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Qualities of individuals in a replacement stock of blue grouse Low, David J. 1975

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QUALITIES OF INDIVIDUALS IN A REPLACEMENT STOCK OF BLUE GROUSE by DAVID JAMES LOW B . S c , U n i v e r s i t y o f B r i t i s h C olumbia, 1971 A t h e s i s s u b m i t t e d i n p a r t i a l f u l f i l l m e n t o f the r e q u i r e m e n t s f o r t h e degree o f MASTER OF SCIENCE i n the Department o f ZOOLOGY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1975 In present ing th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for s c h o l a r l y purposes may be granted by the Head of my Department or by h is representa t ives . It is understood that copying or pub l i ca t ion of th is thes is for f i n a n c i a l gain sha l l not be allowed without my wr i t ten permission. Department of <3O JLJOG. XI The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 ABSTRACT An ent i r e breeding population of blue grouse (Dendraqapus  obscurus) was removed i n 1970 from an area of 900 acres of second-growth forest land on c e n t r a l Vancouver Island. The population had been d e c l i n i n g since 1954. A nearby area with i t s grouse population i n t a c t was retained as a c o n t r o l . The a r t i f i c i a l l y removed population was completely replaced at the f i r s t breeding season, - almost completely by y e a r l i n g birds, which i s evidence for there being a surplus of i n d i v i -duals i n the spring. This new population resembled the o r i g i n a l residents and other grouse i n surrounding areas. The use of behaviour evaluation techniques revealed that the recolonizing population was as aggressive as the o r i g i n a l residents had been. The removal experiment gave strong evidence that blue grouse space themselves out through t e r r i t o r i a l behaviour. i i TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS i i LIST OF TABLES i v INTRODUCTION 1 MATERIALS AND METHODS 3 P o p u l a t i o n a n a l y s i s 3 Be h a v i o u r 4 a) M i r r o r t e s t b e h a v i o u r 4 b) Grouse b e h a v i o u r r e c o r d e d by o b s e r v e r s i n t he e v e n i n g s 5 RESULTS 6 P o p u l a t i o n t r e n d s . . . . 6 M o r t a l i t y r a t e s 6 P r o d u c t i o n : 7 G e n e r a l p r o d u c t i o n i n d i f f e r e n t y e a r s 7 P r o d u c t i o n o f c h i c k s i n r e l a t i o n t o age of hen 9 Se a s o n a l d i f f e r e n c e s i n w e i g h t s o f grouse on b o t h a r e a s 11 Movements o f r e s i d e n t male grouse on s p r i n g range . . 12 B e h a v i o u r o f t e r r i t o r i a l cocks i n a t e s t a rena . 13 Grouse a c t i v i t y as r e c o r d e d a t l i s t e n i n g p o s t s : "the s p r i n g o f 1971, 1972, and 1973" . . . 15 DISCUSSION 17 P o p u l a t i o n t r e n d i n t h e new p o p u l a t i o n 17 TABLE OF CONTENTS (CONTINUED) i i i Page Were t h e new b i r d s b e h a v i o u r a l l y d i f f e r e n t t h a n the o l d s t o c k ? 18 Where does t h i s l e a v e us i n e x p l a i n i n g r e g u l a t i o n o f a n i m a l numbers? 20 SUMMARY 22 LITERATURE CITED 2 4 i v LIST OF TABLES T a b l e Page 1 D e n s i t y o f t e r r i t o r i a l males (number/100 a c r e s ) 6 2 M o r t a l i t y r a t e s o f males (1971-73) 7 3 Numbers and comparison o f grouse i n h u n t e r s ' bags (1969-72) 8 4 P r o d u c t i o n o f young on e x p e r i m e n t a l and c o n t r o l a r e a s 1971, 1972, and 1973 combined . 10 4 (a) Hens w i t h broods 10 4 (b) P e r c e n t a g e b r o o d l e s s hens 10 5 Age o f hen and p r o d u c t i o n o f c h i c k s , 1972 and 1973 11 6 Response o f males t o arena t e s t and comparison w i t h d a t a o f Mossop (1969) . . . . 