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A study of the hole-nesting avifauna of south-western British Columbia Kelleher, Kevin Edmond 1963

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A STUDY OF THE HOLE-NESTING AVIFAUNA OF SOUTHWESTERN BRITISH COLUMBIA by Kevin Edmond Kelleher B.Sc, Gonzaga University, I960 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of . Zoology We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1963 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I f u r t h e r agree that per-mission, for extensive copying of t h i s t h e s i s for s c h o l a r l y purposes may be granted by the Head of my Department or by h i s representatives,, I t i s understood theft copying, or p u b l i - • c a t i o n of t h i s t h e s i s for f i n a n c i a l gain s h a l l not be allowed • r " without my w r i t t e n permission. 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. i i ABSTRACT This study relates the species composition, numbers, and habits of a hole-nesting avifauna to i t s environment i n successional stages of a coniferous forest i n south-western B r i t i s h Columbia. Emphasis i s placed upon explain-ing an observed presence or absence of nest-site competition. In two breeding seasons, the hole-nesting avifauna was found to be low i n numbers of both species and i n d i v i d u a l s . Most of these birds were able to excavate t h e i r own nesting c a v i t i e s , and commonly d i d so, f o r which a c t i v i t y the habi-tat generally provided ample opportunity. As the species present often dif f e r e d widely from one another i n the type and placement of t h e i r preferred nest c a v i t i e s , there was usually a surplus of di f f e r e n t cavity types present. Secondary hole-nesters either concentrated t h e i r a c t i -v i t i e s around the buildings in the nearby town, neglecting the more "natural" s i t e s available; were not obligated to use c a v i t i e s when nesting; or occurred i n such low densities, and were so positioned i n the available suitable habitat, as to suggest that nest-site competition had no effect upon the populations. Only scattered indications of nest-site compe-t i t i o n were observed i n wooded areas. Four species nested i n crevices i n buildings and in bir d boxes i n a small town, where t h e i r breeding population densities were much higher than i n the surrounding ' country-side. Nest-sites were judged to be present i n excess, and nest-site competition, observed infrequently, was so rare, and apparently without s i g n i f i c a n t harmful e f f e c t s , that i t i i i was judged to be of n e g l i g i b l e importance as a population-regulating factor. The ov e r a l l absence of nest-site competition i s c o n t r i -buted to not only by the preferences of the species regard-ing t h e i r n e s t - s i t e s , but also by the fact that the r e s u l t s of t h e i r habitat selection processes, and t h e i r l i v i n g habits within these habitats, tend to keep them ec o l o g i c a l l y d i s -t i n c t . i x ACKNOWLEDGEMENTS Sincere thanks are extended for the help and guidance of a l l the persons and organizations who contributed to t h i s study: - especially to Dr. M.D.F. Udvardy, who supervised the project. - to Drs. I . McT. Cowan, CV. Finnegan, C.C. Lindsey, and W.B. Schofield, who served as members of the committee responsible f o r the writer's t r a i n i n g . - to Otto Horvath, resident b i o l o g i s t at the Thacker Ecological Reservation, for the assistance given by both his' knowledge of the study area, and his frequent cooper-ation in the f i e l d work. - to fellow students Douglas Dow, Fred Gornall, Dave Johnston, and es p e c i a l l y B i l l McLaren, a l l of whom contributed information or ideas. - to Mr. Robert Houlden for the camping f a c i l i t i e s used during the f i r s t season's work. Fi n a n c i a l support f o r t h i s study was provided by..-the National Research Council of Canada, through a grant to Dr. Udvardy, and by a bursary donated by the Kiwanis Club of Vancouver, B.C. i v TABLE OF CONTENTS Page INTRODUCTION . 1 The Purpose of the Study 1 The Area of the Study 1 The Time of the Study 2 METHODS 3 THE AVIFAUNA AND THE HABITAT 5 The Subjects of the Investigation . . 5 Description of the Study Areas 8 REVIEW OF THE AVIFAUNA 22 Wood Duck 22 Hooded Merganser 23 Sparrow Hawk 23 Hole-Nesting Owls . . . . . . 26 Red-Shafted F l i c k e r 29 P i l e a t e d Woodpecker 34 Lewis Woodpecker 35 Red-Breasted Sapsucker . . . . . 36 Hairy Woodpecker 42 Downy Woodpecker 47 Black-Capped Chickadee 49 Chestnut-Back Chickadee . . . . 56 Black-Capped and Chestnut-Backed Chickadees . . . . 57 Red-Breasted Nuthatch 6 l Brown Creeper . . . . . . . . 65 Winter Wren 65 Bewick Wren - 69 Western Bluebird 69 Mountain Bluebird • 69 Non-Avian Hole-Users . . . . . . . 70 The Elimination Experiment . . . 72 The Environmental Resources 77 The Town Study Area 79 Violet-Green Swallow 79 Tree Swallow 100 English Sparrow 104 S t a r l i n g " 109 House Finch 114 DISCUSSION 119 The Process of Nest-Site Competition. . . . . . . . 119 Synthesis of Data 132 V Page SUMMARY 146 LITERATURE CITED 150 APPENDIX 165 0 v i FIGURES Figure to f o l l o w page 1 The Province of B r i t i s h Columbia, showing the l o c a t i o n of Hope 1 2 The Region of Hope, showing the l o c a t i o n of the main study areas 9 3 The Main Study Area 9 4 Study Area "F" 13 5 Chickadee T e r r i t o r i e s 50 6 Chickadee Nests 60 v i i TABLES Table Page 1 Hole-Nesting Birds of the Study Area 6 2 Sparrow Hawk Nests 27 3 Red-Shafted F l i c k e r . Nests 30 4 Red-Breasted Sapsuc'ker Nests 41 5 Downy and Hairy Woodpecker Nests 45 6 Black-Capped Chickadee Nests 53 7 Chestnut-Backed Chickadee Nests . 5$ 8* Red-Breasted Nuthatch Nests 63 9 Habitat Preferences and Population Densities of the Common Hole-Nesting Birds 134 v i i i PLATES Plate Page I ( l ) The southern slope of the Reservation . . . . 158 I I (2) The southeast slope of the Reservation . . . 15$ I I I (3) The upper southeast slope of the Reservation. 159 IV (4) The northern portions of area "F" . . . . . . 159 V (5) The southern h a l f of area "F" . . . . . . . ... 160 VI (6) The town of Hope 160 VII (7) Bridge at old Mining Camp l 6 l VIII (£) The Laidlaw Study Area. . . . . . . . . .... l 6 l IX (9) The snag 2-1-2 162 X(10) The rock b l u f f by Schkam Lake . . V . . . '. . 162 X I ( l l ) Bird Boxes by the marsh ' 163 XII(12') Nesting c a v i t i e s i n a building 163 XIII ( 1 3 ) Nesting c a v i t i e s i n a b u i l d i n g I64 XIV(14) The House Finch Nest 164 INTRODUCTION The Purpose of the Study Species of birds that nest i n tree-holes are dependent upon a l i m i t e d environmental resource. I f the number of holes i s small i n r e l a t i o n to the number of birds that re-quire the use of them, competition may occur. The birds involved i n t h i s competitive s i t u a t i o n suffer as a r e s u l t of t h e i r p a r t i c i p a t i o n . This study r e l a t e s the numbers and species composition of a hole-nesting avifauna to the environment in which i t occurs. Emphasis i s placed upon explaining an observed presence or. absence of nest-site competition. The Area of the Study A large part of the work was done on the University of B r i t i s h Columbia's Thacker Ecological Reservation near the town of Hope, B r i t i s h Columbia. I t i s located at 1 2 1 ° 25 f W. longitude and 49° 23 ' N. l a t i t u d e , and has a base alt i t u d e of 160 feet (49m.) . Additional study areas were near and i n the town i t s e l f , while survey t r i p s were made reg u l a r l y into the surrounding country. Hope i s situated at the head of the Fraser Valley, and i s approximately 90 miles upstream from the Fraser River's mouth i n the extreme southwest corner of B r i t i s h Columbia. (Fig. 1) to follow page 1. Figure 1.. The- province of B r i t i s h Columbia showing the location of Hope. , The Time of the Study Two summers were spent i n the f i e l d ; from May 1 to August 31 , 1961; and from A p r i l 28 to September 9 , 1962. A d d i t i o n a l l y i n 1962, day-long v i s i t s to the study area were made on March 1$, March 3 1 , and A p r i l 9 . - 3 -METHODS Observation of hole-nesting birds in t h e i r natural environments composed the greater part of t h i s study. The nature of both the habitat and the hole-nesting b i r d popu-l a t i o n reqaired that observations be conducted on a survey-type basis, the intention being to v i s i t many nests as often as possible. Color-banding was employed where e a s i l y prac-t i s e d , 7# hole-nesters being so marked i n order to give the observations greater accuracy. A study . of nest-site competition among hole-nesting birds, conducted through the analysis of measurements of the nest c a v i t i e s , was done by McLaren (1963) i n another region of B r i t i s h Columbia. I n i t i a l l y i t was hoped that i n the present study enough holes might be measured to allow comparisons to be drawn. However, almost a l l of the holes were i n dead snags that were often of considerable height and very few of which could be climbed with safety and f a c i l -i t y . Also, since few of the holes were occupied, even i f the majority of them were measured, there would not be a large enough sample to permit accurate comparisons. F i n a l l y , the value of such comparisons i s questionable, as nearly a l l the birds found u t i l i z i n g holes were capable of digging t h e i r ojwn, and in many cases apparently did so. Notes were made concerning each occupied snag and such data are often tabu-lated i n order to delimit the requirements of in d i v i d u a l species. Inspection of every snag on over one-half of the Reservation established the comparative abundance of hole-bearing snags, of which a substantial proportion were found - 4 -to possess c a v i t i e s . Two small experimental aspects were added i n the second season. Ten b i r d boxes were erected along the marsh on May 23, 1962, i n order to test a facet of the s i t e - s e l e c t i o n process i n Tree and Violet-Green Swallows. A new area, separate from but similar to the Reservation, was surveyed f o r hole-nesting birds during the f i r s t h a l f of May, 1962. As many as possible (10) were shot during the next two weeks, and observations were continued through the remainder of the summer to detect any changes i n position or composition of the remaining hole-nesting avifauna. The surroundings of the main study areas were surveyed during June, July, and August, 196 2. Weekly t r i p s were made up the Hope-Princeton Highway as f a r as Pinewoods, 41 miles from Hope, and down the Fraser Valley (approximately 27 miles) toward Chilliwack, stopping at selected areas, where the kinds and numbers of a l l birds seen were recorded. These observations were considered to be supplementary to the main parts of the study, and t h e i r purpose was to provide a broader background for generalizations. In addition, the many nests.located contribute to the value of the data to be presented on the habitat preferences of the i n d i v i d u a l species. - 5 -THE AVIFAUNA AND THE HABITAT The Subjects of the Investigation Table 1 presents the species involved i n t h i s study. Under Observed Resident Breeders are l i s t e d a l l those hole-nesting birds which were observed on the studied areas. Not Observed Resident Breeders includes those species which regional l i s t s indicate as breeding i n t h i s area, but which were not personally observed. Some were seen by Horvath (1963, and personal communication) - the separate treatment given to each of these species d e t a i l s such occurrences. The d i g i t after each species indicates i t s status as a p r i -mary ( l ) or a secondary (2) hole-nester. This c l a s s i f i c a -t i o n i s based upon the a b i l i t y of the b i r d to excavate i t s own nesting cavity - a primary hole-nester can do so; a secondary cannot (McLaren, 1963) . Some primary hole-nesters do not always excavate the c a v i t i e s that they use, and any such instances known are detailed i n the text. The Npn-Resident category, included f or completeness, l i s t s non-breeding hole-nesting species which may occur i n the study area. Asterisks indicate those species observed during t h i s study. TABLE 1. HOLE-NESTING BIRDS OF THE STUDY AREA RESIDENT BREEDERS OBSERVED NOT OBSERVED Wood Duck 2 American (Common) Merganser 2 Hooded Merganser 2 Pigeon Hawk 2 Sparrow Hawk 2 Screech Owl 2 2 Red-Shafted F l i c k e r 1 . Great Horned Owl 2 P i l e a t e d Woodpecker 1 Pygmy Owl 2 Red-Breasted Sapsucker 1 Spotted Owl 2 Hairy Woodpecker 1 Saw-Whet Owl 2 Downy Woodpecker 1 Lewis Woodpecker 1 Violet-Green Swallow 2 Hou se Wren 2 Tree Swallow 2 Western Bluebird 2 Rough-Winged Swallow 2 Black-Capped Chickadee 1 Chestnut-Backed Chickadee 1 Red-Breasted Nuthatch 1 Brown Creeper 2 Winter Wren 2 Bewick Wren 2 Mountain Bluebird 2 S t a r l i n g 2 House (English) Sparrow 2 House Finch 2 -1» S c i e n t i f i c names of a l l species (plant and animal) mentioned in the text are given i n Appendix B. 2. The presence of the Great Horned Owl (Horvath, 1963) , while possible, i s believed to be based on i n s u f f i c i e n t evidence. TABLE 1. Cont inued NON-RESIDENT MIGRANT ONLY IRREGULAR VISITANT * Common Goldeneye Barrow's Goldeneye * Bufflehead Hawk Owl Boreal Owl Yellow-Breasted Sapsucker A r c t i c Three-Toed Woodpecker Northern Three-Toed Woodpecker Purple Martin Mountain Chickadee White-Breasted Nuthatch -8-Description of the Study Areas Munro and Cowan (1947) i d e n t i f y 13 b i o t i c areas i n t e r r e s t r i a l B r i t i s h Columbia, basing a d i v i s i o n on the pre-sence of d i s t i n c t i v e animal and plant species, and the absence of plant and animal species found i n other b i o t i c areas. Their Puget Sound Lowlands B i o t i c Area consists of the Fraser River Delta and the basal portions of the adjoining h i l l s , -the v i c i n i t y of Hope, at the apex of the delta, marks i t s eastern boundary. As Hope i s clo s e l y surrounded by mountains that r i s e steeply from the v a l l e y f l o o r , t h i s b i o t i c area i s here very l i m i t e d i n extent, and grades into the Coast Forest B i o t i c Area occupying the higher slopes. This t r a n s i t i o n i s indicated by the dominance of coniferous vegetation, into which the deciduous growth common i n the v a l l e y gradually inter grades at elevations above 500 feet. The deciduous forests prevalent i n the Puget Sound Lowlands B i o t i c Area consist of red alder, broad-leaf maple, flowering dogwood, cascara, black cottonwood, western b i r c h , and vine maple i n association. Much of t h i s deciduous forest i s of recent o r i g i n , replacing p r i m i t i v e coniferous stands, scattered remnants of which s t i l l remain. The r a i n forest of the Coast Forest B i o t i c Area t y p i c a l l y has successional stages of Douglas f i r , broad-leaf maple, and red alder, which are preliminary to climax forests of Sitka spruce, western and mountain hemlock, western red cedar, and grand f i r . Undergrowth and l i t t e r may be extensive. - 9 -The Thacker Ecological Reservation, and i t s Surroundings The Thacker Ecological Reservation i s located on L i t t l e Mountain, which i s northeast of the town of Hope (Fig. 2 ) . The Reservation i s approximately 180 acres in extent. The area studied, which included.most of the Reservation, t o t a l -led 400 acres. The highest part of the Reservation i s approximately 700 feet (216 m.) above sea l e v e l - the lowest portion, at the mountain's base, i s at 160 feet (49 m.) ele-vation (Horvath, 1963) . The Reservation i s roughly t r a n s i -t i o n a l between the two b i o t i c areas mentioned above, and many of the common bird species of the Puget Sound Lowlands B i o t i c Area breed on i t . Horvath (1963) presents the f i r s t detailed vegetational analysis of the Thacker Ecological Reservation, from which , much of the following information i s adapted, and to which reference should be made i f a thorough description i s desired. The main study area, consisting of most of the Reserva-t i o n and some adjacent areas, f o r purposes of vegetational description may be considered to be composed of seven sub-d i v i s i o n s : west, south, southeast, and northeast slopes; open and heavily wooded upper portions; and a wooded f l a t lower area (S and T) (Fig. 3 ) . A l l nest-site tables relate the nests described to the areas i n which they were located. West slope - Logging and burning (the l a s t f i r e i n July of 1 9 6 l , and a previous severe burn i n 1951) has reduced the vegetation to an early successional stage, and a large part of t h i s slope i s covered by shrubby thickets dominated by vine maple and hazel. Small sections of the canopy, to follow page 9. SCHKAM L A K E £?Stu<ly Area to Fraser Valley f= Reservation!* Kakawa Lake Figure 2. The region, of'Hope^ showing the location of the main study areas. to follow page 9. Figure 3 . The main study area. Wooded areas on only. the upper portions, of L i t t l e Mountain have-been shaded for c l a r i t y . -10-predominantly Douglas f i r , escaped destruction, but most of the area has no overstory. Many t a l l snags dotted t h i s slope before the 1961 f i r e , though most of them were cut down during the f i r e as a fire-preventive measure. South slope (Plate 1) - This i s steep, dry, and ex-tremely rocky. I t was heavily burned in 1951 and 1959. A t a l l , very discontinuous canopy i s present over most of the slope, and i s composed of commercially worthless Douglas f i r s , with a few broad-leaf maples and birches. A shrub layer i s s t i l l developing, and i s composed mainly of hazel and vine maple, with p l e n t i f u l mock orange, and scattered young birch and broad-leaf maple. Most of the t a l l snags i n the western portions were cut down at one time, but many remain elsewhere. Smaller snags of f i r , maple, and birch are scattered through-out the area. Southeast slope (Plates 2 and 3) - The vegetation on the upper slope d i f f e r s from that on the lower, where s o i l accumulation and seepage allows a r i c h e r growth. A t a l l canopy of Douglas f i r i s almost continuous over the upper portions, being interrupted above extremely rocky areas. A very sparse under story i s contributed to by broad-leaf maple and dogwood. A shrub layer, usually dense, i s composed mainly of hazel, vine maple, mock orange, saskatoon berry, ocean spray, and young broad-leaf maple. The steepness of the rocky slope has r e s t r i c t e d logging operations to p e r i -pheral portions. The lower slope, which i s less steep, supports a high, dense, mostly undisturbed canopy of ragged outline, to which i -11-several species contribute, notably Douglas f i r , western hemlock, red cedar, broad-leaf maple, and to a lesser extent, birc h . Vine maple and young hemlock are p l e n t i f u l understory species, with dogwood s l i g h t l y less common, and young birch and cedar scattered throughout. Moss i s common in areas of densest shade, and f a l l e n branches and trunks make up an omnipresent l i t t e r . Northeast slopes - The southern parts of t h i s area have only small patches of canopy, made up mainly of commer-c i a l l y worthless f i r s , due to logging and a subsequent f i r e i n 1951. Most of the northern portions were logged, but escaped burning, so that a denser coniferous canopy prevails© A stream bed runs along the bases of these slopes, and toward these moister areas a higher proportion of deciduous trees occur, u n t i l alder and cottonwood dominate on the wettest portions, which are very l i m i t e d in extent. The canopy, where i t occurs, i s almost e n t i r e l y Douglas f i r , some of the trees bearing i n j u r i e s from the logging operations, which often leave many broken-topped small t h i n snags. L i t t e r i s extensive. On moister areas, large broad-l e a f maples, birches, and clumps of vine maple are mixed with the f i r s . A deciduous second-growth i s growing i n on the open areas, and i s composed of young broad-leaf maple, birch, vine maple, Douglas f i r , hazel, dogwood, and willow i n approximately that order of importance. This growth may be dense or sparse depending upon l o c a l conditions. Upper Portions - The upper portions of L i t t l e Mountain, though never f l a t , can be considered r e l a t i v e l y l e v e l . They -12-may be thought of as being, bisected by an i r r e g u l a r belt of canopied area running from east to west, though t h i s i s ; p r a c t i c a l l y non-existent i n the middle. The majority of t h i s canopy has not been burned i n at least the l a s t 30 years, while the open portions were burned over i n 1951, after the logging operations of that year which affected most of the top of L i t t l e Mountain. The open portions carry only a scattering of t a l l t h i n f i r s , which were l e f t i n small groves i n places, and a few broad-leaf maple, but these are r a r e l y dense enough to affect the undergrowth. Numerous broken-topped t h i n f i r snags dot the entire area, but many of those i n the southern portions were cut down during the 1961 f i r e . Second-growth succession-a l stages compose an undergrowth varying i n vigor on d i f f e r e n t s i t e s : usually a mixture of bir c h , scrub willow, broad-leaf maple, hazel, dogwood, and Douglas f i r , in.approximately that order of importance. Young Douglas f i r are common i n the more open areas. This general vegetation type i s modified by fac-tors of s o i l and moisture, varying from extremes of a dry grass-lichen growth with a few f i r s , to dense 30 foot sapling groves on wetter spots. Canopied.areas on the mountain's upper portions, through-out which f i r i s nearly always dominant, also r e f l e c t x e r i c to hydric conditions. Ridges i n the western part carry a high ragged f i r canopy, with some young f i r s and lodgepole pine beneath. Moving eastward, a mixed coniferous-deciduous growth i s entered, but t h i s i s interrupted in the middle of the " b e l t " . As the swamp i n the eastern portion i s approached, -13-the fir-dominated canopy gives way to a mature growth of cedar, broad-leaf maple, alder, and b i r c h . Areas S and T - These areas were included mainly because t h e i r h istory of f i r e (at least two) and logging, and r e l a -t i v e moisture, has allowed a varied habitat of predominantly deciduous growth that i s i d e a l f o r Black-Capped Chickadees. Vegetation types ranged from small open grassy areas, to a dense but l i m i t e d canopy of mature alder i n the center of "T", and a dense mixed canopy, i n "S" of Douglas f i r , broad-l e a f maple, and bi r c h . Young post-burning stands, predom-inantly of birch and willow, are extensive i n each area, and provide many potential chickadee nest-stubs. T a l l f i r s , remnants of a previous canopy, are very sparsely and i r r e -g ularly d i s t r i b u t e d over the area. Area "T" especially bears numerous old t a l l snags. Area F - I l l u s t r a t e d i n Plates 4 and 5, t h i s study area i s about one mile north of the town of Hope, and i s comparable to the southern portions of L i t t l e Mountain that have a simi l a r a l t i t u d e and exposure. The area (Fig. 4), which i s 80 acres i n extent, i s quartered by two old survey l i n e s that give the major compass points. The slope i s general to the southwest. L i t t l e Mountain i s approximately one mile distant. Most of the study area was heavily burned i n the spring of 1951 - the outlines, of t h i s 170 acre burn are given by the edges of the heavily canopied areas. This was the only f i r e since 1931, when the B.C. Forest Service's records started. The vegetation of the area i s d i v i s i b l e into four -14-main types, variants of which exist as permitted by s o i l s u i t a b i l i t y . A large part of the southern half of the area supports a low second growth, that has established i t s e l f after the f i r e on the well-drained rocky s o i l . Only a half dozen t a l l l i v i n g t r e e s , and numerous t a l l snags, remain from the pre-dominantly coniferous forest that once covered the area, and s t i l l e x i s ts off to the south and east. The second-growth trees are young, almost e n t i r e l y deciduous, range up to 20 feet (6 m.) i n height, and seldom exceed 2g inches (6.4 cm.) i n diameter. A dense growth i s usual and an open scrub exists on the ro c k i e r portions. Birch and willow i n approximately equal quantities make up the bulk of the vege-t a t i o n ; vine maple and hazel occur commonly but less abund-antly, and ind i v i d u a l s of red alder, broad-leaf maple, and young Douglas f i r are scattered throughout. Both the nature of the pre-burn canopy and the int e n s i t y of the burn are l i k e l y the reasons f o r the absence of smaller hardwood snags and stumps, which i n turn i s undoubtedly why the Black-Capped Chickadee was absent as a breeding species from most of the southern h a l f of the study area. In wetter, lower areas of the burn, as i n shallow g u l l i e s , t h i s young second growth vegetation i s more vigorous, forming a denser, t a l l e r stand. Birch predominates, and alder and vine maple are present i n increased proportions, while willow and hazel are less common. Vegetation height i s usually around 30 feet (9m.). In the northern part of the area, where burning was apparently less intense, several -15-sections of t h i s type bear quantities of smaller hardwood snags suitable f o r use by the smaller hole-nesters. Unburned areas i n the northern h a l f of the study area, where the s o i l i s moister and r i c h e r , support a high dense canopy of mixed coniferous and deciduous trees. They have a l l been modified to some extent by selective logging and occasional woodcutting, which has l e f t some irregu l a r open-ings i n the canopy. The canopy i s dominated by red cedar and broad-leaf maple; mixed throughout are i n d i v i d u a l t a l l grand f i r s , birches, and red alders. Douglas f i r , of which only scattered individuals exist i n the lower portions, i s more common up the slope of the east h i l l , gradually becoming the most abundant canopy species. An under story, varying i n height but always dense, i s composed mainly of young black Cottonwood, b i r c h , broad-leaf maple, and vine maple. A thick tangled almost universal undergrowth i s nearly impene-trable i n places. Many of the larger deciduous trees bear dead portions, and those situated along edges provide many pot e n t i a l nest s i t e s for the larger hole-ne sters. The Downy Woodpecker and Red-Breasted Sapsucker nested in such s i t u a -tions (F-4 and F - 2 ) . Most of the west h i l l supports a vegetation type d i f -ferent from the above, as the s o i l i s shallow, rocky, and dry. Spotty burning on the upper portions did not affect the small area covered by t h i n coniferous canopy of 30 to 60 foot (9 to 18 m.) Douglas f i r , and smaller lodgepole pine. Very l i t t l e underbrush i s present and ground cover i s l i m i t e d mainly to low evergreens, s a l a l , false box, and Oregon grape. -16-Down the southern slope i s a small area canopied by Douglas f i r , and down the eastern slope of the h i l l stand several very t a l l Douglas f i r s , some with dead upper portions, and three t a l l dead f i r snags. None of these were used by hole-nesters during t h i s season. A short f i r snag on the top of the h i l l had an unmistakable nuthatch nest from a previous ye ar. The Town of Hope Study Area The portions of the town surveyed each year are indicated on F i g . 2. Both areas "A" and "B", approximately 115 acres, were surveyed during 1961. In 1962, when observations were more intensive, only the 40 acre area "B" was covered. The best description of the area i s given by Plate 6 , which looks toward the northeast, over the center of the 1962 study area. The Hope-Princeton Highway Study Areas Some of the following b r i e f descriptions are superfluous i n terms of t h i s study's r e s u l t s . They are included because they i l l u s t r a t e the background from which conclusions were drawn and because they contribute to an understanding of the area. This highway runs eastward into the mountains. Survey t r i p s were taken every 7 to 10 days, during June, July, and August, 1962. The f i r s t 4 areas described were usually v i s i t e d at length; the others i n t e r m i t t e n t l y as time allowed. 3 mile: - located 3 l miles from Hope at 775 foot (236 m.) a l t i t u d e . The highway runs along a northward-facing slope, which i s often very steep, the accessible portions of which , -17-have been logged . Numerous sma l l streams run down the s l o p e , and the moi s ture , ' shading , and d i s r u p t e d v e g e t a t i o n combine to crea te c o n d i t i o n s g e n e r a l l y s i m i l a r to the eastern wooded upper p o r t i o n s of the R e s e r v a t i o n . Here a Rough-Winged Swallow nest was l o c a t e d : i n a t i l e d d r a i n i n a cement bank-i n g suppor t ing the r o a d . 