i n a p o p u l a t i o n of blue grouse, Dendragapus obscurus f u l i g i n -osus, on i t s summer range. The e f f e c t s of s o c i a l i n t e r a c t i o n and h a b i t a t s e l e c t i o n on d i s p e r s i o n of t e r r i t o r i a l males, n o n - t e r r i t o r i a l males, females, and j u v e n i l e s are examined. P a r t i c u l a r a t t e n t i o n i s p a i d to c e r t a i n questions in as yet l i t t l e s t u d i e d ©a t h i s s p e c i e s . Some of these questions are: 1. How f u l l y can the d i s p e r s i o n of the grouse be explained by i n t r a -s p e c i f i c i n t e r a c t i o n ? 2. How important i s t h i s i n t e r a c t i o n i n the c o n t r o l of numbers? 3. Other than i n t e r a c t i o n , what f a c t o r s a f f e c t the d i s p e r s i o n of the population? 4. How important to spacing are summer movements and the d i s p e r s a l of j u v e n i l e b i r d s ? 5. What s o r t of s o c i a l o r g a n i z a t i o n i s shown by these b i r d s on t h e i r breeding range? These questions were framed w i t h the male blue grouse i n mind and the r e p o r t s t r e s s e s e x p l a n a t i o n of d i s p e r s i o n i n the males. D i s p e r s i o n of females and young i s discussed more b r i e f l y . Since i n f o r m a t i o n on d i s p e r s i o n i n b i r d s i s s c a t t e r e d through the l i t e r a t u r e , a complete review of the subject w i l l not be included here. Many s t u d i e s on t e r r i t o r i a l i t y , h a b i t a t s e l e c t i o n , and s o c i a l o r g a n i z a t i o n have appeared and r e l e v a n t papers w i l l be mentioned throughout the t e x t . The term " d i s p e r s i o n " i s used i n t h i s report as i n Wynne-Edward's (1962) book which i s the most recent general work on d i s p e r s i o n . The most recent and d e t a i l e d work on the b i o l o g y and ecology of the c o a s t a l blue grouse i s that of B e n d e l l (1954). The reader should keep i n mind that these c o a s t a l b i r d s show an a l t i t u d i n a l m i g r a t i o n , descending from upland winter range at about the end of March and ascending from J u l y through September. 2 DESCRIPTION OF STUDY AREA AND VEGETATION The study area was l o c a t e d i n the Quinsam Lakes r e g i o n of Vancouver I s l a n d approximately eleven miles southwest of Campbell R i v e r , B r i t i s h Columbia. F i g . 1 shows the r e g i o n covered, a roughly c i r c u l a r area a p p r o x i -mately three miles i n diameter, bounded on>the south by Middle Quinsam Lake. The study area used by B e n d e l l from 1950 to 1953 l i e s s i x miles to the east ( B e n d e l l , 1954). Most of the area c o n s i s t s of low h i l l s separated by temporary ponds, small streams, swamps, or peat bogs i n the depressions. P r i o r to logging and burning the area possessed a humid l i t t o r a l c l i m a t e w i t h an average annual temperature of about 50° Fahr. and r a i n f a l l of 40-80 i n . per year. The o r i g i n a l s o i l was concretionary brown or minimal podzol ( K r a j i n a , 1959; 1954). oThroughout the study there was a greater range i n temperature and humidity on the study area than i n surrounding f o r e s t e d s e c t i o n s . At t h i s time i t was a l s o c l e a r that f i r e and e r o s i o n had much reduced the upper l a y e r s i n the s o i l p r o f i l e . O r i g i n a l l y the area was mature f o r e s t , defined by Rowe (1959) as the southern coast s e c t i o n of the Coastal Forest Region. By K r a j i n a ' s c l a s s i -f i c a t i o n the area was a mixture of Douglas f i r (Pseudotsuga m e n z i e s i i ) and western hemlock (Tsuga h e t e r o p h y l l a ) b i o c l i m a t i c zones. Two severe f o r e s t f i r e s have a f f e c t e d the area ( F i g . 1) and the v e g e t a t i o n i s now that of e a r l y s u c c e s s i o n a l stages. The extent of the f i r e s , the type of regener-a t i o n , and the presence of p l a n t a t i o n s of Douglas f i r ( r e s u l t i n g from r e f o r e s t a t i o n programs) have caused the, area to develop four main types of v e g e t a t i o n . On the b a s i s of s t r u c t u r e and d e n s i t y these are c a l l e d Very Open, Open, Dense, and Very Dense..' The Very Open and Open types were found w i t h i n the area burned i n Study area, showing plots (see text), main zones of vegetation, lakes and swamps. Dashed lines separate vegetational zones. Scale: 1/8" = 200'. 4 1952, Very Open p a r t s were those showing a l i g h t cover of w i l l o w ( S a l i x spp., mainly S. s i t k e n s i s ) and p r a c t i c a l l y no coniferous cover, even on some s e c t i o n s where f i r p l a n t i n g had been attempted i n 1958 ( F i g . 2 ) . This was the most common type over the study area. Open areas showed a s l i g h t l y heavier deciduous cover and much more c o n i f e r . These areas were r e f o r e s t e d i n 1953 ( F i g . 3) and, as i n the f i r s t type, most of the coniferous cover was Douglas f i r . The Dense and Very Dense types were lo c a t e d w i t h i n the boundaries of the 1938 f i r e and apparently obtained t h e i r c oniferous cover through n a t u r a l as w e l l as a r t i f i c i a l r e g e n e r a t i o n . The cover by deciduous trees was about the same i n these two types and was heavier than that of the open types. The two d i f f e r e d i n amount of c o n i f e r . The Dense areas were p a r t l y r e p lanted and showed a mixture of red cedar (Thuja p l i c a t a ) , f i r , and hemlock ( F i g . 4 ) . The Very Dense areas showed the heavie s t cover by c o n i f e r s and, although s e v e r a l species were present, the mixture was dominated by hemlock ( F i g . 5 ) . Some p l a n t i n g had been done here but most regeneration seemed to have been n a t u r a l . This was the l e a s t common type over the study area. Hundred-foot l i n e - i n t e r c e p t s and yard-square quadrats were used to d e s c r i b e the four types of v e g e t a t i o n more r i g o r o u s l y . The length of each p o r t i o n of a t r e e or other major s t r u c t u r e that was " c u t " by a l i n e was measured to the nearest 0.1 f t . , and the height to the nearest 0.5 f t . The quadrats were located at 20 f t . i n t e r v a l s along the l i n e s and, on these, the area covered by l o g s , r o c k s , l i t t e r , bare s o i l , and each p l a n t species was estimated to the nearest 10%. Species covering l e s s than 10% of a quadrat were l i s t e d only as being present, and were l a t e r given an a r b i t r a r y value of 2 or 5% depending on the s i z e of the s p e c i e s . Some p l a n t species Figure 2. Photograph of Very Open habitat, f a l l , 1962. Rod shown i s divided into one-foot intervals. 6 Figure 5. Photograph of Very Dense habitat. 7 and other elements were estimated by both methods and, i n these cases, the quadrat figures were remarkably close to the more accurate l i n e - i n t e r c e p t f i g u r e s . The more important t o t a l s are given i n Table I below and further information from these analyses i s given i n the appendices. Table I. D e s c r i p t i o n of vegetative and other cover on four main habitats from l i n e - i n t e r c e p t s and quadrats measured i n September, 1 9 6 2 . Figures i n f i r s t four rows are from l i n e s , l a s t three rows from quadrats. S t r u c t u r a l element Very Open Type of vegetation Open Dense Very Dense Coniferous species 2 7 . 2 8 7 , 4 5 7 o 7 5 7 o Deciduous species 1 3 1 6 2 6 2 4 S a l a l (Gaultheria shallon) 1 0 1 5 2 2 3 1 Logs and stumps 1 4 1 1 2 4 1 5 Number of li n e s 1 3 1 3 1 3 1 1 Number of quadrats 7 1 6 3 6 8 6 0 Ground vegetation 2 1 % 2 0 7 . 3 6 7 » 4 4 7 o Bare ground and rock 2 4 1 7 3 5 Duff and l i t t e r 6 8 7 3 8 1 8 3 Willows are the main deciduous species r e f e r r e d to i n the table but some alder (Alnus rubra) and huckleberry (Vaccinium spp.) are included i n t h i s category. S a l a l i s included since i t was the dominant species at the ground l e v e l ( 6 4 7 , of ground vegetation, on the average). Bracken fern (Pteridium aquilinum) can be seen i n the photographs .which were taken i n the f a l l . Since t h i s species i s a late-developing one, and since I was mainly concerned with the spring aspect of the vegetation, bracken has 8 been omitted from the t a b l e . The duff and L i t t e r category includes dead leaves and other parts of plants, mosses, rotten wood, and s i m i l a r m a t e r i a l . The change i n t o t a l cover by trees and shrubs from Very Open to Very Dense, neglecting any overlap of deciduous and coniferous species, gives some idea of the density of the brush. The t o t a l s are, s t a r t i n g with the Very Open, 15%, 4 4 % , 7 1 % , and 9 9 % . It i s d i f f i c u l t to show the gradation i n these habitats even with the help of photographs. Because the four types are mentioned often i n the text and because the density of vegetation was a basic factor determining the spacing of grouse, I include a diagrammatic representation of the four habitats which should show the differences more c l e a r l y ( F i g . 6). For each habitat the l i n e - i n t e r c e p t c l o s e s t to the average was used i n the figure (some measurements were adjusted s l i g h t l y to make the coverage along the l i n e more l i k e the average). Some species were omitted and the remainder were categorized just as i n Table I. Other types of vegetation were obvious on the area but occurred less frequently. Some of these were: 1. Dense stands of pure alder or willow, usually i n wet depressions. 2. Riparian thickets of various shrubs such as Cornus o c c i d e n t a l i s , Rubus s p e c t a b i l i s , and R. p a r v i f l o r u s . 3. Dense sedge areas (Carex spp.) i n moist depressions. 4 . Swamps i n areas of slowly moving water (Lysichitum americanum, Opoplanax horridus, etc.) 5. Bogs i n areas of stagnant water (Sphagnum spp., Ledum groenlandicum, Pinus contorta, etc.) 9 J V V I n , Vfl m . ^ 1 . 1 V , . H 3 7 ? y rSH 17, „ ..tt 0 100' Very Open habitat mumm I 1 Uli. TTTii I I I I r~ Open habitat M l l l l l l l V l l l l f l l l H I IJ Dense habitat • 1 1 > ill 11 1 1 1 1 1 I 11 V l u l l , i n V l l l l l l l l l ml I «T U w • I I I I In I V I VI Very dense habitat coniferous cover. \y deciduous cover, M I I I s a l a l cover. ' I log and stump cover. Figure 6. Diagram showing an average line-transect for each major type of habitat over the study area, spring aspect, 1962. 10 METHODS Bendell's (1954) procedures were used f o r observing, handling, and i n d i v i d u a l l y banding fefee grouse. So that t h e i r l o c a t i o n s could be mapped, a l l observations were r e l a t e d to known po i n t s on the study area. Captured or c o l l e c t e d b i r d s were c l a s s i f i e d as j u v e n i l e , y e a r l i n g , or a d u l t by t h e i r outer r e c t r i c e s and l a s t two primaries ( B e n d e l l , 1955). Weights and b u r s a l depths were used i n some cases. Each time a grouse was discovered i n the f i e l d , notes were made on i t s behaviour, i t s p o s i t i o n r e l a t i v e to any neighbours, and the h a b i t a t immediately around i t . I An experiment was used to t e s t the e f f e c t of i n t e r a c t i o n and h a b i t a t s e l e c t i o n on the d i s p e r s i o n of males. During the summers of 1959 through 1962 males were removed from two 46-acre p l o t s , each 1000 by 2000 f t . , s t a r t i n g as e a r l y i n the breeding season as p o s s i b l e . This was done mainly to e s t a b l i s h whether removed males< would be replaced by other males, e i t h e r w i t h i n the same summer (breeding season) or i n succeeding summers. The experimental p l o t s were searched at i n t e r v a l s through the summers and removal was continued as long as males could be found. For comparison, s e v e r a l 23-acre c o n t r o l p l o t s , each 1000 by 1000 f t . , were e s t a b l i s h e d nearby. On these, as over most of the study area, grouse were observed and, where p o s s i b l e , caught and banded. Observers t r i e d to cover these areas more i n t e n s i v e l y than the areas outside the p l o t s . Data on hours spent on these p l o t s are given i n the appendices. The f a i r l y d i s t i n c t boundaries of the main zones of v e g e t a t i o n suggested a n a t u r a l experiment on h a b i t a t s e l e c t i o n . F i g , 1 shows that the four major types of v e g e t a t i o n came together near the f i e l d camp. Because of t h i s the c o n t r o l and experimental p l o t s were set out i n p a i r s ( s t i p p l e d p l o t s i n F i g . 1). One removal p l o t was e s t a b l i s h e d i n Very Open 11 v e g e t a t i o n ( s i m i l a r to that shown i n F i g . 2) and the other i n Very Dense adjacent to i t (as i n F i g . 5 ) . Removal of males from the c o n t r a s t i n g areas was done to t e s t h a b i t a t preferences of incoming males as w e l l as to t e s t the e f f e c t of r e s i d e n t males on other b i r d s . The main p a i r of c o n t r o l p l o t s was a l s o set i n c o n t r a s t i n g h a b i t a t s but here the d i f f e r e n c e was not so s t r i k i n g s i n c e one was i n Dense v e g e t a t i o n (as shown i n F i g . 4) and the other i n Open (as i n F i g . 3 ) . In areas where searching was known to have been thorough some e x t r a c o n t r o l p l o t s were e s t a b l i s h e d f o r comparison of numbers ( c l e a r p l o t s shown on F i g . 1). E i g h t of these were used, three i n Very Open, two i n Open, two i n Dense, and one i n Very Dense. For each year, a l l observations of males were mapped, the s c a l e s being 1 i n . to 200 f t . f o r study p l o t s and 1 i n . to 500 f t . f o r other areas. Some maps were made of observations on females as w e l l , and a l l maps were used f o r analyses on d i s p e r s i o n , as shown l a t e r . The s i t e s used by some 80 r e s i d e n t males were described i n d e t a i l and, f o r comparison, s i m i l a r d e s c r i p t i o n s were made f o r a s e r i e s of p o i n t s chosen randomly over the study area. Bendell's (1954) work suggested that the areas used by r e s i d e n t males should be searched i n succeeding years to give i n f o r m a t i o n on death r a t e and replacement, and t h i s was done f o r a l l banded males that used an area c o n s i s t e n t l y over a summer. Some other methods were employed and, where these are r e l e v a n t to the problem of d i s p e r s i o n , they w i l l be mentioned i n the next s e c t i o n on R e s u l t s . Fieldwork was c a r r i e d out by a number of workers during the summers of 1959 (May 16 - August 31), 1960 (March 15 - August 30), 1961 (May 1 -August 31, September 4 - 7 ) , and 1962 (March 24 - 28, A p r i l 15 - 18, May 1 -September 7). I worked on the area during the summers of 1961 and 1962, and paid s p e c i a l a t t e n t i o n to the removal experiment and other s t u d i e s of d i s p e r s i o n i n 1962. 12 RESULTS I n t e r a c t i o n between males on c o n t r o l areas Results from experimental work w i l l mean l i t t l e unless the p a t t e r n of d i s p e r s i o n under normal c o n d i t i o n s has been examined. Therefore, t h i s s e c t i o n discusses the spacing of males on the c o n t r o l p l o t s and other areas away from the removal p l o t s . A f t e r a n a l y z i n g the spacing mathematically, I consider the year-to-year use of p l o t s by males, the s i z e of area used, replacement on vacated areas, and the d i f f e r e n c e s i n numbers and behaviour of a d u l t and y e a r l i n g males on c o n t r o l areas. Those males that hooted and d i s p l a y e d on a s p e c i f i c area showed a tendency toward uniform spacing. This was determined by measuring nearest-neighbour distances f o r the r e s i d e n t males found over most of the area shown i n F i g . 1 i n 1962, e x c l u d i n g the experimental p l o t s . I n an area of 936 acres the minimum number of r e s i d e n t males was estimated from the map to be 157. By the method of C l a r k and Evans (1954) the mean nearest-neighbour d i s t a n c e f o r an i n f i n i t e l y l a r ge and random p o p u l a t i o n of t h i s d e n s i t y was c a l c u l a t e d to be 255 f t . The a c t u a l mean from map measurements was 381 f t . and, when t h i s was d i v i d e d by the t h e o r e t i c a l mean, an index of departure from randomness (R) of 1.49 was obtained. This i n d i c a t e s a trend to u n i f o r m i t y s i n c e a random p o p u l a t i o n would give a f i g u r e of 1.00 and a uniformly spaced p o p u l a t i o n would give a f i g u r e of about 2.15. C l a r k and Evans formula f o r t e s t i n g the s i g n i f i c a n c e of R was used and showed that the d i f f e r e n c e from randomness was h i g h l y s i g n i f i c a n t . The type of d i s t r i b u t i o n was a l s o checked by comparison w i t h a set of random p o i n t s . On the 1962 map, 157 random p o i n t s were e s t a b l i s h e d and the d i s t a n c e from each of these to the nearest r e s i d e n t male was measured. 13 Ten of these distances were l e s s than 100 f t . and 43 were l e s s than 200 f t . None of the male-male distances were l e s s than 100 f t . and only 16 were l e s s than 200 f t . The average d i s t a n c e was 344 f t . as against 381 f o r the males. The two f i g u r e s d i f f e r s i g n i f i c a n t l y at the 5% l e v e l by Chi-square. I f the measurements are grouped by 50 f t . i n t e r v a l s (0-50 1, 51-100', e t c . ) and compared, the d i f f e r e n c e (shown by sum of Chi-square) becomes even more a. s i g n i f i c a n t , showing that males were d e f i n i t e l y f a r t h e r apart than random spacing would a l l o w . The near-uniform spacing was caused by t e r r i t o r i a l behaviour on the par t of most of the males. F i g . 7 shows how the main c o n t r o l p l o t s were used by a d u l t and y e a r l i n g males over the four summers. Some males were not banded and some s i g h t i n g s were not long enough f o r band combinations to be checked so that much time was given to cross-checking times of observations, e t c . , to a l l o w observations to be assigned to a p a r t i c u l a r male. P o i n t s of observations were then j o i n e d so as to give a maximum area f o r each male. The maps show only three p o i n t s where t e r r i t o r i e s seemed to ov e r l a p . In 1959 adu l t No. 17 was found near a d u l t No. 14 on June 1 but No. 17 was s i l e n t and showed no signs of d i s p l a y i n g when seen. The t e r r i t o r i e s of Nos. 26 and 210 touch on the 1960 map but the observations l e a d i n g to t h i s were made on separate days. The same a p p l i e s to the case i n v o l v i n g No. 131 i n 1962. T e r r i t o r y s i z e s ranged from 0.2 to 9.2 acres (average 2.6) but many of these were based on only a few observations. I f areas mapped from l e s s than ten observations are omitted the average becomes 3.7 acres (range 2.3 to 6.5). Males showed no tendency to hold t e r r i t o r i e s of constant s i z e from year to year. Only one case i s based on more than t e n observations 14 A43 • \ — j - — \ — v -1959 Y340 I960 Figure 2. Areas used by males on main control plots. The l e f t plot was i n Dense habitat, the right mostly i n Open habitat. Scale 1" = 440'. Ages and numbers are given for banded males (A - adult, Y - y e a r l i n g ) . C i r c l e s show single observations (open-silent male, closed-hooting). Dots show observations on resident males. x - adult a c c i d e n t a l l y k i l l e d . U - unhanded. 