14 7 Average number o f h o o t i n g males h e a r d per e v e n i n g 16 1 INTRODUCTION P r e v i o u s removal e x p e r i m e n t s on r e d grouse (Watson and J e n k i n s , 1968) demonstrated r a t e s o f r e c r u i t m e n t t h a t d i f f e r e d w i t h seasons o f t h e y e a r i n wh i c h t h e removal t o o k p l a c e . I f the removal t a k e s p l a c e i n the autumn the numbers o f b i r d s o c c u p y i n g t e r r i t o r i e s i n t h e f o l l o w i n g s p r i n g u s u a l l y r o s e t o the p r e - e x i s t i n g d e n s i t y . The r e d grouse removal e x p e r i m e n t s showed a l s o t h a t t h e s i z e o f b r e e d i n g s t o c k s was d e t e r m i n e d by t e r r i t o r i a l b e h a v i o u r . However, no s t u d y so f a r has m o n i t o r e d a r e c r u i t m e n t p o p u l a t i o n o f g r o u s e , a f t e r i n i t i a l r e c o l o n i z a t i o n , t o i n s p e c t f o r emerging changes i n s t o c k q u a l i t y . I t has been shown t h a t i n a l l g r o u s e - r e m o v a l . e x p e r i m e n t s r e p l a c e m e n t b i r d s are drawn from t h e p o o l o f n o n - t e r r i t o r i a l young b i r d s . I n 1970 B e n d e l l e t a l performed a removal e x p e r i m e n t i n a p o p u l a t i o n o f b l u e g r o u s e . I n 1971 t h e p o p u l a t i o n r e t u r n e d t o t he same d e n s i t y as b e f o r e and i n a p p r o x i m a t e l y even sex r a t i o . A p p r o x i m a t e l y 90% o f t h e r e c r u i t i n g b i r d s were y e a r l i n g g r o use. The r e s u l t s s u b s t a n t i a t e d the c o n c l u s i o n t h a t b l u e t grouse a r e s p a c i n g themselves out th r o u g h t e r r i t o r i a l b e h a v i o u r . The purpose o f my s t u d y i s t o a n a l y z e the q u a l i t y o f r e c r u i t s i n the new p o p u l a t i o n . The p r i n c i p a l q u e s t i o n s I asked were: 1. What t r e n d s d i d t h e new p o p u l a t i o n f o l l o w ? 2. Were b i r d s e n t e r i n g the removal a r e a d i f f e r e n t from t h o s e e n t e r i n g the c o n t r o l area? 2 3. Where does t h i s l e a v e us i n e x p l a i n i n g the r e g u l a t i o n o f a n i m a l numbers? My st u d y was conducted on the e a s t s i d e o f Vancouver I s l a n d on the same p o p u l a t i o n as r e p o r t e d on by B e n d e l l e t a l (1972). 3 MATERIALS AND METHODS T h i s s t u d y was c a r r i e d o u t i n t h e s p r i n g s and summers o f 1971, 1972, and 1973 a t M i d d l e Quinsam Lake, a p p r o x i m a t e l y 15 m i l e s west o f t h e town o f Campbell R i v e r , B.C., a t an a l t i t u d e o f a p p r o x i m a t e l y 1,000 f e e t . I t was d i r e c t e d t o the a n a l y s i s o f the a r e a from w h i c h a l l r e s i d e n t b i r d s had been removed i n 19 70 and on the a d j a c e n t c o n t r o l a r e a . Removal (MQL-X) and c o n t r o l (MQL-C)areas, a p p r o x i m a t e l y one m i l e a p a r t , were e s t a b l i s h e d w i t h i n a 40,000-acre a r e a t h a t had been l o g g e d and l a t e r burned by w i l d f i r e i n 1952. The two areas were chosen because o f t h e i r s i m i l a r i t y i n appearance. P o i n t i n g dogs were used t o l o c a t e t e r r i t o r i a l males and t o d e t e c t t h e p r e s e n c e o f o t h e r b i r d s on the a r e a s . P o p u l a t i o n a n a l y s i s E s t i m a t e s o f p o p u l a t i o n d e n s i t y o f h o o t i n g t e r r i t o r i a l males were based on r e s i g h t i n g s o f p r e v i o u s l y banded