7 m i l e : . - l o c a t e d 7 m i l e s from Hope, at 1100 foo t (335 m.) e l e v a t i o n , where the highway r u n s between steep mountain s lopes through a s m a l l v a l l e y . The a r e a surveyed, a long an o l d l o g g i n g road p a r a l l e l i n g the highway, has r e l a t i v e l y r i c h mois t g round , and t h i s supports a h igh cedar-hemlock canopy tha t conta ins s c a t t e r e d t r e e s o f Douglas f i r and grand f i r . Smal l cottonwood and a lder stands occur i n wet-t e r s i t e s . Dead snags of a l l s i z e s are uncommon, except a long the banks of a sma l l r i v e r running down the v a l l e y . A dense undergrowth, almost i m p a s s i b l e i n p l a c e s , covers much o f the ground below the canopy. Two Winter Wren nes t s on low c o n i f e r branches were found h e r e . Old M i n i n g Camp: - l o c a t e d m i l e s from Hope at 1850 r f oo t (564 m.) e l e v a t i o n . Logging and f i r e have g r e a t l y d i s r u p t e d the h a b i t a t . Under a s m a l l highway b r i d g e , a p a i r each of Rough-Winged and V i o l e t - G r e e n Swallows nes ted i n t i l e d d r a i n h o l e s 30 f ee t (9 m.) apart ( P l a t e 7 ) . Three Rough-Winged p a i r s nested i n a nearby sandy bank. Nests o f Sparrow Hawks ( l ) and Red-Breasted Sapsuckers ( l ) were l o c a t e d a t t h i s s t o p . Qutram Lake : - l o c a t e d 1 0 | m i l e s from Hope, at 2200 foot (671 m.) e l e v a t i o n . A t a l l dense u n d i s t u r b e d canopy e x i s t s to the east, and i s almost exclusively western hemlock, with a l i t t l e cedar, and very few amabilis and Douglas f i r . To the west i s a heavy burn now covered with l i t t e r , f e l l e d snags, and second growth. Small Outram Lake i s nearby. One nest each of Red-Breasted Sapsuckers and Chestnut-Backed Chickadees was found at the forest edge and a Hairy Woodpecker roost (?) was l a t e r located in a similar s i t u a t i o n . Sand Pit.: - located at 2150 foot (655 m . ) elevation, 15 miles from Hope. A small burn by the highway contained many poten-t i a l nest-snags, i n which were found nests (1 each) of Sparrow Hawk, Chestnut-Backed Chickadee, and Red-Breasted Nuthatch. One Rough-Winged Swallow pair nested i n a bank. Other small areas v i s i t e d infrequently were: -24 miles from Hope, at 2650 foot (#08 m.) elevation. Here Violet-Green Swallows nested semi-colonially, both i n niches i n rock faces and in t i l e d drain holes i n a series of cement bankings supporting the highway. - 2 5 i miles from Hope, at 2475 foot (754 m.) elevation. One Red-Breast ed Sapsucker nest was located here. -28 miles from Hope, at 2950 foot (900 m. ) elevation. One Pileated Woodpecker roost (?) was found here. Pinewoods: - located 40 miles from Hope at 4000 foot (1219 m.) elevation. The lodgepole pine, and engelmann spruce-alpine f i r growth here d i f f e r s greatly from that on the main study areas. Nests of Tree Swallow ( 7 + ) , Rough-Winged Swallow ( l ) , Red-Breasted Nuthatch ( l ) , Red-Breasted Sapsucker ( l ) , Red-Shafted F l i c k e r ( 2 ) , and Flying S q u i r r e l ( l ) , were located i n natural c a v i t i e s and Violet-Green Swallow ( 4 + ) , Mountain -19-Bluebird ( l ) , and St a r l i n g ( l ) , in c a v i t i e s i n the buildings of the Pinewoods resort. The Upper Fraser Valley Study Areas The roughly triangular Fraser Valley runs southwest from Hope, which i s at i t s apex, and begins to widen appreciably where the Riverside Study Area was located. Laidlaw Study Area: - located 10 miles from Hope on the east-ern edge of the f l a t v a l l e y f l o o r , which i s predominantly pasture and c u l t i v a t e d land. The 16 acre area studied i s about one-half open scrubby pasture, which i s continuously grazed, and i s dotted with scattered shade trees and numerous broken-topped alder snags, many of them bearing holes (Plate 8 ) . The property's owner reported that occasional high winds caused the breakage and subsequent death of the alders. This i s excellent Flicker-Starling-Swallow habitat, but the t o t a l number of hole s did not appear to be f u l l y exploited. As the S t a r l i n g population increases, t h i s type of habitat, which i s very uncommon i n the region, may support nest-site competition. The uncleared half of the area sup-ports a dense 40 foot (12 m.) canopy of alder, cedar, and broad-leaf maple, with scattered large birches and cotton-woods. Nests were found of Starling ( 7 ) , Red-Shafted F l i c k e r ( 2 ) , Black-Capped Chickadee ( 2 ) , and Tree Swallow ( 5 ) . A l l but one chickadee nest were i n snags i n the open h a l f of the area. Two other places were v i s i t e d occasionally: - a rock bl u f f by the highway 16 miles from Hope, where -20-one pair each of Rough-Winged and Violet-Green Swallows nested i n holes d r i l l e d , i n the rock. - a small highway bridge 2 1 miles from Hope, where 8 pair of Rough-Winged Swallows nested i n 1 0 drain holes i n the cement foundations. The Riverside Study Area: - located 2 5 miles from Hope, by the bank of the Fraser River. A high 7 0 foot ( 2 1 m.) canopy i s exclusively cottonwood; there i s l i t t l e suggestion of an understory. Seasonal flooding occurs on any low portions and these are, usually bare of cottonwoods and underbrush, and may have low P a c i f i c willow trees around t h e i r edges. Nests were found of Black-Capped Chickadee ( l ) , Tree Swallow ( l ) , Downy Woodpecker ( l ) , and Flying S q u i r r e l ( 2 ) . The Chapman Road Study Area: - located 28 miles from Hope, i n the middle of the l e v e l v a l l e y . Impressions of the hole-nesting avifauna were gained by walking along two country roads; f o r approximately 4 4 0 0 feet ( 1 3 4 1 m.) along one bor-dering the stagnant Camp Slough, and for approximately 3 0 0 0 feet ( 9 1 4 -m.) along one running through farmlands. A l l suitable ground i s under c u l t i v a t i o n or pasture and trees of a l l sizes are found only along sloughs and ditches, around houses, occasionally along f i e l d borders and roadsides, and i n whatever small orchards happen to be. present. The borders of the slough carry s t r i p s of woodland, with maple, cedar, cottonwood, birch and alder growing over dense undergrowth. The farms in the area, being long-established, often have sizeable trees around the houses, and large broad-leaf maples l i n e the roads i n places. These t a l l bushy trees bear many -21-dead portions, thus providing potential nesting s i t e s . Nests were found of Tree Swallow ( l ) , S t a r l i n g (2), and Flying Squ i r r e l (1), and many farm buildings, which could not be inspected closely, appeared to house Violet-Green Swallows and English Sparrows. -22-REVIEW OF THE AVIFAUNA Each of the observed "Resident Breeders" (Table l ) i s treated separately. These descriptive sections, containing both o r i g i n a l and published material, include such informa-t i o n , mainly on habitat and nest-sites u t i l i z e d , and breeding habits, that; defines the species i n terms of nest-site compe-t i t i o n . Wood Duck The appearance of a brood on Kawkawa Lake i n I960 i n d i -cated the s u i t a b i l i t y of the habitat f o r t h i s species. In 1961, the regular, though infrequent, sighting of a pair throughout May, and of a female during June and July, indicates that a nesting was probably attempted. The birds were most often flushed from the sluggish stream running be-tween Kawkawa Lake and the marsh. E f f o r t s to locate the nest f a i l e d , i t being impossible to follow the birds very far by sight. (Wood Ducks i n I l l i n o i s may nest up to one-half a mile from water, Bellrose, 1955). No young were ever seen on the marsh cr the western end of the lake, so a nesting, i f attempted i n the area, was l i k e l y unsuccessful; or the birds may have nested at a distance (as across the lake), coming to the stream to feed. In 196 2, Wood Ducks (up to f i v e pair at once) were flushed from the marsh and stream almost d a i l y u n t i l the middle of May. The remainder of the summer yielded only three more sightings of lone birds; two i n July and one i n August. Here at the head of the Fraser Valley, the preferred -23-habitat type (Bellrose, 1955, among others) i s uncommon, tre e - l i n e d sluggish streams and sloughs being much more p l e n t i f u l as the v a l l e y widens. There may be a shortage of nesting s i t e s i n the study area, although at least one s u i t -able cavity existed i n I960. Three Pileated Woodpecker ex-cavations (inaccessible, so s u i t a b i l i t y undetermined) were found within 9 0 0 feet (274 m.) of the stream. The s c a r c i t y of suitable habitat i n the studied areas, plus a possible shortage of nesting c a v i t i e s , w i l l keep the Wood Duck popu-l a t i o n density low. I t i s not known whether competition f o r nest s i t e s i s a. contributing factor - i f so, i t operates after the bird's habitat selection mechanisms have been ex-pressed. Hooded Merganser The Hooded Merganser i s a resident i n t h i s d i s t r i c t (Brooks, 1917; Brooks and Swarth, 1925; Munro and Cowan, 1947). There are no records from the Fraser Valley i n the B.C.N.R.S.1' On May 11, 196l, a pair was seen on Kawkawa Lake. This constituted the only record of the study. Sparrow Hawk In 196l, two pa i r of Sparrow Hawks were present through out the summer months, and though no nest s i t e s were located •'-'British Columbia Nest Records Scheme, Department of Zoology, University of B r i t i s h Columbia, Vancouver, B.C. Reference i s made only to nests found i n B r i t i s h Columbia. Data from t h i s study have not been included i n any nest t o t a l s given. 2 # , ,Nests" of Horvath (1963) refer to f l e d g l i n g groups. - 2 4 -the appearance of f l e d g l i n g s indicates successful breeding. One pair concentrated t h e i r a c t i v i t i e s along the western slope of the Reservation, moving with t h e i r fledged young ( f i r s t seen on June 28) to the southern slope after the f i r e of Ju l y 1 -4 . Members of the other p a i r were regularly seen i n area "T" , and i t might be supposed that nesting took place here (as i t did the following year). In 1962, again two pair of Sparrow Hawks occupied por-tions of the Thacker Ecological Reservation, and both nest s i t e s were located. B r i e f notes on these, and three other nests, follow. Nest T-4? The nest s i t e was discovered on May 6 , when the male was seen to enter i t . Although many apparently suitable s i t e s were present i n near-by snags, on which these birds spent a great deal of t h e i r time, they were never seen to express interest i n them; apparently nest-site selection had already taken place. On July 7, young hawks were heard from the nest, and on July 15, they were seen outside i t . Nest 1-4: Red-Shafted F l i c k e r s nested here in 196l, and while the hole was undoubtedly dug by F l i c k e r s , when t h i s was done i s unknown. In I960, Red-Shafted F l i c k e r s reared a brood i n a nearby hole (Horvath, personal communi-cation) which went unused i n the following summers. Sparrow Hawks were r a r e l y seen i n t h i s area during 1961. On May 5, the pair was seen copulating i n the v i c i n i t y , and l a t e r the female entered the hole f o r a few seconds. The male meanwhile b r i e f l y investigated another hole i n a nearby snag. Young were s t i l l i n the nest on July 20. - 2 5 -A t h i r d nesting occurred on the experimental area, the birds surviving f o r reasons d e t a i l e d i n the section describing the experiment. The pair was present i n the area when ob-servations started in May. On May 10, the p a i r copulated i n a tree on the south h i l l , and shortly a f t e r , the female clo s e l y inspected a v e r t i c a l s p l i t i n the top of a t h i c k , broken-topped, Douglas f i r snag. On May 14, the male was seen looking i n the future nest cavity; he then mounted the nearby female. Young were s t i l l in t h i s nest on July 27. Two add i t i o n a l nests were discovered on July 25, during a survey t r i p up the Hope-Princeton Highway. A l t i t u d i n a l l y located*, at 1350 feet (564 m.) and 2150 feet (655 m.), they both contained young on t h i s date. The fledged young seen on June 28 i n 1961 apparently resulted from an early nesting, i n which nest-site selection must have been completed by early A p r i l . Generalizing from the above data, i t can be concluded that i n t h i s area Sparrow Hawks w i l l be i n i t i a t i n g the s i t e - s e l e c t i o n process by at least the beginning of May. ("Actual dates i n any l o c a l i t y are probably dependent l a r g e l y on l o c a l weather conditions." Roest, 1957) . Their habitat i s : "Typically, open t e r r a i n such as pla i n s , deserts, f i e l d s , meadows and unforested portions of mountain-sides, where ground surface affords adequate prey-supply, but only where perching places are present." (Grinnell and M i l l e r , 1944).- 5 * From at least the middle of A p r i l on, 3» Data from "The D i s t r i b u t i o n of the Birds of C a l i f o r -n i a " i s frequently included, as i t i s a major d i s t r i b u t i o n a l publication dealing with,the western North American avifauna. - 2 6 -suitable habitat, which i s widespread throughout the v a l l e y , must possess unoccupied F l i c k e r - s i z e d (or larger) holes in s u f f i c i e n t quantity to house the nests of rather widely separated ( i n r e l a t i o n to the number of potential s i t e s available) pairs of Sparrow Hawks. Competition for holes with other species can be imagined i n only the rarest of cases. Cade (1955) reports that the only area defended' during the nesting period i s the immediate v i c i n i t y of the nest, and Roest (1957) did not observe t e r r i t o r i a l i t y among breeding pairs (cf. Nagy, 1963). No l i m i t s can be set to the Sparrow Hawk's radius of a c t i v i t y from t h i s studies' observations, though individuals were frequently seen making f l i g h t s of several thousand feet. Enderson ( i960) found the average maximum diameter of the home range of four breeding pairs i n I l l i n o i s farmland to be 1.4 miles. Comparing the. ranges of the pairs on the Reservation i n 1 9 6 l and 1962 implies that the species i s not u t i l i z i n g a l l of the poten-t i a l l y suitable habitat. The population density of the species i n both summers approximated 0.5 pairs per 100 acres. Table 2 presents d e t a i l s on the nest s i t e s found. Bent (1938), McLaren,(1963), and Roest (1957), among others, give additional data. Hole-nesting Owls None was observed during the study. Horvath (1963) i n the summer of i 9 6 0 found a newly-fledged Pygmy Owl brood on the northeast slope of the Reservation, but no nest s i t e was located. TABLE 2. SPARROW HAWK NESTS NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS 1-4 D. F i r 33* t (10,0) 32* (9.8) 26.5 (67.3) 14* (35.6) U (typ-RSF) Red-Shafted F l i c k e r Sparrow Hawk, 1962. NE slope. , 1961. Lower T-4 D. F i r 40* (12.2) 20* ( 6.1) 46.3 (117.6) 40* (101.6) U 1962. Area "T». F-6 D. F i r 55* (16.8) 45* (13.7) 59.5 (151.1) 24* (60.9) U 1962. Area "F». HPH 9 Mile Western Hemlock 75* (22.9) 74* (22.6) 32.3 (82.0) 10* (25.4) U 1962. HPH 15 Mile - 55* (16.8) 35* (10.7) - - U 1962. Legend f o r Tables 2 t® 8: TREE and HOLE HEIGHTS - given i n feet (upper number) and meters (lower number). DBH and DHH - given in inches (upper number) and centimeters (lower number). DBH - the diameter of a tree trunk measured l+h. feet above ground l e v e l . DHH - the diameter of a nest tree measured at the cavity entrance. SOURCE - the excavator of the cavity. * - an estimated measurement. Due to snag i n a c c e s s i b i l i t y , many measurements were estimated, and while they consequently lack accuracy, they s t i l l have comparative value. Legend f o r Tables 2 to # - Continued U - source unknown. (typ) - appearance of entrance i s t y p i c a l of, and suggests excavation by, the resident species or a species indicated (as above). Other c a v i t i e s not so marked may s t i l l have been produced by the occupants. HPH - Hope-Princeton Highway. Mileage r e f e r s to distance from Hope. RSF - Red-Shafted F l i c k e r . RBS - Red-Breasted Sapsucker. DW - Downy Woodpecker. i HW - Hairy Woodpecker. oa BCC - Black-Capped Chickadee. CBC - Chestnut-Backed Chickadee. RBN - Red-Breasted Nuthatch. -29-Red-Shafted F l i c k e r Regional l i s t s indicate that the Red-Shafted F l i c k e r i s , and has been, a common resident in the Fraser Val l e y . Horvath (personal communication) located two nests on the Reservation i n I960. Four nests were located on or near the Reservation during 1961. Data on 12 nests, s i x on or near the Reservation, were gathered i n the 1962 season. Table 3 l i s t s information only on those nests found in the v a l l e y . Summarizing very generally, F l i c k e r s excavate t h e i r nest s i t e s i n la t e A p r i l and early May, and fledging occurs i n the l a t t e r h a l f of June. The B.C.N.R.S. provides l i t t l e information from the area. This timetable may be varied greatly by individual pairs, as i l l u s t r a t e d by the following example. On A p r i l 30, 1962, a pair was excavating i n 14-2, at an inaccessible spot where an old small hole had been the previous year. Work was w e l l advanced at t h i s date. Incon-clusive sightings in the area followed, and on May 22, the pair was seen i n the v i c i n i t y of 2-15-1. No excavation had started, but on the next v i s i t on May 26, the female was flushed from a new cavity. Young were looking out of the nest on June 29, and had l e f t i t by July 7• Production of unused ca v i t i e s was noted in connection with two other nest-ings in 196 2 (cf. Happ, 193 5 ) . Although the species i s a permanent resident (Munro and Cowan, 1947) the status of wintering individuals i s unknown. Happ (1935) is s i m i l a r l y vague concerning the post-breeding TABLE 3 . RED-SHAFTED FLICKER NESTS NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS 12-20 D. F i r 40 (12.2) 39.5 (12) 18.6 (47.2) 7 (17 .8) U ( typ) 1961. T©p West s l o p e . 16-1 D. F i r 24* (7.3) 22* (6.7) 11.3 (28.7) - U (typ) 1961. Top West s l o p e . 1-4 D. F i r 33* (10) 32* (9 .8) 26.5 (67.3) 14* (35.6) U ( typ) 1961. Bottom NE s l o p e . Sparrow Hawk i n 1962. N - l D. F i r 75* (22.9) 71 * (21.6) - 7.5* (19) U (typ) 1961. Bottom SE s l o p e . M-2 Alder 35* (10.7) 3 4 . 5 * (10.5) 19 (48.3) 10* (25.4) RSF 0 1962. Mar sh . Abandoned 1 f o r 2 -24-1 . 2-24-1 D. F i r 85* (25.9) 84* (25.6) 42.3 (107.4) 16* (40.6) RSF 1962. Bottom South s l o p e . 2-15-1 D. F i r 12 .5* (3 .8) 9.7 (3 .0) 19.8 (50.3) 19 .5 (49.5) RSF 1962. Top West s l o p e . 14-2 B. Maple 28* (8.5) 21* (6.4) 17.8 (45.2) 13* (33) RSF 1962. Upper open p o r t i o n s , abandoned f o r 2-15-1. 15-11 D. F i r 20* (6.1) 18* (5.5) 16.7 (42.4) 12* (30.5) RSF 1962. Top West s l o p e . F-7 D. F i r 23* (7) 22* (6.7) 14.2 (36) 9* (22.9) RSF 1962. Area " F " . Nest o f f i r s t p a i r . TABLE 3. Continued NEST . NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS F-9 D. F i r 25* (7.6) 22* (6.7) 20.8 (52.8) 15* (38.1) RSF 1962. Area " F " . second p a i r . Nest of 2-S-2 B. Maple 43* (13.1) 40* (12.2) 24.8 (62.9) 11* (27.9) U (typ) 1962. Area »»S". Abandoned. Laidlaw Alder 9.1 (2.8) 7.6 (2.3) 8.9 (22.6) 8.8 (22.4) U (typ) 1962. Laidlaw Alder 28* (8.5) 15* (4.6) 17.2 (43.7) 14* (35.6) U (typ) 1962. - 3 2 -movements of the Yellow-Shafted F l i c k e r i n the eastern United States. I t i s possible that breeding birds remain i n t h i s region the whole year, although migration does occur through the Fraser Valley (Udvardy, personal communication). F l i c k e r s are highly t e r r i t o r i a l i s t i c i n early May, but much le s s so toward the end of the month. Birds i n adjoin-ing t e r r i t o r i e s may respond to one another, but i t i s more common for a bi r d to advertise alone. However, t e r r i t o r i e s are presumably well-established by May, and more c o n f l i c t s may occur e a r l i e r i n the season. Exact t e r r i t o r i a l boundaries could not be determined from the observations made. Happ (1935), believed that Yellow-Shafted F l i c k e r s did not behave t e r r i t o r i a l l y with regard to treel e s s areas, which were used as common feeding grounds. He also found widely varying t e r r i t o r y s i z e s , with the larger t e r r i t o r i e s located in poorer habitats. That t e r r i t o r i a l i s m i s operative in t h i s species was i l l u s t r a t e d by the experimental r e s u l t s . Area "F" was i n -habited by one pair of Red-Shafted F l i c k e r s , the members of which were seen at one time or another i n every portion of i t , and sometimes were traced beyond i t s boundaries. Obser-vations on this pair showed that they ranged over a minimum of 100 acres. (The only neighbouring f l i c k e r known was occasionally heard i n the distance, far to the south). On May 15, they were seen investigating an old hole in the top of a 60 foot (let m.) f i r snag, and on May 19, a hole, s t i l l being excavated, was discovered (F - 7 ) . The birds were c o l -lected on May 28. On June 7, a pair of Red-Shafted F l i c k e r s -33-was found excavating a new hole (F-9). The male was giving high-intensity high c a l l s , and l a t e r copulation was seen. The female was at the nest on June 22, but the success of th i s nesting was never determined. F l i c k e r s continued to be heard throughout the area during the remainder of the summer. The Red-Shafted F l i c k e r i s an "edge" b i r d (Grinnell and M i l l e r , 1944; Weydemeyer and Weydemeyer, 1928). I t i s t y p i -c a l l y associated with open areas that bear soft tree trunks of s u f f i c i e n t size f o r nesting. The Fraser Valley f l o o r con-tains much edge-type habitat due to man's a c t i v i t i e s , and the F l i c k e r a t t e s t s to i t s s u i t a b i l i t y by remaining abundant. In the preferred habitat, apparently t e r r i t o r i a l i s m can have some effect on the spacing of the pairs. This was im-p l i e d from observations on the southern and western portions of the Reservation where i n 1962, three pairs concentrated t h e i r a c t i v i t i e s in an area of approximately 80 acres. Addi-t i o n a l support was given by the experimental r e s u l t s reported above, obtained on an area that had l i t t l e open ground, and where the o r i g i n a l p a i r had only one known distant neighbour. The average population density obtained both summers on the Reservation and i t s surroundings was one pair per 100 acres and comparison of the ranges used i n each year suggests that the available habitat was not being u t i l i z e d to the maximum. Douglas f i r snags are most commonly u t i l i z e d for nesting (Table 3), and are very abundant wherever logging or burn-ing has occurred. The F l i c k e r ' s a d a p t a b i l i t y regarding i t s nest s i t e s i s well-document ed (cf. Bent, 1939; G r i n n e l l and M i l l e r , 1944), but here l i t t l e v a r i a t i o n was observed, the -34-d r i l l i n g of a hole (during I960) under the eaves of a city-building being the only example of "aberrant" nesting behavior. The hole i s usually placed close to the top of a broken snag of suitable thickness, and as most of the f i r snags are of considerable height, the nest i s r a r e l y close to the ground. In the few nests located, the hole almost i n v a r i a b l y faced away from the prevailing wind d i r e c t i o n . Entrance flyway requirements are presented by Erskine (i960) and McLaren (1963); the "bounding" f l i g h t habit l i m i t s the bird's manoeu-v e r a b i l i t y , and requires a certain amount of height, so us-u a l l y the holes face a clear area, and are w e l l above obstruc-ti o n s , especially since the birds often " s t a l l - i n " to the nest i n an upward swoop. While excavation was detected (as by fresh chips) at 10 of the 16 s i t e s , a l l but one had the appearance of fresh c a v i t i e s (not counting two small ones known to have been enlarged), and i t i s believed that a new hole is usually produced f o r each nesting. Bent (1939), Happ (1935), McLaren (1963), among others, present data on nest dimensions. L i t t l e i s known of roosting habits, and though holes are not required (Happ, 1935), they may be excavated s o l e l y for t h i s purpose (Bent, 193 9 ) . Pileated Woodpecker In spite of i t s regular occurrence, very l i t t l e informa-t i o n was gathered on the species. No nests were found, and the sighting of two Pileated Woodpecker on the edge of the marsh on July-27, 1962, was the only time two birds were seen - 3 5 -together. During the breeding season, observations were l i m i t e d to sightings of single birds, and were completely un-predictable i n time or location . The birds were r a r e l y viewed for any length of time, as they range widely, move quickly, and usually remain s i l e n t . Attempts to follow individuals i n v a r i a b l y f a i l e d . How many birds contributed to the obser-vations i s unknown, and d e t a i l s on t e r r i t o r y s i z e , preferred habitat and nest s i t e s , and other breeding habits i n t h i s region could not be obtained. Two observations regarding cavity production were made in 1962. On July 20, a juvenile male was found excavating a hole (on the experimental area "F"). I t was just started i n the top of a broken-off 30-foot ( 9 m . ) b i r c h , and on July 27 the hole was found to have been continued through to the other side, as the snag was t h i n here due to a portion of i t s p l i t t i n g away. On July 9 , at 2950 feet (900 m.) al t i t u d e 28 miles east on the Hope-Princeton Highway, a P i l e at ed was starting a hole 21 feet ( 6 . 4 m.) up i n a 25-foot (7.6 m.) cedar snag. A f u l l size entrance was seen on the next t r i p . Lewis Woodpecker One pair resided on the Reservation during the summer of I960 , perhaps breeding, although a nest s i t e was not located (Horvath, 1963) . They were always seen on the south-ern slopes, i n keeping with t h e i r known preferences for open fo r e s t s , old burns, and logged-over areas (Grinnell and M i l l e r , 1944) . The following two summers yielded only one observation; -36-that of an adult on May 27, 196l, by Horvath (personal communication). Red-Breasted Sapsucker In I960, Horvath (personal communication) located two Red-Breasted Sapsucker nests, and new holes were excavated i n the same snags during the following spring (W-2 and 1-2). W-2 contained f i v e other c a v i t i e s , apparently old Sap-sucker workings, that were never used by other bi r d s . I t was close to the cabin used during 1961, and was passed several times a day. Yet July 1 was the only time drumming was heard, when one bird drummed near the now-empty nest.. The birds were very quiet and secretive, and except when they were feeding young, were located mainly by an occasional contact c a l l (Kilham, 1962a). They were known to range up to 1150 feet (350 m.) from the nest. They apparently l i v e d i n complete i s o l a t i o n from other Sapsuckers. 1-2 contained three other Sapsucker-sized openings, a l l of which were unused. The only drumming d e f i n i t e l y a t t r i -butable to t h i s pair also was detected on July 1, from a pos-i t i o n near the now-empty nest. The b i r d was responding to an unhanded drumming Sapsucker 400 feet (122 m.) away, who remained un i d e n t i f i e d and was not seen again. The adults ranged up to 750 feet (229 m.) from the nest, and most of the feeding was done in a grove 575 feet (175 m.) distant. As t h e i r t e r r i t o r y was near the edge of the area r e g u l a r l y surveyed, there i s a geater chance that these birds had neighbours of the same species. I f so, they gave no i n d i -cation of i t . -37-At t h i s nest, the adults and young were color-banded. The only sighting of any of the young occurred on August 21 , when two of them, in. company with two other unhanded young Sapsuckers, were found feeding in a grove 860 feet (262 m.) away from t h e i r birthplace. One of the adults was found dead i n February, 1962, at the same co-ordinates, i l l u s t r a t i n g i t s non-migratory status (Howell, 1953)- The other adult was seen once the following year, on May 8 , 1100 feet (335 m.) from the now-fallen 1-2. As the area in which i t was seen was used by another pair of Sapsuckers i n 196 2, i t probably moved off the study area e n t i r e l y . In 1962,.the range of the p a i r at ¥-2 was better known, the birds t r a v e l l i n g at least 1500 feet (457 m.) to the east * of the nest, and 1150 feet (350 m.) to the west. Of i n t e r -est was t h e i r feeding at a small group of t h i n Douglas f i r s 1500 feet (457 m.) from the nest. They were seen here regu-l a r l y u n t i l the middle of May, and cessation of the habit was probably due to the demanding nesting a c t i v i t i e s . There was no apparent reason why these trees, which were used ex-tensively, should have been selected from the thousands ava i l a b l e . When feeding the young, repeated f l i g h t s of 900 feet (274 m») were undertaken. Again there were no neigh-bouring Sapsuckers. In area "F", the single pair.present had started two-c a v i t i e s i n F-2 by May 14, 1962, when they were collected. Although the area was v i s i t e d frequently during the next two weeks, the f i r s t i n d i c a t i o n of new a r r i v a l s came around - 3 8 -9 P.M. on June 3,.-.when two Sapsuckers ca l l e d b r i e f l y at the north end of the study area, presumably just before roosting. At 5 A.M. the following day, a Sapsucker began drumming on a resonant branch of F - 2 , and at 5:13 A.M. was joined by a second b i r d , which flew from the roosting area after the drumming bird gave several breeding c a l l s (Kilham, 1962a) . At 5 :25 , drumming was performed on an exposed ins u l a t o r support on a telephone pole by the old,highway, the b i r d , then f l y i n g towards F - l l , where excavation was to be seen at a l a t e r date. On June 7 and 11, birds were.seen at F - 2 , but whether additional digging was done at either of the already-started holes i s unknown. Drumming at high i n t e n s i t y (which made t h i s p a i r exceptional) was continuing on June 22, when the pair was seen at a cavity being excavated in F - l l , the working b i r d being able to enter about h a l f the length of i t s body. Constant drumming was continuing on July 1 . On July 20, tapping on the f a v o r i t e pole e l i c i t e d an answer-ing drum (only with t h i s particular Sapsucker did such imita-tions ever "work"), and one adult, accompanied by two juven-i l e s , was located nearby. These birds were seen again on July 27 and August 9» While the presence of juveniles might be i n d i c a t i v e of an un-located successful nesting by t h i s • p a i r , i t did not occur on the study area, as the v o c a l i z a -tions of the nestlings would c e r t a i n l y have been heard. Also, the pair behaved rather abnormally, ex h i b i t i n g continual drumming, and excavation, at a time when Sapsucker fl e d g l i n g s are appearing. The 1961 observation on the four juveniles reported above i l l u s t r a t e s that juveniles may wander onto - 3 9 -strange t e r r i t o r y , where other juveniles may constitute a s o c i a l a t t r a c t i o n . Howell (1952) reports how a begging juvenile Sapsucker was attacked by adults engaged i n feeding t h e i r own unfledged young. "The juvenile obviously reacted to these adults as i t would to i t s own parents, even after i t was attacked." A similar explanation l i k e l y accounts for the appearance of juveniles under these conditions. The Red-Breasted Sapsucker i s a permanent re sident. What r e l a t i o n the breeding t e r r i t o r y has t o the winter range i s unknown. I t was found that the birds are paired, and nest-site selection i s accomplished, by the beginning of May, and that very l i t t l e t e r r i t o r i a l i s m i s shown at t h i s time, most drumming being heard during a b r i e f period a f t e r the young have l e f t the nest. In the area studied, the pop-u l a t i o n l e v e l , calculated at 0.5 pairs per 100 acres i n each season, did not appear to be high enough to demand maximum u t i l i z a t i o n of the available habitat. Yet the elimination ex-periment suggested that the presence of Sapsuckers in an area prevents others from establishing themselves there. Howell (1952) found that Sphyrapicus varius daggetti and S. v. nuchalis generally defended areas around t h e i r nests to a radius of 150 to 225 feet (45 to 68 m.) and that the birds would range f a r beyond these l i m i t s , up to 600 or 900 feet {,182 to 273 m.) provided that another t e r r i t o r y was-not encountered. Territory sizes appeared to depend on how heavily the area was wooded with smaller t e r r i t o r i e s held i n denser groves. He also found that nesting Sapsuckers exhibited aggressive behavior p r i n c i p a l l y toward others of -40-t h e i r own species and other s i m i l a r - s i z e d Woodpeckers. Non-pic i d s were not attacked, even though they attacked the Sap-sucker. Kilham (1962a) found a high l e v e l of t e r r i t o r i a l ism in the eastern race of t h i s Sapsucker - i n one case t h i s apparently contributed to the neglect of breeding duties. Guiguet (1954) reports that in 1946 and 1947, the Red-Breasted Sapsucker was one of the commonest birds on the Queen Charlotte Islands, but i n 195 2, i t was not recorded there. B. Foster (personal communication) who spent the summers of I960 and 1961 investigating the. fauna of the Queen Charlottes, never saw a Sapsucker during t h i s time. Nothing i s known about these population fluctuations. Possibly the density recorded on the study areas represents a "low". The Red-Breasted Sapsucker tends to choose a dead tree i n an "edge" situation for a nest s i t e . The hole w i l l be in the most open side of the trunk and that part of the tree containing the nest w i l l be free of obstructing' branches, and w i l l be several feet higher than the immediate surround-ings. In t h i s area, dead maples are preferred (Table 4), l i k e l y because a few years after death the entire inner por-ti o n of the trunk becomes very soft and spongy, the exterior layer remaining r e l a t i v e l y hard. Prominent features of s u i t -able habitat w i l l be nesting snags as described, stands of l i v i n g trees, and possibly nearby clear areas, f o r when feed-ing young, these birds may take insects on the wing f o r hours at a time, demonstrating the importance of this food source. The above conditions are widespread along the edges of the v a l l e y , and why the birds are not more common i s unknown. TABLE 4. RED-BREASTED SAPSUCKER NESTS NEST TREE TREE HOLE NUMBER SPECIES HEIGHT HEIGHT DBH DHH SOURCE REMARKS W-2 B. Maple 55* (16.8) 33* (10) 30.5 (77.5) - RBS 1961. Bottom SE s l o p e . W-2 B. Maple 55* (16.8) 30* (9.1) 30.5 (77.5) - RBS 1962. Bottom SE s l o p e . 1-2 B. Maple 25* (7.6) 20* (6.1) 12 (30.5) - RBS 1961. Lower NE s l o p e . 