16 every year. This male, No. 9, showed t e r r i t o r i e s of 3 . 7 , 2 . 6 , 4 . 5 , and 4 .4 acres over the four years, suggesting that some constancy might have been uncovered with increased numbers of observations. Unfortunately the sizes c o r r e l a t e d better with the number of observations than they did with the year or ages of the males, as the graph below shows ( F i g . 8 ) . The spread of points i s s u f f i c i e n t that d i v i d i n g each s i z e by the number of observations used to make i t does not give any more usable f i g u r e s . The largest t e r r i t o r y was based on only a few observations (male No. 14 i n 1959) . Late i n the summer No. 14 was twice observed away from the open p l o t near females which he had probably pursued. Omitting these two sightings gives an acreage close to that used by No. 14 i n 1960. As expected from Bendell's (1954) work, males "homed", or showed a very close return, to t h e i r t e r r i t o r i e s once these were established. F i g . 7 shows t h i s , and i t was equally true for a l l males banded on t e r r i t o r y over the study area. Known banded males were seldom found away from t h e i r t e r r i t o r i e s , and, i f they were, the males were always s i l e n t . The obser-vations made on males away from t h e i r t e r r i t o r i e s came l a t e i n the summer (past mid-July) or, r a r e l y , very early i n the summer (early A p r i l ) . In a l l cases the unusual locations of males could be explained by assuming that they were migrating to or from the winter range. S l i g h t s h i f t s i n t e r r i t o r i a l boundaries were f a i r l y common, as shown on F i g . 7. For example, No. 9 expanded his t e r r i t o r y with the loss of his neighbours i n 1962. The unbanded males i n the centre of the plots s h i f t e d t h e i r locations s l i g h t l y from year to year. Some adjustment of boundaries probably took place a f t e r the removal of three males from the plots i n 1959, although none of these three positions; were a c t u a l l y overtaken by neighbours i n that year. These and other examples show that males would adjust t h e i r 17 » Cfl to w 6 PS PS w 2 « X Male No. 9 \ 5 10 15 NUMBER OF OBSERVATIONS 20 25 Figure 8. Graph showing relationship between size of territory and number of observations. 18 t e r r i t o r i a l boundaries as the p o s i t i o n s of t h e i r neighbours changed. F i g . 7 a l s o shows, however, that most of the observations on w e l l -known males were d i s t i n c t l y w i t h i n the t e r r i t o r i a l boundaries. This suggests t h a t , over most of the breeding season, males were not p a t r o l l i n g the boundaries of t h e i r t e r r i t o r i e s or a c t i v e l y defending them. D i r e c t f i g h t -i n g between neighbouring males was p r a c t i c a l l y never seen. Over two summers I observed only one such encounter and that took place on a removal p l o t . I t appeared that males knew the boundaries of t h e i r neighbours' t e r r i t o r i e s s i n c e , f o r example, the areas used by three a d u l t s k i l l e d on the main c o n t r o l p l o t s i n 1959 were l e f t vacant f o r the r e s t of that summer. On these p l o t s neighbouring males were o f t e n seen or heard hooting q u i t e near each other, but contact between hooting males was never observed. These p o i n t s suggest two p o s s i b l e mechanisms that might lead to the observed spacing between t e r r i t o r i e s . One mechanism would be a short intense p e r i o d of boundary adjustment through aggression immediately a f t e r males descended to the summer breeding range. This i s an u n l i k e l y p o s s i b i l i t y f o r s e v e r a l reasons. In 1960 s observation was s t a r t e d on the study area before males a r r i v e d and no unusual f i g h t i n g or s h u f f l i n g of areas was seen. As mentioned, males, a f t e r e s t a b l i s h i n g t e r r i t o r i e s , r e t u r n to these i n succeeding summer regardless of the number or l o c a t i o n of neighbours. A near-uniform d i s t r i -b u t i o n produced by strong aggression might be expected to lead to equal use of a l l p a r t s of the area but many areas of apparently s u i t a b l e h a b i t a t were never used as t e r r i t o r i e s . I t i s more l i k e l y that the hooting and other sounds produced by a t e r r i t o r i a l male, l o c a l i z e d around one or more favoured d i s p l a y spots, a d v e r t i s e d h i s presence and kept other t e r r i t o r y - h o l d e r s at some minimum d i s t a n c e away. This mechanism allows f o r the p o s s i b l e formation of loose groups of v o c a l males, mentioned below. Using t h i s idea i t i s much e a s i e r to account f o r l i t t l e f i g h t i n g , unused h a b i t a t , and p r e c i s e homing by males. Although mathematical a n a l y s i s showed males to be spaced somewhat uniformly, f i e l d observations suggested that males sometimes formed l o o s e l y -k n i t groups w h i l e hooting or d i s p l a y i n g . . This i s not c o n t r a d i c t o r y s i n c e the mathematical treatment depended on measurement from the. estimated centres of t e r r i t o r i e s . These groups could have been formed by neighbouring males that were w i t h i n t h e i r t e r r i t o r i e s provided they approached each other as c l o s e l y as the boundaries would a l l o w . As mentioned, direct: contacts between males were very r a r e l y seen. However, a c t u a l measurements of distances between neighbouring hooting males were made f o r some f o r t y cases and the distances averaged consid e r a b l y l e s s than the 381 f t . mentioned i n the mathematical analyses. In a l l areas there was a good deal of synchron-i z a t i o n of hooting but w i t h i n these "groups" hooting seemed to go on longer and be more communal than observed f o r more i s o l a t e d males. Evidence pre-sented l a t e r suggests that such groups were o f t e n a s s o c i a t e d w i t h p a r t i c u l a r types' of cover and landform. When c o n s i d e r i n g i n t e r a c t i o n i t i s important to e s t a b l i s h whether or not a l l males were able to e s t a b l i s h t e r r i t o r i e s . No n o n - t e r r i t o r i a l a d u lts were found on the c o n t r o l p l o t s although one of the three a d u l t s k i l l e d a c c i d e n t a l l y i n 1959 was s i l e n t when c o l l e c t e d and may not have been on t e r r i t o r y . Banded adu l t No. 124 was seen on the open p l o t e a r l y i n 1962 ( F i g . 7) but he was apparently s t i l l m i g r a t i n g from the winter range s i n c e he was found l a t e r i n the summer back on h i s former t e r r i t o r y some di s t a n c e from the p l o t s . This i s one of the r a r e examples, mentioned above, of a male o f f h i s t e r r i t o r y e a r l y i n the summer. Two other s i l e n t . 2 0 males on the p l o t s may have been y e a r l i n g s or r e s i d e n t s that were not i d e n t i f i e d . Observations over a l l c o n t r o l areas suggested that there were few, i f any, a d u l t males not h o l d i n g t e r r i t o r y . This suggestion was strengthened by a simple a n a l y s i s of r e p l a c e -ment i n those t e r r i t o r y - h o l d e r s that died or were c o l l e c t e d . Once i t was c l e a r that males homed p r e c i s e l y to t h e i r t e r r i t o r i e s i n successive summers, males that f a i l e d to show t h i s r e t u r n were, assumed to have d i e d . F o r t y - f o u r of these "emptied" t e r r i t o r i e s ( i n c l u d i n g some where banded males were c o l l e c t e d ) were examined i n the f o l l o w i n g summer. Newly a d u l t males used the vacant areas i n 2 0 cases, neighbouring males expanded t h e i r t e r r i t o r i e s to i n c l u d e p a r t of the vacant area i n 1 1 cases, and 1 3 areas were apparently l e f t vacant. Twenty-four other t e r r i t o r i e s , emptied by shooting, can be used here to increase the sample s i z e s i n c e the c o l l e c t -i n g was done i n areas that were searched r e g u l a r l y . 'In t h i s group 9 cases of replacement were discovered i n the summer f o l l o w i n g that of removal. In the combined group the f r a c t i o n showing replacement i n the f o l l o w i n g summer was 4 3 7 o . I compared t h i s f i g u r e w i t h that given by a group of males that were c o l l e c t e d from w e l l - s t u d i e d areas e a r l y i n the summers. Twenty-seven emptied t e r r i t o r i e s were examined and f i v e of them were used by another male w i t h i n the summer, g i v i n g a replacement r a t e of about 1 8 % . One of the f i v e was an a d u l t and some of the others may have been. However, experimental r e s u l t s , given below, suggest that some of the other four males may have been y e a r l i n g s . The r a t e of replacement by a d u l t s x ^ i t h i n a summer may then have been l e s s than 1 8 % . The a n a l y s i s suggests t h a t , although emptied t e r r i t o r i e s were o f t e n used by other males, the r e p l a c e r ment seldom took place u n t i l the summer f o l l o w i n g the death of the occupant. More than two-thirds of the y e a r l i n g males banded or c o l l e c t e d out-s i d e the experimental p l o t s showed no signs of hooting or other t e r r i t o r i a l behaviour (32 of 46 males). This includes e i g h t y e a r l i n g s banded on the c o n t r o l p l o t s . Of these, two were located w e l l w i t h i n an a d u l t ' s t e r r i t o r y w h i l e two were on the edges of t e r r i t o r i e s and four were o u t s i d e . This might suggest that y e a r l i n g s were a t t r a c t e d to t e r r i t o r i a l males or t h e i r t e r r i t o r i e s s i n c e these covered only o n e - t h i r d of the area of the two p l o t s . However, because of a t t r a c t i o n to hooting males and delay involved i n observing and banding, observers probably spent more than one-third of t h e i r time w i t h i n t e r r i t o r i e s w h i l e on the c o n t r o l p l o t s . Male No. 131, who e s t a b l i s h e d t e r r i t o r y near the west corner of the p l o t s i n 1960, was banded as a y e a r l i n g on the edge of male No. 45's t e r r i t o r y i n 1959. He s h i f t e d j u s t over 1000 f e e t and made use of an area that had no r e s i d e n t s on i t i n 1960. None of the other seven y e a r l i n g s returned to the c o n t r o l p l o t s but s e v e r a l showed up i n l a t e r seasons on the experimental p l o t s or near the p l o t area. L a t e r evidence suggests that s i l e n t y e a r l i n g s do i n f a c t frequent the t e r r i t o r i e s of a d u l t s . A few y e a r l i n g males held t e r r i t o r i e s and showed behaviour s i m i l a r to that of t e r r i t o r i a l a d u l t s . These were three males banded outside of the p l o t s , male No. 340 near the north corner of the c o n t r o l p l o t s , and s e v e r a l more males that were assumed to be t e r r i t o r i a l s i n c e they were hooting when c o l l e c t e d . The banded y e a r l i n g s xrere observed to hoot and d i s p l a y to females i n t y p i c a l a d u l t f a s h i o n . Three of the four returned to t h e i r y e a r l i n g t e r r i t o r i e s when they were ad u l t s (on F i g . 7, n o t i c e p o s i t i o n of No. 340 over three summers). Dates of l a s t o b servation suggest that the t e r r i t o r i a l y e a r l i n g s may have l e f t the breeding range before the t e r r i t o r i a l a d u l t s . A \few y e a r l i n g males held t e r r i t o r i e s and showed behaviour s i m i l a r to that of t e r r i t o r i a l a d u l t s . These were three males banded outside of the p l o t s , male No. 340 near\the north corneA of the controls p l o t s , and s e v e r a l more males that were assumed to be t e r r i t o r i a l s i n c e chey were hooting when c o l l e c t e d . The banded y e a r l i n g s were observed to\hoot and d i s p l a y to femal\es i n t y p i c a l a d u l t f a s h i o n . Three of the fourVreturned to t h e i r y e a r l i n g \ t e r r i t o r i e s when they were adults (on F i g . 7, n o t i c e p o s i t i o n of No. 340 over three summers). Dates of \ l a s t observation suggest that the t e r r i t o r i a l ^ y e a r l i n g s may nave l e f t the breeding range before the t e r r i t o r i a l a d u l t s . To b e t t e r understand i n t e r a c t i o n between males i t would be u s e f u l to know what f r a c t i o n of the males on the breeding range were y e a r l i n g s and how many of these y e a r l i n g s were t e r r i t o r i a l . This would a l l o w com-parisons w i t h r a t i o s from the experimental p l o t s and other s t u d i e s . These f i g u r e s are d i f f i c u l t to estimate s i n c e i t was much e a s i e r to l o c a t e hoot-i n g males on the summer range than s i l e n t ones. A rough method of c a l c u l -a t i o n can be used which depends on the assumption that a l l t e r r i t o r i a l males hooted f o r approximately equal amounts of time ( B e n d e l l , J . F. s pers. comm.). The assumption should be v a l i d f o r ad u l t s but may be i n e r r o r f o r y e a r l i n g s s i n c e there was some evidence to suggest that y e a r l i n g s hooted l e s s o f t e n and w i t h l e s s volume than a d u l t s . During the months of March through June, 1959-1962, 158 s i g h t i n g s were made of males that were d e f i n i t e l y a d u l t . Of these, 126 (807») were hooting when the observation or c o l l e c t i o n was made. Using the above assumption, i t f o l l o w s that hooting a d u l t s were four times e a s i e r to l o c a t e than s i l e n t a d u l t s . As mentioned e a r l i e r , 14 of 46 known y e a r l i n g s xrere hooting when observed or c o l l e c t e d . I f a l l hooting males are "converted" to the s i l e n t category by d i v i d i n g by f o u r , the f r a c t i o n of y e a r l i n g s i n the whole group i s 36 i n 1G0, or 36%. By the same scheme the f r a c t i o n of the y e a r l i n g males h o l d i n g t e r r i t o r y would be roughly 10%. To summarize, i n t e r a c t i o n between males had a considerable e f f e c t on t h e i r spacing at t h i s f a i r l y low d e n s i t y (about 0.15 males per a c r e ) . A l l the a d u l t males and a f r a c t i o n , p o s s i b l y one-tenth, of the y e a r l i n g males were considered to be t e r r i t o r i a l and t h i s group showed a near-uniform type of d i s p e r s i o n . T e r r i t o r i e s were v a r i a b l e i n s i z e and showed no obvious change i n s i z e w i t h age or year. Once t e r r i t o r i e s were estab-l i s h e d the owners used the same area i n succeeding summers except f o r minor boundary changes r e l a t e d to number and closeness of neighbours. N o n - t e r r i t o r i a l y e a r l i n g s may have been a t t r a c t e d to t e r r i t o r i e s oa t h e i r d i s p l a y i n g owners. Several of these conclusions or suggestions are con-firmed by experimental r e s u l t s i n the next s e c t i o n . I n t e r a c t i o n between males on removal p l o t s A n a l y z i n g data from the experimental p l o t s shows how males shot from t h e i r t e r r i t o r i e s were replaced by other males. Again, i t i s important to d i s t i n g u i s h two types of replacement - that o c c u r r i n g w i t h i n the summer (breeding season) of removal and that o c c u r r i n g i n a subsequent season. Once the two types of replacement have been examined, another s e c t i o n w i l l compare r e s u l t s from c o n t r o l and experimental areas. . Over four summers, 32 a d u l t and 25 y e a r l i n g males were taken from on or very near the two removal p l o t s . A few others were c o l l e c t e d f u r t h e r away from the p l o t boundaries. F i g . 1 shows that the zone of Very Open ve g e t a t i o n extended on to the Very Dense removal p l o t along the common boundary of the two p l o t s . F o r t u n a t e l y , the area involved was approximately 24 equal the area of the la r g e swamp on the Very Open p l o t (where no males were ever taken). Therefore, i n the t a b l e below, the "open" f i g u r e s i n c l u d e any males found i n the s t r i p on the Very Dense p l o t . The 46-acre s i z e of the dense removal p l o t was preserved by e x t e n d i n g . i t s boundaries s l i g h t l y to the northwest, i n t o an area of s i m i l a r v e g e t a t i o n . As i t happened, males were u s u a l l y removed from the l a t t e r s t r i p when found s i n c e observers had d i f f i c u l t y seeing boundary markers along the northwest l i n e of the dense p l o t and tended to c o l l e c t s when they had the chance. Table II s p l i t s the 57 c o l l e c t e d males by year and a c t i v i t y when taken. A few a d u l t s , c o l l e c t e d very l a t e i n the summers, were assumed to be migrants and omitted from the t a b l e . Table II. Males found on removal p l o t s , 1959-1962. Boundaries of the p l o t s were modified s l i g h t l y f o r t h i s t a b l e (see e x p l a n a t i o n above) . Adults Hooting y e a r l i n g s S i l e n t L j ear 1 ings Open Dense Open Dense Open Dense 1959 4 a 5 1 0 3 0 1960 9 a, c 5 a, b 8 b 0 3 0 1961 2 0 2 0 1 0 1962 6 1 a 4 0 2 1 TOTAL 21 11 15 0 9 1 Symbols: a - one woundec , not recovered, assumed to be a d u l t r e s i d e n t b - one observed, not c o l l e c t e d c - two observed, not c o l l e c t e d A f t e r I960, a drop i n numbers of ad u l t s was evident f o r the Very Dense removal p l o t . This s i t u a t i o n was a l s o observed on some of the denser 25 c o n t r o l p l o t s (discussed i n a l a t e r s e c t i o n on h a b i t a t s e l e c t i o n ) . The l a c k of y e a r l i n g s on the dense area i s f a r more s t r i k i n g than i t was on the main c o n t r o l p l o t s . Since these lowered numbers were apparently a r e s u l t of h a b i t a t s e l e c t i o n , most of the d i s c u s s i o n of i n t e r a c t i o n between males w i l l centre on the open removal p l o t . I t i s c l e a r that no great i n f l u x of a d u l t s occurred on the open p l o t a f t e r removal of r e s i d e n t s s i n c e the average number of a d u l t males per 23 acres per year was 2.6 here as compared w i t h 3.4 on a l l the c o n t r o l p l o t s , e x c l u d i n g the very dense ( f i g u r e s f o r c o n t r o l p l o t s given l a t e r ) . Cases i n v o l v i n g replacement of an a d u l t by another a d u l t were r a r e , as shown below. More commonly, ad u l t s were replaced by y e a r l i n g s . Table I I I shows that 607. of the y e a r l i n g s were hooting when taken from the removal area. This percentage i s almost twice that found i n c o n t r o l areas, suggesting that more y e a r l i n g s would attempt to hold t e r r i t o r y on an area c l e a r e d of a d u l t s . One way to examine i n t e r a c t i o n i n a removal experiment i s to consider removal and r e p o p u l a t i o n on c e r t a i n favoured areas. I o u t l i n e d such areas as o b j e c t i v e l y as p o s s i b l e w i t h i n the two p l o t s and found that a l l the observations and p o i n t s of removal of males could be enclosed w i t h i n areas that involved l e s s than one~quarter of the area of the p l o t s . F i g . 9 shows the areas which were d e f i n e d , i d e n t i f i e d by l e t t e r s . I t should be mentioned that t h i s a n a l y s i s was f i r s t done on a l a r g e r s c a l e , using some areas which were completely outside the boundaries of the experimental p l o t s . The s h o r t e r a n a l y s i s gave r e s u l t s which were e x a c t l y comparable to those of the longer, and i s presented here, being e a s i e r to f o l l o w . The 18 areas cannot be c a l l e d t e r r i t o r i e s s i n c e , i n many cases. 