b i r d s and f r e q u e n t s i g h t i n g s o f newly banded b i r d s . S i n c e t h e sex r a t i o i s even i n b l u e grouse ( B e n d e l l , 1967), d e n s i t y i s e x p r e s s e d as h o o t i n g t e r r i t o r i a l males per 100 a c r e s . From c a p t u r e and r e s i g h t d a t a , the sex and age r a t i o and m o r t a l i t y r a t e s can be d e t e r m i n e d i n any one y e a r . The m o r t a l i t y r a t e o f a d u l t males can be c a l c u l a t e d s i m p l y and a c c u r a t e l y because of the f a i t h f u l n e s s w i t h w h i c h they r e t u r n t o t h e i r t e r r i t o r i e s i n s u c c e s s i v e y e a r s ( B e n d e l l , 1967). I t can t h e r e f o r e be assumed 4 that f a i l u r e to record a banded adult male on his t e r r i t o r y of the previous year means that he i s dead. For a more detailed description of general methods and f i e l d procedures see Bendell (1955), Zwickel (1965), Zwickel and Bendell (1967), S t i r l i n g and Bendell (1966). Grouse were c l a s s i f i e d as adults (over two years) or yearlings, according to the roundness of the outer two primaries (Boag, 1965). Male grouse were c l a s s i f i e d as t e r r i t o r i a l or transient. A t e r r i t o r i a l b i r d being one frequently seen i n one l o c a l i t y , a transient being one resighted once or twice over a very large area, or not being seen again after banding. Body weights of adult and yearling males and females were obtained at time of banding. The weights of yearling and adult males and females on both areas were tested by means of a two-way analysis of variance. Behaviour I evaluated the qu a l i t y of individuals i n two ways: d i r e c t l y by using t e r r i t o r i a l movements on the summer range and the mirror-testing of t e r r i t o r i a l cocks, and i n d i r e c t l y by recording undisturbed sexual and t e r r i t o r i a l a c t i v i t y i n the evenings. a. Mirror test behaviour Mirror image stimulation i s a technique for studying aggressive and s o c i a l patterns i n a wide variety of animals which respond to t h e i r r e f l e c t i o n i n a mirror. Previous studies on marmots-} finches, and parakeets demonstrated that responses of animals to t h e i r r e f l e c t e d image are consistent with t h e i r 5 b e h a v i o u r a l d i s p l a y s n o t e d d u r i n g s o c i a l i n t e r a c t i o n s i n t h e f i e l d ( G a l l u p and Capper, 1970; Svendsen and A r m i t a g e , 1973). Mossop (1971) used t h e m i r r o r image t e c h n i q u e on t h r e e d i f f e r e n t p o p u l a t i o n s o f b l u e grouse and e s t a b l i s h e d an i n v e r s e c o r r e l a t i o n between d e n s i t y o f b l u e grouse and r e a c t i o n s towards t h e i r m i r r o r images. I a p p l i e d t h i s method i n the s p r i n g o f 1973 t o examine f o r d i f f e r e n c e s . i n b e h a v i o u r o f t h e t e r r i t o r i a l males o f t h e two s t o c k s . I p l a c e d t h r e e p l a t e g l a s s m i r r o r s 40 cm by 60 cm w e l l w i t h i n the t e r r i t o r y o f a male, t o g e t h e r w i t h a dummy hen b l u e grouse i n s q u a t t i n g c o p u l a t i o n p o s i t i o n about two f e e t away. Each t e s t began;.when a male a r r i v e d i n response t o a tape c o n t a i n i n g p r e c o p u l a t o r y c a l l s from a hen b l u e grouse. One t e r r i t o r i a l male was t e s t e d on the e x p e r i m e n t a l a r e a , a n o t h e r on t h e c o n t r o l a r e a each day t h r o u g h o u t s p r i n g . Times f o r t e s t i n g were as f o l l o w s : 0600-1030 hours and 1930-2215 h o u r s . b. Grouse