2 - N - l B . Maple 45* (13.7) 25* (7.6) 12.5 (31.8) 7.5* (19) U ( typ) 1962. Near R e s e r v a t i o n . S i m i l a r t© NE s l o p e . F-2 B. Maple 55* (16.8) 45* (13.7) 22.3 (56.6) 11* (27.9) RBS 1962. Area " F » . F - l l D. F i r 65* (19.8) 50* (15.2) 45 (114.3) 30* (76.2) RBS 1962. Area " F " . HPH 9 M i l e Western Hemlock 60* (18.3) 50* (15.2) - - U ( typ) 1962. HPH 10 M i l e Western Hemlock 125* (38.1) 70* (21.3) 37.8 (96) 20* (50.8) U (typ) 1962. HPH 25 M i l e C o t t o n -wood 70* (21.3) 60* (18.3) 33.2 (84.3) 10* (25.4) U ( typ) 1962. HPH 40 M i l e Engelv' ' Spruce 80* (24.4) 58* (17.7) 34 (86.4) 23* (58.4) U ( typ) 1962. -42-Capable of digging t h e i r own nests, they apparently a l -ways do so (Kilham, 1962a). On the Reservation, t h i s occurs i n late A p r i l and ear l y May; young fledge during the l a s t week of June. Measurements of t y p i c a l excavations are given by Bent (1939), and Howell (195 2), and apparently the c a v i t i e s are enlarged during nesting (Kilham, 1962b). Hairy Woodpecker In 196.0, Horvath (1963) found the species on the Reser-vation, though no nests were located. In 196l, only one of the two nesting attempts located on the Reservation was successful. The nests were approximately 3500 feet (1066 m.) apart. Fledging occurred at 1-3 on June 9. A c t i v i t i e s of the other pair were concentrated at 11-3 on May 14; the hole was l a t e r found to be a shallow " s t a r t " . On May 30, the birds were at a fresh excavation (inaccessible) i n 12-3, 230 feet (70 m. ) away. Nothing resulted, and the birds were subsequently seen i n the area only i n t e r m i t t e n t l y . Three of the four nests located i n 1962 supported the generalization of Guiguet (1954) that the young of t h i s single-brooded species usually fledge by June. The fourth nest held fully-developed young on June 29. Nest-selection and excavation was not seen, as t h i s usually occurs p r i o r to May. A permanent resident, the Hairy Woodpecker maintains i t s t e r r i t o r y and pair-bond throughout the year (Kilham, I960; Staebler, 1949). Drumming i s considered a courtship a c t i v i t y by Staebler (1949); Kilham (i960) has shown i t also functions i n pair-formation, and possibly t e r r i t o r i a l i s m . - 4 3 -Drumming was heard i n f r e q u e n t l y during t h i s study, as i t becomes r a r e : - j u s t before excavation s t a r t s (Kilham, I960); - a f t e r excavation s t a r t s (Kingsbury, 1932) ; - a f t e r the hatching of the eggs ( S t a e b l e r , 1949). Two i n t r a s p e c i f i c c o n f l i c t s , c h a r a c t e r i z e d by prolonged dance d i s p l a y (Kilham, I960; Skutch, 1955), and presumably t e r r i t o r i a l i s t i c , were observed, one during each year. The places where they occurred were approximately 400 f e e t (122 m.) apart - two females were i n v o l v e d i n 1 9 6 l ; two males i n 1962. Staebler (1949) found that a Hairy Woodpecker p a i r ranged over an #00 acre t e r r i t o r y i n w i n t e r , a f i g u r e w i t h which Dennis (1951) agrees, and when f o r a g i n g f o r t h e i r n e s t l i n g s would t r a v e l up to 900 yards (823 m.) from the nest, f r e q u e n t l y making 200 to 400 yard (183-366 m.) t r i p s . I n the study area, the H a i r y Woodpecker was judged to range at l e a s t as w i d e l y , fo r even though no b i r d s were marked, they were o f t e n - seen making f l i g h t s i n v o l v i n g hundreds of yards, and doing t h i s r epeatedly, as when f o r a g i n g f o r n e s t l i n g s at a favored but d i s t a n t l o c a t i o n . The species occurred i n population d e n s i -t i e s of 0 .5 and 0 .75 p a i r s per 100 acres i n the r e s p e c t i v e seasons. The experimental r e s u l t s from area "F" concerning t h i s species are r e p o r t e d l a t e r , and p o s s i b l e reasons f o r t h e i r i n c o n c l u s i v e n e s s are o u t l i n e d . The s i g h t i n g of one of the color-banded young from 1-3 on August 25, 1961, 11 weeks a f t e r f l e d g i n g , provided a l i t t l e i n f o r m a t i o n on d i s p e r s a l . This b i r d was i n the company of three a d u l t s , a male and two females, 3300 f e e t (1006 m.) - 4 4 -from i t s birthplace. The two females l a t e r became involved i n a t e r r i t o r i a l c o n f l i c t . G r i n n e l l and M i l l e r (1944) describe the habitat of Dendrocopos v i l l o s u s h a r r i s i (the subspecies resident i n t h i s area) as edges, logged areas, and burns of coniferous f o r e s t , with Douglas f i r being preferred for foraging. The nests (Table 5) found during t h i s study were in dead trees, and the appearance of each suggested recent excavation. A l l of them faced open areas that allowed unobstructed access and they were also alike in that they were positioned at a • considerable height above the underlying vegetation. Capable of digging t h e i r own holes, they always do so (no references to the contrary). Typical nest s i t e s are dimensioned i n Bent (1939) and Staebler (1949). After the completion of breeding, i t may be common for. new roost holes to be excavated. Three such s i t e s were located (Table 5 ) , and although roosting was observed in only one of them, the other two were not watched enough to eliminate the p o s s i b i l i t y . As l i t t l e i s reported on similar occurrences, greater d e t a i l i s presented. 21-6. Located on July 16, 1 9 6 l , because of the fresh chips l i t t e r i n g the vegetation beneath. The b i r d roosted i n the hole on July 19, and was frequently heard c a l l i n g when entering or leaving i t i n the evenings or mornings during the remainder of the summer. I t commonly came from the slopes to the west, and i t i s believed, though proof i s lacking, that i t was one of the birds involved i n the unsuccessful nesting attempt at 1 2 - 3 . During 1962, the cavity-bearing portion TABLE 5 . DOWNY AND HAIRY WOODPECKER NESTS NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS Rivers ide P a c i f i c Willow 22* (6 .7) 20* (6 .1) 14.2 (36) 5 * (12.7) U (typ) Downy woodpecker. 1962. Rivers ide Study Area. F-4 Alder 50* (15) 4 5 * (13.7) 16.5 (41.9) 8* (20.3) DW Downy woodpecker. 1962. Area " F n , unburned po r t i on . 1-3 B. Maple 55* (16.8) 17* (5 .2) 13 .7 (34.8) 11 .2 (28.4) U (typ) Hairy woodpecker. 1961. Bottom NE slope. 12-3 B. Maple 45* (13.7) 32* (9.8) 12.6 (32) 9* (22.9) U (typ) , Hairy woodpecker. 1961-62. Upper ©pen por t ions . Two nearby holes , ©ne dug each year. 2-6-1 B. Maple 30 * (9 .D 18* (5 .5) - - U (typ) Hairy woodpecker. 1962. Upper ©pen por t ions . P - l D. F i r 48* (14.6) 46 * (14) 14.1 (35.8) 8 . 5 * (21.6 U (typ) Hairy woodpecker. 1962. NE s lope. D. F i r 70* (21.3) 66 * (20) 30.2 (76.7) 15* (38.1) U (typ) Hairy woodpecker. 1962. Area " F " , burned po r t i on . 21-6 Birch 40* (12.2) 3 7 * (11.3) 9.9 (25.1) (17.8) HW Hairy w©©dpeeker. 1961. Roost. Lower SE slope. 2 - M - l Alder 40 * (12.2) 35 * (10.7) 14.5 (36.8) (17.8) HW Hairy w©odpecker. 1962. Roost (?) Marsh. HPH 10 M i l e Western Hemlock 23* (7) 21* (6 .4) 17.3 (43.9) 1 5 * (38.1) HW Hairy woodpecker. 1962. Roost (?) - 4 6 -f e l l , and the hole was found to be dimensioned as a t y p i c a l nest. 2-M-2. - was discovered on June 9, 1962, when a pair of Hairy Woodpeckers which had just successfully raised a brood i n 12-3 (young i n the nest on May 31 ) , were found paying a great deal of attention to the upper dead portion of a 40 foot (12m.) red alder i n the western wooded end of the marsh. Ex-cavation had barely started on t h i s date, and eventually a f u l l - s i z e d hole appeared, though the completeness of the cavity was never checked. Once when the female displaced the excav-ating male, the male l e f t the s i t e i n "Floating F l i g h t " , a display considered by Kilham ( i960) to be connected with pair formation, and then given only by the female. This i n t r o -duces the p o s s i b i l i t y that digging of holes at t h i s time i s connected with a recrudescence of sexual a c t i v i t y i n t h i s single-brooded'species. A male was discovered at a freshly-started hole on June 19, 1962, near Gutram Lake. Inaccessible, i t was also apparently completed. I t was d r i l l e d near the top of a 23 foot ( 7 m . ) snag, which was located on the edge of the dense forest i n a hollow down below the l e v e l of the nearby road-way. Rather than facing the open half of i t s surroundings, the hole instead was aligned toward a narrow f l i g h t path between the branches of two adjacent trees. A l l three of these holes were situated i n sheltered locations, quite the opposite from those i n which nest s i t e s were t y p i c a l l y located. -47-Downy Woodpecker Horvath (1963) did not f i n d the species on the Reserva-t i o n i n the summer of I960. Their occurrence here in the 196l summer was l i m i t e d to a few sight ings in la te Ju ly and ear ly August which involved both adult and juveni le b i r d s . A juveni le was seen on J u l y 17 excavating very b r i e f l y at 12-26 (Table 8), where a hole had been d r i l l e d sometime after the snags i n the area were surveyed on June 2. Presumably a roost , i t was used the fo l lowing summer by re-nes t ing Red-Breasted Nuthatches, who excavated add i t iona l ma te r i a l . Observations scattered throughout the 1962 season suggest that Downy Woodpeckers nested on or near the Reser-va t ion , though ce r t a in ly not on the portions surveyed. Two nests were located, one on the experimental area " F " , and the other on the Rivers ide Study Area (Table 5) . The p a i r on the experimental area was discovered on May 4, and the male was found excavating a nest (F-4) on May 10 (about f ive percent complete). No neighbouring Downies were known; that the studied pai r was very secret ive supported t h i s f ac t . Very occas ional ly one of the b i rds would make a t r i p down the center of the gulch, stopping to drum on resonant branches; the rest of the time t he i r p o s i -t i o n was discovered only by accident, and t h e i r t e r r i t o r i a l l i m i t s could not be determined. The female of the pair on the study area was shot on May 15, and although the male was in t ens ive ly hunted during the next two weeks, he was not seen again and the area apparently remained devoid of Downy -48-Woodpeckers f o r the rest of the breeding season. On June 7, a drumming and c a l l i n g Downy was heard i n the distant timber to the east of the study area. On July 13, a Downy was heard drumming l i g h t l y and b r i e f l y on at least three snags i n the old nest-site area: i d e n t i f i e d by an occasional c a l l , i t could not be seen to determine i t s sex, and was soon l o s t . During a t r i p on August 9, a Downy was heard c a l l i n g b r i e f l y from the same area - again i t was not seen. The absence of any reaction after the nesting disruption was l i k e l y due to a lack of neighbours occasioned by u n s u i t a b i l i t y of the sur-rounding habitat. Young were being fed i n the nest in the Riverside area when i t was discovered on June 10: they had l e f t the nest by June 16, the date of the next v i s i t . Considered to prefer deciduous woodland, the Downy Woodpecker i s more common i n the lower half of the Fraser Valley (Brooks and Swarth, 1925; personal observation). I t may be termed an uncommon resident of the Hope region. That i t i s not more abundant i n the surrounding mountains i s i n -dicated by i t s r a r i t y i n Manning Park (C a r l , Guiguet, and Hardy, 1952; Anon., I960). Aspects of the species' nest sites are outlined by Bent (1939) and Staebler (1949). The l a t t e r author found that nests, averaging 15 feet (4.6 m.) high, were placed i n dead trees. One brood per year i s raised, always in a cavity f r e s h l y excavated by the birds themselves. Fresh holes are also excavated on an in d i v i d u a l basis i n the f a l l f o r winter roosting (Kilham, 1962c) ; d e t a i l s on - 4 9 -t h e i r size and placement are unrecorded. The Violet-Green Swallow, Tree Swallow, S t a r l i n g , English Sparrow, and House Finch, though nesting i n the area, did not occur as nesting species on the Reservation or area "F"; therefore a separate section (The Town Study-Area) i s devoted to t h e i r treatment. Black-Gapped Chickadee The resident status of this species f a c i l i t a t e s the early inception of breeding a c t i v i t i e s . The winter flock gradually disappears as pairs are formed, some of which d r i f t away i n search of suitable habitat, and probably not establishing a t e r r i t o r y u n t i l a suitable nesting s i t e i s found (Odum, 1941a). Brewer (I96l) refers to a permanent pair-bond. Five t e r r i t o r i e s , four of banded bi r d s , on which most of t h i s study's observational work was done, averaged 8 .6 acres (7*4 to 1 0 . 4 ) . T e r r i t o r i e s are sometimes p a t r o l l e d by the male or the p a i r , when the t e r r i t o r i a l c a l l i s given more often. C o n f l i c t s , always vocal but r a r e l y physical, may occur along mutual boundaries. Of interest were two isol a t e d observations of males, deep within t h e i r own t e r r i -t o r i e s , a l t e r n a t i n g "fee-bee" c a l l s with neighbouring males, who were so far i n the distance that they could just barely be heard under the pr e v a i l i n g s t i l l - a i r conditions. Confirmation of the impression that t e r r i t o r i a l i s m might l i m i t the area occupied by a chickadee pair was one result of the elimination experiment. The male of the studied p a i r was the area's only banded b i r d , making i d e n t i f i c a t i o n of him and his t e r r i t o r i a l boundaries p a r t i c u l a r l y easy. A -50-mutual boundary with another p a i r existed at only one point (Fig. 5), and the p o s s i b i l i t y of other neighbours was elimin-ated by the nature of the habitat. The boundary location was approximated on May 4, when the two males vigorously answered one another's t e r r i t o r i a l c a l l s , being about 100 feet (30 m.) apart, and on either side of a conspicuous snag. Unfortun-ately, the nest of the studied pair could not be located, but the feeding of the female by the male (seen on May 10) indicated that incubation was l i k e l y i n progress (Odum, 1943)• At 9 A.M. on May 15, t h i s pair was shot. (The male had been banded as a nestling the previous year near the Reservation, a s t r a i g h t - l i n e distance of two miles away.) The next day, at 8 A.M.,,, t e r r i t o r i a l c a l l s were heard from approximately 150 feet (46 m.); inside the now-abandoned t e r r i t o r y , and the neighbouring male was followed, by means of his c a l l s , back past the marker snag i n t o h i s own t e r r i t o r y . Subsequent sightings of the pair and single individuals showed that at least the area (approximately 2.5 acres) indicated on F i g . 5 was added to t h e i r t e r r i t o r y . On June 7, a pair feeding a recently fledged family was found w e l l inside t h i s newly acquired area, demonstrating that new a r r i v a l s had not been involved, as they could not have raised this brood in less than a month. From t h i s time on, l i t t l e attention was paid to chickadees in t h i s area, as juveniles, and perhaps vagrant adults, confused the observations. Competition with a small mammal (supposed) for a cavity resulted i n the loss of a 1961 brood. This nest was discovered on June 22, when both parents were attending to follow page 50. Figure 5« Chickadee Territories., text (page 50). Explanation i n the -51-newly hatched young. This was the p a i r s ' second brood of the season for although the f i r s t nest-site was not located, a family group was seen in t h i s t e r r i t o r y on June 1. That the cavity had been recently excavated by the chickadees was known from i t s c h a r a c t e r i s t i c s , and the f a c t that the stump had been checked e a r l i e r f or c a v i t i e s when searching for t h e i r f i r s t nest. On June 23, the cavity was f u l l of moss, and the opening was s l i g h t l y enlarged. The parents were not seen. While the competitor's i d e n t i t y was never established i n numerous subsequent v i s i t s , a deer mouse i s considered the most l i k e l y intruder. The Black-Capped Chickadee occupies deciduous woods, with young second-growth stages preferred when establishing the nesting s i t e . Odum (1941a) points out, and Brewer (1963) quantitatively evaluates, the Black-Capped Chickadee's tendency to locate i t s nest in stubs in more open edge s i t -uations than those which i t uses for i t s feeding and resting a c t i v i t i e s . The l a t t e r author suggests that since suitable stubs i n denser forest are not used, t h i s dual habitat pre-ference i s not the r e s u l t of the requirement f o r soft wood nest trees, but that the c h a r a c t e r i s t i c s of edge situ a t i o n s , where such trees are more frequent, " are merely 'sign posts' used by the birds as an aid i n f i n d i n g such trees." In 1962, eight pairs occurred on the study area, giving a population density figure of 2 .0 pairs per 100 acres. Since Hope i s at the head of the v a l l e y , and occupies a t r a n s i t i o n zone between two b i o t i c areas, with the chickadee resident i n only one (the Puget Sound Lowlands) of them, the - 5 2 -d i s t r i b u t i o n of t h i s bird i s necessarily l i m i t e d i n this area. Inspection of the mountainsides bordering the valley f l o o r shows that deciduous growth becomes rare (except along moist drainages) above roughly 700 feet (213 m.) elevation, where the coniferous dominants of the Coast Forest predom-inate. Once the valley f l o o r i s l e f t , the habitat becomes more and more marginal f o r the species. This was i l l u s t r a t e d by i t s occurrence at the areas surveyed along the Hope-Princeton Highway. I t was a nesting species at the f i r s t stop, at 775 feet (236 m.) elevation 3s miles from Hope, where that portion of the habitat surveyed was roughly simi-l a r to the Reservation. The next stop, at 1100 feet (335 m.), 7 miles from Hope, contained a much higher percentage of Coast Forest species, a l i m i t e d growth of alder, bir c h , and maple being confined to the margins of a small r i v e r . The Black-Capped Chickadee occurred here, but only after the peak of the breeding season, the f i r s t sighting being made late i n July. Most l i k e l y these records were of wandering in d i v i d u a l s . There i s only one sight record from Manning Park (D. Dow, personal communication), which t h i s highway enters 17 miles from Hope. Table 6 presents c h a r a c t e r i s t i c s of the nests found. Additional data on Black-Capped Chickadee nest s i t e s i n other regions, as given by Bent (1946), Brewer (1961, 1963), N i c k e l l (1956), and Odum (1941b) indicates general s i m i l a r i t y . Brewer (1963) suggests that height and s u i t a b i l i t y f o r exca-vation are the most important c h a r a c t e r i s t i c s determining a stub's s u i t a b i l i t y . Cavities are required for nesting, and TABLE 6 . BLACK-CAPPED CHICKADEE NESTS NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS 3-4 Birch 5.5 (1.7) 4.8 (1.5) 6.2 (15.7) 6.2 (15.7) BCC 1961. Upper wooded port ions . Presumed second brood. 11-5 Bireh 10* (3) 5.9 (1.8) 6.7 (17) 6.6 (16.8) u (typ) 1961. Upper ©pen por t ions . F i r s t brood. W-5 Alder 6.3 (2.1) 6.3 (1.9) 5.5 (14) 5 (12.7) U (typ) 1961. F i r s t brood. Area " S M . 2 -S- l B i r c h 12.5 (3.8) 11.6 (3.5) 4*6 (11.7) 3.9 (9.9) U (typ) 1962. Area " S " . F i r s t brood. , 2-1-100 Birch 4 (1.2) 3.2 (1) - 4.6 (11.7) U (typ) 1962. NE slope. Presumed y second brood. 2-1-7 Birch 7.5 5.2 U (2.3) (1 .6) (13.2) (12.7) (typ) 2-1-2 Birch 40* 37* 9 3.3 BCC (12.2) (11.3) (22.9) (8 .4) 2 - T - l B i r ch 7.1 6 .2 3 .1 2.8 U (2.2) (1 .9) (7 .9) (7.1) (typ) 2-T-2 Birch 7.8 6 2.5 2.5 u (2.4) (1 .8) (6 .4) (6.4) (typ) Laidlaw Alder 20* 18* 10.3 4* u (6.1) (5.5) (26.2) (10.2) (typ) 1962. Bottom NE s l o p e . F i r s t broed.Second brood i n 2-1-2. 1962. Bott©m NE slope. Second brood. 1962. Area "T" . F i r s t brood. Second br©od i n 2 - T - 2 . 1962. Area »T«. 1962. F i r s t brood. 7 TABLE 6. Continued NEST NUMBER . TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS Laidlaw Alder 12* 4.8 8.4 8.4 U 1962. Presumed second (3.65) (1.5) (21.3) (21.3) (typ) brood. Rivers ide Alder 12.5 8.6 4.8 4.1 U 1962. Presumed second (3.8) (2.6) (12.2) (10.4) (typ) brood. I I the b i r d i s capable of digging i t s own nest. In only 2 cases (of 12) was i t d e f i n i t e l y established that the b i r d dug i t s own, but the appearance of every other ca v i t y , ex-cept one, suggested recent excavation by Chickadees. The exception was a s o i l e d cavity i n which a second brood (pre-sumed from the date) was r a i s e d , and just above i t s entrance was a f r e s h l y started, but incomplete excavation. These observations do not contradict the supposition that the Black-Capped Chickadee has a "psychological need" f o r excavation (Brewer, 1961; Drury, 1958; Kluyver, 1 9 6 l ) , and thus i s nearly always responsible f o r producing i t s own nesting cavity (Odum, 1941b). The frequency of second broods, judged from t h i s l i m i t e d f i e l d work, may be much higher in t h i s area than has been reported elsewhere (cf. Brewer, 1961) . Of the 12 nests l o -cated, 6 contained f i r s t broods. Two others had second broods of marked pairs. Two had broods lat e i n the season, i n t e r r i t o r i e s where recently fledged young i n family groups had been seen e a r l i e r , and the remaining 2 nests contained young at a time suggesting second broods. Additional obser-vations would be desireable. Three color-banded pairs observed closely during 1962 had the following h i s t o r i e s . One pa i r r a i s e d t h e i r f i r s t brood i n 2-1-7, and t h e i r second in a fresh cavity i n 2-1-2, 520 feet (159 m.) away. A second pair nested successfully i n 2-T-l, and then raised another brood i n 2-T-2, 245 feet (74 nu) distant; the cavity appeared f r e s h l y excavated. The t h i r d pair raised a brood from 2-S-l, and a second nest, i f -56-any, was not located, although the birds started excavating a hole which was l a t e r abandoned, and continued maintenance of t h e i r t e r r i t o r y , with a t e r r i t o r i a l c o n f l i c t with a neigh-bouring pair last seen on July 16. Odum (1941a) reports that t e r r i t o r i a l defense stops when the young leave the nest. Chestnut-Backed Chickadee Horvath (1963) saw fledglings on the Reservation in I960, while only one pair inhabited those portions surveyed during t h i s study. Details of the annual cycle of t h i s species remain generally unknown, with l i t t l e information available on p a i r -formation, nest-site selection, and t e r r i t o r i a l i t y . The species was recorded on area "F" only once during the la t e summer, and was not involved i n the elimination experiment. The birds nesting on the Reservation in both years i n -habited a steep rocky slope (Plate 3 ) , and generally confined t h e i r a c t i v i t i e s to the upper portions of the t a l l conifers, making observations d i f f i c u l t and time-consuming. Nests were located only i n 1962. There were no known neighbouring p a i r s , and no c o n f l i c t s of any type were detected. Dixon (1954) found t e r r i t o r i a l i t y to be exhibited only b r i e f l y during the spr ing. Though usually found high i n the same general situation, where Golden-Crowned Kinglets were common, the Chestnut-Backed Chickadee was not l i m i t e d to t h i s portion of the habi-t a t , and occasionally foraged in deciduous trees. I t was not recorded from the v a l l e y areas surveyed, (except for a c a l l heard on July 14 i n the Riverside Study Area), but was observed at nearly every stop made along the Hope-Princeton Highway. G r i n n e l l and M i l l e r (1944) describe the habitat of the species as coniferous forest and adjacent mixed growth woodland, with a l l the conifers of the humid coast belt being frequented to about equal degree. They found an apparent preference for dead deciduous trees when excavating nests. I t requires a cavity f o r nesting, and i s capable of digging i t s own, which i t almost in v a r i a b l y does (Bowles, 1909). Cavities found i n use during t h i s study (Table 7) p a r a l l e l most cl o s e l y i n general c h a r a c t e r i s t i c s those u t i l -i zed by the Red-Breasted Nuthatch i n f i r s . How often new c a v i t i e s are produced i s unknown. Existing tree hole cavi-t i e s , and bird.boxes (2 of 11 records i n the B.C.N.R.S.), may be used. Both Bowles (1909) and Burleigh (1930) found the nests averaged less than 10 feet (3 m.) i n height and were often placed in dead f i r stubs. The pair observed most closely i n 196 2 used two d i f f e r -ent c a v i t i e s (approximately 350 feet (107 m.) apart), but i t i s not known i f they were prepared by these birds. The absence of neighbours, location of the nests, and timing of the broods makes i t almost certain that the same unmarked pair was involved. The commonness of second broods i s unknown. Black-Capped and Chestnut-Backed Chickadees There i s the p o s s i b i l i t y that these two closely related species might a f f e c t one another i n some way. For instance, they co-inhabit a large part of B r i t i s h Columbia, but on TABLE 7. CHESTNUT-BACKED CHICKADEE NESTS NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS 2-1-2 Birch 40* 39* 9 3.31 CBC Bottom NE slope. 1962. (12.2) (11 .9) (22.8) (8.4) Cavity incomplete. 2-1-6 D. F i r 40* 17* 37.8 30* U Middle SE slope. 1962. (12.2) (5.2) (96) (76.2) (typ) F i r s t brood. Second brood of t h i s p a i r i n 2-21-2. 2-21-2 D. F i r 95* 85* 53.8 12* U Middle SE slope. 1962. (28 .9) (25.9) (136.6) (30.5) (typ) Second brood. HPH D. F i r do* 79* 41 20* U 1962. 15 Mil e (24.4) (24) (104.1) (50.8) HPH Red 55* 40* 20.5 13* U 1962. 10 Mile Cedar (16.8) (12.2) (52) (33) WINTER WREN NEST 22 Birch 32 14.3 12.7 9.4 U Used i n I960. F e l l i n (9.8) (4.4) (32.3) (23.9) August, I960. - 5 9 -those portions of the Province (as Vancouver Island) where the Chestnut-Backed i s the only chickadee, i t apparently u t i l i z e s a wider, niche, becoming more of a "backyard garden" type of b i r d . Where both species regularly occurred together in the Hope area (on the Reservation and the 3-mile study area), observations, necessarily casual, suggest that each species e s s e n t i a l l y ignores the other during the breeding season, inhabiting niches which are almost t o t a l l y d i s t i n c t , and f u l -f i l l e d best i n separate habitats. The Chestnut-Backed i s usually found high i n the mature trees of predominantly con-iferous stands - the Black-Capped i n the lower half of decid-uous vegetation, which i s frequently second-growth and may be quite young. In 1962, whenever Chickadees were seen feeding, notes were made on t h e i r l o c a t i o n . This resulted i n numerous observations on the Black-Capped and much fewer on the Chest-nut-Backed, from which these generalizations can be made. The Black-Capped Chickadee r e s t r i c t s i t s feeding almost e n t i r e l y to deciduous trees during the breeding season. While conifers are commonly entered, i t i s only because they happen to be i n the bird's l i n e - o f - t r a v e l . Only three is o l a t e d feeding attempts i n conifers were observed. S. Smith (per-sonal communication) has seen Black-Capped Chickadees occasionally feeding i n conifers during the summer i n the Vancouver area. A l l types of deciduous growth, from shrubs to mature trees, were u t i l i z e d . No impression of prefer-ences for particular height classes or species was obtained, -60-th ough these may e x i s t and change throughout the season. These birds alsmot invariably follow the general rule of con-f i n i n g t h e i r feeding a c t i v i t y to the bottom half of the foliage of whatever they happen to be in - whether t h i s i s a 4 foot high brush tangle or a 45 foot high alder stand. The upper canopy of a stand, or the crown of more iso l a t e d trees i s very r a r e l y v i s i t e d , though feeding up to 3/4 height i s occasional. Ground feeding i s very rare. The Che stnut-Backed Chickadee i s commonly found high i n t a l l conifers, but. i s not confined to them and may feed i n deciduous growth from low brush p i l e s ( r a r e l y observed) to t a l l e r trees. Here i t s ' manner of feeding i s i n d i s t i n g u i s h -able (to casual observations) from that of the Black-Capped, though i t may use a l l parts of the f o l i a g e . So, while the foraging habits of these two species i n t h i s region do overlap, a l l observations indicated that the amount of overlap i s n e g l i g i b l e . They were never seen f o r -aging together during either summer. On A p r i l 29, 1962, a pair of Black-Capped Chickadees was being followed (movements are traced on F i g . 6 ) . They were p a t r o l l i n g t h e i r t e r r i t o r y and the male was giving t e r r i t o r i a l c a l l s at high frequency and i n t e n s i t y . Moving slowly along the top of the logged-over ridge, the pair stopped at "X", and here the male, perched i n the top of a small bush, gave the t e r r i t o r i a l c a l l repeatedly f o r several minutes. No other Black-Capped could be heard and there were no immediate neighbouring pairs along t h i s boundary. The pair then started down o f f the ridge, the male s t i l l c a l l i n g , to follow page 60. and i n doing so passed within 50 to 75 feet (15 to 23 m.) of 2-1-2 (Plate 9 ; Tables 6 and 7 ) , at the top of which two Chestnut-Backed Chickadees were excavating a cav i t y , repeat-edly changing places at i t and keeping up an excited c a l l i n g . Each p a i r apparently ignored the other, the Black-Capped Chickadees continuing on past, the male s t i l l c a l l i n g , u n t i l they entered the heavily wooded borders of the narrow road below and were l o s t . Their f i r s t nest (2-1-7) was l a t e r located i n a low birch stump, 520 feet (159 m.) away from 2-1-2. The eight young fledged before May 30, probably on May 2 9 , and allowing 37 days from the laying of the f i r s t egg (Brewer, 1 9 6 l ) , on A p r i l 29 the nest, probably contained seven eggs. The Chestnut-Backed Chickadees were never seen i n the area again and t h e i r cavity was never completed. Later the Black-Capped Chickadees (which were by then color-banded) raised their second brood i n 2-1-2, digging a new cavity l g feet (0.5 m.) below the incomplete one, and i l l u s -t r a t i n g that the same portion of the same snag released ex-cavating behavior i n both species. l e t the two p a i r s , at a time when t e r r i t o r i a l i s m was intense, each behaved as though the other did not e x i s t . Red-Breasted Nuthatch The Red-Breasted Nuthatch was found to be one of the commonest hole-nesting species, with 15 nests located, 13 on the Reservation. In 1 9 6 l , three nests were located: 1-11 - On June 15, young were being fed, and the nest was empty on June l i t . I t was not used again that season, - 6 2 -or i n 1962. W-4 - Two broods were reared in t h i s nest with young being fed early i n June, and late in July. The cavity-bearing portion of the tree f e l l before the 1962 summer. 2-1 - This hole was i n the process of being excavated on June 14, the date of discovery, and the two adults i n -volved were accompanied by at least three recently-fledged juveniles. The location of the season's f i r s t s i t e i s un-known. Excavation had probably started on the 13th and the l a s t young b i r d l e f t the nest on July 26, 44 days l a t e r . The s i t e was unused i n 1962. These three nests i l l u s t r a t e three p o s s i b i l i t i e s . A si t e may be used f o r two broods in one-season, for the f i r s t brood only, or f o r the second brood only. The nests located during the second summer generally followed the timing pattern established from the three 196l nests, with excavation occurring i n la t e A p r i l and early May, and fledging of the two broods around the f i r s t t h i r d of June, and the l a s t h a l f of July. Table 8 presents information on the types of nest s i t e s chosen. Bent (1948) contains additional data. Preparation (or selection) of the nest s i t e occurs in l a t e A p r i l and early May, although t h i s generalization i s based on a small number of observations. There i s an isolat e d record from Vancouver Island i n the B.C.N.R.S. of excavation by a pair on March 17. T e r r i t o r i a l i s m was manifested in the Nuthatch's (pre-sumably the male) habit of c a l l i n g loudly for short i n t e r v a l s TABLE 8. RED-BREASTED NUTHATCH NESTS NEST TREE TREE HOLE NUMBER SPECIES HEIGHT HEIGHT DBH DHH SOURCE REMARKS 2-1 Birch 50* (15.2) 42* (12.8) 11.3 (28.7) 3* (7.6) RBN 1961. Upper NE slope. Newly excavated f o r second brood. 