26 y^ - - f ire ro<xd Figure 9. Favoured areas, used for analysis of removal and repopulation on experimental plots. See text and Table IV. Scale: 1" = 440'. 27 more than one male was removed from a given area. They are probably equi-v a l e n t to t e r r i t o r i e s s i n c e they occur w i t h about the same de n s i t y and spacing as the t e r r i t o r i e s on the c o n t r o l p l o t s . Whether or not the areas represented t e r r i t o r i e s i s not too important. The main p o i n t i s that neigh-bouring males and r e p l a c i n g males had to be separated i f t h i s a n a l y s i s was to be u s e f u l . In most cases the s e p a r a t i o n was made f a i r l y e a s i l y by checking i n f i e l d n o t e s which observations were made simultaneously and by measuring map distances between c o l l e c t e d or observed males. In a few cases the a s s i g n i n g of males was d i f f i c u l t and e r r o r s may have been made, as suggested below. Table I I I , below, shows how the 18 areas were used over the four years. The t a b l e w i l l be used i n a l a t e r s e c t i o n on h a b i t a t s e l e c t i o n as w e l l as here. Table I I I . Use of s p e c i f i c areas on the removal p l o t s by males from 1959 to 1962. See F i g . 9 f o r l o c -a t i o n of areas. Time s c a l e i n each year runs from l e f t to r i g h t . Symbols explained, below. Area 1959 1960 1961 1962 A A B h s h C A 5 hy sy, hy, sy hy A, h A, h D s A, A, A, hy by, h A, hy, h E h A, sy, hy hy, h A, hy F hy, hy sy G A, hy, hy, hy s sy , hy, hy H A s s I h*, sy A J A A K A L A M A h* N A 0 h P A h Q s s h* R A sy, A s A, sy Symbols showing use of areas: A - a d u l t (Note: a few l a t e - o c c u r r i n g s i l e n t a d u l t s were assumed to be migrant and omitted. A l l remaining a d u l t s were considered to be t e r r i t o r i a l ) . 28 hy - hooting y e a r l i n g sy - s i l e n t y e a r l i n g h - hooting male, not c o l l e c t e d or i d e n t i f i e d s - s i l e n t male, not c o l l e c t e d or i d e n t i f i e d * - wounded, not recovered During the experiment, there were 19 cases i n which an area was used by only one hooting male during a given season (one of these hooters was known to be a y e a r l i n g ) . In other cases only one observation on a s i l e n t male came out of an area during a summer. There were 8 such cases and again one of the males was a y e a r l i n g . These f i g u r e s immediately suggest that replacement was not the commonest r e a c t i o n to the removal of a male. A count from Table I I I shows that 16 " t e r r i t o r i e s " were used by more than one male and these cases are discussed i n the next few paragraphs. Over four years there were eig h t cases of removed ad u l t s being replaced by hooting y e a r l i n g s . The i n t e r v a l s between c o l l e c t i o n of a d u l t and y e a r l i n g v a r i e d from four days to a month. In one case an a d u l t was s u c c e s s i v e l y replaced by three hooting y e a r l i n g s at i n t e r v a l s of four weeks, one week, and two days. A second a d u l t was replaced by a s i l e n t y e a r l i n g a f t e r f i v e days, a hooting y e a r l i n g a f t e r another four weeks, and a s i l e n t y e a r l i n g a f t e r f i v e more days. A s i l e n t y e a r l i n g was a l s o taken from the area before the a d u l t was found. In another case a h o o t i n g a d u l t and a hooting y e a r l i n g were taken from the same area on the same day. I t may be s i g n i f i c a n t that another a d u l t had been removed from c l o s e by f i v e days e a r l i e r . Perhaps my boundaries were not r e a l i s t i c i n t h i s case, and the y e a r l i n g was a c t u a l l y r e a c t i n g to the vacancy created by c o l l e c t i o n of the l a t t e r a d u l t . Y e a r l i n g s may have replaced a d u l t s i n some other cases. One area used by an a d u l t l a t e r y i e l d e d a s i l e n t y e a r l i n g . Two vacated areas were used by u n i d e n t i f i e d hooting males. Another area produced a s i l e n t y e a r l i n g 29 a f t e r a hooting male had been wounded but not c o l l e c t e d . Y e a r l i n g s a c t i n g i n an a d u l t manner may have replaced removed a d u l t s i n up to 13 cases (or 14, as suggested i n the next paragraph). Only one area showed use by two a d u l t s i n the same summer (area D i n 1960 produced a s i l t e n t a d u l t and, three weeks l a t e r , a hooting a d u l t ) . Hooting was heard on nearby area C two weeks a f t e r c o l l e c t i o n of the s i l e n t male and, e v e n t u a l l y , a hooting y e a r l i n g was c o l l e c t e d there. The hooting or d i s p l a y of the s i l e n t a d u l t may have been centred c l o s e r to C than D. This explanation i s strengthened by the f a c t that the hooting y e a r l i n g on C was the one mentioned above, the only known y e a r l i n g among the group of hooters that were never replaced w i t h i n a season. Since the s i l e n t a d u l t was taken on A p r i l 12 another explanation might be that he was s t i l l m i g r a t i n g and had not yet s e t t l e d on t e r r i t o r y when he was c o l l e c t e d . J u s t outside the open removal p l o t another apparent case of a d u l t replacement was found i n 1962. In t h i s case one of the two a d u l t s c o l l e c t e d was a banded male, whose t e r r i t o r y from 1959 to 1961 was s e v e r a l hundred f e e t from h i s p o i n t of c o l l e c t i o n i n 1962. the shortage of cases of a d u l t replacement suggests that there was no surplus of a d u l t s present during the time of the experiment. On f i v e areas the f i r s t male to be c o l l e c t e d was a hooting y e a r l i n g . Although some of these might be explained i n the manner described above, there were apparently some y e a r l i n g s h o l d i n g t e r r i t o r y i n a d u l t f a s h i o n from the s t a r t of the season, j u s t as there were on c o n t r o l areas. Y e a r l i n g s may have found i t e a s i e r to e s t a b l i s h t e r r i t o r y on the removal p l o t s s i n c e they would only have to compete w i t h new males, not r e s i d e n t s of e a r l i e r years. J u s t outside the open removal p l o t a s i l e n t a d u l t and a hooting y e a r l i n g were taken from the same area on the same day. In t h i s case the y e a r l i n g 30 must have been h o l d i n g t e r r i t o r y i n s p i t e of neighbouring a d u l t s . Several of the 25 y e a r l i n g s taken from the removal area, then, were apparently t e r r i t o r i a l along w i t h the a d u l t r e s i d e n t s . But, what f r a c t i o n of the y e a r l i n g s showed t e r r i t o r i a l behaviour only a f t e r the r e s i d e n t s were removed? This percentage can be estimated i n s e v e r a l ways. The simplest i s to consider the f r a c t i o n that were hooting when c o l l e c t e d . This would give a replacement r a t e of 64% (Table I I I ) . Some of these were t e r r i t o r i a l i n t h e i r own r i g h t , as mentioned, and some of the s i l e n t y e a r l i n g s may have been showing t e r r i t o r i a l behaviour, even though they were not hooting when c o l l e c t e d . Therefore, I t r i e d to estimate from Table I I I the maximum and minimum number of cases of replacement by y e a r l i n g s . A minimum estimate of the percentage of y e a r l i n g s that became t e r r i t o r i a l only a f t e r removal of r e s i d e n t s (adult or y e a r l i n g ) was 44% (11 out of 25). This f i g u r e was reached by c o n s i d e r i n g only those that were hooting when c o l l e c t e d ( t o t a l 16) and assuming t h a t , when a hooting y e a r l i n g was taken f i r s t from an area, i t was a t e r r i t o r i a l r e s i d e n t before removal ( f i v e c a s e s ) . A maximum estimate was 77% (23 out of 30). This was obtained as f o l l o w s : by counting a l l hooting y e a r l i n g s but three that were taken a f t e r a r e s i d e n t was c o l l e c t e d , and i n c l u d i n g f i v e other u n i d e n t i f i e d hooters that came onto areas a f t e r r e s i d e n t s . The l a t t e r f i v e a l s o had to be added to the t o t a l y e a r l i n g count which then became 30. Between these two extremes the best estimate of the f r a c t i o n that r e p l a c e d , c o n s i d e r i n g time i n t e r v a l s between c o l l e c t i o n s and f i e l d n o t e s on hooting heard at c o l l e c t i o n times, was 62%. Thus, almost two-thirds of the y e a r l i n g s on the study area would not take up t e r r i t o r y u n t i l the r e s i d e n t t e r r i t o r y - h o l d e r s were removed. This f i g u r e would be higher than that r e p r e s e n t i n g the percentage of ad u l t s replaced by y e a r l i n g s s i n c e some 31 a d u l t s were followed by more than one y e a r l i n g . A l s o , the three y e a r l i n g s assumed to be o r i g i n a l r e s i d e n t s had some replacements. One tendency mentioned i n the f i r s t s e c t i o n i s confirmed by these past few paragraphs. Many of the r e p l a c i n g y e a r l i n g s were found on a " t e r r i t o r y " only a few days a f t e r the r e s i d e n t was shot. Two s i l e n t y e a r l i n g s were removed from areas which l a t e r produced a hooting r e s i d e n t . Only one s i l e n t y e a r l i n g was c o l l e c t e d from an .area that gave no t e r r i t o r i a l male i n the same summer. Y e a r l i n g s were not c o l l e c t e d on the p l o t outside of the areas shown i n F i g . 7. A l l these data i n d i c a t e that y e a r l i n g s were found on t e r r i t o r i e s much more o f t e n than chance would a l l o w . Since y e a r l i n g s c o l l e c t e d l a t e r i n the summers chose areas that were p r e v i o u s l y occupied over empty ones, the a t t r a c t i o n was c l e a r l y to the t e r r i t o r y - h o l d e r r a t h e r than the t e r r i t o r y i t s e l f . These p o i n t s do not apply to the few y e a r l i n g s that were t e r r i t o r i a l from the s t a r t of the season. Notice a l s o , from Table I I , that these preferences are superimposed on a d e f i n i t e h a b i t a t preference, discussed i n a l a t e r s e c t i o n . I t i s a l s o i n t e r e s t i n g to examine which areas were not used by males. In va r i o u s years, 29 areas out of a p o s s i b l e 72 were not used (Table I I I ) . Most of the vacancies were r e l a t e d to h a b i t a t s e l e c t i o n and t h i s w i l l be discussed i n a l a t e r s e c t i o n . One p o i n t that seemed to be r e l a t e d to i n t e r a c t i o n was that only one vacancy occurred i n 1960 w h i l e 1959, 1961, and 1962 had 9, 9, and 10. This d i f f e r e n c e must be explained and s e v e r a l p o s s i b i l i t i e s are explored. The most l i k e l y reason f o r such a low number of unoccupied t e r r i t o r i e s i n 1960 would be a higher d e n s i t y of males i n that year. F i g . 10, given l a t e r , shows t h a t , w h i l e 1960 d i d have p o s s i b l y the highest d e n s i t y of males, the f i g u r e s were c l o s e to those of 1961 and 1962. The 32 number of new males was d e f i n i t e l y higher i n 1960 than i n f o l l o w i n g years, and t h i s i s probably more s i g n i f i c a n t i n e x p l a i n i n g the vacancies s i n c e t h i s group was s e t t l i n g the removal p l o t s . Another explanation can be proposed here, i n v o l v i n g the times of searching on the removal p l o t s . 1960 was the only year i n which the p l o t s were covered thoroughly i n March and A p r i l (see t a b l e i n appendices). Hooting males were never found on the removal p l o t s i n March but i n A p r i l , when hooters were present, some emigration could have taken p l a c e . Any males that l e f t at t h i s time would have been c o l l e c t e d only i n 1960. I t may be s i g n i f i c a n t that the only d i r e c t aggression between a p a i r of males that I ever observed took p l a c e on the open experimental p l o t on A p r i l 16, 1962. The t h r e a t e n i n g and chasing may have been between an a d u l t and a y e a r l i n g , however, s i n c e an a d u l t and a hooting y e a r l i n g were l a t e r c o l l e c t e d on t h i s area (area E, Table I I I and F i g . 9 ) . An argument s i m i l a r to t h i s was r e j e c t e d when the mechanism causing the observed spacing of t e r r i t o r i e s was discussed e a r l i e r . The c o r r e l a t i o n between the low number of vacancies and the high number of nextf males i n 1960 seems to be the s i g n i f i c a n t one. An e x p l a n a t i o n i n v o l v i n g e a r l y searching i n 1960 might be used to e x p l a i n the lower number of males c o l l e c t e d on the experimental p l o t s i n 1961 (Table I I ) . Evidence given l a t e r shows t h a t males of two years u s u a l l y took up t e r r i t o r i e s w i t h i n h a l f a m i l e of the l o c a t i o n s they occupied as y e a r l i n g s . Over the four summers, 5, 11, 3, and 7 y e a r l i n g s were shot on or near the removal p l o t s . The number was highest i n 1960, probably because searching was s t a r t e d e a r l i e r . Some e a r l y searching was done i n 1962, the year which gave the second highest number of y e a r l i n g s . A suggestion emerging from t h i s i s that some y e a r l i n g s may have come onto the study area and l e f t i t again before the end of A p r i l . I f t h i s i s t r u e , the higher 33 collection i n 1960 may have lowered recruitment of new adults to the same area in 1961. One of the two adults collected in 1961 was a male that was banded as a hooting yearling late in 1960 and allowed to remain on the removal plot. The results in this section confirm some of the suggestions made in the f i r s t section. Replacement of removed adults by other adults within a given summer occurred in very few cases, i f at a l l . About half of the removed adults were replaced by yearlings, and calculations suggest that nearly two-thirds of the yearlings on the area would only try to take up territory when residents were removed. At least 60% of the yearlings on the removal plots were hooting males as compared to one-third or less on control areas. As on the control areas, a few yearlings were apparently holding territory in the presence of adults. The number of adults removed in each year suggests that removal in one summer was not causing an abnormal influx of adults to the removal plots in the next summer. This question, however, must be decided by comparing control and experimental areas. Comparison of control and experimental plots The main question to be examined here is whether the presence of resident males affected the settling of new males on a given area ("new" referring to those adults that had not held a territory i n the previous year). This is best answered by comparing numbers from control and experimental plots in Very Open, Open, and Dense habitats. A rough com-parison can also be made from the plots in Very Dense habitat but selection of habitat seemed to have far more effect on settlement here than interaction between males. The comparisons w i l l involve only 1960 through 1962, since 34 numbers of new males could not be determined f o r 1959. I t was q u i t e easy to determine numbers of new males f o r the open experimental p l o t s i n c e removal was c a r r i e d out i n a l l y ears. The only c o m p l i c a t i n g f a c t o r was a few s i t u a t i o n s i n v o l v i n g wounded males and males that were not c o l l e c t e d (see Table I I ) . Once these cases had been assessed the best estimates f o r new males on the open removal p l o t (with s l i g h t l y modified boundaries, as i n Table I I ) were s i x i n 1960. One i n 1961 and s i x i n 1962. I t was more d i f f i c u l t to determine the number of new males e n t e r i n g the c o n t r o l p l o t s (estimates given i n F i g . 10). Two methods were used i n e s t i m a t i n g these numbers so that they would be as accurate as p o s s i b l e . The more t h e o r e t i c a l method used the t o t a l numbers f o r each year and the death r a t e of a d u l t males. An appendix shows t h i s c a l c u l a t i o n as w e l l as the c a l c u l a t i o n of death r a t e . In some cases i t was d i f f i c u l t to decide whether one or two males occupied a given area on the c o n t r o l p l o t s . When t h i s happened the lower f i g u r e was used so that estimates f o r t o t a l numbers of r e s i d e n t males and f o r new males are minimal. By t h i s method the numbers of new males were 18 f o r 1960, 10 f o r 1961, and 10 f o r 1962 (38 i n a l l , e x c l uding the Very Dense p l o t ) . In the second method, new males were reckoned from map p o s i t i o n s , the method being made more accurate by the presence of many banded males among the unmarked ones. This estimate gave 18, 12, and 14 new males f o r the three years and the t o t a l of 44 was probably more accurate than the t o t a l of 38 from the f i r s t method. The numbers of new males shown i n F i g . 10 are those determined by the second method. I f s u b - t o t a l s are e x t r a c t e d , i t becomes c l e a r that the p r o p o r t i o n of new males was higher f o r the c o n t r o l p l o t s i n Very Open than i t was f o r those i n Open or Dense h a b i t a t s . On the Very Open p l o t s 59% of the 35 Figure 10. T o t a l numbers of r e s i d e n t males found on c o n t r o l p l o t s over four summers. A f t e r 1959, an estimate of the number of males that were new to each h a b i t a t i s given i n brackets f o r each t o t a l . 10 / 1 9 8 2 3 5 7 4 6 Nos. 3 and 5 were the o r i g i n a l (main) c o n t r o l p l o t s . // Removal p l o t s P l o t s ( r e f e r to sketch) 1959 1960 1961 1962 M/P/yr NM/P No. 1 (Very Dense h a b i t a t ) 1 4 (3) 1 (0) 0 1.5 3.0 Nos. 2, 3, 4, (Dense hab.) 8 12 (6) 12 (5) 9 (2) 3.4 4.3 Nos. 5, 6, 7, (Open hab.) 8 11 (5) 14 (4) 11 (5) 3.7 4.7 Nos. 8, 9, 10, (Very Open hab.) 8 9 (7) 7 (3) 13 (7) 3.1 5.7 Totals f o r years (new each year) 25 36 (21) 34 (12) 33 (14) M/P/yr - Males per p l o t per year NM/P - New males per p l o t , t o t a l f o r three years males were "new" w h i l e only 39% were new on the s i x c o n t r o l p l o t s i n Dense and Open h a b i t a t s . - This suggests t h a t , when the comparison between numbers of new males on c o n t r o l and experimental areas i s made, only c o n t r o l p l o t s 36 i n Very Open h a b i t a t should be used. This comparison i s made below and the experimental p l o t I s a l s o compared w i t h a l l the c o n t r o l p l o t s taken together, excepting the s i n g l e one i n Very Dense v e g e t a t i o n . Table IV. Comparison of numbers of new males on c o n t r o l and experimental p l o t s . The f i g u r e s i n d i c a t e hew males per p l o t (23 a c r e s ) . C o n t r o l p l o t s Experimental p l o t Nine p l o t s i n V,0,, Three p l o t s i n Large p l o t i n 0., and D. l a b i t a t V.O. h a b i t a t V.O. h a b i t a t 1960 2.0 2.3 3.0 1961 1.3 1.0 0.5 1962 1.6 2.3 3.0 TOTAL 4.9 5.7 6.5 None of the comparisons u s i n g the f i g u r e s f o r new males give s i g n i f i c a n t d i f f e r e n c e s when Chi-square t e s t s are a p p l i e d (using a 5% l e v e l of s i g n i f i c a n c e ) . This statement holds f o r a l l comparisons between c o n t r o l and experimental p l o t s , whether t o t a l f i g u r e s are compared or Chi-square values f o r each year are summed and compared. Apparently, new males made approximately equal use of emptied p l o t s and p l o t s having r e s i d e n t s when they f i r s t took up t e r r i t o r y . During 1960 - 1962, then, the presence of . r e s i d e n t males had no s i g n i f i c a n t e f f e c t on immigration of new males. This c o n d i t i o n even he l d f o r the p l o t s i n Very Dense h a b i t a t . A rough comparison shows t h a t , from 1960 through 1962, s i x a d u l t s were taken from the 46-acre removal area i n Very Dense v e g e t a t i o n (Table 110 and three new males were estimated to be present on the 23-acre c o n t r o l area i n s i m i l a r h a b i t a t . As mentioned, h a b i t a t s e l e c t i o n was probably more important here than i n t e r a c t i o n judging by the l a c k of r e s i d e n t s a f t e r 1960. 