b e h a v i o u r r e c o r d e d by o b s e r v e r s i n the e v e n i n g s L i s t e n i n g p o s t s , from w h i c h o b s e r v e r s would r e c o r d a c t i v i t y o f grouse o n e - h a l f hour a f t e r s u n s e t f o r 40 t o 50 minutes were p i c k e d on b o t h a r e a s . The same p o s t s were used d u r i n g the s p r i n g s and summers o f 1972 and 1973, whereas i n 1971 b e h a v i o u r a l a c t i v i t y was r e c o r d e d w h i l e I w a l k e d on t h e roads i n the e v e n i n g s . A t 10-min i n t e r v a l s , c a l l s / m i n u t e were r e c o r d e d f o r t h e f i r s t t h r e e minutes o f l i s t e n i n g . D u r i n g the r e m a i n i n g seven m i n u t e s , i n t e n s i t y o f grouse c a l l s and t h e numbers o f grouse h e a r d were n o t e d . L i s t e n i n g s t a r t e d e a r l y i n A p r i l and c o n t i n u e d u n t i l t h e m i d d l e o f -June. 6 RESULTS P o p u l a t i o n t r e n d s Between 1970 and 1973 grouse numbers i n the Campbell R i v e r a r e a dropped from s i x t o f o u r t e r r i t o r i a l males p e r 100 a c r e s (Table 1 and B e n d e l l , 1972). TABLE 1. D e n s i t y o f t e r r i t o r i a l males (no./lOO a c r e s ) . A l l b i r d s on t h e e x p e r i m e n t a l a r e a (MQL-X) were removed i n 1970. MQL-X (90 0 a c r e s ) MQL-C (800 ac r e s ) No. o f B i r d s D e n s i t y No. o f B i r d s D e n s i t y 1970 64 6.1 48 6.0* 1971 46 5.1 52 6.5 1972 38 4.1 45 5.6 1973 35 4.0 30 3.8 T h i s t o t a l i s p r o b a b l y low, as the census was i n c o m p l e t e M o r t a l i t y r a t e s The m o r t a l i t y r a t e o f a d u l t t e r r i t o r i a l males (Table 2) was a p p r o x i m a t e l y 30% p e r y e a r , which agrees w i t h t h a t r e p o r t e d f o r o t h e r b l u e grouse p o p u l a t i o n s ( B e n d e l l , 19 67) . The d e c l i n e i n t he p o p u l a t i o n appears t o r e s u l t from the r e c r u i t m e n t o f y e a r l i n g s b e i n g i n a d e q u a t e t o r e p l a c e t h e l o s s e s o f a d u l t s : o n l y i n 1971, on t h e c o n t r o l a r e a d i d enough y e a r l i n g s e n t e r 7 t h e p o p u l a t i o n t o p r e v e n t numbers from d r o p p i n g . TABLE 2. M o r t a l i t y r a t e s o f males (1971-73) MQL-X MQL-C No. No. % Mor- No. No. % Mor-Banded Ret u r n e d t a l i t y Banded Returned t a l i t y t e r r i t o r i a l 22 16 28 53 41 23 a d u l t s t e r r i t o r i a l 16 15 8 7 6 14 y e a r l i n g s P r o d u c t i o n There i s much v a r i a t i o n from y e a r t o y e a r i n the p r o d u c t i o n and s u r v i v a l o f young t o autumn, but p a s t s t u d i e s o f b l u e grouse have a l l shown t h a t t h e r e a re more th a n enough y e a r l i n g s the f o l l o w i n g s p r i n g t o r e p l a c e a d u l t m o r t a l i t y ( B e n d e l l , 1955; R e d f i e l d , 1972; Z w i c k e l and B e n d e l l , 1967; Z w i c k e l and B e n d e l l , 1972). G e n e r a l p r o d u c t i o n i n d i f f e r e n t y e a r s P r o d u c t i o n o r b r e e d i n g s u c c e s s was d e f i n e d f o r t h e purposes of t h i s s t u d y as number o f c h i c k s r a i s e d p e r br o o d by August. I n 1971, broods were t h e s m a l l e s t o f the f o u r y e a r s (1970-1973). However, when I compared p r o d u c t i o n d a t a f o r 1971 w i t h the p r o d u c t i o n d a t a f o r 1970, 1972, and 1973, I found no s i g n i f i c a n t d i f f e r e n c e i n numbers o f broods o b s e r v e d , o r i n numbers o f c h i c k s p e r brood e a r l y i n t h e season. There was a l s o no 8 s i g n i f i c a n t d i f f e r e n c e i n the p