1-11 Birch 20* (6.1) 19* (5.8) 7.8 (19.8) 5.9 (15) U (typ) 1961. Upper NE slope. F i r s t brood. W-4 Alder 36* (10.9) 30* (9.1) 16.5 (41.9) 6* (15.2) U (typ) 1961. Lower SE slope. Tw© br©ods. 15-15 D. F i r 70* (21.3) 55* (16.8) — — U (typ) 1962. Upper W slope. Tw© broods i n two d i f f e r e n t nearby c a v i t i e s . 2-12-1 B. Maple 50* (15.2) 40* (12.2) 18 (45.7) 5.5* (14) RBN 1962. Upper wooded (edge). Abandoned, perhaps for 12-26. 12-26 B. Maple 50* (15.2) 48* (14.6) 13.3 (33.8) 6.5* (16.5) DW and " RBN 1962. Upper open portion. One breed. 1-2 D. F i r 20* (6.1) 18* (5.5) - - RBN 1962. Upper SE sl©pe. F i r s t brood. 2-W-l B. Maple 50* (15.2) 45* (13.7) 19.2 (48.8) (12.7) U 1962. Lower SE slope. Second(?) brood. 2-H-2 D. F i r 80* (24.4) 35* (10.7) 39 (99) 28* (71.1) U (typ) 1962. Lower W slope. Second(?) brood. 2-1-5 D. F i r 50* (15.2) 49* (14.9) - - U (typ) 1962. Upper NE slope. F i r s t brood. TABLE 8 . Continued NEST NUMBER TREE SPECIES TREE HEIGHT HOLE HEIGHT DBH DHH SOURCE REMARKS 1-20 D. F i r 45* (13.7) 42* (12.8) 19 .5 (49.5) 13* (33) U (typ) 1962. Upper SE slope. F i r s t brood. 2-8-1 B. Maple 50* (15 .2) 45* (13.7) 13.5 (34.3) 8* (20.3) U (typ) 1962. Upper wooded por tio n s . Two broods. HPH 15 Miles D. F i r 55* (16.8) 54* (16.5) - - U 1962. HPH 40 Miles Lodgepole Pine 55* (16.8) 15* (4.6) 12.7 (32.3) 11* (28) U 1962. L i v i n g tree. - 6 5 -from the tops of trees in i t s t e r r i t o r y , and sometimes from the nest, snag i t s e l f . Occasionally, series of c a l l s a l t e r -nating from two separate areas were heard. These were the only c o n f l i c t s (presumed) of any type that Nuthatches were found engaged i n . L i k e l y the observed spacing of the nests was the r e s u l t of t e r r i t o r i a l i s m but t h i s apparently was determined before observations began at the end of A p r i l . Ten pairs occurred on the study area in 1962, giving a popu-l a t i o n density figure of 2.5 pairs per 100 acres. Nuthatches did not nest on the experimental area, though they had done so i n previous years. They were f r e -quently heard i n the denser timber in the distance. While.deciduous trees are frequently used f o r nesting purposes (Table 8), and occasionally f o r feeding, conifers are much more commonly used when foraging. This association i s very d e f i n i t e i n t h i s area (of. G r i n n e l l and M i l l e r , 1944)* Brown Creeper This b i r d i s a resident of the area (Brooks, 1917; Brooks and Swarth, 1925; Munro and Cowan, 1947), and a pair spent the summer of I960 i n the wooded upper portions of the Reservation, although no nest s i t e was found (Horvath, 1963). The sighting of a juvenile on June 22, 196l, i s the only observation from the Reservation i n the last two summers. Four of 11 nests from southwestern B r i t i s h Columbia and Vancouver Island (B.C.N.R.S..) were i n holes in trees; the other 7 were b u i l t behind loose bark. Winter Wren Regional l i s t s agree on i t s commonness in the Hope -66-area - Horvath (personal communication) confirms t h e i r presence i n winter. An established male probably spends the year on the same area - Armstrong (1956) found that t e r r i t o r y was defended p r a c t i c a l l y throughout the year. As the species was of minor i n t e r e s t , l i t t l e e f f o r t was expended i n marking in d i v i d u a l s and determining t e r r i t o r i a l boundaries. Those males i n the study area (at least 5 i n 1962) were sep-arated nat u r a l l y by habitat discontinuity, which makes the population density f i g u r e of 1.25 breeding males per 100 acres r e l a t i v e l y meaningless, as the birds are much more p l e n t i f u l in larger areas of better habitat near the Reser-vation. The following example i l l u s t r a t e s not only the effect of habitat discontinuity, but also a possible influence of t e r r i t o r i a l i t y upon the bird's spacing. A small closely wooded area at the bottom of the south-east slope represented preferred Wren habitat, and was occu-pied by one male and ;an unknown number of females during the summers of I960, 1961, and 1962, with three, two and one breeding nests located i n i t during those years. Only during the 1962 summer was an adjacent area ( s l i g h t l y higher on the slope) occupied, with one breeding nest located. Other un-located nests may have existed in either t e r r i t o r y . The l a t t e r t e r r i t o r y , with a r e l a t i v e l y sparse and unvaried vegetation on a stony dry slope (Plate 3), must have repre-sented poor habitat, and the f a c t that the two males could hear each other cannot be without significance. Winter Wrens did not nest on the experimental area "F", although the habitat appeared suitable at the densely wooded - 6 7 -northern end, where a Wren was seen on May 1 - the only observation. Preferred habitat i n t h i s region i s found under mature dense stands of mixed coniferous and deciduous trees, where the high moisture and extreme shade promoted by the heavy canopy contribute to the environmental constancy experienced by the forest f l o o r where the Wrens l i v e , which frequently possesses a good deal of l i t t e r ( f a l l e n trunks and branches) and a heavy moss layer (Horvath, 1963; P h i l l i p s and Black, 1956). Winter Wrens were found at almost every area surveyed along the western h a l f of the Hope-Princeton Highway, i l l u s -t r a t i n g their widespread occurrence i n t h i s region. A t o t a l of 25 nests 'was located, mostly by Horvath, during the 1960-1962 summers, and they may be c l a s s i f i e d as follows: i n tree c a v i t i e s : 1 breeding nest , 1 a u x i l i a r y nest .ary i n s p l i t upright trunk: 1 breeding nest on low conifer branches: 4 breeding nests 1 a u x i l i a r y nest 11 nests of unknown status i n the ground (banks): 4 breeding nests 1 a u x i l i a r y nest 1 (unknown) nest for a t o t a l of 25 . Table 7 includes measurements of the tree cavity used for breeding. Found by Horvath i n I960, i t f e l l after the 'Horvath (1963) l i s t s three additional tree-hole nests that remained unknown to the author. An a u x i l i a r y nest remained unlined (Armstrong, 1 9 5 0 ) . -68-breeding season, eliminating the p o s s i b i l i t y of re-use. No measurements were obtained from the second cavity. Discov-ered by Horvath i n 196l, i t was destroyed before inspection. The Wren cannot excavate a tree cavity, nor does i t require one. Published accounts (as Armstrong, 1955, 1956) indicate that the bi r d i s an opportunist regarding the place-ment of i t s nest, and i t i s undoubtedly due to t h i s behavior-a l p l a s t i c i t y that tree holes are used. A widespread hole-nesting habit could never be expected, for i n the habitat types u t i l i z e d by the Wren i n t h i s area, short hole-bearing snags are rare. This i s due not only to the uncommonness of short snags, but also to the lack of birds that would dig holes i n such s i t u a t i o n s . Horvath (1963) suggests that the Wren places i t s nests only i n situations providing precise microclimatic conditions. I f inve s t i g a t i o n , currently under-way, should show th i s to be the case, the number of tree c a v i t i e s a c t u a l l y used by the Wren i n an area w i l l l i k e l y be much less than the t o t a l number of ca v i t i e s p o t e n t i a l l y a v a i l a b l e . Armstrong (1955; 1956; 1958) states that the s u i t a b i l i t y of a habitat, primarily as r e f l e c t e d i n the a v a i l a b i l i t y of food, determines the "vigor" of the resident male. Propor-t i o n a l to the male's "vigor" i s the size of the t e r r i t o r y (perhaps), the number of nests he w i l l b u i l d , the number of females he w i l l serve, and the number of broods (1 or 2) raised i n a season by each female. Up to 12 nests may be constructed i n a year by one male, though 6 i s the average, and poorer t e r r i t o r i e s may contain l e s s . Usually a new nest -69-i s used for each brood. Apparently the analysis of the Wren's breeding biology i n any particular area i s somewhat involved. Generalizing from the available data, in t h i s region a f i r s t brood i s out of the nest by the t h i r d week of May (or e a r l i e r ) , and a second fledges i n the f i r s t h a l f of July. Bewick Wren On June 16, 1962, an adult and three young were seen together i n the Riverside Study Area, but a nest s i t e was not located. The species was also • recorded once in the Chapman Road Study Area. Their multiple breedings (Bent, 1948) start e a r l y - young were being fed i n a nest at White Rock, -B.C., on A p r i l 19, 1961. Of 19 records i n the B.C.N.R.S., 5 nest s i t e s were i n c a v i t i e s i n low stumps, 2 were in b i r d boxes, and 12 occupied what can only be des-cribed as miscellaneous crevices. Absent from the main study areas, i t s status as a nest s i t e competitor remains unknown. Western Bluebird The single record from the 1960-1962 summers was made by Horvath on June 5, 1962. Brooks (1917), considered i t a " f a i r l y common breeder, i n the Valley", and Munro and Cowan (1947) c a l l i t an abund-ant summer v i s i t a n t to the Puget Bound Lowlands b i o t i c area (with a few wintering). There are no records from the Fraser Valley i n the B.C.N.R.S. and at present i t i s e s s e n t i a l l y absent from t h i s area (Cowan, personal communication). Mountain Bluebird During i 9 6 0 , two pair s frequented the upper portions -70-of the Reservation from approximately May 13 to July 8, perhaps breeding, although nest s i t e s were not located (Horvath, 1963). A c t i v i t y centered around the open grassy areas at the top of the south slope. In the following two breeding seasons, only one record from the Hope area was obtained, that of a male seen near the c i t y during a v i s i t on A p r i l 9, 1962. Non-Avian Holes-Users Various, small mammals and insects may inhabit c a v i t i e s in trees, but t h i s has e l i c i t e d no more than scattered re-ferences i n the o r n i t h o l o g i c a l l i t e r a t u r e . An evaluation of the possible competitive effectiveness of the animals to be described i s not possible, though a competitive influence could be exerted by the destruction of adults, young, eggs, or nests; by occupancy of a cavity; or by f i l l i n g the cavity with material so that i t becomes unusable f o r some potential avian occupant. Insects - (Hymenoptera) Single large bees were found i n two small c a v i t i e s ; one on the Reservation i n 196l, and one on the Riverside Study Area i n 1962. Hornet-like hymenoptera were found at four c a v i t i e s ; two small ones (1962), and two of unknown size (1961). Large papery nests f i l l e d the two former c a v i t i e s - none was close-l y investigated. Mammals Chipmunk - Two young chipmunks were seen looking out of an inaccessible medium-sized hole on the Reservation on -71-June 21, 1961. Specific i d e n t i f i c a t i o n was not made. Douglas Squi r r e l - Chickarees were observed at four tree c a v i t i e s , two during each summer, a l l on the Reservation. Cowan and Guiguet (I960) state, "Nests are usually i n c a v i t i e s of dead trees Outside nests b u i l t in the tops of coni-ferous trees are less common." As squirrels are common, during 196l a l l observations made on these and other cavity-inhabiting mammals were recorded, but t h i s procedure yielded nothing and was abandoned. A l l four instances of cavity occupancy are based on single observations. Each snag was subsequently v i s i t ed several times, but the animals were never flushed again. The sight, of a chickaree on the ground near t h e i r nest (which contained young) e l i c i t e d an alarm reaction from a pair of Black-Capped Chickadees, though the s q u i r r e l did not climb the nest snag. Flying S q u i r r e l - These nocturnal animals were the most frequent non-avian hole occupant detected. Three holes were found in use i n 1 9 6 l on the Reservation - one of which contained young squirrels on July 21 . In 1962, Woodpecker holes used by Flying Squirrels were found in the Chapman Road Study Area ( l ) , i n the Riverside Study Area ( 2 ) , and at Pinewoods on the Hope-Princeton Highway ( l ) . In addition, occupied nests i n tree branches were discovered on the Reservation, one during each summer. Deer Mouse - The destruction of a Black-Capped Chickadee brood i n 1 9 6 l has been t e n t a t i v e l y attributed to t h i s species. A small Woodpecker cavity ( l i k e l y a Downy roost) low - 7 2 -i n a birch stub on the Reservation, that had been excavated during the winter of 1961-1962, prior to March 18, when i t was discovered, remained unused u n t i l a deer mouse b u i l t a bulky nest in i t sometime between May 8 and 16. The meagerness of these data would suggest that these animals would play a negligible r o l e as nest-site competitors. Tree c a v i t i e s are indispensible to none of them. No further conclusions seem possible. The Elimination Experiment This procedure was conceived as a possible means to detect nest-site competition. . Design - A separate area, d i s t i n c t from but comparable to the Reservation, would be thoroughly surveyed for hole-nesting birds as early in the breeding season as possible, to obtain data on the numbers, t e r r i t o r i e s , i n t e r - s p e c i f i c r e l a t i o n s h i p s , and e s p e c i a l l y the nest- s i t e s , of the resident species. As soon as such information was reasonably complete, a l l the hole-nesters would be shot, t h i s also being done as quickly as possible. Special attention would then be given to the detection of new a r r i v a l s and t h e i r p o s i t i o n i n g . I f possible, these would also be shot, and so- on. Observations on the undisturbed control area would be continued throughout. Some of the following r e s u l t s could be expected: no re-action at a l l ; new a r r i v a l s establishing themselves at holes used by t h e i r predecessors, or investigating new holes i n the same t e r r i t o r i e s ; neighbouring t e r r i t o r i e s being expanded into the vacant areas. Depending upon the movements, and -73-the species involved, these r e s u l t s could then be i n t e r -preted in terms of nest-site competition; i n t r a s p e c i f i c t e r r i t o r i a l i s m . ; i n t e r s p e c i f i c t e r r i t o r i a l i s m (which i n such a l i m i t e d experiment would have to be detected before the shooting); or the absence of any of these. Explanations not involving competition could also be advanced. Execution - Area "F", d i s t i n c t from, but s i m i l a r to, the Reservation, was surveyed f o r 26g hours on seven days between May 1 and 12, with hole-ne sters, t h e i r t e r r i t o r i e s and nests, being noted. The following species were present': Sparrow Hawk - One pair ranged a l l over and beyond the study area. They were s i t e - s e l e c t i n g on May 10. Hairy Woodpecker - A pair was feeding young at a nest near the southern boundary on May 1. Another pair made v i s i t s i r r e g u l a r l y to the northern portions, but t h e i r n e s t - s i t e , presumably off the area, was unknown. Downy Woodpecker - A pair occupied a .territory in the northern portions, and nest excavation had just started on May 10. Red-Breasted Sapsucker - A pair started two ca v i t i e s in a tree in the northern half of the area. Excavation had commenc ed on May 1. Pileated Woodpecker - Individuals, presumably members of a pa i r , were seen or detected regularly, but ranged far beyond the study area's boundaries. Red-Shafted F l i c k e r - One pair ranged a l l over the study area, and were s t i l l s i te-sele ctimg on May 15. Their nest cavity was not discovered u n t i l May 19, when excavation was - 7 4 -i n progress. Winter Wren and Red-Breasted Nuthatch - Single records of these species were obtained within the study area - on May 1 for the former species, and March 31 for the l a t t e r (during a preliminary t r i p ) . Black-Capped Chickadee - One pair held a t e r r i t o r y i n the north half of the area, and had a mutual boundary with another pair at one point only. Their nest was not found, but the pair's behavior indicated incubation was l i k e l y in progress on May 10 . -Thus a t o t a l of 16 hole-nesting birds inhabited the 80+ acres of area "F". Elimination, of these birds was begun on May 14, but hunting conditions, to which both the behavior of the birds and the nature of the habitat contributed, were so d i f f i c u l t that t h i s phase was not abandoned u n t i l June 7, by which time 10 of the o r i g i n a l 16 hole-nesters had been collected, with a time expenditure of 56g hours over 14 d i f f e r e n t days. The c o l l e c t i o n s were made as fol l o w s : May 14 - the nesting pairs of Hairy Woodpecker and Red-Breasted Sapsucker were collected. May 15 - the male Downy, and the Chickadee pair were collected. May 16 - the female Hairy of the "northern" pair was taken. May 28 - the Red-Shafted F l i c k e r pair was collected. This l e f t a male Downy, a male Hairy, a p a i r of P i l e a t -eds, and a p a i r of Sparrow Hawks on the area. -75-The male Downy apparently deserted, and never returned to the n e s t - s i t e , which was often watched during the late evening and early morning. Elimination of the pair was apparently accomplished. The male Hairy of the "northern" pair continued to roam t h i s portion of the study area at irregular i n t e r v a l s . An opportunity for c o l l e c t i n g never occurred. The Sparrow Hawks were too wary to permit the r e l a t i v e l y close approach necessary f o r c o l l e c t i n g , and eventually nest-ed successfully on .the area. During the c o l l e c t i n g period, time was not available for the intensive hunting that would have been necessary to shoot these birds. Though they were seen at t h e i r nest as early as May 14, the true status of t h i s cavity was not r e a l i z e d u n t i l much l a t e r . The Pileateds were so wary, and t h e i r occurrences so unpredictable, that an opportunity f o r c o l l e c t i n g never pre-sented i t s e l f . After cessation of the c o l l e c t i n g , observations were continued up to August 24, e n t a i l i n g ; an additional 32$. hours on 9 days. Results - Details of the replacements are given in the sections devoted to the appropriate species, and are summar-ized here. Hairy and Downy Woodpeckers - No apparent reaction re-sulted from the elimination of these bi r d s . The Hairy's breeding season was so far advanced that replacement would be u n l i k e l y . - 7 6 -F l i c k e r - A mated p a i r , of which the male was ex h i b i t -ing intense t e r r i t o r i a l i s m , was found on June 7 excavating a cavity w e l l w i t h i n the range of the pair that had been c o l -lected on May 2 8 . Sapsucker - A mated pair was f i r s t seen on June';3 at the nest snag of the pair that had been shot on May 14« The birds were s t i l l at t h i s snag a week l a t e r , but were excav-ating i n a dif f e r e n t snag on June 22. Their breeding behav-i o r appeared abnormal, and no successful nest was discovered. Chickadee - On May 16, one day after the resident p a i r had been eliminated, the neighbouring male was detected w e l l within the now-vacant t e r r i t o r y , a portion of which was used by t h i s p a i r up to at least June 7. The rest of the vacant t e r r i t o r y remained unused up to this time. Conclusions - This experiment did not demonstrate that nesting c a v i t i e s were i n great demand among the hole-nesting b i r d population. I t did suggest, f or three presumably r e s i -dent t e r r i t o r i a l i s t i c hole-nesting species, that the exis-tence of established birds i n a portion of suitable habitat i n some way, presumably through t e r r i t o r i a l i s m , prevented the establishment of other pairs of the same species. That replacement occurred in two species suggests the existence of a f l o a t i n g population of p o t e n t i a l l y breeding birds, a l -though the p o s s i b i l i t y of movement of nearby pairs cannot be overlooked i n t h i s small-scale work. The fact that the new Sapsuckers attended the holes excavated by t h e i r predecessors does not indicate nest-site competition, but more than l i k e l y merely i l l u s t r a t e s a s i m i l a r i t y in habitat selection processes -77-(cf. Stewart and A l d r i c h , 1951; Hensely and Cope, 1951). The Environmental Resources A consideration of nest-site competition requires that some sort of evaluation be placed upon the types (and numbers of each type) of ca v i t i e s a v a i l a b l e . As an i n i t i a l step i n th i s process, i n the l a t t e r half of the 1961 season a survey was made of selected areas of the Reservation, which were chosen so as to be representative of a l l the vegetational types present. Each segment was traversed systematically, so that no snag of any size went unnoticed; each one being inspected from a l l sides. Every snag that bore an entrance to a possible, cavity was numbered, and positioned on a map. The great majority of these holes were not e a s i l y inspected, so that whether they represented actual c a v i t i e s or not re-mained unknown. Approximately one-half of the Reservation was surveyed i n t h i s manner, as were some smaller sections of adjoining woodland. A t o t a l of 212 snags bearing one or more holes was located on these areas. In order to establish a r a t i o of hole-bearing snags to cavity-bearing snags, during the l a t t e r part of the 1962 summer the following sampling procedure was i n i t i a t e d . Sixty snags were picked at random, and the status of those i n which the holes were not e a s i l y inspected was to be determined by cutting down the snag. This rather time-consuming process was started, but the following considerations led to i t s abandonment. I t was evident from the types of hole-nesters present - 7 8 -i n the area, t h e i r r e l a t i v e abundances, and thei r ecological demands, that there was very l i t t l e chance f o r nest-site competition to be occurring. In a sit u a t i o n where the f a r greater majority of hole-nesters present were capable of excavating t h e i r own nesting c a v i t i e s , often doing so at the sta r t of each breeding season, and usually lo c a t i n g t h e i r nests i n areas often glutted with potential cavity-bearing snags, i t would be expected that a large surplus of unused holes would exist. This i s precisely what i s happening i n the study area. Hole mortality due to the f a l l i n g of snags i s not extensive enough to prevent, the formation of a large surplus of c a v i t i e s , e s p e c i a l l y since many of the larger snags, which are very long-lived, eventually bear a whole series of c a v i t i e s that are apparently going unused. (Emphasis i s given to "snags" because nests were never found to be d r i l -l e d through l i v i n g wood, and a l i v i n g tree usually bore a cavity only i n a large branch or portion of the trunk that had died. Very few c a v i t i e s were found i n l i v i n g trunks, where they had originated due to a combination of branch loss and rot.) Being able to state how many holes are t h e o r e t i c a l l y available per hole nester, when the bi r d i s very l i k e l y not going to use any of an obvious surplus of holes, i s essen-t i a l l y meaningless. However, in the course of previous work, the status of the holes i n 22 of the 60 snags had been determined, either by d i r e c t observation, by seeing animals entering them, or by inspecting the snags aft e r they had f a l l e n . Nineteen of the 22 snags bore holes representing actual c a v i t i e s (of -79-several type and s i z e s ) . Two of the 19 also had "false s t a r t s " , one i n one snag, two in the other. Even though the means by which these determinations were made obviously fav-ored the discovery of the true c a v i t i e s i n the sample of 60, the resul t s supported the conclusion,' that the environment carries a surplus of c a v i t i e s . The Town Study Area In 196l, regular observations d i d not begin u n t i l June 18, when nesting was w e l l underway. This delay was occasion-ed by the following situation.. There are accounts of t r e e -hole nesting Violet-Green Swallows, and t h i s , in conjunction with t h e i r commonness,,led to the expectation that they would be present as a hole-nesting species on or near the Reserva-t i o n . I n i t i a l l y l i t t l e importance was attached to the large mixed flocks of swallows often seen coursing over the marsh, lakeshore, or upper slopes. While t h e i r r a r i t y on the upper central portions of L i t t l e Mountain was noticed, no importance was attached to i t , u n t i l , as time passed, two fa c t s became obvious: swallows were present i n numbers over the marsh only i n times of poor weather, and nesting a c t i v i t i e s were well underway i n the town with nb such behavior being observed elsewhere. The survey i n the town was then i n i t i a t e d . Violet-Green Swallow This species has bred in the v a l l e y only since 1887 (Brooks, 1917), and i s now one of the commonest hole-nesters of the area. Observations on t h i s species during the f i r s t summer were too l a t e i n the year to detect any competition which might -80-have existed during the s i t e - s e l e c t i o n process, and only-provided some information on the timing of the breeding events, and on the nest-site types u t i l i z e d by t h i s species. Twenty-six occupied nests were located i n the town in . 1 9 6 l , of which 25 were i n crevices, v e n t i l a t i o n holes, etc., i n huildings, usually under the eaves. The remaining nest was i n a b i r d box. The f i r s t f l e d g l i n g s were seen on July 7, and most of the nests.were empty by the end of the second week i n July. -One nest contained young on July 28, the l a t e s t date of t h i s season. In 1962, the weather throughout the spring and early summer was generally cloudier and cooler than during the previous year. This was r e f l e c t e d i n the timing of the bird's breeding cycle (cfw Mayhew, 1958; Johnston and Hardy, 1962) . In the University area. (Vancouver, B.C.), the f i r s t Viblet-Green Swallows were seen ..on March 17, 1 9 6 l , but not u n t i l March 29 i n 1962 (personal observation). No swallows were seen on March 1 8 , 1 9 6 2 , when a t r i p was made up the v a l l e y , and the town of Hope and i t s surroundings were surveyed for several hours. Of interest was an observation made casually near Vancouver on March 30, 1962, early on a clear, sunny morning. Two Violet-Green Swallows, male and female, were seen, f l u t -tering up to., and c l i n g i n g at, a knothole under the eaves of a b u i l d i n g . The next day a t r i p to Hope was possible, work starting, at 1'.30 A.M. on a cloudless day. Violet-Green Swallows were present i n the town and s i t e selection was - 8 1 -proceeding at high i n t e n s i t y , with a great amount of chatter-ing, f l y i n g around buildings, "and f l u t t e r i n g to investigate possible s i t e s . A c t i v i t y was so concentrated around buildings that there can be l i t t l e doubt that they represent a primary potential source of nesting s i t e s . Johnston and Hardy (1962) estimate that 25 percent of returning Purple Martins are paired when they arriv e at the breeding s i t e s , and that nearly a l l the birds a r r i v i n g i n the f i r s t migratory wave are paired. Eleven of twenty-three notebook entries from March 31 , 1962, r e l a t i n g Violet-Greens to buildings or areas, refer to pa i r s . Considering that pairs may j o i n f l o c k s f o r a while, as when feeding, and that single birds may represent a p a i r , i t would appear that the p a i r , i f not already established, i s quickly formed after a r r i v a l , and that many of the birds were paired at t h i s time. There ex i s t s the p o s s i b i l i t y that the birds seen in late March are transients, eventually moving on to other breeding grounds, as Edson (1943) implies, but engaging in preliminary breeding a c t i v i t i e s as they pass through suitable habitat. This undoubtedly applies to some of the birds seen in the area, but whether members of a pa i r apparently very interested i n a s i t e should be s i m i l a r l y thought of i s more questionable. As observations were short, and no birds were marked, no evidence can be presented on t h i s point, on the permanence of the p a i r bond, or on the degree of year-to-year s i t e - f a i t h f u l n e s s present i n these birds. However, i t would appear strange that such intense a c t i v i t y by so many birds would r e s u l t i n only a f a m i l i a r i z a t i o n with the -82-processes involved i n site-selection and pair-formation. Nests were l a t e r b u i l t i n many of the sites, investigated at t h i s time. Johnston and Hardy (1962) theorize that the pro-curing of a nesting s i t e i s an important factor influencing the early spring a r r i v a l of the Purple Martin, and assume that the general time of a r r i v a l i s genetically determined. L i k e l y the same factor is operative with these swallows, and many of the birds seen at t h i s time probably remained to breed. In any case, the primary purpose of the birds upon a r r i v a l on summer range i s to lay claim to a mate ( i f not already done) and a nesting s i t e , even though they w i l l not lay eggs f o r another two months. Observations continued in the c i t y u n t i l 2 P.M. on March 31, and from 1 P.M. on no swallows were seen. None was found over the marsh by the Reservation (Fig. 3 , a favor-i t e feeding area i n poor weather) shortly after 2 P.M. The c i t y was not v i s i t e d again u n t i l 5:45 P.M., at which time the sun was just setting behind a mountain, and a large flock of swallows (unidentified) was seen high over the nearby Fraser i t i River. A nest s i t e at whitrh a pair of Violet-Green Swallows had been observed e a r l i e r i n the day was then watched u n t i l 6:30 P.M., when quite dusk, without a sign of swallows i n the v i c i n i t y . Apparently the swallows had not entered the c i t y to roost at the newly-chosen nest s i t e s (though much more observation i s needed). The marsh was again v i s i t e d in the semi - dark ne ss, and the borders stoned, without r e s u l t s . These observations might be taken as i n d i c a t i v e of the swallows' transient status, with the i n t e g r i t y of the f l o c k - 3 3 -being maintained f o r further migration. However, Johnston and Hardy (1962) noticed that the i n t e n s i t y of breeding pre-l i m i n a r i e s in the Purple Martin decreases toward n i g h t f a l l , with possible disintegration of new pair-bonds and residence-bonds that seemed strong during the morning - something the same may be happening here. Detailed l a t e r are the movements of feeding f l o c k s (involving up to f i v e species of swallows) i n times of poor weather that leave the town deserted f o r hours at a time. This i s mentioned, not as an explanation for the above events, but to emphasize the gregariousness and mobility that undoubtedly contributed to them. A t h i r d t r i p was made to Hope on A p r i l 9 , work starting at 6:30 A.M. on a cold rainy day - the showers continuing into the early afternoon. No swallows were seen i n the town during the day, or over the marsh when i t was v i s i t e d at 10 A.M. Whether they had l e f t to continue migration, or to v i s i t more suitable feeding grounds, i s unknown. Regular observations began on A p r i l 29, and whenever possible the presence of swallows over the marsh was noted. A b r i e f consideration of these weather movements w i l l be inserted here, since the Violet-Green was the commonest swallow in the town. In 1 9 6 l , systematic observations were not i n i t i a t e d u n t i l June 18, which was too la t e for useful work on weather move-ments. Noted casually e a r l i e r i n the season was the occur-rence of mixed flocks over the marsh only in times