37 The next two s e c t i o n s w i l l examine the e f f e c t of t h i s s e l e c t i o n on the d i s p e r s i o n of the males. One f u r t h e r comparison, concerning the behaviour of y e a r l i n g s , might be drawn i n t h i s s e c t i o n . On c o n t r o l areas, i t was estimated that roughly 10% of the y e a r l i n g s were t e r r i t o r i a l . This would have been perhaps three or four percent of a l l the t e r r i t o r i a l males. On the open removal p l o t over 60% of the y e a r l i n g s were hooting when c o l l e c t e d . The • d i f f e r e n c e , 507o or more, i s the f r a c t i o n t h a t was presumably prevented from e s t a b l i s h i n g t e r r i t o r y by the r e s i d e n t s . This f i g u r e i s q u i t e c l o s e to the 62% f i g u r e estimated from the a n a l y s i s of Table I I I , N o t i c e a l s o t h a t the number of y e a r l i n g males h o l d i n g t e r r i t o r y on the open p l o t before shooting may have been higher than three or four percent, perhaps as high as 12% (three y e a r l i n g s i n a t o t a l of 21 a d u l t s and three y e a r l i n g s ) . I f t h i s i s t r u e , the two estimates agree very w e l l and i n d i c a t e that j u s t over h a l f of the n o n - t e r r i t o r i a l y e a r l i n g s would hoot and d i s p l a y only a f t e r r e s i d e n t s were removed. These comparative r e s u l t s have been presented i n a separate s e c t i o n s i n c e they are b a s i c i n determining what e f f e c t i n t e r a c t i o n had on the r e g u l a t i o n of breeding numbers of males. There was no d e t e c t a b l e s u r -plus of a d u l t males as uncovered i n other a v i a n species by Stewart and A l d r i c h (1951), Jenkins (1963), or Choate (1963). The y e a r l i n g males that replaced c o l l e c t e d a d u l t s might be considered surplus but r e s u l t s from other s e c t i o n s show that the y e a r l i n g ' s r a t e of death was not n o t i c e -a b l y higher than that of the a d u l t s . Simard's (1965) work i n d i c a t e s t h a t , although y e a r l i n g s were capable of f e r t i l i z i n g hens, they matured l a t e r and showed a lower l e v e l of t e s t i c u l a r development than a d u l t s . A very low l e v e l of i n t e r a c t i o n may have served to prevent t h i s group from becoming 38 t e r r i t o r i a l . These y e a r l i n g s , w h i l e they d i d not c o n t r i b u t e to the uniform p a t t e r n of spacing and l i k e l y d i d not mate w i t h females, showed no i l l e f f e c t s from t h e i r i n t e r a c t i o n w i t h other males. Hab i t a t s e l e c t i o n by males on c o n t r o l areas This s e c t i o n t r i e s to answer the q u e s t i o n "What s o r t of h a b i t a t i s p r e f e r r e d by males f o r t h e i r t e r r i t o r i a l and other a c t i v i t i e s ? " I t was c l e a r from o b s e r v a t i o n i n the f i e l d t hat males used c e r t a i n types of h a b i t a t more f r e q u e n t l y than others when hooting and d i s p l a y i n g . On a l a r g e r s c a l e , when the v e g e t a t i o n and topography of t e r r i t o r i e s were examined, preferences could again be seen. This s e l e c t i o n l i k e l y had an e f f e c t on d i s p e r s i o n as great as i n t e r a c t i o n , perhaps greater at some ages. The f o l l o w i n g paragraphs, t h e r e f o r e , examine these preferences and a l s o provide background f o r the next s e c t i o n which w i l l examine preferences i n the absence of i n t e r a c t i o n . For t h i s and the next s e c t i o n there i s an important p r e l i m i n a r y p o i n t . The d e n s i t y of v e g e t a t i o n was apparently i n c r e a s i n g q u i t e r a p i d l y on some parts of the study area during the four y e a r s . An example to show t h i s comes from Table I . Notice that Very Open and Open h a b i t a t d i f f e r e d mainly i n the amount of coniferous cover (2% versus 287.). Other f a c t o r s being equal, t h i s must have been caused by the d i f f e r e n c e s i n time of Douglas f i r p l a n t i n g . The Very Open was planted about f i v e years a f t e r the Open and thus the 267=. d i f f e r e n c e i n cover developed over t h i s short time. Comparing 1962 measurements of v e g e t a t i o n w i t h f i e l d n o t e s d e s c r i b i n g known p o i n t s on the dense removal area led to the same c o n c l u s i o n . The e f f e c t of these changes on the d i s p e r s i o n of the grouse, e s p e c i a l l y i n dense areas, i s mentioned l a t e r . 39 I examined the v e g e t a t i o n and topography of 81 t e r r i t o r i e s and compared these w i t h s i m i l a r analyses done f o r 69 p o i n t s chosen randomly over the e n t i r e study area. Since the area used f o r a n a l y s i s ( c i r c l e of about 0.18 acres) was much l e s s than the s i z e of the average t e r r i t o r y , I t r i e d to do the analyses on the area used most o f t e n by the r e s i d e n t f o r hooting and d i s p l a y i n g . Many features of the areas were assessed and the more important comparisons are given i n a t a b l e i n the appendices, and discussed below. Males apparently favoured open v e g e t a t i o n f o r t h e i r t e r r i t o r i e s . R e c a l l that more new males were found on c o n t r o l p l o t s i n Very Open h a b i t a t than i n other types (preceding s e c t i o n of R e s u l t s ) . Many more t e r r i t o r i e s than random p o i n t s xi/ere l o c a t e d i n the zone of Very Open v e g e t a t i o n and only one t e r r i t o r y was i n Very Dense v e g e t a t i o n . One t e r r i t o r y was l o c a t e d i n an a l d e r area w h i l e nine random p o i n t s were i n a l d e r , swamp, or bog areas. Although cover by trees and shrubs was l e s s f o r t e r r i t o r i e s the d i f f e r e n c e was not s i g n i f i c a n t (Chi-square t e s t , 5% l e v e l ) . Since t e r r i t o r i e s were found more o f t e n i n the open, t h i s suggests that males hooted and d i s p l a y e d near patches of t h i c k e r v e g e t a t i o n on t h e i r t e r r i t o r i e s . T e r r i t o r i a l males o f t e n centred t h e i r a c t i v i t i e s around the edges of c l e a r i n g s or o l d logging roads, e s p e c i a l l y where the v e g e t a t i o n i n general was Dense or Very Dense. T h i s , too, may have r a i s e d the average f i g u r e f o r t r e e and shrub cover on t e r r i t o r i e s s i n c e the v e g e t a t i o n at road-edges was o f t e n t h i c k e r than that of surrounding areas because of water trapped by d i t c h e s or mounds of e a r t h . This was the only choice that might be c a l l e d "edge e f f e c t " , or unusual use of boundaries between d i f f e r e n t h a b i t a t s . The cover by ground v e g e t a t i o n was s i g n i f i c a n t l y l e s s on t e r r i t o r i e s i n d i c a t i n g that males used areas where they could move most f r e e l y over the ground. These comparisons show 40 that males, when f i r s t e s t a b l i s h i n g t e r r i t o r y , p r e f e r r e d areas w i t h open v e g e t a t i o n and sparse cover at ground l e v e l , even though they used t h i c k e t s or heavier patches of v e g e t a t i o n f o r cover when hooting.or r e s t i n g . A comparison of topography shows that males p r e f e r r e d elevated areas f o r t e r r i t o r i e s . One-quarter of a l l the a c t u a l s i t e s examined were on obviously elevated p o s i t i o n s w h i l e p r a c t i c a l l y none of the random p o i n t s were. In a d d i t i o n , many of the other t e r r i t o r i e s had elevated p o i n t s near-by but outside of the c i r c l e used f o r a n a l y s i s . . L i k e l y some of these p o i n t s were included w i t h i n the t e r r i t o r i e s of the males concerned. Beyond the above, there was l i t t l e d i f f e r e n c e i n the s e t s , o f data from t e r r i t o r i e s and random p o i n t s . There was no evidence to suggest that p a r t i c u l a r p l a n t s p e c i e s , wet areas, g r i t and d u s t i n g m a t e r i a l , d i r e c t i o n of slopes or height of trees had any e f f e c t on the l o c a t i o n of t e r r i t o r i e s . An attempt was made to judge areas f o r escape and r o o s t i n g cover but i t was very d i f f i c u l t to do t h i s o b j e c t i v e l y and no d i f f e r e n c e s were uncovered. A simple comparison u s i n g the 44 "emptied" t e r r i t o r i e s mentioned i n the f i r s t s e c t i o n of the Results a l s o shows what areas were favoured f o r establishment of t e r r i t o r i e s by new males. The t a b l e below shows how the r a t e of replacement v a r i e d w i t h type of h a b i t a t . Table V. Comparison of v e g e t a t i o n at vacated t e r r i t o r i e s and use of these t e r r i -t o r i e s i n succeeding years. Type of v e g e t a t i o n Rep. Vac. Very Open 60% 37.5% Open 35 12.5 Open-Dense mixture 0 12.5 Dense 5 21 Very Dense 0 12.5 Dense plus a l d e r grove 0 4 Number of samples 20 24 Rep. - vacated t e r r i t o r y occupied by new male Vac. - vacated t e r r i t o r y occupied by neighbouring male or l e f t vacant 41 The sample s i z e s are not l a r g e , but i t seems s i g n i f i c a n t that 95% of the replacement took p l a c e i n open types of v e g e t a t i o n . Of the areas that were l e f t vacant or taken over by a neighbouring male, only 50% occurred i n the two most open h a b i t a t s . I n both columns h i g h percentages occurred i n the very open category s i n c e t h i s was the most common type over the study area. I a l s o compared the numbers of r e s i d e n t males on c o n t r o l p l o t s i n d i f f e r e n t types of v e g e t a t i o n . F i g . 10 gives the numbers f o r each year and, f o r 1960-1962, shows an estimate ( i n b r a c k e t s ) of the number that were new to the p l o t s i n the given year. The numbers of r e s i d e n t s per c o n t r o l p l o t _ i per year, s t a r t i n g w i t h Very Open and working through Very Dense, were approximately 3.1, 3.7, 3.4, and 1.5. I t would seem that a l l types but the Very Dense were used about e q u a l l y by t e r r i t o r i a l males. Counts of hooting males were made along census l i n e s i n Very Open, Open, and Dense h a b i t a t , and the numbers of r e s i d e n t males here were approximately equal a l s o . However, although the numbers are not s i g n i f i c a n t l y d i f f e r e n t , the estimates f o r new males become g r a d u a l l y higher as the more open p l o t s are considered (right-hand column, F i g . 10). Another count i n v o l v i n g some Very Dense h a b i t a t was made along o l d l o g g i n g roads i n May and June of 1961. Thirty-one hours of counting gave 4.4 "hooters per hour" f o r open h a b i t a t s (two types combined) and 3.3,for dense h a b i t a t s (Dense and Very Dense v e g e t a t i o n ) . While none of these comparisons show s i g n i f i c a n t d i f f e r e n c e s , they seem to r e i n f o r c e the suggestion that males s e t t l e d i n open areas more o f t e n than xrould be expected by chance movements. These preferences were probably r e s p o n s i b l e f o r a drop i n use of some c o n t r o l p l o t s by males. The main c o n t r o l p l o t i n Dense v e g e t a t i o n (No. 3, F i g . 10) i s one example. A f t e r 1959, y e a r l i n g No. 340 was the 42 only new male to e s t a b l i s h t e r r i t o r y on t h i s p l o t and he made frequent use of the main road near the p l o t and areas to the north of the p l o t . No s i l e n t y e a r l i n g s were banded on the p l o t a f t e r 1959 but some could have been present s i n c e , although no t e r r i t o r i e s f e l l w i t h i n the p l o t a f t e r 1959, there were a few observations on s i l e n t males. Hooting was heard deep w i t h i n the p l o t at l e a s t once d u r i n g t h i s time but no new r e s i d e n t was located and the sound was probably made by one of the males l i v i n g near the boundaries ( F i g . 7). This p l o t had more cover by a l d e r and swamp v e g e t a t i o n than d i d surrounding p l o t s , and the cover probably regenerated more r a p i d l y . There were some elevated p o i n t s but the r e l i e f was l e s s broken and the average e l e v a t i o n lower than the main c o n t r o l p l o t i n Open h a b i t a t . The drop i n recruitment was not r e f l e c t e d by other c o n t r o l p l o t s nearby i n Open and Dense v e g e t a t i o n . On the c o n t r o l p l o t i n Very Dense (No. 1, F i g . 10) a s i m i l a r drop occurred. The next s e c t i o n w i l l show that t h i s was r e f l e c t e d by the adjacent removal p l o t . While these drops i n recruitment of t e r r i t o r i a l males are very h e l p f u l i n showing the e f f e c t of h a b i t a t preferences on d i s p e r s i o n , they are perhaps more important i n showing the e f f e c t of i n t e r a c t i o n on the h o l d i n g of t e r r i t o r y . S everal authors have suggested that i n t e r a c t i o n may forc e some members of a p o p u l a t i o n to seek space f o r t e r r i t o r i e s on unfavourable areas away from the p r e f e r r e d h a b i t a t (Jenkins, 1963; Kluyver and Tinbergen, 1953; Svardson, 1949). This apparently d i d not occur on the Middle Quinsam a r e a . Even the y e a r l i n g s that were prevented from e s t a b l i s h i n g t e r r i t o r y d i d not show t h i s emigration to denser h a b i t a t , suggesting that t h e i r urge to take up t e r r i t o r y was loxtf. I t may be concluded that the t e r r i t o r i a l behaviour of males i n favourable (open) areas d i d not f o r c e other males i n t o denser h a b i t a t s . I t f o l l o w s 43 that the use of c e r t a i n h a b i t a t s over others was based on preference alone. The above paragraphs analyze h a b i t a t preferences of males by s e v e r a l methods; comparing t e r r i t o r i e s w i t h randomly-chosen p o i n t s , examining r e p l a c e -ment at t e r r i t o r i e s i n d i f f e r e n t h a b i t a t s , and counting numbers of t e r r i t o r i e s i n d i f f e r e n t h a b i t a t s . Another method i s to examine the s i t e s w i t h i n the t e r r i t o r y used f o r d i f f e r e n t a c t i v i t i e s , e s p e c i a l l y h ooting and d i s p l a y i n g , s i n c e t e r r i t o r i e s appeared to be organized around a few such p o i n t s . This was done f o r the main c o n t r o l p l o t s , and, as expected, the favoured hooting s i t e s were elevated p o i n t s having some cover a v a i l a b l e - small t h i c k e t s , s m a ll Douglas f i r s showing spaces between f o l i a g e and ground, tangles of lo g s , and spaces under logs and stumps. D i s p l a y i n g was apparently done near these p o i n t s , on s i t e s having l i t t l e or no ground v e g e t a t i o n . Accumu-l a t i o n s of droppings showed that males spent much of t h e i r time at these p o i n t s . To show f u r t h e r how use of cover on t e r r i t o r i e s v a r i e d w i t h the male's a c t i v i t i e s , I made a rough comparison of the p o s i t i o n s of hooting and s i l e n t males. The s i l e n t category probably includes a few observations on s i l e n t y e a r l i n g s but i n t h i s approximate comparison I judged that these would make no d i f f e r e n c e . The comparison, based on about 300 observations, i s shown i n Appendix 6. The types of cover had to be kept q u i t e general s i n c e they were described by s e v e r a l d i f f e r e n t schemes i n the f i e l d n o t e s , depending on the observer and the year. The percentages of s i l e n t and hooting males found i n many types of cover were s i m i l a r , suggesting that a male, given a proper s t i m u l u s , might hoot from almost any spot. S i l e n t males, however, were seldom found i n open c l e a r i n g s , on elevated p o i n t s , or on top of logs or stumps. This suggests that males i n t e n d i n g to hoot or d i s p l a y sought out these open or elevated spots. Hooting aiales were 44 seldom found i n low areas near streams or swamps. These were l i k e l y f eeding and s h e l t e r areas and males found here might show the l e a s t tendency to hoot. The p o i n t s of d i f f e r e n c e i n the t a b l e v e r i f y , on a smaller s c a l e , the preferences suggested by the e a r l i e r analyses. Most of the groups or aggregations of males, mentioned e a r l i e r , were located i n Open or Very Open v e g e t a t i o n , p a r t i c u l a r l y along roads or near large c l e a r i n g s . The two best-known groups, both found i n Very Open h a b i t a t , used areas which were probably optimal f o r the formation of such a gathering. One of the groups used an open g r a v e l p i t which was elevated around i t s boundaries and which contained s e v e r a l deciduous t h i c k e t s and mounds of e a r t h . The other group used an area at the j u n c t i o n of s e v e r a l o l d logging roads which was n e a r l y bare of v e g e t a t i o n at the centre and had s e v e r a l ridges and p i l e s of logs around the edges. In a l l cases the open h a b i t a t must have allowed males to see and hear each other e a s i l y w h i l e s t i l l keeping a minimum di s t a n c e between the t e r r i t o r i e s . On s i t e s such as the two mentioned the communal nature of the behaviour might be accentuated i f the males used the r i d g e s and promontories f o r hooting and the c e n t r a l bare areas f o r d i s p l a y i n g . One f u r t h e r p o i n t concerning the d i s p e r s i o n of males i n the Very Dense h a b i t a t should be made. The nearest-neighbour analyses of the f i r s t s e c t i o n i n the Results involved very l i t t l e of t h i s type of h a b i t a t , which was apparently avoided by s e t t l i n g males. When the d i s p e r s i o n of the few males in v o l v e d was examined using t h i s method the spacing seemed to be c l o s e r to random. This was a p r e d i c t a b l e r e s u l t which might have come about i n two ways. The d i s t r i b u t i o n would approach randomness i f males were h o l d i n g to t h e i r t e r r i t o r i e s , immigration by new males, was n i l , and . the males were dying at random (Skellam, 1952). The same trend might show 45 i f males s h i f t e d t h e i r p o s i t i o n s so as to be near randomly-located openings i n the i n c r e a s i n g l y dense v e g e t a t i o n . The l a t t e r was apparently r e s p o n s i b l e , at l e a s t i n p a r t , f o r the spacing s i n c e f i e l d n o t e s from 1959 and 1960 