r o p o r t i o n of chicks found i n the hunter road check data comparing hunter k i l l i n 1 9 6 9 , 1 9 7 0 , and 1 9 7 2 against 1 9 7 1 (Table 3 ) . The percentage of j u v e n i l e s shot per ad u l t or y e a r l i n g female was s i g n i f i c a n t l y lower. Another measure of production i s the percentage of broodless hens observed l a t e r i n the season ( i ; e . J u l y and August) a f t e r most broods have hatched. A broodless hen may r e s u l t from: i n f e r t i l e eggs, l o s s of young, nest p r e d a t i o n , the i n a b i l i t y to renest, nest d e s e r t i o n , and the p h y s i o l o g i c a l i n a b i l i t y to produce young. The number of broodless hens observed i n J u l y and August i n 1 9 7 1 on both areas was s i g n i f i -c a n t l y higher than i n the other three years (Table 4(b) P / . O O I ) . TABLE 3 . Numbers and comparison of grouse i n hunters' bags ( 1 9 6 9 - 1 9 7 2 ) 1 9 6 9 1 9 7 0 1 9 7 1 1 9 7 2 T o t a l b i r d s t a l l i e d 5 4 5 7 2 2 4 5 Number of hunters 3 9 3 8 5 8 4 0 % chicks 6 8 6 9 4 0 7 3 The removal area (MQL-X) i n 1 9 7 1 had only y e a r l i n g b i r d s . Since y e a r l i n g cocks are though to be l e s s f e r t i l e and y e a r l i n g hens poorer mothers because of inexperince or p h y s i o l o g i c a l i n a b i l i t y to produce, fewer broods might be expected (Bendell, 1 9 6 7 ) . The year 1 9 7 1 r e s u l t e d i n poorer production of chick grouse on both areas. On MQL-X however, 9 4 3 hens produced t h r e e broods o n l y (7% s u c c e s s ) w h i l e on t h e c o n t r o l a r e a 32 females produced e i g h t broods (25% s u c c e s s ) (Table 4 [Ja] ) . T h i s d i f f e r e n c e i s s t a t i s t i c a l l y s i g n i f i c a n t . The two a r e a s were chosen because they were s i m i l a r , and t h e r e i s no e v i d e n c e t h a t e n v i r o n m e n t a l d i f f e r e n c e s were a s s o c i a t e d w i t h the d i f f e r e n c e s , i n s u c c e s s . I t h e r e f o r e c o n c l u d e t h a t the poor s u c c e s s on the e x p e r i m e n t a l a r e a i n 1971 was due t o the hens a l l b e i n g y e a r l i n g s . P r o d u c t i o n o f c h i c k s i n r e l a t i o n t o age o f hen The s e a r c h f o r broods i n 19 73 was t e r m i n a t e d by the end of June, t h e r e f o r e the numbers o f broods found i n 1972 and e a r l y 1973 were added t o g e t h e r t o i n c r e a s e t h e sample s i z e . The hens on the removal a r e a produced p r o p o r t i o n a t e l y more broods (27) and more c h i c k s p e r brood (2.6) i n 1972 and 1973 than d i d t h e hens on the c o n t r o l a r e a , which produced o n l y 16 broods w i t h an average o f 1.7' c h i c k s p e r brood (Table 5 ) . Because o f t h e r a p i d r e c o l o n i z a t i o n i n 1971, t h e b r e e d i n g hens on MQL-X i n 1972 and 1973 were p r i m a r i l y 2 - y e a r - o l d hens and a few y e a r -l i n g s . T a b l e 5 shows the p e r c e n t o f broods produced by hens of d i f f e r e n t ages. The 2 - y e a r - o l d hens, the m a j o r i t y o f which were th e o r i g i n a l r e c r u i t s i n 1971, a c c o u n t e d f o r t h e g r e a t e r number o f broods and the g r e a t e r number o f c h i c k s pe r b r ood on the removal a r e a . F i e l d o b s e r v a t i o n s r e v e a l e d no d i f f e r e n c e i n the p r o p o r t i o n o f hens t h a t defended b r o o d s , o r i n the b e h a v i o u r o f the c h i c k s . We c o n c l u d e t h e r e f o r e , t h a t t h e d i f f e r e n c e i n b r e e d i n g s u c c e s s i s due not t o t h e d i f f e r e n c e s 10 TABLE 4. P r o d u c t i o n o f young on e x p e r i m e n t a l a r e a s 1971, 1972, and 1973 combined and c o n t r o l TABLE 4(a) Hens w i t h b r o o d E x p e r i m e n t a l C o n t r o l > 10 days (N)<10 days (N) >10 days o l d c/b* o l d c/b o l d ' c / b (N) <10 o l d days c/b (N) 1971 3.0 (3)** 0 (0) 2.8 (8) 1. 