of poor weather. These birds were never seen expressing interest i n the holes v i s i b l e in the snags around the marsh. The possible importance of these movements i n terms of the Violet-Green Swallow's effectiveness as a nest-site compe-t i t o r was rea l i z e d , and i n 1 9 6 2 they received more attention. When a swallow f l o c k was seen over the marsh, the t o t a l number and species composition was estimated (greater accuracy was impossible to achieve - the birds f l y constantly), and the time and general weather conditions were noted. Whenever the weather was poor, with r a i n , and often wind and compara-t i v e l y low temperatures, a flock would be feeding over the marsh, usually just, above the vegetation. Up to the t h i r d week of May, usually 7 5 to 1 0 0 birds were involved; those movements occurring i n l a t e May and June were composed of 5 0 to 7 5 i n d i v i d u a l s ; and i n J u l y about 2 5 birds would res-pond to the occasional periods of bad weather. Rough-Winged were the most common swallows during the f i r s t two periods, with Violet-Greens contributing 2 0 percent to 5 0 percent of a day's t o t a l . Sometimes up to one-third of the birds seen during May were Tree Swallows - l a t e r t h i s species was represented by but a few individuals. Barn Swallows appeared i n small quantities in late May and early June; the remainder of the summer t h i s species, arid the C l i f f Swallow, contributed very l i t t l e to the t o t a l s . One Bank Swallow was seen on June 3. July movements were composed almost e n t i r e l y of Violet-Greens. In the absence of more quantitative data, the following examples are offered as i l l u s t r a t i o n s of this phenomenon. On May 3, i t rained throughout the morning, and i t had been raining most of the previous week. Periods of clearing - 8 5 -were r e s t r i c t e d to a couple of hours - usually l i g h t d r i z z l e and showers alternated with the heavier r a i n more common during ;the night and early mornings. An estimated 150 swallows (90 percent Violet-Green Swallows) were feeding over the marsh at 11 A.M. , when i t began to clear. At 1 P.M. and 3 P«M. (rain again) t h i s s i t u a t i o n was apparently unchanged. Between these l a s t two checks, every area i n town where swallows might be expected was v i s i t e d , with nega-t i v e r e s u l t s . On May 7, the temperature was near-freezing when the sun f i r s t began to break through the clouds at 7 A.M. On the edge of the town study area, a f l o c k of 56 Violet-Greens was found on telephone wires - another flock of 15 was simi-l a r l y situated a few hundred feet away. The birds were s i t -t i n g motionless, occasionally c a l l i n g , with heads drawn i n and feathers greatly f l u f f e d . As the sun's warmth increased, the birds became more active, c a l l i n g and making short f l i g h t s to change p o s i t i o n . The a c t i v i t y increased, and soon birds started to leave the f l o c k , which ceased to ex i s t a few minutes after 7• The weather remained fine, and throughout the day pairs attended t h e i r chosen nest s i t e s . Besides i l l u s t r a t i n g the bird's response to th i s weather, the occur-rence of fl o c k s under these conditions suggests that the birds do not roost at the nest s i t e . Unfortunately the f l u f f e d feathers of the s i t t i n g b i r d s made sex determination d i f f i c u l t and unreliable. The morning of May 8 was sunny and no swallows were over the marsh at 9:30 A.M. I t soon clouded over, and r a i n -86-started around noon, continuing into the evening. When the marsh was checked at 4 P.M. , about 100 bi r d s , mostly V i o l e t -Greens, were feeding there. On May 9, two pair s each of Rough-Wings and V i o l e t -Greens were s i t e - s e l e c t i n g at a rock face by Schkam Lake (Plate 10). The level of a c t i v i t y was high, and about 40 minutes had been spent i n observation when a sudden heavy 10 minute shower hit the area. The birds then began coursing low over the lake surface, not approaching the nest-sites u n t i l the r a i n slewed to a steady d r i z z l e , when a c t i v i t y re-sumed as before. On May 18, when swallows spent the afternoon over the marsh, i n the evening an attempt was made to detect a move-ment into the town. At dusk, 12 swallows were seen coming from the appropriate d i r e c t i o n , s i n g l y and i n small groups, but only one was low enough to be i d e n t i f i e d as a V i o l e t -Green Swallow. Two C l i f f Swallows were seen going to roost i n a h a l f - f i n i s h e d nest. On May 24, a l i g h t r a i n f e l l a l l day, and an attempt wasq made to locate other feeding areas. About 50 swallows were at the marsh, and an estimated 60 birds were over Schkam Lake. A t h i r d favored location was at the entrance of the Coquihalla River into the Fraser River (Fig. 2), where about 40 birds were coursing low over the water. About 80 V i o l e t -Greens were i n these groups, and perhaps more were at other areas. These three areas are a l l within easy f l y i n g distance of Hope. The e a r l y morning of May 28 was c h i l l y and d u l l , and at -87-8 A.M., the marsh was su r p r i s i n g l y free of swallows. However, at 8:20, a large (60) loose flock slowly d r i f t e d down from the east, and began to break up over the marsh, the main por-t i o n seemingly moving slowly toward the town. Immediately driving into the town, only i s o l a t e d i n d i v i d u a l s , usually coursing high, could be sighted at nesting areas. Around 8:55, waiting at i t s eastern end, a slow movement into town could be detected; f i r s t a loose flock of eight, then two, then a single i n d i v i d u a l . Though too high for species deter-mination, there can be l i t t l e doubt that these birds had just been seen over the marsh. Some d e t a i l has been presented on t h i s subject because of i t s possible importance to a population of hole-nesting swallows. Lack (1956) found that food and nest s i t e re-quirements were of the greatest importance to populations of the European Swift - here probably the same si t u a t i o n e x i s t s . Johnson (1951) warns against interpreting a e r i a l insect populations i n terms of the weather conditions on a p a r t i c u l a r day, but s t i l l a tremendous influence i s present, of which Mayhew (1958) presents a br i e f summary. Poor weather, by af f e c t i n g the swallow's food supply, and causing i t to move (in t h i s case) to a more favorable source, can reduce the bird's effectiveness as a nest-site competitor. I f the i n t e n s i t y of competition was high enough, the population would suffer because t h i s f u l f i l l i n g of the more immediate needs of the i n d i v i d u a l required a temporary abandonment of the chosen s i t e , allowing members of another species to l a y claim to i t . While there was no evidence -Set-t h a t t h i s was o c c u r r i n g dur ing the s tudy , i t cou ld happen i n o ther areas , or p o s s i b l y i n t h i s area i f the p o p u l a t i o n l e v e l s of the competing s p e c i e s should i n c r e a s e (the S t a r l i n g and House F i n c h are r e c e n t a r r i v a l s ) . U n f o r t u n a t e l y i t cou ld not be determined i f r o o s t i n g occurs i n the chosen s i t e s be-f o r e the s t a r t o f s e r i o u s n e s t - b u i l d i n g i n June. Edson (1943) found t h a t t h i s of ten happened. Such a h a b i t might be important i n a competitive s i t u a t i o n . Combellack (1954) found that the f ema le , but never t h e male, roos ted i n the nes t a f t e r the s t a r t of c o n s t r u c t i o n . S u r v e i l l a n c e o f i n d i v i d u a l s i t e s i n the town at n i g h t f a l l was not c o n s i d e r e d p r a c t i c a l . A s m a l l e r p o r t i o n of the town was surveyed i n 1962 ( F i g . 2 ) . A d e f i n i t e handicap was the i m p o s s i b i l i t y o f v i e w i n g the contents of any of the n e s t s , though the a c t u a l number of n e s t i n g p a i r s can be approximated. A t o t a l o f 62 " p o s s i b l e " nest s i t e s were seen being i n v e s t i g a t e d by V i o l e t - G r e e n s . Of t h e s e , 16 were d i smi s sed f o r v a r i o u s reasons (the opening o b v i o u s l y too s m a l l ; , there was no open-i n g i n the p o r t i o n o f the b u i l d i n g be ing i n v e s t i g a t e d ; the i n t e r e s t i n the s i t e was of b r i e f d u r a t i o n , or was never de-t e c t e d (subsequently, e t c . ) . Of t h e 46 r emain ing p o s s i b i l i t i e s , 21 l a t e r conta ined young b i r d s , n e s t - b u i l d i n g or c o p u l a t i o n was observed at 7 o t h e r s , and at an a d d i t i o n a l 11 , b i r d s were seen e i t h e r e n t e r i n g or l e a v i n g the c a v i t y . C o n s i d e r i n g the known h i s t o r i e s of a l l these s i t e s , i t i s e s t imated t h a t t h e r e were between 25 and 30 p a i r s i n breeding c o n d i t i o n on the study a r e a . N e s t - b u i l d i n g was seen between May 17 and June 29, w i t h - 8 9 -the peak of t h i s a c t i v i t y occurring i n the f i r s t week of June. Very l i t t l e was seen before the end of May, when breeding a c t i v i t i e s were judged to have advanced l i t t l e over the s i t u a t i o n observed on March 31. On July 2, audible young i n a nest were f i r s t detected, and the f i r s t f l e d g l i n g s were seen on July 18. Most of the nests were empty by the fourth week of July - the l a t e s t fledging date was August 13. Allow-ing approximately 42 days from the laying of the f i r s t egg u n t i l fledging (Bent, 1942; Gombellack, 1954) > construction of t h i s nest could have been continuing during the f i r s t days of July. In comparison with the previous year, the 1962 breeding season was approximately 10 days l a t e . The obvious influencing factor was the weather - Johnston and Hardy (1962) have demonstrated that the Purple Martin's breeding i s s i m i l a r l y affected. It i s d i f f i c u l t to assess t e r r i t o r i a l i s m i n t h i s species, as certain behavioral t r a i t s , analysis of which time did not allow, tend to complicate i t . Generalizing from observa-t i o n s , active f i g h t i n g for s i t e s r a r e l y occurs - but t h i s i s only an impression. The complicating f a c t o r s re f e r r e d to arise from the f a c t that these birds may breed c o l o n i a l l y , and are always s o c i a l l y i n c l i n e d - though they do not re-quire others of t h e i r own species nearby f o r successful nesting. This potential colonialism i s probably r e l a t e d to the defense only of the'nest s i t e (possibly i t s surroundings -Gul l i o n (1947) describes t e r r i t o r i a l i s t i c defense of a f l y -way " not more than f i f t y feet long nor less than eight feet wide, " — that opened" into a large area from which -90-the b i r d s could c l imb i n t o the sky i n any d i r e c t i o n . " ) . Nes t -s i t e s e l e c t i o n i s an unknown p r o c e s s . I t seems to i n v o l v e a great d e a l of f l i g h t around the g e n e r a l a rea , o f ten i n com-pany w i t h o t h e r V i o l e t - G r e e n s , a l l keeping up a continuous c a l l i n g . I n d i v i d u a l s f l u t t e r a t , o r c l i n g near , p o t e n t i a l s i t e s . Sometimes t h i s appears to s t i m u l a t e others to f l y i n c l o s e , and the o r i g i n a l b i r d i s l o s t from s i g h t as i t j o i n s them. When an a p p a r e n t l y s u i t a b l e s i t e i s l o c a t e d , s i n g l e b i r d s or p a i r s w i l l s i t on w i r e s nearby, f r e q u e n t l y l e a v i n g to f l y about the neighbourhood, j o i n a c a l l i n g f l o c k , or course h i g h e r u p . The presence o f one or two b i r d s on a w i r e almost i n v a r i a b l y i n d i c a t e s a n e s t - s i t e nearby, u s u a l l y w i t h -i n 50 f e e t (15 m . ) . S ince many s i t e s may be i n v e s t i g a t e d s imul t aneous ly i n a s m a l l a rea , and a b i r d r a r e l y perches f o r more than a minute or two when a c t i v i t y i s h i g h , w i t h o u t marked b i r d s i t i s i m p o s s i b l e to f o l l o w an i n d i v i d u a l f o r any-l e n g t h of t i m e . I n t r a s p e c i f i c f i g h t s i n v o l v i n g p h y s i c a l con-t a c t , or p e r s i s t e n t i n t e r r u p t i o n s of a p a i r at a s i t e , were never seen; a c t u a l l y i n t e r s p e c i f i c c o n f l i c t s were more f r e -q u e n t l y observed. There are s e v e r a l p o s s i b l e e x p l a n a t i o n s : an important one. be ing t h a t the behav ior of t h i s spec ies has never been d e s c r i b e d , so perhaps t h r e a t , a t t a c k , r e t r e a t , e t c . , i s o c c u r r i n g w i t h o u t be ing recogn ized (though some elements of aggress ive behavior can be i d e n t i f i e d ) . Another p o s s i b i l i t y i s tha t the b i r d s re spec t t h e choices o f o t h e r s , p r e f e r r i n g to a v o i d , r a t h e r than a t t a c k , an e s t a b l i s h e d p a i r . A d d i t i o n a l l y , an abundance o f nest s i t e s could c o n t r i b u t e to t h i s s i t u a t i o n , e s p e c i a l l y i f they were of equal s u i t a b i l i t y , -91-or even of "super-suit a b i l i t y " , i n both q u a n t i t y and q u a l i t y , i n comparison w i t h a n c e s t r a l n e s t i n g p l a c e s . T e r r i t o r i a l i t y would l i k e l y have l i t t l e e f f e c t upon the spacing of the nests, though the h a b i t a t would, through the p o s i t i o n i n g of p o t e n t i a l n e s t - s i t e s i n r e l a t i o n to one another. Another p o s s i b l e h a b i t a t i n f l u e n c e , r e l a t i v e l y unexplored, i s mentioned by Lack and Owen (1955), who found that breeding c o l o n i e s of the European Swift were spaced about £ to J m i l e apart i n the c i t y of Oxford, and t h a t t h i s spacing was not due p r i m a r i l y to the d i s t r i b u t i o n of n e s t i n g holes. W h i t t l e (1926) makes an e a r l y reference to a s i m i l a r phenomenon i n the Tree Swallow, and i n a d d i t i o n suggests the food supply to be the determining f a c t o r . In many c o l o n i a l b i r d s , the s i z e and spacing of c o l o n i e s c h a r a c t e r i s t i c a l l y v a r i e s w i t h the food supply (Lack, 1954) - a p o s s i b l e mechanism whereby t h i s i s accomplished i s presented by Wynne-Edwards (1962)„ The i n t e n s i t y of i n t e r s p e c i f i c competition can be i n d i -cated o n l y r e l a t i v e l y as "uncommon". In terms of the l o c a l V i olet-Green p o p u l a t i o n s , a l i m i t i n g e f f e c t i s d i f f i c u l t to imagine, though r a r e l y i n d i v i d u a l p a i r s may be s e v e r e l y i n -convenienced, as the f o l l o w i n g examples w i l l i l l u s t r a t e . V i o l e t - G r e e n Swallow v/s S t a r l i n g - No encounters between these two species were detected i n 1 9 6 l , and o n l y two i s o l a t e d b r i e f c o n f l i c t s at nest s i t e s were observed during the 1962 breeding season . V i o l e t - G r e e n Swallow v/s E n g l i s h Sparrow - In o n l y one instance was-, prolonged competition f o r a n e s t i n g s i t e between these two species detected. At f i v e other l o c a t i o n s c o n f l i c t s were seen, but these were b r i e f in duration, appeared inconclusive even at the time, were never seen repeated, and were without apparent long-term r e s u l t s . Since i t also i l l s u t r a t e s i n t e r -esting behavioral t r a i t s , the prolonged c o n f l i c t i s detailed below. The s i t e , a s n a i l hole in the wall of a cement-block building, had been used by Violet-Greens i n 196l. On March 31, 1962, an English Sparrow pai r was here, perching near and frequently entering the si t e . As a favorite feeding place was close by,-; these birds did not have to desert the s i t e for long periods. A nearby sparrow nest was being b u i l t , but the status of the s i t e i n question remained un-known as no v i s i b l e material was carried i n during the ob-servation period. A Violet-Green pair was perched on wires over a lane 50 feet (15 m.) away, and as soon as the sparrows flew out of sight, demonstrated t h e i r intentions by f l y i n g to wires by the opening. Shortly, they l e f t for a minute or so, presumably feeding, and soon after t h e i r return, the sparrows re-appear:ed, the female sparrow driving the female swallow from i t s perch with a short- threatening rush. The swallows returned to the wires over the lane. When the spar-rows l e f t the nest again, the swallows immediately returned to the wires by the s i t e , which the female entered, leaving shortly but returning to c l i n g at the entrance, when the male sparrow returned. The sparrow chattered loudly from near by but neigher swallow moved. I t then flew at the female, which" l e f t immediately, and was followed by i t s mate back to the more distant perch. The swallows were not present when the - 9 3 -s i t e was r e v i s i t e d at roosting time. On May 7 , the nest apparently contained very small sparrows. A Violet-Green pair came to the wires by the opening three times during a short morning observation, but did not remain long, and no encounters occurred. In the late afternoon, the female sparrow was seen i n the nest open-ing, and - the swallows were perched over the lane; Once the sparrow l e f t , the swallows again investigated the s i t e more closely, though not attempting to enter. On May 27, swallows were seen to express interest by a b r i e f v i s i t to the wires by the s i t e . Sparrows l a t e r attended the s i t e - incubation was in progress. A swallow p a i r was found perched by the s i t e on June 2 3 . No sparrows were seen during the short observation period, a brood having fledged a few days before. As late as July 2, a lone swallow was seen perched by the opening. At t h i s time either the egg-laying f o r , or the incubation of, a t h i r d sparrow brood was i n progress. Clearly only i s o l a t e d occurrences are reported from what may have been an intense c o n f l i c t . However, several points are i l l u s t r a t e d . The persistence of the swallows at an occupied s i t e early i n the season suggests that one or both of the birds nested here the previous year. In a l l the movements toward the nest s i t e , the female always took the i n i t i a t i v e , and appeared to be followed by the male. Combellack's (1954) observations on a single pair also sug-gested that choice of the s i t e was c h i e f l y the female's. Even when the swallow's attendance at the s i t e i s permitted -94-by the weather conditions, i t i s not constant, as one or both birds frequently leave for minutes at a time, not coursing i n the immediate neighbourhood as i s more commonly done when feeding young. Presumably feeding i s the purpose of these f l i g h t s , or perhaps f l i g h t i s , a part of courtship a c t i v i t i e s , but whatever the reason, they do take the birds from the nest's v i c i n i t y . I f feeding i s t h e i r purpose, pre-sumably the duration of the absences could be r e l a t e d to the general weather conditions. Emlen (1952) describes f l i g h t s by the C l i f f Swallow, e s p e c i a l l y in the pre-incubation periods, and during the warmer parts of the day, when they may forage up to four miles away, leaving t h e i r colony deserted for hours. I t i s generally true that swallows are much less frequently observed during the e a r l y afternoon, but whether th i s i s asso-ciated with similar social behavior,. a lessening of a c t i v i t y , or the s t i f f breezes that almost invariably p r e v a i l during t h i s time, i s unknown. In any event, the birds are not f a i t h f u l l y attending t h e i r nest s i t e s , which would be s i g n i -f i c a n t i n a competitive situation . The l a s t point i s the apparent willingness of the birds to remain subordinate to the sparrows, only approaching the nest cl o s e l y whenever they were absent. The other b r i e f encounters seen between these two species indicate that the swallow may be more aggressive - a generalization cannot be made. Violet-Green Swallow v/s Tree Swallow - No i n t e r s p e c i f i c competition for nest s i t e s between these species was detected. Apparently the Tree Swallow's preference for b i r d boxes, and their low numbers, was s u f f i c i e n t to preclude such a c t i v i t i e s - 9 5 -i n the small study area. Violet-Green Swallow v/s Rough-Winged Swallow - A l l obser-vations were made at a ro ck face created by highway construc-t i o n (Plate 10) on the edge of Schkam Lake, one mile north of Hope where the birds investigated not only crevices and niches, but also several three inch (7 .6 cm.) diamter holes d r i l l e d into the rock during construction. The following generalizations resulted from the many i n t e r - and i n t r a s p e c i -f i c incidents observed. Two pairs of each species nested here - t h i s was also the number of birds present on the f i r s t v i s i t on May 9 , 1962, though l a t e r "extra" birds of each type, p a r t i c u l a r l y Rough-Wings, were involved. The Violet-Greens were attending t h e i r nest s i t e s on this date, but the Rough-Wings appeared less well-established, and tended to investigate many possi-b i l i t i e s . Both d r i l l e d holes and cracks were investigated by each species - one Violet-Green and both Rough-Wing nests were eventually b u i l t i n the c i r c u l a r d r i l l i n g s . During May, when the weather was f i n e , i n t e r - and i n t r a -specific incidents were f a i r l y common. This was esp e c i a l l y true when "surplus" birds of e i t h e r species were present. On some occasions up to four or f i v e additional Rough-Wings and one or two extra Violet-Greens p a r t i c i p a t e d in the s i t e -selection process, but how seriously cannot be judged. Since swallows are quite s o c i a l , even int e r s p e c i f i c a l l y , i t cannot be determined whether those birds f l y i n g up and down the- rock face are doing so because of the nest s i t e s , or because they were stimulated into action by the sight of others investigat -96-c a v i t i e s . One swallow a l i g h t i n g at a cavity, or swooping about i n front of one, appears to i n c i t e others to behave s i m i l a r l y , even though they may be of a di f f e r e n t species, ••. and are already associated with another nest s i t e . The owner may a l i g h t at the entrance, and snap i t s . b i l l at birds f l u t t e r -ing near; i t may j o i n these b i r d s , apparently p a r t i c i p a t i n g ; or i t may attack a more persistent investigator. Short chases, with one b i r d r i g h t behind another, were frequently seen, and were i n some cases d e f i n i t e l y t e r r i t o r i a l i s t i c . One f l u t t e r -ing combat between a Violet-Green and a Rough-Wing was ob-served, both birds f a l l i n g to the ground before separating. Whenever a'chase involved both species, i t was always a Rough-Wing which was pursued. This may be due to a basic behavioral difference, or possibly to the fact that the Violet-Greens had advanced farther into nesting a c t i v i t i e s , and were there-fore more intense. I f a Violet-Green happened to a l i g h t at a Rough-Wing s i t e , Rough-Wings would f l u t t e r near, but would never attack as a Violet-Green would i f positions were re-versed. Despite Gullion's (1947) description of interspec-i f i c (with Tree Swallows) and i n t r a s p e c i f i c t e r r i t o r i a l i s t i c defense by Violet-Greens of a flyway i n front of the s i t e , the impression remained that only the s i t e i t s e l f was of importance. I t i s true that the sight of several birds swooping and f l u t t e r i n g by i t s cavity w i l l cause a V i o l e t -Green to leave i t s perch, j o i n them and perhaps chase one, without any having alighted at the entrance, but t h i s i s l i k e l y only because the presence and behavior of these i n -truders i s recognized by the owner as a threat to i t s posses- . - 9 7 -sion. Most of the time birds may pass through the flyway, close to the s i t e , without e l i c i t i n g h o s t i l i t y . One V i o l e t -Green male f o r a short while defended other cracks and d r i l l holes near i t s nest. In spite of t h i s a Rough-Wing nest was b u i l t i n one of these holes, eight feet ( 2 . 4 m.) away from the Violet-Green s i t e . Despite the l i m i t e d survey of the Hope area, these two species were also found nesting close to one another at a rock face 16 miles west of Hope, and i n the t i l e d drain holes of a concrete bridge foundation (Plate 7 ) , #3 miles up the Hope-Princeton Highway, in d i c a t i n g that this i s not due to chance, but may occur commonly. This competitive s i t u a t i o n was not anticipated, and i s of interest only because i t involves the Violet-Green Swallow. During t h i s study, the Rough-Wing was found nesting only i n holes i n sandy or rocky banks, or i n t h e i r a r t i f i -c ially-constructed equivalents. Bank and Tree Swallows also may use the l a t t e r (Hollom, 1 9 4 3 ) , but these species are rare. In t h i s region, only one brood per year i s ra i s e d . Bent (1942) found no reports of second broods though S u l l i o n (1947) commonly found two broods per p a i r per year i n western Oregon. The Violet-Green Swallow i s a potential inhabitor of several cavity types (Bent, 1 9 4 2 ) , but i n no case does i t prepare i t s own. Human a c t i v i t i e s have.greatly increased t h i s species' nesting s i t e s , This -98-was i l l u s t r a t e d again by i t s occurrence at Pinewoods, 41 miles east of Hope, at 4000 feet (1219 m.) elevation. Now commonly nesting i n the buildings, i t was absent from the area i n 1949, before t h i s small resort was established (R.Y. Edwards, personal communication). Such a variety of ca v i t i e s are used that t h e i r physical measurements l i k e l y have very l i t t l e influence on de s i r e a b i l i t y , provided they are w i t h i n certain very wide l i m i t s of tolerance. Only 6 of 127 records in the B.C.N.R.S. were provided by tree c a v i t i e s , with 48 each by nest boxes and c a v i t i e s in buildings (where the birds are much more con-spicuous). The remaining 25, most of them from one observer describe nests i n rock b l u f f s . This species' ancestral nest ing s i t e i s thought to be tree c a v i t i e s . (Kalmbach and McAtee, 1957; though Johnston and Hardy (1962) apparently disagree), but the. above figures, and the observed s i t u a t i o n could suggest otherwise. The wide habitat tolerance of t h i s species i s noted by Johnston (1943) and G r i n n e l l and M i l l e r (1944), and the l a t t never mentioning nests in buildings, describe two basic habi ta t types: one of them the v i c i n i t y of c l i f f faces, where nests are b u i l t i n crevices, the other being broken or open woods, or the margins of heavy forest, where hole-bearing trees are present. No preference f o r the presence of water was found'j: and the species i s termed " s o l i t a r y or weakly c o l o n i a l , apparently as according with the number of nesting s i t e s available i n any one place." The s i t u a t i o n observed at the marsh i l l u s t r a t e s a facet -99-' of the bird's s i t e - s e l e c t i o n processes. The birds were here constantly whenever, the weather was poor, usually remaining an hour or two after i t cleared. Yet on only one occasion i n two summers wa s a pair seen b r i e f l y investigating two unused c a v i t i e s i n the only large snag in the middle of the marsh. (Later i n the summer, when Starlings roosted i n numbers i n the marsh, individuals would sometimes be seen exploring these c a v i t i e s , thus demonstrating t h e i r spaciousness). None of the other holes v i s i b l e in snags beyond the marsh's east end were u t i l i z e d , norswas at least one true cavity i n shorter snags on a bank above the eastern margin ever seen to be i n -vestigated. Yet Violet-Greens nested i n the outbuildings of a t r a i l e r court approximately 500 feet (152 m.) from the marsh's west end. On May 23, ten b i r d boxes (dimensions given i n Appendix A) were erected on trees at the marsh's west end (Plate 11). Site selection by Tree Swallows was f i r s t seen on May 2 8 , and by Violet-Greens on May 30, and four nests (two of each species) were eventually b u i l t . Only one was successful, a re-nesting attempt by V i o l e t -Greens occasioned by vandalism. In both Tree Swallow boxes, the approximately three day old nestlings died due to un-known causes, and an unknown predator destroyed the fourth nest. This small experiment suggests that, as f a r as the birds were concerned, suitable nest s i t e s (other than the nearby buildings) did not exist u n t i l the bir d boxes were erected. This could be further investigated by erecting boxes on the hole-bearing snags themselves, most of which were further back (around 100 to 800 feet)(31 to 244 m.) -100-from the marsh. Koskimies ( 1 9 5 6 ) , theorizing on the o v e r a l l wide nest-s i t e tolerance shown by the European Swift (tree holes the ancestral s i t e ) , and the f a c t that d i f f e r e n t population seg-ments have diffe r e n t s i t e preferences, offers the opinion that breeding i n a human environment resulted from a non-genetical experimentation by part of the population. Such a habit was continued as a " t r a d i t i o n " , with the young being conditioned to t h e i r nest habitat by an imprinting - l i k e psychological habituation. Perhaps i n i t i a t e d by population pressure, the process has resulted i n segments of the population being apparently r e l a t i v e l y separated from both ecological and genetical points of view. Something similar may be occurring i n the Violet-Green Swallow population, and while evidence on t h i s question would be d i f f i c u l t to obtain (as by banding), s t i l l i t introduces an additional complicating p o s s i b i l i t y that would need consideration i f the role, of competition f o r nest s i t e s in the population dynamics of the Violet-Green Swallow was ever to be described completely. Tree Swallow Brooks (1917) found i t a common breeder i n the Fraser Valley. The 1961 season, with i t s late s t a r t , yielded no observations on nest-site competition. Five nests, a l l in bird boxes, were located. The f i r s t fledglings were seen on July 11, and the middle of July is the approximate aver-age f l e d g l i n g date. -101-On the smaller 1962 study area, 3 nests were found, a l l i n b i r d boxes. Sixteen additional nests were located, 2 i n boxes erected at the marsh, and 14 at other areas studied. Again the end of the second week of July was the average f l e d g l i n g date estimated from the few nests followed closely. A migrant, the time of i t s spring a r r i v a l in B r i t i s h Columbia i s apparently roughly coincidental with that of the Violet-Green Swallow (Munro and Cowan, 1947). L i t t l e i s known about the processes of s i t e - s e l e c t i o n and p a i r -formation (Chapman, 1955). He found that few, i f any, • swallows arrived at his colony as mated p a i r s . However, some birds bred with mates of the year before, occupying d i f f e r e n t boxes, or i n some cases, t h e i r old nests, allowing the conclusion that a pa i r bond may exist between certain p a i r s , and that re-mating i n other cases may be caused by no more than the birds returning to the same box, and meeting there. As with the Violet-Green, pairs were found at s i t e s ( i n which nesting subsequently occurred) on March 31, 1962, shortly after t h e i r a r r i v a l . Their early selection of nest-s i t e s was noticed by Gullion (1947) and Weydemeyer (1934), who found t h i s behavior exhibited immediately a f t e r the birds' arr iv a l . Johnston and Hardy (1962) believe the Purple Martin's early spring a r r i v a l i s influenced by the search f o r nest-s i t e s - possibly the same factor operates i n t h i s species. Up to the end of May, the weather movements to the marsh occasionally involved large numbers of