mentioned that males on and near the p l o t s i n Very Dense were c o l l e c t e d or seen near c l e a r i n g s . Before l e a v i n g t h i s s e c t i o n , passing mention should be made of c e r t a i n h a b i t a t s that were v i r t u a l l y never used by males during the breeding season. On the study area males apparently avoided extensive swamps, extensive stands of mature a l d e r , peat bogs, and l a r g e unbroken areas of f a l l e n l o g s . The smaller and d r i e r stands of a l d e r , showing some grass and other v e g e t a t i o n at the ground l e v e l , were o c c a s i o n a l l y used by males. The stands avoided were those that had a heavy covering of l i t t e r and dead leaves on the ground. This suggests that the above areas were avoided because they lacked open areas at ground l e v e l . These negative comments on h a b i t a t s e l e c t i o n apply e q u a l l y w e l l to females and j u v e n i l e s . To summarize, t h i s s e c t i o n shows that males p r e f e r r e d c e r t a i n spots f o r t h e i r t e r r i t o r i a l a c t i v i t i e s and t h a t , i g n o r i n g the e f f e c t of i n t e r a c t i o n , these preferences l e d them to s e l e c t c e r t a i n h a b i t a t s over others f o r the t e r r i t o r i e s . The main preferences were f o r open v e g e t a t i o n and, beyond t h i s , elevated p o i n t s and patches of ground f r e e of low v e g e t a t i o n . The next s e c t i o n w i l l explore these preferences f u r t h e r u s i n g the experimental areas. Habitat s e l e c t i o n by males on removal p l o t s Several s i g n i f i c a n t r e s u l t s on s e l e c t i o n of h a b i t a t emerged from the removal experiment. Most-of the data used here again comes from Table I I and I I I . Evidence f o r h a b i t a t s e l e c t i o n i s shown f i r s t by comparing 46 the two p l o t s , and then by l o o k i n g at p o s i t i o n s used w i t h i n the p l o t s . When the Very Dense and Very Open p l o t s are compared the most s t r i k i n g d i f f e r e n c e i s that v i r t u a l l y a l l the y e a r l i n g s were found i n the open. Only one of 25 y e a r l i n g s was found i n the Very Dense p l o t and t h i s s i l e n t male x^as l e s s than 200 f t . from open h a b i t a t . I t i s c l e a r that the d i f f e r e n c e was not caused by a t t r a c t i o n to a d u l t s s i n c e ten adults x^ere taken from the dense area i n 1959 and 1960, during which time no y e a r l i n g s were found on the same area. S i l e n t y e a r l i n g s may have been harder to f i n d i n dense than open, and t h i s b i a s might be used to e x p l a i n some of the d i f f e r e n c e . However, almost o n e - t h i r d of the lone females found on the experimental p l o t s were i n the dense h a l f and these females were as d i f f i c u l t to f i n d as the s i l e n t males. The h i g h l y s i g n i f i c a n t d i f f e r e n c e must have been based on h a b i t a t preference. This preference l i k e l y caused.the drop i n use of the dense removal p l o t by a d u l t s beyond 1960. In the l a s t s e c t i o n i t was mentioned that males c o l l e c t e d or seen i n Very Dense h a b i t a t were u s u a l l y next to open-ings . Most of the f i e l d n o t e s d e s c r i b i n g t h i s came from the removal p l o t i n Very Dense. I t appears that regeneration had closed most of these openings by 1962, although some small areas on the p l o t could s t i l l have been described as Dense or even Open h a b i t a t . From t h i s and from i n f o r m a t i o n i n the l a s t s e c t i o n i t appears that new a d u l t males' kept the h a b i t a t pre-ferences they had shown as y e a r l i n g s . I f the preference i s as strong as suggested, why d i d at l e a s t three a d u l t s , and p o s s i b l y f i v e , use the area i n 1960 (Table I I ) ? Two p o i n t s , mentioned e a r l i e r , may be important i n e x p l a i n i n g t h i s . One i s that the Very Dense h a b i t a t was probably much more open i n 1960 than i t was i n 1962, when analyses of v e g e t a t i o n were done. Then, c o l l e c t i n g d i d not s t a r t u n t i l 47 May i n 1959. A few y e a r l i n g s could have been a t t r a c t e d to t e r r i t o r i a l a d u l t s on the dense p l o t , and l e f t before May. These might have returned as adults and found the dense p l o t a t t r a c t i v e enough to cause them to e s t a b l i s h t e r r i t o r i e s there. In 1960 searching s t a r t e d e a r l i e r and more y e a r l i n g s were taken so that t h i s r e t u r n l i k e l y would not occur. Even i f t h i s argument i s r e j e c t e d , i t must be remembered that the experimental procedure d i d not a l l o w determination of t e r r i t o r i a l boundaries. The t e r r i t o r i e s of some of the males i n the dense h a b i t a t may have extended on to the open. R e c a l l a l s o that t h i s drop i n numbers of t e r r i t o r i a l males a f t e r 1960 was observed on the c o n t r o l p l o t i n Very Dense and on one of the Dense c o n t r o l p l o t s . Another way of examining d i f f e r e n c e s i n use of the two areas i s to consider the 29 vacancies i n Table I I I . Of these, 19 involved t e r r i -t o r i e s that were i n the dense area. Over four years, 37 areas were not used at a l l by hooting males. Of t h i s group, 21 were i n the dense p l o t . The number of vacancies on the open p l o t , then, jumps from 10 to 16 when an area i s taken to be vacant unless used by at l e a s t one hooting male i n a season. The corresponding increase on the dense p l o t i s two vacancies. The d i f f e r e n c e was l i k e l y caused by a higher d e n s i t y of s i l e n t y e a r l i n g s on the open p l o t . I f t r u e , t h i s adds to the evidence f o r a strong preference on the p a r t of the y e a r l i n g males. Because the two types of v e g e t a t i o n on the removal area were q u i t e s h a r p l y defined along the boundary common to the two p l o t s , the importance of "edge e f f e c t " i n h a b i t a t s e l e c t i o n by males can be t e s t e d . Four of the l e t t e r e d " t e r r i t o r i e s " used e a r l i e r l a y across t h i s boundary area. I f the more complex a n a l y s i s i n v o l v i n g t e r r i t o r i e s outside the p l o t boundaries (mentioned e a r l i e r but not presented) i s employed the 48 number of t e r r i t o r i e s on the edge becomes f i v e out of 23 (22%). On the f i v e t e r r i t o r i e s , f i v e out of 28 known ad u l t s (18%) and three out of 27 known y e a r l i n g s (11%) were found over the four y e a r s . The f r a c t i o n of ad u l t s found on the f i v e areas i s not s i g n i f i c a n t l y d i f f e r e n t from what would be expected i f these areas were being used randomly. The use by y e a r l i n g s i s s i g n i f i c a n t l y lower than would be expected. This might r e s u l t from avoidance of dense h a b i t a t by the y e a r l i n g s or from s e l e c t i o n of more favourable t e r r i t o r i e s away from the edge. The l a t t e r i s discussed f u r t h e r i n a l a t e r paragraph. Of the t e r r i t o r i e s shown i n F i g . 9 only three were used by at l e a s t one hooting male i n every year. These areas (C, D, E) were located on the most elevated and prominent area of the open removal p l o t , which was i t s e l f the most elevated p a r t of the study area. The preference f o r open and elevated p o i n t s , then, was as n o t i c e a b l e on removal p l o t s as i t was on c o n t r o l areas. There i s some evidence to suggest that the mentioned t e r r i t o r i e s were used by more males than xrould be expected, even i f only the open p l o t i s considered. When t e r r i t o r i e s i n the open removal area only are examined, nine out of 16 known ad u l t s were found on areas C, D, and E. The expected number would be f i v e , i f a l l t e r r i t o r i e s i n the open were used e q u a l l y . When known y e a r l i n g s are counted, 13 out of 25 were on the three areas, and here the expected number would be between 7 and 8. The d i f f e r e n c e i n numbers of ad u l t s i s not q u i t e s i g n i f i c a n t w h i l e that of the y e a r l i n g s i s s i g n i f i c a n t (Chi-square). S i x of the remaining y e a r l i n g s were found on area G ( F i g . 9) and t h i s was a l s o a high and prominent area. I f C, D, E, and G are considered together the use by y e a r l i n g s becomes h i g h l y s i g n i f i c a n t . This probably came about through 49 a double preference by the y e a r l i n g s - a tendency to stay near elevated p o i n t s and near e s t a b l i s h e d t e r r i t o r i e s . The open p a r t of the experimental area, considered as a whole, must have been a h i g h l y favourable area f o r settlement by males. This i s shown by evidence j u s t presented, and by the f a c t that a number of y e a r l i n g s banded some d i s t a n c e from the open p l o t were c o l l e c t e d as a d u l t s w i t h i n the p l o t i n the season f o l l o w i n g t h e i r banding. Another a d u l t taken from the open p l o t had been banded as a c h i c k near the main c o n t r o l p l o t i n Open h a b i t a t . I t i s s i g n i f i c a n t that even t h i s a t t r a c t i o n , based on h a b i t a t s e l e c t i o n , was not s u f f i c i e n t to produce a higher than expected number of new males on the experimental area. This r e i n f o r c e s the e a r l i e r c o n c l u s i o n that r e s i d e n t males were not f o r c i n g new males i n t o empty areas. Results from c o n t r o l areas suggested a preference f o r open and elevated areas on the p a r t of males, and analyses from removal areas confirm t h i s . More important, the p o s i t i o n s of males on the removal p l o t s show that the preferences are very pronounced i n the y e a r l i n g males. E x c l u d i n g the e f f e c t s of i n t e r a c t i o n , t h i s i s probably the most important f a c t o r determining the d i s p e r s i o n of males, and the use of a given h a b i t a t by males. I t has already been mentioned that males showed l i t t l e tendency to s h i f t t h e i r summer p o s i t i o n s once they had e s t a b l i s h e d t e r r i t o r i e s . Examining the movements of males p r i o r to t h e i r t a k i n g up t e r r i t o r y , as w e l l as the s p a t i a l r e l a t i o n s h i p between females and males, should show how important these h a b i t a t preferences are to the p o p u l a t i o n as a whole. D i s p e r s a l of j u v e n i l e s and movements of y e a r l i n g males I t i s c l e a r that t e r r i t o r i a l males would take no p a r t i n any wholesale s h i f t i n l o c a t i o n of a p o p u l a t i o n . Movements of t e r r i t o r i e s 50 from year to year were always small and could be classed as minor changes allowing for presence or absence of neighbours, movements involving changes in a "group" of males, or artifacts resulting from two few observations on a given male. The data given in the sections below on females show that females two years and older also exhibit a f a i r l y close return to their locations of the previous year. It is suggested as well that females are attracted to territories in the early part of the breeding season. The use of any suitable new habitat by grouse must depend on the movements shown by birds before they become adult. With these points in mind, this section examines the dispersal of chicks and the movements of males before they become adult. When considering dispersion and the use of habitat by grouse i t is important to know whether juveniles return to the area of their birth or f i r s t few weeks of l i f e , to an area of similar habitat only, or to an unrelated area. It is d i f f i c u l t to obtain large samples for such ah analysis since mortality of juveniles is very high in the f i r s t few weeks. For example, out of some 250 chicks that were banded on the Middle Quinsam area, only five were recovered in later summers. This does not include some chicks that were taken by hunters in the autumn following their banding. These were omitted because the movements here involved migration to the winter range rather than dispersal over the breeding range. Of the five, only two were males and both were recovered as adults, two years after they were banded. One of the males was recovered as a silent adult on an elevated part of the open removal plot 2300 f t . from his point of banding in Dense vegetation. The other was found in Open vegetation approximately 7000 f t . from his point of banding which was in Very Open vegetation. These few data suggest that males were not returning to the areas they used as 51 chicks or to areas of similar habitat. Also, the fact that three juvenile females were recovered as yearlings while no juvenile males were, suggests that some yearling males may not have descended to the summer range. For drawing further conclusions about dispersal of juveniles i t is convenient to lump male and female chicks into one group. When a l l five of the chicks mentioned are considered the average distance from point of banding to point of recovery was very close to one mile. This again suggests that chicks were not showing any "homing" behaviour. It is likely that few returned chicks were missed since one of the two males was found as a silent bird and the three females were a l l found in early summer when females were harder to locate. The next step was to estimate the number of chicks that should have appeared on the area to see i f dispersal really was occurring or i f the low return was caused by mortality. From banding records an approximate count was made of a l l those chicks that were large enough to wear adult leg-bands. In any case, none was counted that was less than 200 grams. This gave approximately 140 banded chicks that were assumed to have escaped the very high early mortality found in broods. However, I rated the mortality for this group at 50% rather than 25%, the figure suggested by results given earlier. If the between-season movements of these chicks averaged one mile, a few of them would be expected to show up outside of the area searched, when they returned. The number would not be large since most of the chicks were banded near the centre of the study area. If this fraction was 20% at the most, then about 56 juveniles should have been found on the study area as yearlings. Since some yearling males may not have appeared on the summer range, i t might be better to say that an estimated juveniles should have been found on the study area as adults 52 (figure obtained by omitting chicks banded in 1961 and applying death rate of yearlings, discussed below). It is clear that the estimated figure is significantly higher than the number that actually returned. This holds even i f the first-winter mortality is assumed to be 75%. It appears that, when chicks returned to the breeding range, they dispersed widely enough to take most of them outside the study area. The last section showed that yearling males preferred open vegetation x^hile on the breeding range. This was an important factor affecting dispersion and i t is useful to establish how far yearlings move between their second (yearling) and third summers, and whether they show the same preference as adults. The table below presents some relevant data from nine banded yearlings. I have already indicated that a few yearlings, not included below, held territories and returned to them in adult fashion. The nine below were those recovered out of a group of 16 and i t is possible that a tenth was relocated although identification was not certain. The survival of these males to age two was, then, at least 56%. The distances shown below suggest that some of the yearlings may have returned to some point outside the study area when they were adult. It is clear that the mortality rate for this group of yearling males was not significantly higher than that of the adult males, even though some of these yearlings were being prevented from establishing territory by the presence of adults. Only one of the nine settled more than 0.5 miles from his point of banding, the average distance moved being just over 2000 f t . It appeared that some yearling males, such as numbers 34 and 466, started to localize on an area in the season before they established territory there. The preference for open vegetation shown by yearlings is apparently 53 Table VI. Movements of males from point of banding as yearlings (Y) to point of recovery as adults (A), with an estimation of habitat of each point. Number Season Distance Habitat (Y) (A) (Y) (A) 34 1959 1962 560 f t . Dense Dense 131 1959 1960 1100 Open-Dense Open 386 1960 1961 1300 Very Open Very Open 364 1960 1961 1200 Open Very Open 466 1960 1961 300 Very Open Very Open 620* 1961 1962 2500 Very Open Very Open 638 1961 1962 1900 Very Open Very Open 678* 1961 1962 2600 Open Very Open 721 1961 1962 6900 Very Open Open S t r a i g h t - l i n e distances were measured from maps to the nearest 20 f t . * seen three times as y e a r l i n g , measurement made from l a s t known p o s i t i o n . continued i n the year of t e r r i t o r y establishment. Five of the yearlings used the same type of habitat as adults (Very Open i n four cases), three of them chose a more open type, and one chose a less open type. None of these observations were made i n Very Dense type. Using maps compiled from f i e l d n o t e s , I estimated the number of t e r r i t o r i a l males within an a r b i t r a r y distance (300 f t . ) of the posit i o n s i n Table VI.. The average figures obtained from this analysis were: 1. number of males wit h i n 300 f t . of y e a r l i n g ( l a s t known pos i t ion) 1.6 2. number of males within 300 f t . of returned adult 0.6 3. number of males within 300 f t . of y e a r l i n g ( l a s t known p o s i t i o n ) , i n following summer .... 