Tree Swallows - these were very l i k e l y migrants, or at least transient i n the -102-area. For instance, on May 3 a flock of 30 was seen going to roost i n the marsh vegetation . Tree Swallows apparently participated i n the weather movements to the same extent as the Violet-Green Swallow, and presumably the same implica-tions can be drawn. Too few nesting birds were present to allow a more accurate generalization. Such responses to poor weather by t h i s species are mentioned by Chapman (1955), and Paynter (1954). I n t r a s p e c i f i c t e r r i t o r i a l i s m i s d i f f i c u l t to evaluate, as these birds are r e l a t i v e l y s o c i a l , may nest c o l o n i a l l y , and have not been adequately described i n terms of the be-havioral mechanisms employed. Apparently only the nest s i t e i s defended, a l l other areas being open to communal use (Gullion, 1947, describes defense of a flyway by t h i s species a l s o ) . During May, c o n f l i c t s were observed at a l l three nests i n town, but, lacking marked birds, any changes re-s u l t i n g from them remained unknown. No persistent interrup-tions or physical contacts were seen. The impression some-times received was that the sight of birds attending a box . would stimulate others to similar behavior. Song has a de-f i n i t e t e r r i t o r i a l i s t i c r o l e , as the chirruping of an estab-li s h e d b i r d , already paired, becomes p a r t i c u l a r l y intense when a r i v a l of the same species nears the nest. Possible i n t e r s p e c i f i c c o n f l i c t s involving Tree Swallows (versus English Sparrows and Starlings) were de-tected at three locations, and i n each case swallows bred i n the s i t e . The status of t h e i r opponents, and consequently the i n t e n s i t y of t h e i r involvement, i s unknown. For instance -103-at the L a i d l a w Study A r e a , on May 24 a p a i r o f E n g l i s h Sparrows had apparent ly become r e c e n t l y e s t a b l i s h e d (be-h a v i o r was "nervous" (Summers-Smith, 1958)) at a c a v i t y i n a snag, from the v i c i n i t y of which the male sparrow was seen to chase a p a i r of S t a r l i n g s . Tree Swallows, present i n the a rea , p a i d no a t t e n t i o n . Dur ing the next v i s i t on June 1, no sparrows were seen and a Tree Swallow p a i r was at the c a v i t y , where ' swal lows e v e n t u a l l y n e s t e d . Whi le i t i s d i f f i c u l t to p r e d i c t when and where sparrows are go ing t o breed , s i t e - s e l e c t i o n at t h i s t i m e , and i n t h i s l o c a t i o n , i s not what would commonly be expected, and they may have l e f t o f t h e i r own a c c o r d . The Tree Swallow appears t o d i f f e r from the V i o l e t -Green i n i t s behavior at the n e s t , as the f o l l o w i n g i m -p r e s s i o n s i l l u s t r a t e . The V i o l e t - G r e e n ' s attendance at the s i t e d u r i n g the p r e l i m i n a r y breeding stages i s f a r from constant even when the weather i s f i n e , being broken by f requent p e r i o d s of absence, perhaps f o r f e e d i n g . The Tree Swallow appears more f a i t h f u l to the n e s t , w i t h at l e a s t one b i r d r e g u l a r l y perched i n i t s v i c i n i t y . G u l l i o n (1947) makes a s i m i l a r o b s e r v a t i o n . A l s o , i t s h a b i t of w a i t i n g i n the nest entrance i s seldom d u p l i c a t e d by the V i o l e t - G r e e n . G e n e r a l i z i n g from a l i m i t e d number of o b s e r v a t i o n s , the Tree Swallow seems more aggress ive toward p o t e n t i a l n e s t -s i t e u s u r p e r s . Apparent ly t e r r i t o r i a l i t y has no e f f e c t upon the spac ing of the n e s t s , though the h a b i t a t has, through i t s s u p p l y i n g of both food and c a v i t i e s . An e f f e c t of f a v o r a b l e h a b i t a t -104-upon the establishment and size of a colony i s suggested by Chapman (1955), and Paynter (1954), among others. One brood per year i s normal f o r t h i s region, and i t must be raised in a pre-existing cavity. So much material may be used in the nest that a tree cavity i s made unsuitable f o r use by other species (McLaren, 1963). (While the V i o l e t -Green and Rougn-Winged Swallows behave s i m i l a r l y , the other species i n t h i s region that u t i l i z e the types of s i t e s that these three species favor would probably be l i t t l e affected by t h i s habit.) In town, only b i r d boxes were u t i l i z e d by the small Tree Swallow population, though on two occasions birds were seen investigating small c i r c u l a r holes i n the sides of buildings. Outside the town, besides b i r d boxes, only tree c a v i t i e s were found i n use. The Tree Swallow w i l l nest i n ca v i t i e s that d i f f e r widely i n dimensions and preferences within these tolerance l i m i t s are not demonstrable (McLaren, 1963). Though, use of other cavity types i s reported (Bent, 1942) , i n t h i s region the Tree Swallow appears to r e s t r i c t i t s e l f when choosing nest s i t e s (EvC.N.R.S.)• Roosting i n the nest cavity i s done by the female only, and generally not u n t i l after the nests are nearly completed (Weydemeyer, 1934). English Sparrow The English Sparrow i s a sedentary permanent resident around concentrations of humans, and usually occupies b u i l d -ings. I t has recently colonized the area, a r r i v i n g i n Vancouver around 1890 (Brooks and Swarth, 1925), and i n -105-Hope about 1902 (Thacker , 1922) . Sunny days w i l l e l i c i t i n t e r e s t i n p o t e n t i a l nest s i t e s anytime from January on, though the l a c k of observa t ions i n the months p reced ing May prevents g e n e r a l i z a t i o n s on the average t imes o f s i t e - s e l e c t i o n and ne s t - b u i l d i n g . A t r i p to Hope on March 3 1 , 1962, found high i n t e n s i t y t e r r i t o r i a l -ism common w i t h many p a i r s apparent ly s t a b i l i z e d at s u i t a b l e breeding l o c a t i o n s and some b i r d s b u i l d i n g n e s t s . The f o l l o w i n g n e s t i n g a c t i v i t y o u t l i n e i s taken from Summers-Smith (1958) . Young b i r d s show i n t e r e s t i n p o t e n t i a l s i t e s i n the e a r l y f a l l , but there i s no s e r i o u s attempt t o adopt a permanent s i t e . They a p p a r e n t l y l e a r n about s u i t a b l e c a v i t y types and l o c a t e vacant r o o s t i n g p l a c e s . A young male w i l l t a k e up a permanent s i t e e a r l y the next year , a d v e r t i s e from i t , and may soon a t t r a c t a mate. Once they have bred , a p a i r i s r e l a t i v e l y permanent, each b i r d remaining at tached to the o r i g i n a l s i t e f o r t h e r e s t of i t s l i f e . Up to three broods per year may be r a i s e d i n one s i t e . The sparrow i s a c o l o n i a l n e s t e r , and t e r r i t o r i a l i s m i s l i m i t e d to defense of the nest s i t e (Summers-Smith, 1958) . Owen (1957) found t e r r i t o r i a l s i z e s to be i n v e r s e l y propor-t i o n a l to the abundance of a v a i l a b l e n e s t i n g s i t e s , and to range from 18 i n . (46 cm.) to 20 f t . (6 m.) i n d iameter . A l l o ther areas are subject to communal u s e . The sparrow i s f r e q u e n t l y s u c c e s s f u l i n i n t e r s p e c i f i c compet i t i on f o r nest s i t e s i f i t i s e s t a b l i s h e d at the s i t e before c o n f l i c t s t a r t s (no i n s t a n c e s to the c o n t r a r y were r e c o r d e d ) . The few p e r t i n e n t observa t ions made suggest t h a t i f the sparrow - 1 0 6 -i s new to the s i t e , i t is much le s s effective as a competi-t o r , but since nothing i s known of the status of the p a r t i -cipants or the d e s i r e a b i l i t y of the s i t e , no conclusions are possible. For instance, i n March a male had claimed a portion of a building where no c a v i t i e s even existed. Once i t was courting three females here, when another pair arrived. The courting b i r d grappled with the other male, both f e l l to the ground, and f i n a l l y the intruding pair was chased out of sight across the street. Why t h i s spot was selected i n i t i a l l y i s puzzling and though the other pair may have been attracted by the displays, su.ch an occurrence casts doubt on the v a l i d -i t y of conclusions drawn from other observations on unmarked birds. The possible intensiveness of nest-site competition was indicated when a b i r d box with a trap door was erected i n place of a double compartmented b i r d house at which sparrows had been expressing i n t e r e s t . This was on March 20, 1962, i n White Rock, B.C. Put up at 8:30 A.M., the males of two pairs were trapped and destroyed by 9 A.M. At 9:05 A.M., two additional males, apparently unpaired, engaged in a short battle at the box. Then from 10:30 A.M. on, no spar-rows were seen, and a few da3rs of poor weather apparently suspended nesting a c t i v i t i e s , with investigation of the box next seen on March 25. The spacing of nests of t h i s p o t e n t i a l l y c o l o n i a l species i s l i t t l e affected by t e r r i t o r i a l i s m , though i t i s by the placement of suitable nesting s i t e s , which were in surplus i n the study area. There i s the p o s s i b i l i t y -107-that some potential s i t e s go unoccupied because the food r e-sources of the immediate surroundings are inadequate f o r the support of a larger population. This i s suggested by the tendency of the birds to concentrate feeding a c t i v i t i e s at a few good sources, as pigeon coops, the public park, etc. Residential blocks devoid of such feeding areas had few, and often no, sparrows, although swallows and st a r l i n g s found nest s i t e s there. Summer-Smith (1959) offers a more sophis-t i c a t e d explanation. In B r i t a i n , the food supply appears to exercise the greatest l i m i t i n g effect when the population i s at i t s maximum i n the summer, the young suffering more than the adults. At the beginning of the.breeding season, control i s exercised i n some way by the colonial, behavior of the b i r d . Available habitat i s not f i l l e d uniformly, the birds tending to congregate i n colonies. In these colonies, non-breeding adults of either sex e x i s t , even though potential nest s i t e s are abundant. "Presumably i t must be a psychological factor that l i m i t s the colony size. Observations suggest that i n good feeding areas there i s a greater density of colonies rather than an increase i n colony s i z e . " The habitat of the -English Sparrow i s buildings and their immediate surroundings. While i t may b u i l d nests i n trees (Kalmbach, 194-0), and i n ivy or similar growth on buildings (B.C.N.R.S.), in the Town Study Area only c a v i t i e s i n buildings (3$), bird boxes (5), and C l i f f Swallow nests ( l ) were u t i l i z e d (1962 data only). The var i e t y of ca v i t i e s used indicates a wide tolerance concerning nest-site dimensions. A d e f i n i t e preference was indicated for s i t e s having perches -108-i n front of them. This was i l l u s t r a t e d on several buildings (as Plates 12 and 1 3 ) , where, i n a series of otherwise i d e n t i -c a l c a v i t i e s , only the ones with perches were used. This contrasts with the selections of Violet-Green Swallows and Star l i n g s , as these birds usually choose the corner cavity of a series, perhaps because i t i s easier to orient to, or offers greater freedom of approach. Direct observation of the contents was not possible at any nest, so that data on the extent of u t i l i z a t i o n of i n d i -vidual c a v i t i e s is. often vague. Of the 44 nests discovered i n 1962 (1961 data, being incomplete, are not included), 1 was destroyed, in at least 2 others laying apparently never occurred, and 7 others were so situated as to preclude s a t i s -factory observations. In 13 nests, at least one brood was raised; 15 nests.had at lea s t two broods; and three broods occurred i n each of 6 s i t e s (cf. Weaver, 1943) ' Since the existence of young had to be determined by sound, or by the bringing of food by the parents, obviously the number of multiple-brooded nests must have been higher than the weekly observation t r i p s indicated. This i s a d d i t i o n a l l y i l l u s t r a t e d by the f a c t that at 26 s i t e s , sparrows were recorded in at leas t three different months. Also, no allowance can be made fo r nestings which did not achieve the success of l i v e young. From these considerations, up to 40 pairs i n breeding con-d i t i o n are estimated to have occupied the study area. A new cavity, i s not required f o r every brood (though a pair may hold and breed in two s i t e s , e s p e c i a l l y when s i t e s are p l e n t i f u l (Summers-Smith, 1958)), and broods follow one -109-another at approximately s i x week i n t e r v a l s . Fledging gen-e r a l l y occurs i n the t h i r d week of May, the l a s t half of June, and the f i r s t week of August, but how many pairs raise three broods i s unknown. More than three broods per year has not been proved in North Ameiri ca (Bent, 1958). The end of the main breeding season i s indicated by the formation of adult-containing f l o c k s by the middle of August. Many of these birds are obviously i n molt. Bulky nests are constructed in March and A p r i l , and may be added to between broods. The presence of nest material may make a s i t e less desirable to future occupants of the same or di f f e r e n t species. An English Sparrow nest appar-ently discourages a s i t e - s e l e c t i n g Purple Martin (Allen and Nice, 1952). Starling The history of the S t a r l i n g i n B r i t i s h Columbia up to 1957 i s reviewed by Myres (1958) and as predicted (page 47, ibid) has since that date established i t s e l f as a breeding species throughout the length of the Fraser Valley (B.C.N.R.S., and personal observations). Up to 1957, the status of the S t a r l i n g on the coast was that of a winter v i s i t o r ; ,r only the development of a non-migratory habit i n certain i n d i v i -duals can a l t e r the present s i t u a t i o n . Probably during the next ten years t h i s w i l l happen" (Myres, 1958). A nest found i n 196 2 i n a build i n g at Pinewoods, Manning Park, in which two broods were rais e d , represents a range extension not predicted by Myres. The species was f i r s t recorded from Manning Park i n I960 (D. Dow, personal communication). -110* I t s es tabl i shment as a r e s i d e n t i n Hope has been r e -c e n t . Some o f the town ' s i n h a b i t a n t s , ques t ioned i n 1 9 6 l , were not f a m i l i a r w i t h t h e spec ie s , a l though some S t a r l i n g s r e p o r t e d l y w i n t e r e d i n the town i n 1960-1961. Seven nests were l o c a t e d d u r i n g the abbrev ia ted 196 l summer obse rva t ion p e r i o d (from June let on ) , and i t i s p o s s i b l e t h a t up to h a l f a dozen p a i r s nested i n the town the p r e v i o u s y e a r . The f o l l o w i n g summary i s taken from K e s s e l ' s (1957) obse rva t ions on a r e s i d e n t p o p u l a t i o n in-New York . S t a r l i n g s d i s p l a y an i n t e r e s t i n n e s t i n g s i t e s throughout the autumn and w i n t e r months, and tend to choose nest s i t e s e lose to the ones they used, the p r e v i o u s y e a r . A n e s t i n g t e r r i t o r y i n c l u d e s a 10 to 20 i n c h r a d i u s about the n e s t i n g h o l e . S t a r l i n g s w i l l nes t i n c lo se p r o x i m i t y to o ther S t a r l i n g s and other s p e c i e s . They of ten have communal s i n g i n g perches and feeding a r e a s . Davis (1959), a l so s tudy ing a r e s i d e n t p o p u l a t i o n , found t h a t de fens ive behav ior , u s u a l l y e x h i b i t e d i n c o n f l i c t s be-tween a s t ranger and the owner of a nest h o l e , " begins i n August , at l e a s t f o r some b i r d s , i n c r e a s e s t i l l November, decreases i n . December, and then increa se s g r e a t l y from January to A p r i l . The defense r e v i v e s before r e n e s t i n g — " . He summarizes the .annual c y c l e : " D u r i n g J u l y and August the b i r d s moult and are re p r o d u c t i v e l y i n a c t i v e . By October most males have obta ined nest h o l e s which they defend. The females also defend ho le s but the f i g h t i n g i s not v igorous and hence i s i n c o n s p i c u o u s . Defence of the holes becomes l e s s a c t i v e i n w i n t e r but by February becomes more a c t i v e . - I l l -Copulation occurs i n early A p r i l and eggs are l a i d in l a t e A p r i l " . Without regular observations before the beginning of May, this increasing interest i n nesting s i t e s could not be traced. I t i s assumed that the l o c a l population i s b a s i c a l l y resident. I f migration does occur, the usual SSW to WSW direc t i o n taken i n the f a l l (Myres, 1958) would allow only a few miles of movement to the lower Fraser wintering grounds. In 196 2, display at some nests was seen on March 18, and t h i s advertising.was more common on March 31. A p r i l 9 had the highest a c t i v i t y , with many pairs established at nest s i t e s , some of them building nests. Working backward from the aver-age f i r s t brood fledging date of the end of the t h i r d week in May, and allowing 38 days (Dunnett, 1955 ; Kessel, 1957) , the average laying date of the f i r s t egg must have been around the end of the second week in Aprdl. From the l i m i t e d observations, la t e in the spring, the intensiveness of t e r r i t o r i a l i s m i s impossible to judge. Ident-i f i c a t i o n of individuals, permitted by marking techniques, would allow the intentions of the parti c i p a n t s , and any re-placements at a s i t e , to become known. Confusing t h i s s i t -uation i s the presence of unmated birds that may become i n -volved at established nests (Kessel, 1957) . For example, the most intensive i n t r a s p e c i f i c c o n f l i c t seen occurred on May 25, at a s i t e from which one brood had already fledged. I t involved f i v e birds, of which at least the defending two were paired, and perhaps two of the i n t r u -ders. A rapid series of short chases occurred, with the--112-defending b i r d always the pursuer. As soon as pursuit stopped, about 70 to $0 feet (21 to 24 m.) from the s i t e , the intruder would return, only to be chased again. Some-times the defending b i r d would leave the s i t e to displace one or more of the other Starlings even though they happened to be perched up to 50 feet (15 m.) ,away from the nest. The intruders l e f t after about ten minutes and the defending male then sang and displayed b r i e f l y at the s i t e before also leav-ing. However, the nest s i t e went unoccupied f o r the remainder of the summer. The possible vagueness of such observations was i l l u s -strated again on July 14, i n the Laidlaw Study Area, where an independent young-of-the-year was watched for at least a half hour as i t investigated holes i n the area. Many of the snags bore deep i r r e g u l a r scars created by feeding wood-peckers, some of these were up to two inches deep in places, and the S t a r l i n g would frequently perch at them and then t r y to enter the non-existent cavity, pushing and straining u n t i l i t s head was bent back over the top of i t s back. I t was only a matter of time u n t i l a nearby Tree Swallow nest containing large young was v i s i t e d and when the S t a r l i n g did so, the male Swallow flew at i t , s t r i k i n g i t and d r i v i n g i t away. The few additional i n t e r s p e c i f i c c o n f l i c t s seen were simi-l a r l y inconclusive. In the l a s t week of May and f i r s t week of June there i s a recrudescence of the preliminary sexual a c t i v i t i e s p r i o r to the laying of the second clutch. Singing and displaying near s i t e s i s common, occasionally exploration of s i t e s not -113-previously used by Starlings occurs, and nest-building i s seen again. Excellent S t a r l i n g habitat, described by Kessel (1957) consists of scrubby pasture and hayfields, bordered by hedge-rows and scattered trees i n a pr i m a r i l y a g r i c u l t u r a l d i s -t r i c t . The lack of this habitat i n the surroundings of Hope w i l l l i m i t the bulk of the area's Starling population to the town i t s e l f . I t i s possible that i n the future, up to half a dozen pairs w i l l nest on the ,Reservation, but at present they v i s i t only the marsh for roosting. The f l o o r of the Fraser Valley, as t y p i f i e d by the Laidlaw and Chapman Road Study Areas, would appear to offer ideal habitat, which i s not yet being f u l l y exploited. The normal Starling nest site i s a cavity i n a tree or building, and no deviations from t h i s were observed. I-t can-not provide i t s own cavity, although an old one may be cleaned out (Kessel, 1957). Thirty of the 34 nests- located within the study area in 1962 were i n buildings, 2 were in b i r d boxes, and 2 i n holes i n trees (of the 7 nests found i n 1961, 5 were re-used i n 1962 and 2 were sealed o f f ) . Thirty-three nests were followed c l o s e l y : at 2 nest-building occurred, but no young resulted; 9 were used f o r two broods; and 22 contained one brood. Twelve of the l a t t e r had f i r s t broods and 10 con-tained "second" broods. The h i s t o r i e s of these 10 are un-certain. Possibly they represent i n i t i a l breeding attempts of the season, or perhaps there were f i r s t broods raised i n them that went undetected (considered l i k e l y at 3 s i t e s ) . -114-Also, e s p e c i a l l y since s i t e - s e l e c t i o n occurs during the i n t e r -v a l between broods, i t i s possible that new ca v i t i e s were chosen from the surplus of s i t e s f o r the rearing of second broods. Kessel (1953) reports that many of the same nesting sites are used twice and Dunnett (195 5) states that second broods usually occur i n nest-sites used f o r the f i r s t broods; banding studies would be required f o r c l a r i f i c a t i o n of this point. The broods fledged by the end of the t h i r d week i n May and the end of the f i r s t week i n July. An estimated 35 breeding pairs occupied the study area in 1962. Starlings are rare i n the town toward the end of July. An indication of the increase in the town's S t a r l i n g population over these two years i s given by comparing the 19 nests occupied on the reduced study area from June 18, 1962 with the 6 nests located on the same area during the same time i n 1951 (when the season's weather was more favorable). House Finch The current range expansion of the House Finch i s re-ported by Edwards and S t i r l i n g (1961). From i t s f i r s t appear-ance on the coast around 1951, i t has slowly advanced up to Hope at the head of the Fraser Valley, where a singing male was recorded in 1 9 6 l . During t h i s study, single birds were seen on two occa-sions during June, 196'1. In 1962, the species was much more common, being recorded i r r e g u l a r l y throughout the summer. A l l the sightings were made i n the town, with the four following exceptions. On A p r i l 30 and May 30, single birds were noted on the top of -115-L i t t l e Mountain and on June 12, a male, female, and one juv-enile were seen here. In the Laidlaw Study Area, a male, f e -male, and one juvenile were seen on June 16. In the Hope Study Area, one, l i k e l y more, pair c o n t r i -buted to the sightings. The few observations indicate that they roam f r e e l y over a neighbourhood (cf. Evenden, 1957; S a l t , 1952). No successful nests were located but the pre-sence of young birds indicates breeding. On May 27 one nesting attempt was discovered. As the circumstances indicated competition, and t h i s i s the only such instance noted, the d e t a i l s are presented. In the l a t e afternoon, four birds were seen from a distance to be perch-ing near, and f l u t t e r i n g up to , a point under the eaves of a l i t t l e - u s e d b u i l d i n g . Two of them f e l l to the ground-in f l u t t e r i n g combat. When close enough.to. i d e n t i f y the b i r d s , two of them, now s i t t i n g on nearby wires, were seen to be English Sparrows and the other two were House Finches, engaged i n nest-building (Plate 1 4 ) . The English Sparrows l e f t the area shortly and the female House Finch, accompanied by the singing male, made four t r i p s to gather nest material. As the female was working one load of dried coarse grasses into the nest, an English Sparrow returned to the area. The male House Finch, which had been singing from the peak of the roof, immediately moved to perch closer to the nest s i t e . The sparrow then made a f l u t t e r i n g attempt as i f to land at the nest, but turned without a l i g h t i n g and l e f t the area. The House Finches, which had kept to t h e i r respective positions, resumed nest-building, but shortly after l e f t the area -116-themselves, about h a l f an hour having elapsed since the birds were f i r s t noticed. This s i t e was v i s i t e d on every subse-quent observation t r i p and although a b i t more material was added to the nest, no birds were seen here again. While i t i s d i f f i c u l t to judge i f such a s i t e would be chosen by V i o l e t -Green Swallows or Starlings, because of i t s shallowness and open aspect, i t i s s i g n i f i c a n t that English Sparrows success-f u l l y nested in a similar site i n a building several hundred feet away. The above attempt almost c e r t a i n l y represented a second nesting of the season, as two days later., a male House Finch was seen feeding two begging juveniles a few hundred feet away. On June 13, an uncounted flock of about a dozen, mostly young, was feeding throughout the same area. Isolated sight-ings i n which no pattern can be found f i l l e d out the summer. On July 24, a flock of 13, mostly juveniles, was seen at the study area's southern corner. The House Finch has r i s e n markedly i n numbers i n the Hope area i n the past two years, and following the pattern of i t s establishment in B r i t i s h Columbia, i t can be expected to become one of the commoner residents of the area. Edwards and. S t i r l i n g (196l) report that in.the l a t e f a l l of 1 9 6 l , this b i r d was the commonest passerine observed i n the Fraser River delta area. They conclude, "Man with his buildings and gardens, f i e l d s and i r r i g a t i o n , appears to have created new and suitable physical habitat f o r the House Finch in both the v a l l e y s extending northward from the Columbia Basin and the dry parts of the B a c i f i c Coast." -117-There are 52 House Finch records i n the B.C.N.R.S. -a l l of them describe nests b u i l t i n shrubby trees and bushes, many of them ornamental evergreens. Cant (1962) reports that the nests of an introduced and expanding House Finch popula-t i o n in New York state are about equally divided between such evergreens and buildings. "The single reguirement which appears to be s a t i s f i e d i n a l l such situations i s that the nest be either covered or shaded by vegetation or some other structure." (Salt, 1952) . The House Finch i s an early breed-er and usually builds a new nest f o r the second brood (Bergtold, 1913; Thompson, I960). I t may nest semi-colonially, and has i n d e f i n i t e , r e l a t i v e l y narrow, t e r r i t o r i a l boundaries (Thomp-son, I960). Just what effect the r i s i n g population may have upon the already established hole-nesters i s unpredictable. The House Finch start s nesting early, but not as early as the English Sparrow, which also r a i s e s more offspring per year. The presence of a large House Finch population in Denver, Colorado, did not prevent the rapid increase of English Sparrows around the turn of the century (Bergtold, 1913) . Nor has the pre-sence of English Sparrows prevented House Finches from ex-panding through B r i t i s h Columbia (Edwards and S t i r l i n g , 1961) and the eastern United States ( E l l i o t t and Arbib, 1953) . Perhaps only i n r e s i d e n t i a l and suburban areas (as i n Hope) w i l l the habitat be suitable enough, and the preferred nest s i t e s p l e n t i f u l enough, to allow the population to bu i l d up to the extent that a si g n i f i c a n t amount of i n t r a - and i n t e r -s p e c i f i c competition might occur (as described by Bergstrom, -118-1913; Evenden, 1957) . How d r a s t i c a l l y a high House Finch population could a f f e c t populations of other cavity nesters i s unknown. -119-DISCUSSION There are two sections in the discussion, that present: a) the possible mechanisms through which nest-site competi-t i o n may be effected, with a summary of some related studies; and b) a synthesis of t h i s study's data. The Process of Nest-Site Competition Andrewartha and Birch (1954, pp. 23-25) i l l u s t r a t e the process of competition with an imaginary example, consider-ation of which indicates that competition involves many elements: - a p l u r a l i t y of organisms - these organisms overlap i n t h e i r demands on an envir-onment a l re sour c e - t h e i r demands are made together, i n d i c a t i n g s p a t i a l . and temporal contiguity - the environmental resource i s so l i m i t e d that the demand exceeds the supply - the implication of harmful e f f e c t s as a r e s u l t of competition. A d e f i n i t i o n incorporating these elements, taken from Udvardy (1951), i s e s s e n t i a l l y similar to those given by Birch (1957); McLaren (1963); and Milne (1961); "Competi-t i o n i s the demand at the same time by more than one organism f o r the same resources of the environment i n excess of immed-iate supply." This discussion i s l i m i t e d to competition for nest-sites among hole-nesting avifauna that u t i l i z e holes in trees, or equivalent c a v i t i e s . Consideration must f i r s t be given to the r e s t r i c t i o n s imposed by the quantity of holes available, which by i t s e l f -120-w i l l l i m i t the population of hole-nesting birds, and thus establishes the basic framework within which competition must operate.. Prerequisite to the existence of such competition i s the presence together of hole;- nesting birds that are poten-t i a l l y inhabitors of the same c a v i t i e s . I f competition e x i s t s , i t has already, through the harmful effects implied, been affecting the populations of the birds involved. I t i s not possible to observe the process i n i t s entir e t y , a l -though when an area i s invaded by a previously absent species, i t s effect as a competitor upon a r e l a t i v e l y s t a b i l i z e d hole-nesting b i r d population could be evaluated. The absence of certain hole-nesters from areas where they "should" be (as i n Table l ) i s d i f f i c u l t to explain. With attention focussed on competition, i t i s tempting to advance t h i s process as an explanation of t h e i r exclusion. The p o s s i b i l i t y e x i s t s that severe competition for nest c a v i t i e s can operate as one of many factors l i m i t i n g a pop-u l a t i o n , but whether such competition (necessarily i n t e r -s p e c i f i c ) could be the factor determining a species' absence from an area i s highly debatable. Hardin (196l) i l l u s t r a t e s the i m p o s s i b i l i t y of proving whether competitive exclusion can occur between species of i d e n t i c a l ecology. Later, Cole (1961), i n reviewing Skellam's t h e o r e t i c a l example in which even complete competitors can coexist, theorizes that i t can e a s i l y be applied to hole-nesting birds " where the a v a i l -a b i l i t y of 'spots' suitable f o r reproduction l i m i t s popula-t i o n s i z e . " I f i t i s impossible to prove competitive ex--121-clusion between species of i d e n t i c a l ecology, and competi-t i v e exclusion i s not even a necessary result of the co-exis-tence of complete competitors, then the s i t u a t i o n i n a hole-nesting avifauna of widely divergent evolutionary backgrounds and ecological demands (as McLaren, 1963, points out) must be vague regarding the concept of competitive exclusions- How-ever, the fact that only one environmental resource, of the many required f o r the perpetuation of the competing species, i s sought in common, would f a c i l i t a t e the. analysis of compe-t i t i o n per se, provided that the other ecological demands of the species involved were thoroughly understood. Results ob-tained would necessarily remain r e l a t i v e . , Working from theory^ Patten (l96l) concludes that competitive exclusion should be regarded as. only a small segment of a broad class of i n t e r -s p e c i f i c phenomena. In practise, habitat selection mechanisms w i l l almost i n v a r i a b l y intervene before the advent of s i g n i -f i c a n t i n t e r s p e c i f i c competition (Bond, 1957; Dixon, 196l; Udvardy, 1951). McLaren (1963) suggests " that the reason f o r t h e i r /±e.- several hole-nesting birds7 apparent s c a r c i t y might more p r o f i t a b l y be sought in considerations related to aspects of the niche other than nest-site competition." Hole-nesters are either able to excavate t h e i r own ca v i t i e s or not (primary and secondary hole-nesters of McLaren, 1963) . That primary hole-nesters are able to pro-vide t h e i r own c a v i t i e s does not mean that they w i l l always i n t h i s way add to the environmental resources. Also, many hole-nesters (often but not always secondary) have such broad nest-site requirements as to permit nesting in situations -122-other than tree holes. (Thorough knowledge of the l i f e h i s t o r i e s of the species involved i s e s s e n t i a l f o r the complete analysis of a competitive s i t u a t i o n . F i r s t , the most important aspects of the "demand" w i l l be outlined; t h i s w i l l be followed by a consideration of possible e f f e c t s . In competition for nesting c a v i t i e s , the "demand" i s made through the behavioral reactions of two or more bird s , oriented toward a p a r t i c u l a r nest s i t e , and occasioned by t h e i r need f o r i t . Excluded i s a l l behavior directed toward other environmental elements, or the whole habitat, although these demands are always i n t e r r e l a t e d i n varying degrees. The habitat selection mechanisms, and the bird's behavior towards i t s habitat as a whole, once selected, are often closely related to i t s reactions at the n e s t - s i t e , and f o r this reason w i l l be considered l a t e r . The demand f o r a hole may be made by birds of one, or two or morey species. I t i s possible that a hole may not be suitable f o r the nest of a species, yet i n d i v i d u a l s of that species, may exhibit a need f o r i t , t h i s behavior being released by certain aspe cts of.the cavity, and the l e v e l of the individual's motivation. This behavior would have v a l i d -i t y only from the point-of-view of the b i r d exhibiting i t , and would be allowed by the imperfections necessarily i n -volved i n a r e l a t i v e l y simple s i t e - s e l e c t i o n mechanism. I n t r a s p e c i f i c competition occurs between individuals that presumably make the same demands, i n much the same, way, from the environment, and thus react i d e n t i c a l l y to a -123-potential n e s t - s i t e . However, the p o s s i b i l i t y e x ists that a l l the members of a species do not react in t h i s way, but that, possessed with a degree of p l a s t i c i t y regarding nest-s i t e requirements, and allowed by the existence of s i t e s of d i f f e r i n g types, certain i n d i v i d u a l s , or segments of the pop-u l a t i o n , become psychologically accustomed or conditioned to one type of s i t e , thus producing an i s o l a t i n g effect be-tween population segments, or indi v i d u a l s (cf. Koskimies, 1956; Svardson, 1949; Thorpe, 1945). Such a phenomenon could a l l e v i a t e or i n t e n s i f y nest-site competition, depending upon the conditions, and would require separate analysis i n each i n d i v i d u a l case. The demand for a pa r t i c u l a r nest hole i s expressed through the. behavior of in d i v i d u a l birds. I n t r a s p e c i f i c a l l y j t h i s competition could be implemented i n two d i f f e r e n t ways. F i r s t , individuals might compete a c t i v e l y , reacting toward one another with behavior drawn from presumably i d e n t i c a l repertoires. Or,, the actions of one bird or pa i r at a cavity might change i t i n such a way that other individuals pros-pecting during the same breeding season would f i n d i t l e s s a t t r a c t i v e than i t was i n i t s o r i g i n a l condition. The birds would never have to meet. The existence of t h i s p o s s i b i l i t y would require separate determination f or each species. This more passive aspect i s c l a s s i f i e d as competition, rather than a form of environmental conditioning, as the condition of "same time" appears to apply. Such actions extending t h e i r effects from one breeding season to the next cannot be termed "competition". Milne (1961) points out that even -124-though the p a r t i c i p a n t s might never meet, s t i l l a competi-t i v e process can exist between them, provided that t h e i r "endeavour" i s considered to occur within a proper temporal i n t e r v a l . I n t e r s p e c i f i c competition for nest-sites might also be "active" or "passive". When two birds of different species a c t i v e l y compete, one or both behaving aggressively, one species w i l l l i k e l y win more often than the other, since t h e i r behavioral repertoires, and hence t h e i r competitive effectiveness, w i l l l i k e l y not be i d e n t i c a l . The more passive competitive process i s probably more common i n t e r s p e c i f i -c a l l y than i n t r a s p e c i f i c a l l y - the introduction of nest material by one b i r d preventing the establishment of another type of b i r d i s an example (cf. Busse and Gotzman, 1962) . This being " n e s t - s i t e " competition, "same time" would apparent l y apply to such interactions occurring within the time from the s t a r t of s i t e - s e l e c t i o n in one species to the end of t h i s process in the other. Competition necessarily implies a harmful e f f e c t , and must be considered as a possible population-controlling factor. I f i t e x i s t s , i t becomes in t e r r e l a t e d with a l l other population-controlling f a c t o r s , influences t h e i r action, and in.turn i s influenced by t h e i r e f f e c t s . Such a population-controlling factor, which enters t h i s discussion, i s t e r r i t o r i a l i s m (cf. Tompa, 1962) . One reason for i t s i n c l u s i o n i s that a potential nest-site i s involved, at least i n d i r e c t l y , when a bi r d selects i t s breeding habitat, and once a b i r d defends a portion of suitable habitat, i t i s , at least i n d i r e c t l y , defending i t s n e s t - s i t e . Some birds -125-defend only the nest-site and i t s immediate surroundings, allowing communal use of a l l other areas; t h i s behavior i s also referred to as t e r r i t o r i a l i s t i c . With species of the l a t t e r type, establishment of a t e r r i t o r y depends on the presence of a nest-site (cf. von Haartman, 1956) - there are indications that the presence of potential nest-sites i s indispensible to t e r r i t o r y estab-lishment even i n hole-nesting species that defend a large area (as the Black-Capped Chickadee, Odum, 1941a). T e r r i t o r -i a l i s m may be i n t r a s p e c i f i c or i n t e r s p e c i f i c . An i n t e r s p e c i -f i c c o n f l i c t concentrated at a pa r t i c u l a r part of the t e r r i -tory i s not i n t e r s p e c i f i c t e r r i t o r i a l ism (Simmons, 1951), and t h i s allows the creation of examples l i k e the following: a b i r d of one species (which defends only the nest cavity) i s competitively involved with a b i r d of another species (which defends a large area around the nest) at a nest cavity. The former would be exhibiting i n t e r s p e c i f i c t e r r i t o r i a l i s m , but the l a t t e r would not. This d i s t i n c t i o n , although not of im-portance, i s the reason that "nest-site competition" i s to be preferred i n reference to such s i t u a t i o n s . Kluyver and Tin ber gen (1953) proposed that t e r r i t o r i a l behavior produced a den s i t y - l i m i t i n g e f f e c t through the habitat selection mechanisms on populations of European T i t s . The number of nesting c a v i t i e s per se would have permitted a denser population - some nest s i t e s went unused. Birch (1962) notes that organisms which have large requirements f o r space, and defend t h e i r space as a t e r r i t o r y , are less l i k e l y to be l i m i t e d d i r e c t l y by absolute shortage of environmental -126-resources than n o n - t e r r i t o r i a l animals. T e r r i t o r i a l i s m i s thus p o t e n t i a l l y highly involved i n studies of nest-site competition; the extent of involvement can be expected to •d i f f e r in each species. I t i s a fact that the size and spacing of colonies of c o l o n i a l birds (several hole nesters show colonialism) varies with the "excellence" of the environment (Lack, 1954). This effect may perhaps be accomplished with.the aid of e p i d e i c t i c displays (specially-timed communal display sensu Wynne-Edwards, 1962, p. 16), through which the t o t a l population, .-. and the number of breeders, i n an area i s evaluated, and re-lated to the environmental resources, then to be regulated accordingly. Whether the number of potential nest-sites i s d i r e c t l y involved in the assessment of the environment i s unknown, though the process w i l l c e r t a i n l y affect the i n i -t i a l demand made upon the existing c a v i t i e s . The various aspects of competition having been presented, next i t s effects w i l l be considered. Harmful effects are im-p l i c i t i n the d e f i n i t i o n given; other d e f i n i t i o n s , e s s e n t i a l l y s i m i l a r , s p e c i f i c a l l y mention harmful effects (Andrewartha and Birch, 1954; Birch, 1957). From the competitive processes themselves, there i s f i r s t the p o s s i b i l i t y of physical harm. This i s occasion-a l l y reported (as loss of eggs, young, or i n j u r y t o , or death of, the adult p a r t i c i p a n t s ) , but i s probably rare, and seldom i s quan t i t a t i v e l y evaluated. An exceptional case i s reported by Bergtold (1913); a loss of 16 percent of House Finch eggs and young due to destruction by the -127-the English Sparrow - t h i s i n t e r s p e c i f i c competition for nesting s i t e s between dense urban populations of these species was the largest single factor in the loss of House Finch eggs and young. Another harmful fac t o r , d i f f i c u l t to evaluate, i s the expenditure of energy in competitive processes. I t i s essen-t i a l l y wasted, not contributing to the well-being of the individuals involved. P a r t i a l l y a function of energy waste..- i s the loss of time, which may assume great importance. The timing of breed-ing a c t i v i t i e s of birds i s often rather d e l i c a t e l y adjusted to seasonal changes. A delay i n the start of breeding, as might occur under severe competitive conditions, could re s u l t i n no brood at a l l ; a brood reduced in number; less success in r a i s i n g a brood to independence; or reduced success i n , or absence of, additional broods during that season. As an example, Kessel (1953) found that successful second broods could be expected, i n an Ithaca, N.Y. Starling population, only from those females that had raised the f i r s t brood successfully and without interruption. This loss of time affects both birds (or pairs) p a r t i c i p a t i n g (Udvardy, 1951) . Even the dominant species i n i n t e r s p e c i f i c c o n f l i c t s may enjoy a Pyrrhic v i c t o r y (Ripley, 1959, .1961), and the term "aggressive neglect" now describes such situations (Hutchin-son and McArthur, 1959) . This coverage of the main theore-t i c a l points of nest-site competition i l l u s t r a t e s i t s poten-t i a l complexity, and points out the need f o r thorough l i f e -h i s t o r y knowledge of a l l species involved. B r i e f consider--128-ation i s now given to examples of North American hole-nesting birds involved i n competitive relationships, though not nec-e s s a r i l y f o r nest-sites (as this has not been extensively studied), i n order to i l l u s t r a t e related aspects of competi-t i o n which have been found to be represented i n nature. In southern Wisconsin, Bond (195 7) surveyed the breeding birds of 64 upland hardwood stands, which represented a grad-ient of vegetational differences. One of his* con elusions i s quoted: "Differences i n d i s t r i b u t i o n of the various b i r d species along t h i s vegetational gradient are but one expres-sion of t h e i r ecological d i s s i m i l a r i t y . Even though several species may be si m i l a r i n one or more of t h e i r requirements (e.g., n e s t . s i t e s ) , there are other differences which separate them e c o l o g i c a l l y and, hence, reduce possible competition. Using the hole-nesters as an example, the four woodpeckers i n the study have d i f f e r e n t trends along the vegetational grad-ient, different n e s t - s i t e s , and differ e n t feeding habits, while the remaining hole-nesters, the Crested Flycatcher, Black-Capped Chickadee, and White-Breasted Nuthatch d i f f e r from each other and the Woodpeckers i n response to the gradient, nest construction and, mainly, in feeding habits." Dennis (1951) censused the Woodpecker populations of differe n t plant communities i n F l o r i d a , during the non-breed-ing season. He found s i g n i f i c a n t differences i n the feeding habits of a l l eight species involved, some of which were migratory. I n t e r p s e c i f i c c o n f l i c t ^ between Woodpeckers, while noted, could not be associated with population changes i n any habitat (as of a l o c a l species when a migrant species - 1 2 9 -arrived), and were considered to be seldom serious enough to cause any unbalance. Intraspecif i-c competition, and i n t e r -s p e c i f i c competition with birds other than Woodpeckers, were uncommonly observed. Staebler (1949) studied the l i f e h i s t o r i e s of the Hairy and Downy Woodpeckers comparatively, and concluded that there was no ecological, competition, any associations between the two being purely passive. Believed among the more important i s o l a t i n g factors were the differences both i n th e, nest- s i t e s used, and i n the times of breeding. No i n t e r s p e c i f i c con-f l i c t s f o r nest-sites or ne sting t e r r i t o r i e s were observed. Feeding behavior of the two species was found to be markedly d i f f e r e n t . . Bond's l a t e r (1957) study showed that the two species demonstrated opposite trends along a vegetational gradient, f o r while both occurred in woods representing any point of the gradient, the Hairy was more common i n the denser, more mesic types, and the Downy's abundance was greatest in xe r i c woods... Considering Staebler Ts work,. Bond concluded that this difference would have to be explained by habitat selec-t i o n mechanisms. McLaren (1963) studied nest-site competition among the 17 hole-nesting b i r d species occurring i n the Cariboo region of B r i t i s h Columbia (Fig. l ) . , The c a v i t i e s available i n th i s predominantly aspen-parkland type habitat were d i v i s i b l e into three natural groups on the basis of entrance s i z e : small, medium (excavated by F l i c k e r ) , and large. The large hole "cycle" of primary and secondary hole-nesters was too poorly known, and too d i f f i c u l t to work with, to be general--130-ized upon, and the small hole cycle was composed mainly of primary hole-nesters, among which competition was d i f f i c u l t to envision. In the medium-hole cycle, only s i x species were common: Tree Swallow, Sparrow Hawk, Bufflehead, Mountain Blue-b i r d , S t a r l i n g (which occurred as a nesting species only in the 10 years or so preceding the s t a r t of the study i n 1958), and the hole-producing F l i c k e r . The study was based mainly on data c o l l e c t e d concerning the ecological and physical c h a r a c t e r i s t i c s of the medium holes, and i t was clear that, i n terms of the parameters considered, the requirements of the species involved showed an impressive degree of overlap. This demonstrated quantita-t i v e l y the possible occurrence of competition, but since selection f o r different c a v i t y types had not occurred among the native species, the existence of s i g n i f i c a n t competition could be argued against. The greater majority of c a v i t i e s available were found to be in use, with the recently-arrived S t a r l i n g occupying roughly one-quarter of them, which allowed the conclusion that the hole-nesting b i r d population was being l i m i t e d by the number of holes, and that, es p e c i a l l y since the advent of the S t a r l i n g , comparative competitive a b i l i t y might be determining the proportion of the t o t a l population taken up by each component species. Selander and G i l l e r (1959) found that two c l o s e l y re-lated, morphologically similar Woodpeckers, the Red-Bellied and the Golden-Fronted, were sympatric only w i t h i n a narrow zone i n central Texas, which coincided with a marked east-west faunal and f l o r a l "break". Within t h i s overlap zone, -131-differences i n habitat occurrence l i m i t e d contact and compe-t i t i o n , but where both species occurred together, they held mutually exclusive t e r r i t o r i e s , t h i s i n t e r s p e c i f i c t e r r i t o r -i a l i s m i l l u s t r a t i n g the competition f o r space and nesting s i t e s . D etails of feeding and nesting, and vocalizations and displays, were found to be si m i l a r in both species. They demonstrated ecologic differences elsewhere than i n the zone of overlap, where there was no conspicuous narrowing of habi-t a t . "The overlap i n habitat occurrence i s s u f f i c i e n t l y ex-tensive, however, to warrant the hypothesis that either species would, i n the absence of the other, occur i n greater density i n the overlap zone. ...Reproductive i s o l a t i n g mechanisms, the nature of which are unknown, have evolved, but the species have not made ecologic adjustments which would permit exten-sive sympatry." The t e r r i t o r i e s of a pair of Red-Bellied and a pair of Red-Headed Woodpeckers, observed i n the same area, overlapped broadly, and no i n t e r s p e c i f i c antagonism was seen. Suggested as factors i n permitting extensive sympatry of these species were their differences in foraging habits and habitat occurrence. Yet when presented with dummy mounts of Red-Bellied Woodpeckers, the Red-Headed exhibited vigorous aggressive behavior (this near the i r nest). "These tes t s help account f o r the fact that the pair of carolinus avoided perching i n the v i c i n i t y of the nest-tree of erythrocephalus." Ripley (I96l), apparently referring t o - a l l three species, comments on th i s work, " I t seems conceivable that, should the nesting t e r r i t o r i e s of these species in a zone of over-lap become accidentally compressed, the phenomenon of aggres--132-sive neglect might come into play." From t h i s consideration of the implications t h e o r e t i c a l l y inherent i n a study of nest-site competition, and the examples of comparative study of some North American hole-nesting birds, i t would appear that such competition, though always possible, i s probably never severe, and i s perhaps non-existent, f o r many of the species composing the hole-nesting avifauna of any region. The conclusion of Bond. (1957), quoted on page 128, undoubtedly t y p i f i e s the s i t u a t i o n i n many b i o t i c areas, with the o v e r a l l r e s u l t s of the bird's habitat selection proces-ses, and t h e i r l i v i n g h a b i t s k e e p i n g them so ec o l o g i c a l l y d i s t i n c t that such competition, though perhaps occurring occasionally, can generally be disregarded as a population l i m i t i n g f a c t o r . The value of even a s l i g h t amount of compe-t i t i o n as a factor i n selection i s unknown. Synthesis of Data The region i n which the study was conducted i s b a s i c a l l y a temperate r a i n forest that has a heavy growth of predomin-antly coniferous vegetation on a mountainous t e r r a i n . Much of the accessible forest has been logged and th i s d i s t u r -bance i s continuing. F i r e may have affected any portion. Hhese processes have resulted i n large portions of the mountains bordering the v a l l e y being covered by variously aged successional stages. The v a l l e y f l o o r has been exten-s i v e l y modified f o r use as farmland, and supports a high human population. A l l these factors of human or accidental disturbance, and topography, contribute to produce a r e l a t i v e -l y varied habitat. Most of the Reservation has had a recent -133-h i s t o r y of f i r e and logging, and i s representative of a sub-s t a n t i a l portion of i t s surroundings i n that i t supports suc-cessional vegetational stages of different ages. Either logging or burning of timber may produce a quan-t i t y of dead snags that soon become suitable f o r nest-excava-t i o n by hole-nesting birds. Logging may r e s u l t i n an area bearing scattered t a l l t h i n snags, as the f e l l i n g of market-able timber damages smaller trees. Forest f i r e s may produce an area covered with snags. Larger f i r snags may be very long-lived, supported by a hard core, while the outer por-tions are soft enough to be excavated e a s i l y . Other vegeta-t i o n a l conditions do not supply the abundance of accessible snags found on logged and burned areas. Southwestern B r i t i s h Columbia supports a varied hole-nesting avifauna (Table l ) , but only a f r a c t i o n of the poten-t i a l l y - p r e s e n t species were actually observed to be nesting i n any abundance i n wooded areas (Table 9). The majority of species, and of i n d i v i d u a l s , found to be present are poten-t i a l l y primary hole-nesters, with the a b i l i t y to excavate t h e i r own ca v i t i e s in suitable locations. In the preceding sections, i t has been shown that the i n d i v i d u a l s of a l l the p o t e n t i a l l y primary hole-nesting species usually do produce nesting c a v i t i e s each season. Consequently i t i s very l i k e l y that there i s no absolute need f o r the presence of nesting c a v i t i e s i n a portion of suitable habitat i n order to make i t acceptable. Suitable places i n which c a v i t i e s could be exca-vated are more - l i k e l y to be a determining fact o r , but i t has been shown that many suitable unexploited locations for nests TABLE 9. HABITAT PREFERENCES AND POPULATION DENSITIES OF THE COMMON HOLE-NESTING BIRDS BIRD SPECIES HABITAT PREFERENCES AVER. POPULATION DENSITY IN 1962 PAIRS/lOO ACRES Wood Duck Sparrow Hawk Red-Shafted F l i c k e r P i l e a t e d Woodpecker Red-Breasted Sapsucker Hairy Woodpecker Tree-lined sluggish streams and sloughs that provide both cover and food. A suitable nesting cavity must be nearby. N o n - t e r r i t o r i a l , Requires open t e r r a i n , with perching places, that affords an adequate prey supply. A suitable nesting cavity must be nearby. N o n - t e r r i t o r i a l , An "edge" bi r d , preferring generally open areas, that also provide places for nest-excavation. T e r r i t o r i a l , L i t t l e known. Presumably prefers heavy woods. T e r r i t o r i a l , Prefers "edge" situations, not dense f o r e s t . Nests i n maples i f available. T e r r i t o r i a l , Margins, burns, and logged areas of forests. T e r r i t o r i a l , 0 .5 0 .5 0.75 Downy Woodpecker Deciduous woodland. Perhaps "edge". Te r r i t o r i a l , Black-Capped Chickadee A dual habitat preference i n deciduous woodland, with young open second growth stages used for nest-ing, and more mature growth preferred for other a c t i v i t i e s . T e r r i t o r i a l , TABLE 9. Continued AVER. POPULATION BIRD HABITAT PREFERENCES DENSITY IN 1962 SPECIES PAIRS/lOO ACRES Chestnut-Backed Mature coniferous forest and adjacent mixed growth Chickadee woodland. T e r r i t o r i a l . Red-Breasted Mature coniferous and mixed growth forests. Nuthatch T e r r i t o r i a l . 2.5 Winter Wren Under mature dense stands of mixed growth. T e r r i t o r i a l . -136-e x i s t i n the habitat types common to the study region. A consideration of the c h a r a c t e r i s t i c s of the nest-s i t e s found i n use (some of which have been presented in tabular form i n the sections dealing with i n d i v i d u a l species) indicates that the nest-site requirements of most of these birds often d i f f e r widely. This implies the production of many di f f e r e n t cavity types i n some habitats. From these points i t follows that habitat types in t h i s region with many po t e n t i a l nest-sites, and a population of hole-nesting birds, w i l l shortly possess a surplus of abandoned nest c a v i t i e s , ...theoretically useful to hole-nesters i n other breeding seasons. This was the condition observed on the main study areas. .The snag survey, although not completed, nevertheless had progressed far enough to support t h i s con-clusion. The elimination experiment, l i m i t e d i n extent, produced no r e s u l t for which the presence of nest-site competition could be advanced as an explanation. There exists a population of secondary hole-nesters obligated to use prepared c a v i t i e s , that consequently makes a demand i n t h i s regard upon the environment. These birds, and any p o t e n t i a l l y primary hole-nesters that do not i n i -t i a l l y excavate t h e i r own c a v i t i e s , are indispensible to the existence of nest-site competition. However, many of the secondary hole-nesters that could inhabit the region were absent from, or r a r e l y seen on, the study areas, and were e s s e n t i a l l y absent i n terms of the concept of nest-site competition. Other secondary hole-nesters, abundant i n the region, concentrated t h e i r nesting a c t i v i t i e s i n the town, and ignored the supposedly suitable nest-sites available i n -13 7-the nearby woods. This sit u a t i o n i s discussed i n a lat e r section. Several reasons may be advanced f o r the absence of nest-s i t e competition involving those secondary hole-nesting species found nesting on the main wooded study areas. The Winter Wren i s not obligated to build i t s nest i n tree c a v i -t i e s , and r a r e l y does so. I t is t e r r i t o r i a l , and i t s occu-pancy of a tree cavity i s l i k e l y due more to the chance pre-sence of a suitable cavity i n i t s t e r r i t o r y rather than an active searching f o r these p o t e n t i a l nest-sites at the time of t e r r i t o r y establishment. The n o n - t e r r i t o r i a l Sparrow Hawks occurred in such densities, and in dif f e r e n t ranges each summer, as to suggest that a l l the pot en t i a l l y - s u i t able habitat was not being u t i l i z e d , to which s i t u a t i o n a short-age of nest-sites, and possible nest-site competition, was very l i k e l y not a contributing f a c t o r . The n o n - t e r r i t o r i a l Wood Ducks' apparent f a i l u r e to nest during the l a s t two summers i s l i k e l y r e l a t e d to habitat unsu i t a b i l i t y (to which a shortage of nest-sites could contribute) rather than com-p e t i t i o n for any available s i t e s . This i s suggested by the li m i t e d feeding areas ava i l a b l e , and the f a c t that suitable habitat i s more common i n the lower Fraser V a l l e y . The following points are presented i n conclusion. Most of the hole-nesting avifauna of the region i s composed of primary hole-nesters, and many of these excavate t h e i r own nest c a v i t i e s . A l l of the primary hole-nesters, and some of the secondary, are t e r r i t o r i a l , and t h i s tends to lessen the pr o b a b i l i t y of i n t r a s p e c i f i c nest-site competition ever -138-occurring. The nest s i t e types preferred by some species are quite d i f f e r e n t from those used by other hole-nesters. The demands made upon environmental resources other than nest-sites are i n many cases completely separate, and best f u l f i l l e d i n different habitats, or dif f e r e n t parts of the same habitat. These l a t t e r two points w i l l tend to reduce the p o s s i b i l i t y of in t e r s p e c i f i c nest-site competition. A consideration of these habitat conditions and the hole-nesting avifauna found to exist under them, plus the fact that regular observations of thi s s i t u a t i o n over two breeding seasons did not provide any evidence of nest-site competition, allows the following statement. Under the conditions which have been defined above, there i s no com-p e t i t i o n for nest-sites among hole-nesting birds. This means that t h i s type of competition i s not. responsible i n any way for the determination of the observed population densities. These must be determined by other population-regulating factors, which, at the present state of know-ledge, can only be speculated upon.. A l l the hole-nesters nesting on the Reservation during th i s study were observed i n the summer of I960, when there also were present two pairs of Moun&ain Bluebirds, and one pair each of Brown Creeper, Lewis Woodpecker, and Pygmy Owl; the l a t t e r species was known to breed, while the others may have (Horvath,. 