1.4 The l a s t f i g u r e may have been low because of inadequate searching around some points of banding i n following years. However, i t resembles the f i r s t 54 f i g u r e , as would be expected. The f i r s t two f i g u r e s are not s i g n i f i c a n t l y d i f f e r e n t by Chi-square but i f a t>test i s performed on a l l the a v a i l a b l e p a i r s of data i n these two cate g o r i e s there i s a s i g n i f i c a n t d i f f e r e n c e (paired data, t equals 2.9, p_ between 0.02 and 0.01). This i s to be expected s i n c e the males do not u s u a l l y show the e f f e c t of t e r r i t o r i a l spacing u n t i l they become a d u l t . Note that adding one to each f i g u r e i n the second category (that i s , i n c l u d i n g the new a d u l t i n the count of h i s neighbours) would have made the f i r s t two f i g u r e s equal. A l s o , the y e a r l -ings may have been a t t r a c t e d to groups of t e r r i t o r i a l males. Only one case occurred i n which the banding p o i n t showed fewer neighbours than the a d u l t l o c a t i o n , i n the same year. P o s s i b l y some y e a r l i n g s , such as Nos. 34 and 466, returned to t h e i r e a r l i e r l o c a t i o n s and then searched out an area w i t h a lower d e n s i t y of t e r r i t o r i e s . As mentioned e a r l i e r , No. 131 d i d t h i s on the main c o n t r o l area. This simple a n a l y s i s emphasizes the poi n t that the spacing of t e r r i t o r i a l males was being determined by f a c t o r s d i f f e r e n t from those determining the d i s p e r s i o n of n o n - t e r r i t o r i a l males. This s e c t i o n shows how grouse might take advantage of a new area of favourable h a b i t a t . The few data a v a i l a b l e suggest that j u v e n i l e grouse d i s p e r s e w i d e l y and show no tendency to r e t u r n to the area where they were born or brooded. Males i n t h e i r t h i r d summer (new a d u l t s ) show v a r y i n g degrees of f i d e l i t y to the areas they used i n t h e i r second ( y e a r l i n g ) summer. I f the new ad u l t held a t e r r i t o r y as a y e a r l i n g , he returned to the t e r r i t o r y . I f the new a d u l t held no t e r r i t o r y as a y e a r l i n g , he moved anywhere from 300 f t . to over a mile from h i s y e a r l i n g p o s i t i o n and e s t a b l i s h e d t e r r i t o r y i n an area w i t h fewer t e r r i t o r i a l neighbours than he had as a y e a r l i n g . Some new a d u l t s may not have descended to the 55 summer range at a l l as y e a r l i n g s , so that t h e i r t e r r i t o r i e s would probably be s e l e c t e d on the b a s i s of h a b i t a t type and presence of neighbours o n l y . When they moved, j u v e n i l e s and y e a r l i n g s u s u a l l y went to more open h a b i t a t than that around t h e i r previous p o s i t i o n s . The e f f e c t of i n t e r a c t i o n on the d i s p e r s i o n of females and j u v e n i l e s The e f f e c t of i n t e r a c t i o n on the d i s p e r s i o n of females was not studied e x p e r i m e n t a l l y . This s e c t i o n , then, discusses those observations that show how the p o s i t i o n s of females were r e l a t e d to each other, and to the p o s i t i o n s of males. An attempt i s made to separate the observations i n t o categories depending on whether the female was "lone", on a nest, or w i t h a brood. Lone females can be f u r t h e r subdivided i n t o p r e - n e s t i n g hens, hens i n c u b a t i n g but observed away from the nest, and hens that have l o s t t h e i r c h i c k s . For some analyses i t i s assumed that lone hens seen before J u l y were prehatch (mating, n e s t - b u i l d i n g , i n c u b a t i n g , etc.) and that those seen a f t e r June had l o s t t h e i r young. When i n t e r a c t i o n was considered, the most important p o i n t emerging was that no evidence of any aggression between hens was ever uncovered. This can be shown i n s e v e r a l ways, and one set of data be a r i n g on t h i s was obtained by mapping a l l the known p o s i t i o n s of banded females. The r e s u l t i n g map showed t h a t , w h i l e females d i d r e s t r i c t t h e i r a c t i v i t i e s to a c e r t a i n area over the summers,, these areas were much l a r g e r than t e r r i -t o r i e s and overlapped a great d e a l . Females may s t i l l have spaced them-selves by some s o r t of " i n d i v i d u a l d i s t a n c e " phenomenon but t h i s seems u n l i k e l y judging by the observations mentioned below. I t appeared that the spacing of females was dependent on h a b i t a t s e l e c t i o n , random move-ments, the i n f l u e n c e of males, or some combination of these three. 56 There were a number of instances i n which two or more females were seen together. Several p a i r s of hens were seen together i n the i n t e r v a l before incubation, two pairs were seen together during the time of nesting (assumed to be l a s t three weeks i n June), and several pairs were seen together a f t e r June. In some cases broods which appeared to have chicks of only one age were found together with two or more hens. Usually, i n these cases, only one hen would respond strongly to the c a l l s of the chicks. One brood was found with three hens, two of which behaved i n a "broody" manner when chicks gave d i s t r e s s c a l l s . Broods were often seen to intermingle on the range and some broods contained chicks of obviously d i f f e r e n t ages. A l l these points strengthen the conclusion that hens were not antagonistic toward other members of the population. The fact that hens stayed with t h e i r chicks from the time of hatch to the time of upward migration has an obvious e f f e c t on d i s p e r s i o n . The broods can be pictured as aggregations of juveniles around a female, which move at random with respect to each other and become looser with increasing age of the j u v e n i l e s . The l o c a t i o n of broods was probably influenced mainly by habitat s e l e c t i o n , as suggested l a t e r . On t h i s study area the family groups apparently remained together at least u n t i l migration s t a r t e d . There was no evidence of any permanent or even yearly p a i r i n g between males and females i n t h i s population. Males t r i e d to court any hen that came within t h e i r view or hearing. The home ranges of hens were much larger than the t e r r i t o r i e s of males and usually encompassed several t e r r i t o r i e s . Banded hens were often seen near d i f f e r e n t t e r r i t o r i e s at d i f f e r e n t times. However, there was some evidence to suggest that hens l o c a l i z e d t h e i r a c t i v i t i e s near one or two t e r r i t o r i a l males before the 57 time of n e s t - b u i l d i n g and egg-laying. The i n f l u e n c e of t h i s preference may have c a r r i e d over and caused more nests to be b u i l t on t e r r i t o r i e s than chance would a l l o w . In any case, t h i s a t t r a c t i o n must be discussed s i n c e i t has an obvious e f f e c t on d i s p e r s i o n of females i n the e a r l y p a r t of the breeding season. The p o s i t i o n s of females on the p l o t s were mapped and t h i s allowed a comparison of female and male l o c a t i o n s . Since the area covered by t e r r i t o r i e s was known, the,expected and a c t u a l numbers of females o c c u r r i n g w i t h i n t e r r i t o r i e s could be compared. I t was observed that more pre-hatch females than expected occurred on the t e r r i t o r i e s . This may have been due to a search b i a s , of the type mentioned e a r l i e r , but i t was a l s o found that broods occurred on the t e r r i t o r i e s about as o f t e n as the measurements of areas would suggest. I f no b i a s i s i n v o l v e d , then pre-hatch females sought t e r r i t o r i e s w h i l e hens w i t h broods moved at random w i t h respect to t e r r i t o r i e s . I t i s j u s t p o s s i b l e that b i a s was inv o l v e d d e s p i t e the d i f f e r e n c e s i n c e o b servation of males was emphazized i n the f i r s t h a l f of the summers and random searching was s t r e s s e d i n l a t e J u l y , August, and September. Another method can be used to show t h i s preference. I t i s p o s s i b l e to compare numbers of females on c o n t r o l and experimental areas, even though the p l o t s were of d i f f e r e n t s i z e s , and d i f f e r e n t amounts of time were spent searching them. Table V I I , below, shows t h i s comparison. I f the correct e d percentages are examined, i t i s c l e a r that a s i g n i f i c a n t l y higher number of pre-hatch females were found on the c o n t r o l and experimental areas. Fewer broods were found on the Very Dense area, suggesting that h a b i t a t s e l e c t i o n was i n f l u e n c i n g the p o s i t i o n s of broods r a t h e r than the presence of males. Broods could s t i l l have been a t t r a c t e d to t e r r i t o r i e s by the v e g e t a t i o n and topography of the 58 t e r r i t o r i e s but pre-hatch hens were obviously a t t r a c t e d to the males on the t e r r i t o r i e s . Table V I I . Number of females sig h t e d on removal p l o t s and main c o n t r o l p l o t s , as compared to type of v e g e t a t i o n and presence of males. Removal p l o t s Control p l o t s Very Open veg. (36% of area of Very Dense (31%) Open veg. (15%) Dense veg. (18%) four p l o t s ) Pre-hatch females 16 5 22 9 Broods 20 2 11 5 Hours of search on area 90 31 102 53 % of pre-hatch hens* 14% 15% 43% 28% % of broods* 30% 10% 35% 25% * These f i g u r e s have been co r r e c t e d f o r both time and percent of area covered by given type of v e g e t a t i o n . The number of observations was d i v i d e d by the no. of hours spent on the given area and by the percentage of the t o t a l represented by the given area. The r e s u l t i n g f i g u r e s were converted to per-centages. Some other observations and measurements show the r e l a t i o n s h i p between the p o s i t i o n s of females and males. Hens were of t e n found w i t h i n a few fee t of males, e s p e c i a l l y i n the p e r i o d from m i d - A p r i l to mid-May. In some cases the males were banded and were seen near t h e i r usual hooting pos t s , suggesting that the females sought out the males. On a few occasions, two females were found w i t h i n a few fee t of the same male. Outside of t h i s month-long i n t e r v a l i t appeared that females were not seeking males as a c t i v e l y . Females were found near males i n the mid-May to end-of-June 59 i n t e r v a l but o f t e n the male was away from h i s usual centre of a c t i v i t y , suggesting that he had chased the female. Males o f t e n d i s p l a y e d to or chased a f t e r broody females but i n a l l such cases the female showed no a t t r a c t i o n to the male and, i n some cases, the female moved away from the male. S t r a i g h t - l i n e measurements of the movements of banded females w i t h i n a given summer give some inf o r m a t i o n on the a t t r a c t i o n of females to males (about 70 measurements used). I f the distances are p l o t t e d against., number of days elapsed, some " r a t e s " can be c a l c u l a t e d from the slope of f i t t e d l i n e s . Lone females show a r a t e of movement of 18 f e e t / day, compared to 54 f t . / d a y f o r broods. I f some of the broods had s t a r t e d to migrate, the r a t e f o r them would make the average too h i g h . Even w i t h t h i s p o s s i b l e b i a s , i t seemed that lone females were r e s t r i c t i n g t h e i r a c t i v i t i e s to a much smaller area. This i s probably another i l l u s t r a t i o n of t h e i r a t t r a c t i o n to males. A r a t e of 78 f t . / d a y was obtained f o r hens that had l o s t t h e i r broods a f t e r June, suggesting that these females may s t a r t to migrate a f t e r they lo s e t h e i r c h i c k s . S i g h t i n g s of banded females i n d i c a t e that lone hens do not l o c a l i z e t h e i r a c t i v i t i e s around the same male(s) each summer. S t r a i g h t - l i n e measurements from the f i n a l p o i n t of observation i n one summer to the next s i g h t i n g i n another summer show that the homing tendency i s not n e a r l y as strong i n females as i t i s i n t e r r i t o r i a l males. The distances i n v o l v e d are c l o s e r to those of y e a r l i n g males, t r a v e l l i n g between t h e i r second and t h i r d summers. The average f o r about 40 measurements was 1580 f t . and there was no obvious i n d i v i d u a l or seasonal v a r i a t i o n . A rough c a l c u l a t i o n suggests that females might have had a home range of 30-40 acres on the breeding area over the years w h i l e the best-known males 60 h e l d t e r r i t o r i e s of about four a c r e s , on the average. From these r e s u l t s , i t appears that i n t e r a c t i o n had no e f f e c t on the spacing of females w i t h respect to each other whether the females were pre-hatch or w i t h broods. A p o s i t i v e a t t r a c t i o n was obviously involved i n the d i s p e r s i o n of s i n g l e broods around t h e i r hen. No evidence of pair-bonding was uncovered. However, p r i o r to h atching, females seemed to be a t t r a c t e d t o males on t h e i r t e r r i t o r i e s , and nests may a l s o have been on t e r r i t o r i e s more o f t e n than random placement would a l l o w . I f t h i s was a true preference, then the spacing and preferences of males would e v e n t u a l l y determine the d i s p e r s i o n of the whole p o p u l a t i o n i n any gradual movement out of an unfavourable area or i n t o a favourable one. The e f f e c t of h a b i t a t s e l e c t i o n on the d i s p e r s i o n of females and j u v e n i l e s The preceding s e c t i o n showed how the l o c a t i o n of females p r i o r to the hatch was i n f l u e n c e d by the l o c a t i o n of t e r r i t o r i e s . Apparently, i n t e r a c t i o n had l i t t l e e f f e c t on the l o c a t i o n of females or broods apart from t h i s . These data suggest that the d i s t r i b u t i o n of females and c h i c k s , i f i t has a non-random b a s i s , must be determined by h a b i t a t p references. These preferences are examined i n t h i s l a s t s e c t i o n of the R e s u l t s . The best data f o r showing a s e l e c t i o n of h a b i t a t i s the type given i n Table VII. The c o r r e c t e d percentages i n d i c a t e d that broods were found using Very Open, Open, and Dense types of v e g e t a t i o n i n roughly equal numbers, w i t h the Open type showing s l i g h t l y more use. The broods appar-e n t l y avoided Very Dense v e g e t a t i o n . S i m i l a r l y , pre-hatch females used open v e g e t a t i o n s i g n i f i c a n t l y more than dense (57 versus 43%). F i e l d n o t e s suggested t h a t , as w i t h males, a number of the lone females and broods . found on the dense p l o t s were i n or beside c l e a r i n g s . I t can be t e n t a t i v e l y 61 concluded that females prefer open habitats over denser ones for most of the breeding season. There were not s u f f i c i e n t data to test the locations of nests or females that lost t h e i r broods, i n this way. The remaining paragraphs w i l l present descriptions and comparisons based d i r e c t l y on fieldnotes and analyses of vegetation. Where comparisons are drawn using the four main types of habitat, i t must be kept i n mind that these did not occur equally over the study area. The observations used below f e l l , with a few exceptions, within an area that could be s p l i t as follows (omitting any minor types of h a b i t a t ) . Very roughly, 407, of the area was covered by Very Open vegetation, 257. by Open, 251 by Dense, and 107, by Very Dense. The paragraphs discuss the positions of lone females, ne incubating females, and, f i n a l l y , broods. The positions used by lone females, whether pre- or post-hatch, seemed to be much the same as those used by s i l e n t males. Apart from the choice of open vegetation, the only preference that may have affected the i r dispersion was an apparent choice of moist areas - stream-edges, sloughs, sedge areas, or mere depressions with damp s o i l and above-average cover by ground vegetation. About half the pre-hatch, and 407, of the post-hatch females that were found alone occurred within a,few feet of such areas Some 80 measurements done i n the f i e l d showed that lone females were found, on the average, somewhat less than 100 f t . from such places. The same measurement was made for 68 random points (those used i n the section describing t e r r i t o r i e s ) and the average distance here was 130 f t . I t appeared that lone females favoured moist areas, especially within open habitat, either for plant food found there, the shade offered, or the cover made available. Data were obtained from 31 nests and, again, open vegetation was 62 favoured. Of 29 nests properly described, 27 were in Open or Very Open habitat and the other two were in Dense. The 27 were s p l i t about equally between the two open types, suggesting that the Open was favoured since i t covered less of the study area. The small table below suggests why Open might be preferred over Very Open for nest-sites. Table VIII. Comparison of cover at nest-sites with cover in Very Open and Open habitats (from quadrats described e a r l i e r ) . Factor being compared Nest area Habitat (Open) type (Very Open) Coniferous cover 21% 31% 3% Deciduous cover 20 15 12 Ground vegetation 42 20 21 Bare ground and rocks 26 17 24 "Duff" 49 73 68 Logs and stumps 18 12 12 The comparisons suggest that, once within open areas, hens located their nests in sites with better cover than random placement would give. The significant figure is probably that for cover by ground vegetation. It is also interesting that cover by logs and stumps was higher, and cover by "duff" (dead plants, moss, l i t t e r ) was lower than would be expected. The actual positions of the nests bear out these points. Eleven of the nests were under logs, three others were beside fallen logs, and several were within clumps of salal or bracken. Nests were often under the canopy of a conifer, where these were available, and the degree of overhead cover was very high (87% average for 16 measurements). Nest positions showed no obvious relation to water or slope, nest material was available everywhere, and logs and roots with spaces underneath were abundant. A l l these points suggest that there was no shortage of sites for nests in the open'areas. 63 The only data which can be given for incubating females is that obtained from the locations of "docker droppings" passed by the hens while they were off their nests (described by Bendell, 1954). The positions of these show where incubating hens were feeding, watering, and dusting. A few observations indicate that these droppings may also be passed during the f i r s t few days of brooding. About half of some 50 droppings were found beside or in wet areas and on sites having especially heavy cover by grass and herbaceous species. The sites included Carex patches, creek and beaver pond edges, and other moist areas with ground cover. A few were found near dustbstbs which were generally in patches of sand, dry earth, or powdery dead wood. A few others were found on stumps and may have been l e f t either by hens flying by stages to their feeding areas or by hens shepherding very young chicks. Almost a l l the others were found on old logging grades and f i r e roads. It was obviously easier to find droppings here but i t seemed significant that the roads used most frequently were invariably those showing a good cover by Trifolium spp., Hypochaeris radicata. Fragaria spp., or similar plants. Incubating hens, then, seemed to make use of areas with especially heavy ground vegetation while they were off their nests. Large quantities of data were obtained on broods since these were easier to find than lone females. Again, a preference for open vegetation was apparent. The most useful data were collected in 1962 when components of cover were rated for 104 broodsites. Some averages from these' descriptions were: 57% cover by ground vegetation (includes logs and stumps), 25% duff, and 17% bare ground. Comparison with Table V I I I shows that the f i r s t two are significantly different from the figures given for open habitats. Broods must have occurred more often in areas with heavy cover at ground level than 64 chance would allow. The duff figure could be explained by assuming that younger broods avoided areas that were choked with dead plants and l i t t e r . Some further analyses can be given to illustrate these preferences. The table below gives a rough breakdown on habitat at 244 broodsites. The categories are quite general because various methods were used to describe the habitat, depending on the observer. Table IX. Approximate classification of habitat at 244 broodsites. Open types of habitat - 80% of broods - as in Very Open plot: 367« - as in Open plot: 19% - as in open plots but showing especially heavy cover at ground level: 16% - within treeless open areas: 9% Dense types of habitat - 6% - as in Dense plot but with some openings: 2% - heavy cover by conifers: 2% - heavy deciduous thickets (alder, Rubus pfarviflorus. Sambucus pubens, etc.): TL Other types of habitats - dense patches of bracken: 8% * - sedge (Carex spp.) areas: 2% * - heavy cover by fallen logs: 4% * these were within open habitats or in clearings in dense habitats When these figures are compared with the fractions of the study area covered by each type of habitat, i t is clear that open areas were favoured (90% of broods versus 65% of area, roughly). About 15% of these broods were immediately beside a moist area and, since this may not always have been mentioned, the percentage may have been higher than 15%. The ages of chicks in about. 