1963). The absence of these species i n the following two summers suggests that they be considered as irr e g u l a r residents of the Reservation. What the sit u a t i o n was when they were present i s unknown, and the p o s s i b i l i t y -139-exists that n e s t - s i t e competition may be present under con-ditions other than those outlined. The lim i t e d surveys that i t was possible to make allows the following generalization, which must be regarded as ten-t a t i v e . Conditions roughly similar to those found on the Reservation exist on the lower portions of the mountains bordering the valley (some of which r i s e above timberline), and on any wooded parts of the v a l l e y f l o o r . I t i s suggested that nest-site competition i s absent or n e g l i g i b l e i n these regions. Additional o r n i t h o l o g i c a l surveys i n these, and other sections of the Coast Forest, are needed to provide a more substantial basis for comparison. The town study area, with a d i s t i n c t set of conditions, i s considered separately. Five species, a l l obligatory secondary hole-nesters, inhabited the buildings and b i r d boxes, where they occurred i n much higher densities than in the surrounding countryside. The possible reasons for these concentrations may vary with the species, but l i k e l y include: habitat u n s u i t a b i l i t y of the surrounding regions (as i n the English Sparrow); " t r a d i t i o n " (perhaps i n the swallows); pre-ferred habitat i n conjunction with a low population l e v e l (Starlings and House Finches may be expected outside the town i n lesser densities as t h e i r populations expand). The buildings i n the town may provide nesting sites superior i n both q u a l i t y and quantity per unit area to those found i n less a r t i f i c i a l habitats. These f i v e species have certain t r a i t s that tend to reduce nest-site requirement overlap. These have already -140-been detailed, and are b r i e f l y summarized here i n an attempt at synthesis. The English Sparrow nests comparatively early, and i s f a i t h f u l to one s i t e throughout the year. Crevices i n buildings (which may be only p a r t i a l l y enclosed), preferably with perches, are most often u t i l i z e d . I t i s pugnacious, may destroy the nests of other species, (though t h i s was not observed), and i s considered to be dominant over the swallows and the House Finch. I t is d i s t i n c t i n being found only around human habitations. The S t a r l i n g i s a recent a r r i v a l , and i s increasing r a p i d l y . I t normally nests i n holes or crevices, and though more open s i t e s may be used under extreme conditions, t h i s has not yet been reported in B r i t i s h Columbia (B.C.N.R.S.). I t may concentrate around human habitations. I t s serious nesting a c t i v i t i e s s t a r t at roughly the same time as those of the English Sparrow. I t may remain attached to one s i t e through the winter and spring, and use i t to r a i s e two broods. Due to i t s s i z e , the c a v i t i e s available to i t are l i m i t e d , with smaller crevices being more common in the study area. I t i s reported to r a i d the nests of other hole-nesters, though t h i s was not observed, and i t s size and persistence have given i t the reputation of an e f f e c t i v e nest-site competitor . The House Finch, while reportedly not the English Sparrow's equal i n competition, nevertheless has been able to expand into areas where the Sparrow i s already established. -Hi-l t seems to prefer the v i c i n i t y of man. I t s independence of buildings when nesting has been noted, and t h i s i n i t s e l f would contribute to i t s success. The available records i n the B.C.N.R.S. (52) indicate that i t s nest s i t e requirements i n B r i t i s h Columbia are almost completely separate from those of the English Sparrow. Whether t h i s indicates a character-i s t i c of t h i s population segment, or merely r e f l e c t s the small sample,, remains to be seen. I t i s an early nester, but the timing of i t s broods cannot yet be worked out in t h i s region In town, the small population of Tree Swallows nested only i n b i r d boxes, and t h i s lack of adap t a b i l i t y makes t h i s species the most l i k e l y to suffer i f competition should increase i n the future. When, nesting in trees, t h i s swallow may use oddly-shaped c a v i t i e s that are.not completely enclosed, and why the birds i n the town should show such a r e s t r i c t i o n i s unknown. The Violet-Green Swallow chooses crevices in buildings, which do not have to be completely enclosed, and does not p a r t i c u l a r l y concentrate on bi r d boxes. I t has become con-ditioned to t h i s a r t i f i c i a l l y - c r e a t e d habitat, and i t s numbers i n the area have r i s e n as a consequence. The effectiveness of both swallow species as nest-site competi-tors i s presumably affected by weather conditions. There was obviously no p r a c t i c a l method of determining how many potential nest sites existed i n the study area. Usually s i t e s would be discovered only because birds were using them. However, i t i s certain that p o t e n t i a l s i t e s f a r outnumbered the combined populations of the hole-nesters. -142-This was judged not only from the existence of buildings containing many unused s i t e s (see Plates 12 and 13) } but also from the fact that many c a v i t i e s not used the f i r s t summer were occupied during the second, and "new" ones were used for re-nestings and second broods. Several b i r d boxes were not u t i l i z e d . Succession of occupancy by different species at one nest occurred only once during each summer, and both times circumstances were such as to cause doubt that competition had occurred. Competition was seen at only a few s i t e s , and rare l y was i t judged to be severe. That which did exist seemed often to be due to what might be termed "behavioral i r r e g u l a r i t i e s " on the part of one of the par t i c i p a n t s , as the defending of a part of a building where no c a v i t i e s existed, or the investigation of a nest seemingly prompted by c u r i o s i t y at seeing another b i r d entering i t , and so on. When severe competition did occur, i t was due to a f a i l u r e on the part of the birds to " r e a l i z e " that other suitable c a v i t i e s existed. In other words, the "demand i n excess of the immediate supply" did not exist i n a c t u a l i t y , but only i n the minds of the birds involved. .This psychological factor, which can include the choosing by an i n d i v i d u a l of a nest-site to which i t i s accustomed, rather than any of those which i t might p o t e n t i a l l y inhabit, could be important i n a problem of t h i s type, and yet would be very d i f f i c u l t to evaluate. The- situation at present i s not s t a t i c , as two new species are invading the area, and what w i l l happen i n the -143-future may be speculated upon. The Starlings w i l l presumably increase u n t i l the sc a r c i t y of preferred s i t e s begins to l i m i t the population's growth (Kessel, 1957), although observations by Anderson (1961) suggest otherwise. Cavities large enough for Starlings are not too p l e n t i f u l in buildings, and t e r r i -t o r i a l i t y might l i m i t the number of birds occupying a series of c a v i t i e s i n one building. A d d i t i o n a l l y , Starlings may be un-welcome due to t h e i r noise and f i l t h , and some c a v i t i e s w i l l be sealed to prevent re-use. This has happened at only two s i t e s on the study area. Even assuming that the S t a r l i n g i s victorious., in a l l competition f o r suitable s i t e s , there re-main the many smaller c a v i t i e s which Starlings can never enter, and of which the English Sparrow w i l l presumably have f i r s t choice, by reason of i t s resident status, and early inception of breeding a c t i v i t i e s . The House Finch i s as yet an unknown, though from data pre sently available, i t should not make great demands on the available resources. Although they arrive early, the Swallows are slow to begin actual nesting, and usually w i l l have second choice of s i t e s . But i f the Sparrow was going to u t i l i z e a l l the smaller c a v i t i e s , i t would have done so by now. Something other than cavity a v a i l a b i l i t y l i m i t s the Sparrow population - t h i s may be food. So the Violet-Green Swallow population (which, i t should be noted, has not increased to the siz e allowed by nest-site a v a i l a b i l i t y ) i s not l i k e l y to suffer because of an actual lack of c a v i t i e s . In addition, t h i s species can u t i l i z e other c a v i t i e s i n rock faces, and t h e i r constructed concrete equivalents, here entering into competition with another -H4--species, the Rough-Winged Swallow, over which i t appears dominant. The Rough-Wing, i n turn, u t i l i z e s other s i t e s the Violet-Green doesn't, so neither species i s l i k e l y to be driven from the area because of increased nest-site competition. However, the Tree Swallow, already i n low numbers (for unknown reasons), and apparently l i m i t i n g i t s e l f to bi r d boxes i n the town, and tree c a v i t i e s throughout the valley f l o o r -si t e s p a r t i c u l a r l y vulnerable to use by other species - may become absent as a nesting species i n t h i s area. To conclude: At present, as far as the supply of nest s i t e s i s concerned, a l l the species breeding i n the town could increase t h e i r populations. The House Finch and S t a r l i n g undoubtedly w i l l do so. Some of the possible result s of t h i s expansion are presented speculatively. At present competi-t i o n for nest s i t e s does occur, but in terms of the popula-tions of any of the species involved, i t very l i k e l y i s of negligible importance. A v i s u a l i z a t i o n of the process of nest-site competition must include something permitting a high population of non-hole-producing birds (these could be either primary or se-condary hole-nesters) i n r e l a t i o n to the amount of potential nest holes available, and being made available by primary hole-nesters (which are predominantly " f o r e s t " b i r d s ) . A high proportion of obligatory secondary hole-nesters i s l i k e -l y to be involved i n such a competitive s i t u a t i o n . There must be present the environmental resources, other than nest-holes, required by these species to allow the mainten-ance of r e l a t i v e l y high populations. However, many of the -145-secondary hole-nesters have widely d i f f e r i n g ecological de-mands, and are brought into association p r i m a r i l y through the hole-nesting habit. This implies that a varied habitat i s the most l i k e l y to support nest-site competition; a f u r -ther implication possible i s that an "edge" habitat w i l l often be varied enough to allow f u l f i l l m e n t of the d i f f e r i n g mod e s - o f - l i f e . Another p o s s i b i l i t y could be conceived: a comparatively very simple ecosystem i n which the requirements of one or two secondary hole-:ne sting species are well-supplied, ex-cept for suitable n e s t - s i t e s . Such a s i t u a t i o n does a c t u a l l y exist i n planted forests and orchards i n Europe (Udvardy, i n l i t t . ) . Areas intermediate to these two are l i k e l y to have fewer such competitive s i t u a t i o n s , and these, when they e x i s t , w i l l l i k e l y have l e s s importance as population-regulating fac-t o r s . Compared to either of the above postulations, a wider array of nest-hole producers w i l l probably be present, with proportionately fewer secondary hole-nesters, as the habitat i s more uniform, and cannot cater as w e l l to the divergent modes-of-life implied. The Cariboo region of B r i t i s h Columbia which has been recently studied and i n v i t e s comparison, and i n which nest-s i t e competition apparently e x i s t s , possesses a great deal of semi-open countryside with many small exposed stands of aspen. None of the birds among which competition may occur are dependent upon the trees when foraging, but rather upon the ground surface (and water), or a i r , allowing development -146-of r e l a t i v e l y high populations i n r e l a t i o n to the amount of edge where nest-sites are available, and thus creating a si t u a t i o n in which nest-sites are more l i k e l y to be a l i m i t -ing factor. The birds concerned, only a part of the t o t a l hole-nesting population, overlap broadly in nest-site r e -quirements, and most lack the a b i l i t y to excavate t h e i r own n e s t - c a v i t i e s . . . The wooded areas studied at the head of the Fraser Valley did not support nest-site competition. I t has been suggested that a s i m i l a r condition e x i s t s i n wooded areas elsewhere i n the v a l l e y and on the surrounding mountainsides. Some of the secondary hole-nesters concentrated t h e i r nesting a c t i v i t i e s in the town of Hope - here competition was observed but i t s infrequency, and the attendant circumstances, allowed the conclusion that i t s effect as a population - regulating factor was n e g l i g i b l e . The S t a r l i n g and-House Finch are re-cent a r r i v a l s , and t h e i r population densities w i l l increase greatly, perhaps modifying the above conditions. In the lower Fraser Valley, which i s much wider, t h i s separation of two hole-nesting populations i s much less d i s -t i n c t , as species nesting mainly in the town i n the v i c i n i t y of Hope may be found around the farms throughout the v a l l e y , i n company with other birds such as the Red-Shafted F l i c k e r , Downy Woodpecker, and Black-Capped Chickadee. .As the habitat conditions here are more closely a l l i e d to semi-open country-side with a large amount of "edge", i t i s suggested that nest-s i t e competition i s more l i k e l y to occur here, especially as the S t a r l i n g increases (though the scarcity of the Tree -147-Swallow, and the almost complete absence of the Western Blue-b i r d , which was common 15 years ago, cannot be attributed to competition with the S t a r l i n g ) . The l i m i t e d surveys carried out do not permit more d e f i n i t e predictions. -148-SUMMARY A study was made of the species composition, numbers, and habits of a hole-nesting avifauna i n southwestern B r i t i s h Columbia. The birds were considered i n r e l a t i o n to the habi-tat they occupied, with the purpose of explaining an observed presence or absence of nest-site competition. The study areas, surveyed over two breeding seasons, were near sea l e v e l i n forested mountainous t e r r a i n . They repre-sented a major portion of t h e i r surroundings in that they contained successional vegetational stages, which may often support large quantities of snags suitable f o r use by hole-ne st er s . Each hole-nesting species found on the studied areas i s considered separately, and those aspects of i t s breeding cycle pertinent to the concept of nest-site competition are detailed. Nest-site competition i s defined, and a review made of i t s possible r e s u l t s , and of the mechanisms that could be involved. A snag survey i l l u s t r a t e d a surplus of abandoned nesting c a v i t i e s . A l i m i t e d experiment involving the elimination of hole-nesting birds gave no result for which nest-site competition could be advanced as an explanation. Non-avian hole-users appeared to play a negligible r o l e as nest-site competitors. Primary hole-nesters nearly always excavated their own nest c a v i t i e s , for which a c t i v i t y the habitat usually pro-vided ample opportunity. These nest c a v i t i e s often d i f f e r e d -149-widely i n type and placement. Secondary hole-nesters either concentrated t h e i r nesting a c t i v i t i e s around the buildings i n the nearby town, neglect-ing the more "natural" s i t e s a v a i l a b l e ; were not obligated to use c a v i t i e s when nesting; or occurred i n such low densities, and were so positioned in the available suitable habitat, as to suggest that nest-site competition had no effect upon th e i r populat ions. Four species nested in crevices i n buildings and i n b i r d boxes i n a small town, where t h e i r breeding population den-s i t i e s were much higher than i n the surrounding couh t r y side. Nest-sites were judged to be present i n excess, and nest-s i t e competition, observed infrequently, was so rare, and apparently without s i g n i f i c a n t harmful e f f e c t , that i t was judged to be of n e g l i g i b l e importance as a population-regu-l a t i n g f a c t o r . The o v e r a l l absence of nest-site competition i s c o n t r i -buted to not only by the preferences of the species regarding t h e i r nest-sites, but also by the fact that the r e s u l t s of t h e i r habitat selection processes, and t h e i r l i v i n g habits within these habitats, tend to.'keep them e c o l o g i c a l l y dis-t i n c t . The factors regulating the populations of these hole-nesting species remain for the most part undetermined. The p o s s i b i l i t y that nest-site competition could operate as such a factor under conditions other than those observed must be allowed. -150-LITER ATURE CITED Al l e n , R.W., and M.M. Nice, 1952. & study of the breeding biology of the Purple Martin (Progne subis). Amer. M i d i . Nat., 47(3):606-6651 Anderson, A., 1 9 6 l . The breeding of the S t a r l i n g i n Aberdeenshire. Scot. Nat., 70(1):60-74« Andrewartha, H.G., and L.C. Birch, 1954* The d i s t r i b u t i o n and abundance of animals. 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A natural h i s t o r y survey of the Manning Park area, B r i t i s h Columbia. Occ. Pap. B.C. Prov. Mus. No. 9:1-130. Chapman, L.B., 1955. Studies of a Tree Swallow colony (Third paper ). Bird-Banding, 26:45-70. Cole, L.C., I960. Competitive Exclusion-. Science, 132: 343-349. Combellack, C.B., 1954* A nesting of Violet-Green Swallows. Auk, 71 :435-442. -152-Cowan, I . McT., and C.J. Guiguet, I 960 . The mammals of B r i t i s h Columbia. B.C. Prov. Mus. Handbook No. 1 1 : 1-413. Davis, D.E., 1959. T e r r i t o r i a l rank i n S t a r l i n g s . Animal Behavior. 7 ( 3 - 4 ) : 2 1 4 - 2 2 1 . Dennis, J.V., 1951. A comparative study of Flor i d a woodpeck-ers i n the non-breeding season. Unpubl. MSc. thesis, .U. of F l o r i d a . 133 pp. Dixon, K . L . , , 1 9 5 4 * Some ecological r e l a t i o n s of chickadees and titmice i n central C a l i f o r n i a . Condor, 5 6 ( 3 ) : 113-124. , 1 9 6 l . Habitat d i s t r i b u t i o n and niche r e l a t i o n * ships i n North American species of Parus. pp. 179-216 i n "Vertebrate Speciation", ed. by W.F. B l a i r . U. of Texas Press, Austin. Drury, W.H. J r . , 1958. Chickadees and nest boxes. Mass. And. Soc. B u l l . , Nov., 1958. Dunnet, G.M., 1955. The breeding of the St a r l i n g Sturnus  vulgaris i n r e l a t i o n to i t s food supply. I b i s , 97 : 619-662. Edson, J.M., 1943- A study of the Viiolet-Green Swallow. Auk, 60 :396-403. Edwards, R.Y., and D. S t i r l i n g , 1 9 6 l . Range expansion of the House Finch into B r i t i s h Columbia. Murrelet, 1+2: 38-42, E l l i o t t , J . J . , and R.S. Arbib, J r . , 1953* Origin and status of the House Finch i n the eastern United States. Auk, 70(1) :31-37 . Emlen, J.T., 1952. Social behavior i n nesting C l i f f Swallows. Condor, 54(4) :177-199 . Enderson, J.H., I 960 . A population study of the Sparrow Hawk i n east-central I l l i n o i s . . Wilson B u l l . , 72 :222-231. Erskine, A.J., i960. A discussion of the d i s t r i b u t i o n a l ecology of the Bufflehead (Bucephala albeola; Anatidae; Aves) based upon breeding bilogy studies i n B r i t i s h Columbia. Unpubl. MA thes i s , U. of B r i t i s h Columbia. Evenden, F.G., 1957. Observations on nesting behavior of the House Finch. Condor, 59:112-117. G r i n n e l l , J;., . and A.H. M i l l e r , 1944. The d i s t r i b u t i o n of the birds of C a l i f o r n i a . P a c i f i c Coast Avifauna, No. 27: 1 -608. -154-Guiguet, C.J., 1954- The birds of B r i t i s h Columbia, ( l ) the woodpeckers, (2) the crows and th e i r a l l i e s . B.C. Prov. Mus. Handbook No. 6 : 1 - 5 1 . G u l l i o n , G.W., 1947. Use of a r t i f i c i a l nesting s i t e s by Violet-Green and Tree Swallows. Auk, 64 :411-415. von Haartman, L., 1956. Territory i n the Pied Flycatcher Muscicapa hypoleuca. I b i s , 98 :460-475. Happ, G.B., 1935. A study of the F l i c k e r , (Colaptes auratus (Linnaeus)). Unpubl. MSc thes i s , Cornell University. Hardin, G., I960 . The competitive exclusion p r i n c i p l e . Science, 131:1292-1298. Hensley, M., and J.B. .Cope, 1951. Further data . on removal and repopulation of the breeding birds i n a spruce-fir forest community. Auk, 6 8 : 4 8 3 - 4 9 3 . Hollom, P.A.D., 1943. Bank Swallows nesting i n a r t i f i c i a l holes. Auk, 60 :270-1 . Horvath, 0 . , 1963 • Contributions to nesting ecology of forest b i r d s . Unpubl. MF t h e s i s , U. of B r i t i s h Columbia. Howell, T.R., 1952. Natural h i s t o r y and d i f f e r e n t i a t i o n i n the Yellow-Bellied Sapsucker. Condor, 54(5):237-282. , 1953. Racial and sexual differences i n migra-t i o n i n Sphyrapicus varius. Auk, 70(2) :118-126. Hutchinson, G.E., and R.H. MacArthur, 1959. Appendix; on the t h e o r e t i c a l significance of aggressive neglect i n i n t e r s p e c i f i c competition. Amer. Nat., 93 (869) : 133-134. Johnson, C.G., 1951. The study of wind-borne • insect popula-tions i n r e l a t i o n to t e r r e s t r i a l ecology, f l i g h t period-i c i t y , and the estimation of a e r i a l populations. Science Progress, 3 9 : 41-62 . Johnston, R.F., and J.W. Hardy, 1962. Behavior of the Purple Martin. Wilson B u l l . , 74(3) :243-262. Johnston, V.R., 1943 • An ecological study of nesting birds i n the v i c i n i t y of Boulder, Colorado. Condor, 45 : 61-68 . Kalmbach, E.R., 1940. Economic status of the English Spar-row i n the United States. U.S. Dept. Agric. Tech. B u l l . No. 711: 1 -66. Kalmbach, E.R., and W.L. McAtee, 1957. Homes for birds. U.S. Department of the I n t e r i o r , Conserv. B u l l . No. 14 : 1 -24. -155-Kessel, B., 1953' Second broods in the European Starling i n North America. Auk, 70:479-433. , 1957. A study of the breeding biology of the European Starling (Sturnus vulgaris L.) i n North America. Amer. M i d i . Nat., 58(2) :257-331. , I960. Courtship and t e r r i t o r i a l behavior of Hairy Woodpecker. Auk, 77(3):259-270. , 1962a. Breeding behavior of Yellow-Bellied Sap-suckers. Auk, 79:31-43* , 1962b. Nest sanitation of Yellow-Bellied Sap-suckers. Wilson B u l l . , 74(l):96-97-, 1962c. Reproductive behavior of Downy Woodpeckers. Condor, 64(2):126-133. Kingsbury, E.W., 1932. A study of the Hairy Woodpecker, Dryobates v i l l o s u s v i l l o s u s . Unpubl. MA .thesis, Cornell University i Kluyver, H.N., 1961. Food consumption i n r e l a t i o n to habitat i n breeding chickadees. Auk, 78:532-550. Kluyver, H.N., and L. Tinbergen, 1953* Territory and the re-gulation of density in titmice. Arch. Neerl. Zool., 10(3):265-289. Koskimies, J . , 1956. Zur charakteristik und geschichte der nistokologischen divergenz beim mauersegler. Apus apus (L.) , i n Nordeuropa. Ornis Fennica, 33(3-4) :77-96. Lack, D., 1954. The natural regulation of animal numbers. Oxford University Press, Oxford. 343 pp. , 1956. Swifts i n a tower. Methuen, London. 239 pp. Lack, D., and D.F. Owen, 1955- The food of the Swift. J . Anim. Ecol., 24:120-136. Mayhew, W.W., 1958. The biology of the C l i f f Swallow i n C a l i f o r n i a . Condor, 60(l ) :7-37 . McLaren, W., 1963. A preliminary study of nest-site competi-t i o n i n a group of hole-nesting birds. Unpubl. MSc thesis, U. of B r i t i s h Columbia. 57 pp. Milne, A., 196l. D e f i n i t i o n of competition among animals, symp. Soc. Exper. B i o l . No. 15:40-61. Munro, J.A., and I . McT. Cowan, 1947. A review of the b i r d fauna of B r i t i s h Columbia. B.C.. Prov. Mus. Spec. Pub. No. 2,: 1-285. -156-Myres, M.T*, 1958. The European'Starling i n B r i t i s h Columbia: 1947-1957- Occ. Papers B.C. Prov. Mus. No. 11:1-59. . Nagy, A.C., 1963• Population density of Sparrow Hawks i n eastern Pennsylvania. Wilson B u l l . , 75(1) :93« N i c k e l l , W.P., 1956. Nesting of the Black-Capped Chickadee-i n the southern peninsula of Michigan. Jack-Pine Warbler, 34 (4) :127-13$. Odum, E.P., 1941a. Annual cycle of the Black-Capped Chickadee-1. Auk, 58(3):314-333. , 1941b. Annual cycle of the Black-Capped Chickadee-2. Auk, 58$518-535. , 1943. 'Courtship feeding' i n the Black-Capped Chickadee. Auk, 60:444-445. Owen, O.S., 1957. Observations on t e r r i t o r i a l behavior i n the English Sparrow. B u l l . Ecol. Soc. Amer., 3 8 ( 4 ) : 101rl02. Patten, B.C., 1 9 6 l . Competitive Exclusions. Science, 134 (3490):1599-l601. Paynter, R.A., 1954- Interrelations between clu t c h - s i z e , brood-size, prefledging s u r v i v a l , and weight i n Kent Island Tree Swallows. Bird-Banding, 25(2):35-58, and 25(3):102-148. P h i l l i p s , R.E., and H.C. Black, 1956. A winter population study of the western Winter Wren. Auk, 73:401-410. Ripley, S.D., 1959. Competition between sunbird and honey-eater species i n the Moluccan Islands. Amer. Nat., 93(869):127-132. ; , 196 l . Aggressive neglect as a factor i n i n t e r -.specific competition i n birds. Auk, 78:366-371. Roest, A.I., 1957. Notes on the American Sparrow Hawk. Auk, 74:1-19. S a l t , G.W., 1952. The r e l a t i o n of metabolism to climate and d i s t r i b u t i o n i n three finches of the genus Carpodacus. Ecol. Monogr., 22:121-152. ..Selander, R.K., and D.R. G i l l e r , 1959. I n t e r s p e c i f i c relations of woodpeckers i n Texas. Wilson B u l l . , 71(2):107-124. Simmons, K.E.L., 1951. I n t e r s p e c i f i c t e r r i t o r i a l i s m . I b i s , 93:407-413. Skutch, A.F., I 9 5 5 . The Hairy Woodpecker i n Central America. Wilson BuiL, 67(1) :25-3'2. -157-Staebler, S.E., 1949 . A comparative l i f e h i s t o r y study of the Downy and Hairy Woodpecker. (Dendrocopos pubescens and Dendrocopos v i l l o s u s ) . Unpubl. PhD thesis, U. of Michigan. 225 pp. Stewart, R.E.,.. and J.W. Al d r i c h , 1951- Removal and repopula-tio'n of breeding birds i n a spruce-fir community. Auk, 68:471-482; Summers-Smith, D., 1958. Nest-site s e l e c t i o n , pair formation, and t e r r i t o r y i n the House Sparrow, Passer domesticus. I b i s , 100:190-203. , 1959 . The House Sparrow Passer domesticus: population problems. I b i s , 101:449-454. Svardson, G., 1949. Competition and habitat selection i n birds. Oikos, 1:157-174-Thacker, T.L., 1922. L i s t of the commoner birds of the neighbourhood of Hope, B.C. Mimeographed notes. Thompson, W.L., I 9 6 0 . Agonistic behavior i n the House Finch. P a r t - i l : Annual cycle and display patterns. Condor, 62(4) : '245-271. Part I I : Factors' i n aggressiveness and s o c i a l i t y . Condor 62 (5).: 3.78-402. Thorpe, W.H., 1945. The evolutionary significance of habitat selec t i o n . J . Anim. EcoIU, 14 (2):6?-70. Tompa, F.S., 1962. T e r r i t o r i a l behavior: the main c o n t r o l l i n g factor of a l o c a l Song Sparrow population. Auk, 7 9 ( 4 ) : 687-697. " Udvardy, M.D.F., 1951. The significance of i n t e r s p e c i f i c competition i n b i r d l i f e . Oikos, 3 ( l ) : 9 8 - 1 2 3 . Weaver, R.L., 1943• Reproduction i n English Sparrows. Auk, 60:60-74-Weydemeyer, W., 1934* Tree Swallows at home i n Montana. Bird-Lore, 36:100-105. Weydemeyer, and D., 1928. The woodpeckers of Lincoln County, Montana. Condor, 30:339-346. Whittle, C.L., 1926. Notes on the nesting habits of the • Tree Swallow. Auk, 43:247-248. Wynne-Edwards, V.C., 1962. Animal dispersion i n r e l a t i o n to s o c i a l behavior. Hafner Pub. Co., N.I. 653 pp. -158-P l a t e I I . The southeast slope o f the Reservation. Kawkawa Lake i s i n the foreground. -159-te I I I . The upper southeast slope of the Reserva-t i o n . This was p r e f e r r e d Chestnut-Backed Chickadee h a b i t a t , and poor Winter Wren h a b i t a t . A wren nest was b u i l t i n r o o t s at the top of the roadside bank during 1962. e IV. The northern p o r t i o n s of area "F", as seen from the west h i l l . -160-P l a t e V. The southern h a l f of area "F", as seen from the top of the west h i l l . L i t t l e Mountain i s the low h i l l i n the background. P l a t e V I . The town of Hope: population 2,500. The view i s t o the n o r t h , over the center of the study area. L i t t l e Mountain, on which the Reservation was l o c a t e d , i s the small h i l l to the r i g h t . - 1 6 1 -Plate VII. The Hope-Princeton Highway crosses this bridge at the Old Mining Camp. Of the three drains in the cement foundation, the middle one was unoccupied, Rough-ringed Swallows nested in the one on the left, and Violet-Greens in the one on the right. Plate VIII. The open portion of the Laidlaw Study Area. -162-Plate IX. The birch snag 2-1-2, at the bottom of the northeast slope. Both Chestnut-Backed and Black-Capped Chickadees ex-cavated i n the same portion of t h i s snag during the same season, though at different times. -163-Plate XI. Two of the ten b i r d boxes erected over the marsh. Swallows fed at the marsh during poor weather. Plate X I I . Under the eaves of t h i s building i s a series of i d e n t i c a l c a v i t i e s . English Sparrows nested only i n the cavity above the wires, which were used as perches. On the opposite side of the building, Violet-Green Swallows nested i n a cavity at a corner. -164-Plate X I I I . A series of c a v i t i e s i s under the overhang. English Sparrows nested both years i n the corner cavity by the support cable, which was used as a perch. Other ca v i t i e s were u t i l i z e d by Star l i n g s , (1 p a i r , 1962), and Violet-Green Swallows, (1 p a i r , both years). Plate XIV. The House Finch nest. Nest material i s v i s i b l e above the arrow. - 1 6 5 -APPENDIX A Dimensions of Bird Boxes Bir d boxes were constructed to dimensions slightly-modified from those given by Kalmbach and McAtee (1957) as suitable for swallows. Lumber 3/4 inch thick was used: a l l measurements are external. Floor - 7h inches square Front - 6-3/4 inches high - 1-3/4 inches i n diameter. Hole c e n t r a l l y located both h o r i z o n t a l l y and v e r t i c a l l y . A perch 2 inches long of h inch dowel was placed 2 inches to one side of, and 2 inches below, the center of the entrance. Rear 9k inches high. Top removable. Sides projected 3/4 inches over the front. each had 2 - J inch diameter v e n t i l a t i o n holes 1 inch below upper edge. Color white -166-APPENDIX B S c i e n t i f i c nomenclature for species mentioned i n the text. Sources used: Plants - Henry, J.K., 1915. Flora of southern B r i t i s h Columbia and Vancouver Island. Gage, Toronto. 363 pages. C a r l , G.C., C.J. Guiguet, and G.A. Hardy, 1952. A natural h i s t o r y survey of the Manning Park area, B r i t i s h Columbia. Occas. Pap. B.C. Prov. Mus. No. 9 : 1 - 1 3 0 . - among others. Birds - A.O.U. Check-List of North American birds, 1957. F i f t h Ed. Baltimore Press, Baltimore. 691 pgs. Mammals- Cowan, I.McT., and C.J. Guiguet, I 9 6 0 . The mammals of B r i t i s h Columbia. B.C. Prov. Mus., Handbook No. 11 :1-413 . Plants: Red Cedar Lodgepole Pine Grand F i r Alpine F i r Douglas F i r •Western Hemlock Mountain Hemlock Engelmann Spruce Sitka Spruce Willow P a c i f i c Willow Black Cottonwood Thu.ja p l i c a t a Donn. Pinus contorta Dougl. Abies grandis L i n d l . Abies lasiocarpa (Hook.) Nutt. Pseudotsuga menziesii (Mirb.) Franco Tsuga heterophylla Sarg. Tsuga mertensiana Carr. Picea engelmanni Engelm. Picea sitchensis Carr. Sal i x sp. Sa l i x lasiandra Benth. Populus trichocarpa T. and G. - 1 6 7 -Hazel White Birch Red Alder Oregon Grape Mock Orange Ocean Spray Saskatoon Berry False Box Broadleaf Maple Vine Maple Flowering Dogwood Sa l a l Birds: Wood Duck Common Goldeneye Barrow's Goldeneye Bufflehead Hooded Merganser Common Merganser Pigeon Hawk Sparrow Hawk Scree ch Owl Great Horned Owl Hawk Owl Pygmy Owl Spotted Owl Corylus cornuta Marsh., var. c a l i f o r n i c a (AD.C.) Sharp. Betula papyrifera Marsh., var. commutata (Regel.) Fern. Alnus rubra Bong. Berber i s nervosa Pursh. Philadelphus gordonianus L i n d l . Holodiscus d i s c o l o r (Pursh) Maxim. Amelanchier f l o r i d a L i n d l . Pachystima myrsinites Raf. Acer macrophyllum Pursh. Acer circinatum Pursh. Cornus n u t t a l l i i T. and G. Gaultheria shallon Pur sh. Aix sponsa (Linnaeus) Bucephala clangula (Linnaeus) Bucephala i s l a n d i c a (Gmelin) Bucephala albeola (Linnaeus) Lophodytes' cucullatus (Linnaeus) Mergus merganser Linnaeus Falco., columbarius Linnaeus Falco sparverius Linnaeus Otus asio (Linnaeus) Bubo virginianus (Gmelin) Surnia u l u l a (Linnaeus) Glaucidium gnoma Wagler. S t r i x O c c i d e n t a l i s (Xantus) -168-Boreal Owl Saw-whet Owl Yellow-Shafted F l i c k e r Red-Shafted F l i c k e r Aegolius funereus (Linnaeus) Aegolius acadicus (Graelin) : Colaptes auratus (Linnaeus) Colaptes cafer (Gmelin) Pileated Woodpecker-Dryocopus.pileatus (Linnaeus) Red-Bellied Woodpecker Golden-Fronted Woodpecker Red-Headed Woodpe cker Lewis' Woodpecker Yellow-Bellied Sapsucker Red-Breasted Sapsucker Hairy Woodpecker Downy Woodpecker Black-Backed Three-Toed Woodpecker Northern Three-Toed Woodpecker Violet-Green Swallow Tree Swallow Bank Swallow Rough-Winged Swallow Barn Swallow C l i f f Swallow Purple Martin Centurus carolinus (Linnaeus) Centurus aurifrous (Wagler), Melanerpes erythrocephalus (Linnaeus) Asyndesmus lewis (Gray) Sphyrapicus varius nuchalis Baird Sphyrapicus varius ruber (Gmelin) Dendrocopos villosus.(Linnaeus) Dendrocopos pubescens (Linnaeus) Picoides arcticus (Swainson) Picoides t r i d a c t y l u s (Linnaeus) Tachycineta thalassina (Swainson ) Iridoprocne bicolor ( V i e i l l o t ) Riparia r i p a r i a (Linnaeus) Stelgidopteryx r u f i c o l l i s ( V i e i l l o t ) Hjrundo r u s t i c a Linnaeus Petrochelidon pyrrhonota ( V i e i l l o t ) Progne subis (Linnaeus) -169-Black-Capped Chickadee Mountain Chickadee Che st nut-Backed Chickadee White-Breasted Nuthatch Red-Breasted Nuthatch Brown Creeper House Wren Winter Wren Bewick 1s Wren Western Bluebird Mountain Bluebird Golden-Crowned Kinglet S t a r l i n g House Sparrow House Finch Parus a t r i c a p i l l u s Linnaeus Parus gambeli Ridgway Parus rufescens Townsend S i t t a carolinensis Latham S i t t a canadensis Linnaeus Certhia f a m i l i a r i s Linnaeus Troglodytes aedon V i e i l l o t Troglodytes troglodytes (Linnaeus) Thryomanes bewickii (Audubon) S i a l i a mexicana Swainson S i a l i a currucoides (Bechstein) Regulus satrapa Lichtenstein Sturnus vulgaris Linnaeus Passer domesticus (Linnaeus) Carpodacus mexicanus (Muller) Mammals: Chipmunk Douglas Squirrel Northern Flying Squirrel Deer Mouse Eutamias sp. Tamiasciurus douglasi m o l l i p i -losus (Audubon and Bachman) Glaucomvs sabrinus (Shaw) Peromyscus maniculatus (Wagner) 

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