60% of the broods used in Table LX were estimated. Broods containing chicks less than a week old were found almost exclusively in areas of sparse vegetation (17 in open habitats, one in a bracken patch, one in an open area covered by log tangles, and one in heavy deciduous 65 vegetation). This choice was obvious for broods of one to three weeks, as well (20 i n open habitats or areas of bare ground, four i n bracken patches, one i n a log tangle). Broods having chicks over three weeks used more types of habitat but s t i l l favoured the open. This category showed very strong use of s i t e s within open habitats that were w e l l -vegetated at the ground l e v e l . Only 2% of a l l broods were found i n vegetation that could be c a l l e d Very Dense and about 3% were found on s i t e s that would be c a l l e d Dense habitat. The use of open habitat seemed to be more d e f i n i t e i n broods than i t was i n lone females. More-over, the s e l e c t i o n seemed to be strongest i n broods having younger chicks. An attempt was made to compare the occurrence of plant species at broodsites with t h e i r occurrence on open h a b i t a t s . After the percent-ages were corrected to allow for the d i f f e r e n c e i n s i z e of area sampled, i t appeared that some species did occur more often at broodsites. Most i prominent were Mahonia. Anaphalls. Hieracium, Vaccinium and Achlys species. The be r r i e s of Mahonia and the buds and leaves of Hieracium were probably important foods for older chicks, as the leaves of Anaphalis may have been. Vaccinium might have been used as a food plant but this could be an instance where the s i z e of the i n d i v i d u a l plant compared to the quadrat s i z e of one square yard gave a f a l s e l y low fi g u r e f or the open p l o t s . S i m i l a r l y , the figures for Achlys on the pl o t s were l i k e l y low due to the early appearance and withering of t h i s annual, e s p e c i a l l y on the open p l o t s . Some other species showed up more frequently i n the broodsite analyses - Lysichitum americanum, Equisetum arvense;, and Polystichum  munitum, for example. There i s a source of error i n these cases since some quadrats on the pl o t s were omitted as being a t y p i c a l when they were located i n a marsh or bog area. However, since broods often occurred i n 66 areas with widespread ground vegetation, these marshy species would be expected to show up more often at broodsites. From this, there is some indication that the dispersion of broods may have been partly determined by the presence of food plants. For about 90 broodsites, the distance to the nearest moist area was measured in the f i e l d . As with lone females, the average here was about 95 f t . , compared to 130 f t . for a set of random points. From pre-ceding paragraphs i t appears that older broods, at least, favoured areas with especially heavy vegetation on the ground. Moist areas per se were probably not important to females and juveniles, but such areas would show lush vegetation, and apparently this was what attracted the broods. There was no shortage of such spots on the Middle Quinsam range but on some breeding areas this might become the most important factor deter-mining the dispersion of females and chicks. With the completion of this section i t is clear that a l l grouse favoured habitats with sparse vegetation while on the breeding range. Beyond this, the location of broods appeared to be governed by the density of vegetation at the ground level, the amount of l i t t e r on the ground, and possibly by the presence of certain plants. 67 DISCUSSION In t h i s d i s c u s s i o n I f i r s t review the m a t e r i a l given i n the Results to see how i t agrees w i t h or d i f f e r s from the work of other i n v e s t i g a t o r s . Subjects are discussed i n the order i n which they were presented i n the Results and some comments and s p e c u l a t i o n s are presented i n the review. I d i g r e s s s l i g h t l y to discuss the e f f e c t of d i s p e r s i o n on the r e g u l a t i o n of breeding numbers, using mainly the experimental r e s u l t s . An attempt i s then made to i n t e g r a t e a l l t h i s i n f o r m a t i o n i n t o an o v e r a l l p i c t u r e of d i s p e r s i o n on the breeding range. F i n a l l y , some comments are given on the adaptive s i g n i f i c a n c e of these processes. The hooting of males has been used as a c r i t e r i o n of t e r r i t o r i a l behaviour i n most st u d i e s on c o a s t a l blue grouse. This p o i n t should be discussed since there was l i t t l e evidence i n t h i s study to show that hooting alone kept males apart. Hooting was performed almost e x c l u s i v e l y by males that were l o c a l i z e d on a given area and i t appeared that any other males found on these areas were s i l e n t and presumably non-competitive because of immaturity. The mechanisms causing the observed spacing i n r e s i d e n t males must have been threat d i s p l a y s , a c t u a l f i g h t i n g , or a v o i d -ance of other males seen or heard. Hooting could have served to space males only i f the l a s t p o s s i b i l i t y was the most important one, s i n c e a g o n i s t i c patterns of behaviour and hooting were q u i t e d i s t i n c t from each other. However, the c o r r e l a t i o n between hooting and the f i d e l i t y to an e x c l u s i v e area was almost p e r f e c t . This suggests t h a t , although hooting may not have been used to e s t a b l i s h a t e r r i t o r y , i t was performed.only by males that were on t e r r i t o r y . The trend toward uniform spacing shown by t e r r i t o r i a l males resembles that shown by B e n d e l l (1954, 1955). This i s apparently the 68 f i r s t time that nearest-neighbour analyses, developed f i r s t by botanists (Dice, 1 9 5 2 ; Hopkins, 1 9 5 4 ) , have been applied to an animal of this kind and there are some obvious weaknesses. The method does not allow for the instantaneous positions of birds but, since males focused their activities around a few central points rather than at the edges of their territories, application seemed worthwhile. The absence of any "boundary patrolling" suggests that the uniformity was a result of recognition and avoidance of neighbours, in the manner suggested by Lack ( 1 9 5 4 ) . Territories were larger and more variable in size than those measured by Bendell ( 1 9 5 4 ) , indicating that size of territory was inversely proportional to density of t e r r i t o r i a l males. For example, better-known territories on the Middle Quinsam range weffe 3 . 7 acres on the average for a density of 0 , 1 5 t e r r i t o r i a l males per acre. On Bendell's ( 1 9 5 4 ) study area the average for better-known territories was 1 . 3 acres, the density being about 0 . 4 per acre. It is interesting that males in the dense population showed an even closer return to territory in succeeding years than that found here. The indications are that older males were never driven from their territories by younger ones, and that avoidance caused a more rigid pattern of spacing to develop in the dense population. Either interaction was never strong enough to affect established territories or older males had an advantage in prior knowledge of an area or earlier arrival on an area. This study seemed unique in showing at least a small fraction of yearling territory-holders. Again, this is probably dependent on density since Bendell found only one hooting yearling in three years of study. Boag ( 1 9 6 4 ) recorded no yearlings holding territory in his population and f e l t that yearling males were forced into marginal habitats by the 69 i n t o l e r a n c e of a d u l t s . Although a d u l t s prevented some y e a r l i n g s from e s t a b l i s h i n g t e r r i t o r y on the Middle Quinsam area, there was no evidence of e v i c t i o n or increased m o r t a l i t y i n these y e a r l i n g s . Some y e a r l i n g s probably d i d not descend to the breeding range but i t i s u n l i k e l y that the f r a c t i o n here was as high as that suggested by B e n d e l l (1954) or Buss and S c h o t t e l i u s (1954). Experimental work confirmed that a l l the a d u l t s present were h o l d i n g t e r r i t o r i e s and c o n t r i b u t i n g to the uniform spacing. The only a l t e r n a t i v e which cannot be dismissed i s the p o s s i b l e e x p u l s i o n of some males i n A p r i l before extensive f i e l d w o r k was under way. This seems an u n l i k e l y p o s s i b i l i t y s i n c e wandering a d u l t s were never found outside of the p e r i o d of m i g r a t i o n , and s i n c e a high number of banded y e a r l i n g s were recovered on t e r r i t o r y i n the year f o l l o w i n g t h e i r banding. A l s o , a good deal of space i n open h a b i t a t s was never used by males, and males were known to use a smaller area i n seasons when they had c l o s e r neighbours. A short-term removal experiment on a more dense p o p u l a t i o n ( B e n d e l l , 1954) gave r e s u l t s s i m i l a r to t h i s study except that there was no replacement of t e r r i t o r i a l males by y e a r l i n g s . Bendell's p o p u l a t i o n apparently had the highest d e n s i t y ever recorded f o r blue grouse so i t seems d o u b t f u l that surplus groups of a d u l t males are a f e a t u r e of blue grouse populations on t h e i r breeding ranges. As might be expected, i n t e r a c t i o n i n the more dense p o p u l a t i o n f i r s t a f f e c t e d the behaviour of y e a r l i n g males. Whether the i n t e r a c t i o n a s s o c i a t e d w i t h even higher numbers would lead to more use of emptied areas i n succeeding years i s s t i l l an open qu e s t i o n . • ^ The s e l e c t i o n of open elevated areas f o r t e r r i t o r i e s and the choice of spots w i t h i n the t e r r i t o r y f o r hooting and d i s p l a y i n g are s i m i l a r to the f i n d i n g s of other workers. However, the c l e a r choice of h a b i t a t by y e a r l i n g 70 males has not been n o t i c e d or discussed before. The use of elevated areas f o r hooting has been mentioned by Caswell (1954) and S c h o t t e l i u s (1951) w h i l e Edson (1925) and S t e i n h o f f (1958) have commented on the c o r r e l a t i o n between height of land and l o c a l occurrence of blue grouse. Boag (1965) showed that t e r r i t o r y s e l e c t i o n i n h i s p o p u l a t i o n could be c o r r e l a t e d w i t h d e n s i t y of v e g e t a t i o n (favoured spots having about 50% canopy cover) but not w i t h p l a n t s p e c i e s . B e n d e l l (1954) s t u d i e d the v e g e t a t i v e s t r u c t u r e of t e r r i t o r i e s and pointed out that t e r r i t o r i a l boundaries were not l i m i t e d by types of v e g e t a t i o n . The present work agrees f a i r l y w e l l w i t h both these s t u d i e s except that the presence of Very Dense v e g e t a t i o n d i d seem to determine the boundaries of some t e r r i t o r i e s . Use of open areas w i t h i n dense h a b i t a t was a l s o noticed by Heebner (1956). D e s c r i p t i o n s of hooting s i t e s w i t h i n t e r r i t o r i e s correspond w e l l w i t h those mentioned by B e n d e l l (1954) and B l a c k f o r d (1958, 1963). These preferences seem to be shown by, males i n a number of p o p u l a t i o n s , both of c o a s t a l and i n t e r i o r races. Apparently the extreme openness of the h a b i t a t caused some groups of males to develop a type of behaviour showing some po i n t s i n common w i t h the communal behaviour of the " p r a i r i e " grouse (Lyrurus t e t r i x , Tympanuchus  cupido, Pedioecetes p h a s i a n e l l u s , and e s p e c i a l l y Centrocerus urophasianus), discussed by Ammann (1957), Hamerstrom and Hamerstrom (I960), Hart et a l (1950), Hohn (1953), Scott (1950), and Wynne-Edwards (.1962). This bears out the suggestion that the type of breeding d i s p l a y i n t e t r a o n i d s can be i n f l u e n c e d by the type of h a b i t a t used as breeding range (Hoffman, 1956). In d i s p e r s i o n and h a b i t a t , Dendragapus, Tetrao (Koskimies, 1957), and Canachites (Lumsden, 1961) species are probably intermediate between s o l i t a r y forms such as Bonasa umbellus (Dorney, 1959; Eng, 1959; Palmer, 1961) and the " l e k " or communal forms mentioned above. The f a c t that 71 interior races of blue grouse, using grassland or other very open areas for breeding, show a tendency to use communal display areas bears out the present observations and supports the thesis of Hoffmann. Coastal blue grouse are obviously closer to the solitary forms and show no use of any traditional display grounds. The "groups" here probably represent clusters of territories around a favourable area, as suggested by Koskimies (1957) and Svardson (1949). The f i d e l i t y of juveniles to their natal area has been the subject of argument in the literature. It appears now that most authors would support the suggestion made here, that juveniles disperse widely between their f i r s t and second summers (Bauer, 1962; Bendell, 1954; Boag, 1965; Mussehl, 1960). It must be pointed out that the assumed dispersal tendency could have resulted from incorrect assumptions about the mortality nec ess a.<c'A^ of juveniles. The few data available suggest that chicks do nonre tu rn to the same habitat as found at their area of birth. The unique data from this study on movements of yearling males show that the locations of males became more localized with increased age up to adulthood, depending largely on when the males took up territory. Lack of aggression between hens seems to be a property of a l l breeding populations of blue grouse. Bendell (1954) mentions one case of apparent h o s t i l i t y between hens and I have found no others in the literature on free-ranging populations. If hens met often at feeding and dusting areas, or near hooting males, one might expect some sort of dominance pattern to arise. This may have happened but, because no fighting was observed and hens were seen together on occasion, i t seems more probable that hens merely ignored or avoided each other when they met. Other authors have noticed intermingling of broods, as well as lone hens travelling with 72 broods, and have presumed that adoption of orphaned chicks would occur (Bendell, 1954; Fowle, 1960; Mussehl, 1960; Wing et a l , 1944). Very l i t t l e has been published on the habitat preferences of females prior to nesting or during incubation. Nest-sites have been studied in a l i t t l e more detail and the only feature common to a l l reports is an apparent preference for open habitat with logs, stumps, or low vegetation as cover for the actual site (Bendell, 1954; Caswell, 1954; Mussehl, 1960). Various workers have related the location of broods to such factors as presence of certain plants (for example, Amelanchier or Ribes spp.), nearness of free water, or to the degree of coverage by vegetation (Bauer, 1962; Bendell, 1955; Marshall, 1946; Mussehl, 1960 and 1963; Wing et a l , 1944). Certain plants may have helped determine the dispersion of broods here but they were not the expected f r u i t or berry-carrying species. Coverage by vegetation was apparently very important, and this agrees with other studies. If the "free-water" areas of other authors showed heavy surrounding veget-ation at ground level then this preference would be comparable to results given here. It is useful to question whether any of the factors affecting dispersion might also have limited breeding numbers. Territorial behaviour seemed the only factor capable of doing this. I have suggested that the failure of many yearlings to hold territories was as much due to their immaturity as to the influence of resident males. T e r r i t o r i a l i t y would limit productivity only i f both sexes were monogamous and hens were pairing exclusively with t e r r i t o r i a l males. This was not the case and there was no evidence of any lowering of nesting or rearing success by the activities of males. Since males took no part in the defence of females, nests, or chicks, t e r r i t o r i a l i t y apparently served only to isolate males sufficiently to 73 prevent any i n t e r f e r e n c e w i t h d i s p l a y i n g and mating. This f u n c t i o n has been suggested f o r other species by a number of authors, f o r example -Lack (1939), Nice (1941), P i t e l k a (1959), Tinbergen (1956). I t i s very u n l i k e l y that i n t e r a c t i o n on t h i s breeding range was having any r e g u l a t o r y e f f e c t on d e n s i t y as suggested f o r other species by Choate (1963), Jenkins (1961), Jenkins et a l (1963), Kluyver and Tinbergen (1953), and Tompa (1962, 1964). On t h i s breeding range, what o v e r a l l p a t t e r n of d i s p e r s i o n i s revealed when both sexes and a l l age-groups are considered together? This i s best described by c o n s i d e r i n g the p a t t e r n found i n favourable h a b i t a t , and then that found i n unfavourable h a b i t a t . The d i s p e r s i o n over favoured areas apparently took the form of small groups of b i r d s spaced i n a near-uniform d i s t r i b u t i o n , each group c o n s i s t i n g of a t e r r i t o r i a l male plus any y e a r l i n g males and lone females that were a t t r a c t e d to him. The two l a t t e r types probably s h i f t e d from group to group, although the females' p o s i t i o n s would soon become f i x e d by t h e i r n e s t i n g . Midway i n the season another p a t t e r n i n v o l v i n g aggregations of b i r d s was superimposed on the f i r s t , the groups here being broods (with t h e i r females) moving randomly w i t h respect to each other and the males. L a t e r i n the season the near-uniform p a t t e r n began to break up as males migrated. The p a t t e r n v i s u a l -i z e d i s an i d e a l i s t i c one s i n c e groups would c o n s t a n t l y be breaking and reforming as b i r d s moved to t h e i r i n d i v i d u a l f eeding or r o o s t i n g areas. On l e s s favourable areas the d i s p e r s i o n probably took the form of randomly-located males, the spacing having changed due to a t t r i t i o n and movement of remaining males to any nearby remnants of favourable h a b i t a t . As the area became l e s s favourable the y e a r l i n g male, and then the female and j u v e n i l e components would disappear through the a c t i o n of h a b i t a t 74 s e l e c t i o n and p o s s i b l y m o r t a l i t y . These patterns of u t i l i z a t i o n seem" adaptive when the nature of the h a b i t a t i s considered. Coastal f o r e s t s which have been logged or burned by f o r e s t f i r e s must be near-optimal breeding range judging by the p o p u l a t i o n expansions and high d e n s i t i e s that occur t h e r e . The d i s p e r s a l of j u v e n i l e s , the h a b i t a t preferences of y e a r l i n g males, and the tendency f o r lone females to occur on t e r r i t o r i e s would a l l o w blue grouse to make r a p i d use of open areas made a v a i l a b l e to them. The s t a b i l i t y brought about i n some species by pair-bonding and e x p u l s i o n of c e r t a i n members would seem i l l - a d a p t e d to a s i t u a t i o n c a l l i n g f o r q u i c k settlement and expansion of numbers. One might expect to f i n d no pair-bonds, no surplus b i r d s , and no unmated females i n such a s i t u a t i o n . Most of the favourable h a b i t a t a v a i l a b l e to these b i r d s would e v e n t u a l l y become unfavourable through regeneration and s u c c e s s i o n . A l d r i c h (1963) and Brooks (1926) mention the use of n a t u r a l openings i n mature c o a s t a l f o r e s t by the f u l i g i n o s u s r a c e . At times these openings and r i d g e s , perhaps together w i t h a l p i n e areas, would be the only breeding h a b i t a t a v a i l a b l e . The preference f o r open and elevated areas shown by t e r r i t o r i a l males would be of p a r t i c u l a r value at such times. Large open areas are c o n s t a n t l y appearing i n c o a s t a l f o r e s t s through the a c t i o n of f i r e s , s l i d e s , and human a c t i v i t i e s . The blue grouse of the f o r e s t s seem to maintain themselves by q u i c k l y e x p l o i t i n g such areas. 75 SUMMARY AND CONCLUSIONS An attempt has been made to analyze the d i s p e r s i o n of a p o p u l a t i o n of blue grouse (Dendragapus obscurus f u l i g i n o s u s ) on i t s breeding range on e a s t - c e n t r a l Vancouver I s l a n d . To do t h i s , grouse were observed and banded over an area of about f i v e square m i l e s , the greatest e f f o r t being concen-t r a t e d on a number of p l o t s set i n d i f f e r e n t h a b i t a t s . The e f f e c t of i n t r a -s p e c i f i c i n t e r a c t i o n on d i s p e r s i o n was s t u d i e d by examining the d e n s i t y , behaviour, l o c a t i o n s , and movements of males, females, and j u v e n i l e s . The e f f e c t of h a b i t a t s e l e c t i o n was s t u d i e d by comparing numbers and l o c a t i o n s of b i r d s i n open and dense h a b i t a t s . The i n f l u e n c e of both these f a c t o r s on the d i s p e r s i o n of males was i n v e s t i g a t e d by removing males from p l o t s i n open and dense h a b i t a t s s t a r t i n g at the beginning of each breeding season. I n t e r a c t i o n had some pronounced e f f e c t s on the d i s p e r s i o n of males. A l l the a d u l t males and a few of the y e a r l i n g males were t e r r i t o r i a l , and t h i s group approached u n i f o r m i t y i n t h e i r d i s t r i b u t i o n . W i t h i n a given season, males removed from t h e i r t e r r i t o r i e s were seldom replaced by other adults suggesting that no surplus of n o n - t e r r i t o r i a l a d u l t s was present. However, the experiment showed that about h a l f of the y e a r l i n g males were prevented from e s t a b l i s h i n g t e r r i t o r y by the presence of t e r r i t o r i a l males, and that these y e a r l i n g s were a t t r a c t e d to the v i c i n i t y of t e r r i t o r i a l males. Removal a l s o showed that the l o c a t i o n of t e r r i t o r i e s by newly-adult males d i d not depend n o t i c e a b l y on the number of t e r r i t o r i a l males already present on a given area, even though the tendency toward uniform spacing was preserved. Comparison w i t h other s t u d i e s i n d i c a t e d that the s i z e s of t e r r i t o r i e s and p o s s i b l y the f r a c t i o n of y e a r l i n g males i n the p o p u l a t i o n were i n v e r s e l y p r o p o r t i o n a l to the d e n s i t y of t e r r i t o r i a l males. 76 Females r e s t r i c t e d t h e i r a c t i v i t i e s to a given area w h i l e on the breeding range but they were not t e r r i t o r i a l . P r i o r to n e s t i n g , females apparently stayed near t e r r i t o r i a l males but there was no s i g n of any l a s t i n g pair-bonds. A f t e r the time of hatch the p o s i t i o n s of females and broods bore, no r e l a t i o n to each other or to the p o s i t i o n s of males. A l l b i r d s , y e a r l i n g males p a r t i c u l a r l y , showed a preference f o r open types of h a b i t a t r a t h e r than dense. This choice was confirmed by a d e c l i n e i n numbers on the study p l o t s i n the most dense type of h a b i t a t . When compared w i t h randomly chosen p o i n t s , t e r r i t o r i e s were found more o f t e n i n areas w i t h sparse v e g e t a t i o n , elevated p o i n t s , and patches of open ground. W i t h i n open h a b i t a t s , nests x*ere u s u a l l y located where cover by l o g s , stumps, and ground-level v e g e t a t i o n was h i g h e r , and cover by dead p l a n t s and l i t t e r was lower than normally found i n these same h a b i t a t s . Broods, although found most commonly i n sparse h a b i t a t s , were a s s o c i a t e d w i t h moist areas and other areas having heavy cover by v e g e t a t i o n at the ground l e v e l . There was some evidence to suggest that j u v e n i l e s dispersed w i d e l y between t h e i r f i r s t and second summers. I n t h e i r t h i r d ( f i r s t a d u l t ) summer males u s u a l l y returned w i t h i n one-half mile of the p o s i t i o n s they used as y e a r l i n g s . Once t e r r i t o r i e s were e s t a b l i s h e d , the a d u l t (or y e a r l i n g ) owners returned very c l o s e l y to them i n succeeding summers. Females past the age of one year showed some f i d e l i t y to t h e i r e a r l i e r l o c a t i o n s , the closeness of r e t u r n being about that of new a d u l t males. The d i s p e r s i o n of the p o p u l a t i o n can be d e s c r i b e d , r a t h e r a r t i f i c i a l l y , by c o n s i d e r i n g the b i r d s to be i n two types of aggregations, A and B. Type A groups were d i s t r i b u t e d somewhat un i f o r m l y , c o n s i s t e d of t e r r i t o r i a l males plus other b i r d s that were a t t r a c t e d to them, and were the major groupings 77 during the f i r s t h a l f of the breeding season. Type B aggregations were broods, moving randomly w i t h respect to other b i r d s , but h o l d i n g to a home range from the time of hatch to m i g r a t i o n . The h a b i t a t preferences mentioned would cause the d e n s i t y of these groups to vary over the breeding area. As areas grew unfavourable, members of the groups would drop out u n t i l only the older males remained. Results on movements and choice of h a b i t a t suggest how blue grouse might move i n t o newly-opened areas i n the c o a s t a l f o r e s t s . Many features r e l a t e d to the d i s p e r s i o n of the p o p u l a t i o n seem to be adaptations a l l o w i n g grouse to use r a p i d l y - c h a n g i n g h a b i t a t s . Among these are the d i s p e r s a l of j u v e n i l e s , the choice of sparse v e g e t a t i o n by y e a r l i n g males, the tendency f o r hens to stay near t e r r i t o r i e s p r i o r to n e s t i n g , and the l a c k of any i n t e r a c t i o n w i t h i n the summer p o p u l a t i o n that might cut down p r o d u c t i v i t y . 73 LITERATURE CITED A l d r i c h , J . W., 1963. Geographic o r i e n t a t i o n of American Tetraonidae. J . W i l d l . Mgmt. 27(4): 528-545. Ammann, G. A., 1957. The p r a i r i e grouse of Michigan. Tech. B u l l . , Mich. Dept. of Cons., 1-200. Bauer, R. D., 1962, Ecology of blue grouse on summer range i n North C e n t r a l Washington. Unpub. M.Sc. t h e s i s , Wash. State Univ., 81 pp. , B e n d e l l , J . F., 1954. A study of the l i f e h i s t o r y and p o p u l a t i o n dynamics of the sooty grouse, Dendragapus obscurus f u l i g i n o s u s (Ridgway). Unpub. Ph.D. t h e s i s , Univ. of. B r i t . C o l . , 155 pp. 1955. Age, breeding behaviour and m i g r a t i o n of sooty grouse, Dendragapus obscurus f u l i g i n o s u s (Ridgway). Trans. N. Am. W i l d l . Conf. 20:367-381. B l a c k f o r d , J . L., 1958. T e r r i t o r i a l i t y and breeding behaviour of a p o p u l a t i o n of blue grouse i n Montana. Condor 60(3): 145-158. 1963. Further observations on the breeding behaviour of a blue grouse p o p u l a t i o n i n Montana. Condor 65(6): 485-513, Boag, D„ A., 1964. A p o p u l a t i o n study of the blue grouse i n southwestern A l b e r t a . Unpub. Ph.D. t h e s i s , Wash. State Univ., 129 pp. Brooks, A., 1926. The d i s p l a y of Richardson's grouse w i t h some notes on the species and subspecies of the Genus Dendragapus. Auk 43: 281-287. Buss, I . 0., and B. A. S c h o t t e l i u s , 1954. Breeding age of blue grouse. J . W i l d l . Mgmt. 18(1): 137-138. Caswell, E. B., 1954. A p r e l i m i n a r y study on the l i f e h i s t o r y and ecology of the blue grouse i n west c e n t r a l Idaho. Unpub. M.Sc. t h e s i s , Univ. of Idaho, 105 pp. Choate, T. S., 1963. H a b i t a t and p o p u l a t i o n dynamics of ( w h i t e - t a i l e d ptarmigan i n Montana. J . W i l d l . Mgmt. 27(4): 684-699. C l a r k e , P. J . and F. C. Evans, 1954. Distance to nearest neighbour as a measure of s p a t i a l r e l a t i o n s h i p s i n p o p u l a t i o n s . Ecology 35 (4): 445-452. Dice, L. R., 1952. Measure of the spacing between i n d i v i d u a l s w i t h i n a p o p u l a t i o n . C o n t r i b . Lab..Vert. B i o l . , Univ. of Mich. 55: 1-23. Dorney, R, S., 1959. R e l a t i o n s h i p of r u f f e d grouse to f o r e s t cover types i n Wisconsin. Wise. Cons. Dept., Tech. B u l l . 18. 79 Edson, J . M., 1925. The hooters of S k y l i n e Ridge. Condor 27: 226-229. Eng, R. L., 1959. A study of the ecology of male r u f f e d grouse (Bonasa umbellus L.) on the Cloquet Forest Research Center, Minnesota. Unpub. Ph.D. t h e s i s , Univ. of Minn., 110 pp. Fowle, C. D., 1960. A study of the blue grouse (Dendragapus obscurus (Say) on Vancouver I s l a n d , B r i t i s h Columbia. Can. J . Z o o l . 38; 701-713. Hamerstrom, F., and F. Hamerstrom, i960. Comparability of some s o c i a l d i s p l a y s of grouse. Proc. X I I I n t e r n . O r n i t h . Congr., 274-293. Hart, C. M., S. L. O r v i l l e and J . B. Low, 1950. The s h a r p - t a i l e d grouse i n Utah. Utah State Dept. F i s h and Game, P u b l . No. 3, 79 pp. Heebner, G. C.3 1956. A study of the l i f e h i s t o r y and ecology of the i blue grouse i n west c e n t r a l Idaho. Unpub. M.Sc. t h e s i s , Univ. Idaho, 51 pp. , n Hoffman, R, S., 1956. Observations on a sooty grouse p o p u l a t i o n at Sage 4 Hen Creek, C a l i f o r n i a . Condor 58(5): 321-337. Hohn, E. 0., 1953. D i s p l a y and mating behaviour...of the b l a c k grouse (Lyrurus t e t r i x L . ) . B r i t . J . Anim. Behav. 1(2): 48-58. Hopkins, B., 1954. A new method f o r determining the type of d i s t r i b u t i o n of p l a n t i n d i v i d u a l s . Ann. Botan. (n.s.) 18(70): 213-227. J e n k i n s , D., 1961. S o c i a l behaviour i n the p a r t r i d g e P e r d i x p e r d i x . I b i s 103a: 155-188. Je n k i n s , D., A. Watson and G. R. M i l l e r , 1963. P o p u l a t i o n s t u d i e s on red grouse, Lagopus s c o t i c u s (Lath.) i n North-East S c o t l a n d . J . Anim. Ecology 32: 317-376. Kluyver, H. N., and L. Tinbergen, 1953. T e r r i t o r y and the r e g u l a t i o n of den s i t y i n t i t m i c e . Arch. N e e r l . Z o o l . 10(3): 265-289. Koskimies, J . , 1957. F l o c k i n g behaviour i n c a p e r c a i l l i e Tetrao u r o g a l l u s (L.) and blackgame Lyrurus t e t r i x ( L . ) . Papers Game Res. 18: 1-32, F i n n i s h Game Found. 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. Botan. Ser. No. 1, Univ. B r i t . C o l . 1964. R e v i s i o n of b i o g e o c l i m a t i c regions and zones i n B r i t i s h Columbia. Dept. B i o l , and Bot., Univ. B r i t . C o l . Lack, D., 1939. The d i s p l a y of the b l a c k cock. B r i t . B i r d s 32: 290-303. 1954. The n a t u r a l r e g u l a t i o n of animal numbers. Clarendon Press, Oxford, 343 pp. 80 Lumsden, H. G., 1961. The d i s p l a y of the c a p e r c a i l l i e . B r i t , B i r d s 54: 257-272. M a r s h a l l , W, H,, 1946. Cover preferences, seasonal movements, and food h a b i t s of the Richardsons grouse and r u f f e d grouse i n Southern Idaho. W i l s . B u l l . 54: 42-52. Mussehl, T. W., 1960. Blue grouse p r o d u c t i o n , movements, and populations i n the Bridger Mountains, Montana. J . W i l d l . Mgmt. 24(1): 60-68. 1963. Blue grouse brood cover s e l e c t i o n and land-use i m p l i -c a t i o n s . J . W i l d l . Mgmt. 27(4): 547-555. Nice, M. M., 1941. The r o l e of t e r r i t o r y i n b i r d l i f e . Am. Midland N a t u r a l i s t 26: 441-487. Palmer, W. L., 1961. A study of r u f f e d grouse drumming s i t e s i n Northern Michigan. Mich. Dept. Cons. Game Div. Rept. 2337. P i t e l k a , F. A., 1959. Numbers, breeding schedule, and t e r r i t o r i a l i t y i n p e c t o r a l sandpipers of Northern A l a s k a . Condor 61(4): 233-264. Rowe, J . S., 1959. Forest regions of Canada. B u l l . 123, For. B r . , Dept. N. A f f a i r s Nat. Res., Ottawa, S c h o t t e l i u s , B. A., 1951. Studies on blue grouse, Dendragapus obscurus  p a l l i d u s Swarth, i n the Methow V a l l e y of Washington. Unpub. M.Sc. t h e s i s , Wash, State Univ., 41 pp. S c o t t , J . W,, 1950. A study of the phylogenetic or comparative behaviour of three species of grouse. Annal. N.Y. Acad. S c i . 51 ( A r t . 6): 1062-1073. Simard, B. R., 1965. The t e s t i c u l a r c y c l e of blue grouse and i t s r e l a t i o n to age, breeding behaviour, and m i g r a t i o n . Unpub. M.Sc. t h e s i s , Univ. B r i t . C o l . , 113 pp. Skellam, J . G., 1952. Studies i n s t a t i s t i c a l ecology. I . S p a t i a l p a t t e r n . Biometrika 39: 346-362. S t e i n h o f f , H, W., 1958. A r a t i n g s c a l e f o r blue grouse i n Colorado. Proc. Soc. Am. For., 1958: 133-138. Stewart, R.: E., and J . W. A l d r i c h , 1951. Removal and re p o p u l a t i o n of breeding b i r d s i n a s p r u c e - f i r f o r e s t community. Auk 68(4): 471-482. Svardson, G., 1949. Competition and h a b i t a t s e l e c t i o n i n b i r d s . Oikos 1: 157-174. Tinbergen, N., 1956. On the fu n c t i o n s of t e r r i t o r y i n g u l l s . I b i s 98: 403 81 Tompa, F. S., 1962. T e r r i t o r i a l behaviour: the main c o n t r o l l i n g f a c t o r of a l o c a l song sparrow p o p u l a t i o n . Auk 79(4): 687-697. 1964. Factors determining the numbers of song sparrows, Melospiza melodia (Wilson), on Mandarte I s l a n d , B.C., Canada. Acta Z o o l . Fenn. 109: 1-73. Wing, L., J . Beer and W. Tidyman, 1944. Brood h a b i t s and growth of 'blue • grouse'. Auk 61: 426-440. Wynne-Edwards, V. C., 1962. Animal d i s p e r s i o n i n r e l a t i o n to s o c i a l behaviour. O l i v e r and Boyd L t d . , Edinburgh, 653 pp. 82 APPENDICES Page Appendix 1. Percent coverage shown by various elements along l i n e - i n t e r c e p t s , 1962. 83 2. The occurrence of c e r t a i n p l a n t groups and species on quadrats l o c a t e d w i t h i n the study p l o t s 8 6 3. T o t a l number of hours spent by a l l observers on study p l o t s , 1959=1962. 87 4. Dates on which removal p l o t s were v i s i t e d , up to end of June, 1959-1962. 88 5. Comparison of v e g e t a t i o n and topography at known t e r r i t o r i e s and randomly-chosen p o i n t s , 89 6. Approximate analyses of some v e g e t a t i v e and topographic components at p o s i t i o n s of hooting and s i l e n t males, 90 7. E s t i m a t i o n of new males on nine c o n t r o l p l o t s i n Very Open, Open, and Dense h a b i t a t . 91 8. C a l c u l a t i o n of death r a t e f o r banded a d u l t males. 92 83 Appendix 1. Percent coverage shown by various elements along line-intercepts, 1962. Key given below: Line No. F C H P W A V S 6 L Open 1 28.4 1.8 4.9 7.6 24.0 6.3 plot 2 21.2 9.2 15.4 47.7 10.7 3 23.0 10,5 27.6 21.4 16.0 4 8.0 1.7 20.7 13.8 48.9 8.4 5 31.6 17.2 16.7 41.0 13.7 6 37,9 13.5 17.9 30.7 9.7 8 30.1 8.2 1.9 0.9 20.2 15.3 9 18.9 11.1 14.5 21.2 35.9 4.4 12 12.9 2.5 0.7 28.4 1.0 17.8 4.9 14.2 13 38.3 1.8 10.7 18.1 45.3 0.7 15 42.4 6.3 27.0 0.6 2.8 3.8 9.1 x-1 18.4 8.6 0.8 18*6 24.9 16.2 24.1 x-2 30.4 9.6 7.9 37.4 11.9 Very 1 0.3 6.0 28.1 36.4 14.1 open 2 0.8 9.8 21.2 7.2 24.8 plot 3 18.5 _ 14.9 11.1 4 16.6 2.9 18.7 5 4.9 2.7 0.5 13.8 18.1 12.7 6 26.0 38.4 7.8 7 2.8 10.2 9.6 18.8 2.8 8 0.7 0.5 2.1 16.1 0.8 0.9 18.6 9 0.8 17.5 0.8 20.9 14.8 12 1.3 13,2 0.7 31.7 10.2 29.4 13 4.0 1.1 7.2 10.1 23.2 8.6 14 9.0 16.8 16.3 15 0.8 15.0 2.2 20.3 4.7 Very 1 92.4 - • 16.6 4.2 37.2 11.3 dense 2 58.3 - - 25.2 3.0 35.2 17.3 plot 3 79.3 - 7.4 38.4 14.2 4 72.4 - - 29.7 7.1 21.9 1.3 11.4 5 69.6 - - 9.1 24.7 6.7 14.7 13.2 6 75.4 - - 26.1 4.5 4.2 4.3 22.5 7 80.9 - - X 34.5 X 18.2 7.2 38.6 8 69.2 - - - X 37.4 X 27.1 12.6 9 94.1 •- - 5.9 2.1 51.3 14.7 4.6 11 51.6 - 18.0 1.9 68.2 3.3 8.3 12 84.6 - - 8.0 34.6 9.6 8.0 Dense 1 3.4 39.8 23.1 12.4 12.0 3.7 44.4 1.2 19.4 2 83.4 - - 12.8 6.3 41.7 29.4 14.3 5 8.3 10.5 8.4 1,4 23.7 4.3 27.7 1.7 45.9 6 3.0 2,6 5.6 41.9 2.4 15.3 19.3 7 40.8 - 13.5 1.6 32.0 3.8 17.0 9 14.5 24.0 9.3 21.4 1.1 25.5 22.5 13.5 10 2.4 40.3 5.4 6.6 4.3 31.5 10.7 24.6 84 Line No. F C H P W A V S B L 11 22.6 - - 25.6 1.8 0.4 19.0 78.8 14.1 12 15.2 19.6 2.5 15.0 14.8 26.3 30.7 13 53.1 - - - 31.1 0.7 2,6 11.5 15.9 14 51.8 - - 36.4 1.1 5.8 30.1 15 6.7 23.1 5.2 42.1 2.1 4.0 5.4 40,7 11 1.6 40.5 1.0 21.9 3.4 25.0 33.2 Key: F - Douglas f i r C - cedar H - hemlock P - pine W - willow A alder V - Vaccinium S salal B - bracken ; L - logs and stumps included under Douglas f i r in this case X included under alder in this case Note: Any line or quadrat that f e l l within an area showing atypical vegetation (peat bog, alder grove, etc.) was omitted from these tables. 85 Appendix 1, cont. Positions of hundred-foot lines used for analysis of vegetation on study plots, 1962. 11 _12 1 2 3 4 5 _2_ _3_ 4 5 _9_ 8 7 _6_ _6_ _7_ _8_ _9_ 11 13 _14 _15 Very dense plot Very open plot Dense plot Open plot 15 14 13 12 11 10 9 8 6 x i _x2 6 1_ _9_ 10. 1 1 1 1 I A _2_ _1_ 11 12. i i _15 1 86 Appendix 2. The occurrence of c e r t a i n p l a n t groups and species on quadrats l o c a t e d w i t h i n the study p l o t s . Very Very Open open dense Dense p l o t p l o t p l o t p l o t T o t a l number of quadrats 63 71 60 68 Percentage occurrence of: A l l coniferous species 71% 32% 97% 78% A l l deciduous species 71 72 78 85 Douglas f i r 67 28 22 12 Red cedar 3 7 53 60 Western hemlock 0 1 88 32 Pinus species 0 0 0 4 S a l i x species 67 68 57 76.5 Red a l d e r 0 0 8 0 Vaccinium species 8 13 35 46 Bracken 73 58 17 32 S a l a l 57 46.5 65 59 Mahonia species 17 28 18 32 Anaphalis margaritacea 44 56 50 46 Rub us v i t i f o l i t i s 70 89 85 81 Hypochaeris r a d i c a t a 63* 63 53 32 Hieracium species 29* 32 30 32 Achlys t r i p h y l l a 0* 0* - 21 * based on 41 quadrats r a t h e r than t o t a l given 87 Appendix 3. Total number of hours spent by a l l observers on study plots, 1959-1962. (Figures represent totals up to the end of June for each hour.) year and are rounded off to the nearest 1959 1960 1961 1962 Total Hours spent ons Open control plot 9 15 18 60 102 Very open removal plot 5 14 3 68 90 Very dense removal plot 2 14 3 12 31 Dense control plot 15 17 3 18 53 Plots (main controls) 18 23 29 11 Plots (removal) 17 19 44 14 Plots - not known specificallyl7 18 14 11 total control 42 55 50 89 236 Total experimental 24 47 50 94 215 Total for a l l plots 83 120 114 194 

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