25 (7) 1972 1973 & 3.0 (9) 3.3 (18) 1.5 (4) 2. 0 (12) * ** c/b denotes c h i c k s p e r brood Number o f i n d i v i d u a l broods TABLE 4 (b) . P e r c e n t a g e b r o o d l e s s hens E x p e r i m e n t a l C o n t r o l W i t h B r o o d l e s s % Brood- W i t h B r o o d l e s s % Brood-b r o o d l e s s b rood l e s s 1970 1971 1972 & 1973 removal y e a r 3 39 18 2 39 92 8 10 11 22 24 4 36 75 26 11 i n q u a l i t y b ut i n age s t r u c t u r e o f b r e e d i n g hens (Table 5) TABLE 5. Age o f hen and p r o d u c t i o n o f c h i c k s , 1972 and 1973 Removal C o n t r o l Age o f Average No. o f % o f hen no. o f broods t o t a l ( years) c h i c k s broods 1** 3.6 11 Average No. o f % o f no. o f broods t o t a l c h i c k s broods 0 0 2 3 3.1 2.6 > 2 (Bird?-1.5 banded as a d u l t ) T o t a l 2.6 17 5 2 ~2A 63 18.5 7.5 1.4 7 1.5 2 2.3 7 1.7 16 44 12 44 * * 1 y e a r o l d hens o m i t t e d from comparison o f p r o d u c t i o n o f c h i c k s w i t h age o f hen. S e a s o n a l d i f f e r e n c e s i n w e i g h t s o f grouse on b o t h a r e a s S e a s o n a l t r e n d s i n w e i g h t were t h e same f o r b o t h MQL-X and MQL-C. R e g a r d l e s s o f sex o r age, a l l showed a peak i n May and a l l e x h i b i t e d a subsequent d e c l i n e toward t h e end o f summer, as r e p o r t e d by R e d f i e l d (1972). I n g e n e r a l , no t r e n d of s i g n i f i c a n c e was found i n any age o r sex c a t e g o r y . There were no d i f f e r e n c e s i n mean w e i g h t s between areas i n the y e a r s 1970, 1971, 1972, and 1973. T h e r e f o r e , I . c o n c l u d e t h a t grouse on the removal a r e a were n o t under any more s t r e s s , as judged by w e i g h t s , t h a n t h o s e found on t h e c o n t r o l . 12 Movements of r e s i d e n t male grouse on s p r i n g range Blue grouse are migratory. However, once on the s p r i n g range the r e s i d e n t breeding males occupy t e r r i t o r i e s to which they.return year a f t e r year (Bendell, 1955). Resident males move about w i t h i n the boundaries of the t e r r i t o r y to feed, breed, and perform other a c t i v i t i e s such a hooting, f i g h t i n g , and e x c l u d i n g other male grouse. Through systematic search, banded r e s i d e n t s were lo c a t e d p e r i o d i c a l l y and t h e i r l o c a t i o n s p l o t t e d on a la r g e f i e l d map. The s i z e of an occupied t e r r i t o r y i s determined by repeated s i g h t i n g s of i n d i v i d u a l l y i d e n t i f i a b l e males. In s p r i n g , a d u l t males are v o c a l and t e r r i t o r i a l w h i l e most y e a r l i n g males are s i l e n t and move about widely (Bendell and E l l i o t , 1967), hence most y e a r l i n g s are c l a s s i f i e d as t r a n s i e n t s unless they e x h i b i t strong t e r r i t o r i a l tendencies and are r e s i g h t e d f r e q u e n t l y i n the same l o c a t i o n . In 1971, a f t e r the k i l l i n g of a l l t e r r i t o r i a l b i r d s i n 1970, the removal area contained approximately 90% y e a r l i n g s (Bendell £t a l , 1972). The y e a r l i n g cocks wandered i n a s i m i l a r manner to that of y e a r l i n g cocks i n a r e s i d e n t c o n t r o l population of mixed ages, or the r e s i g h t i n g distances being evenly d i s t r i -buted w i t h i n the range of 20 to 2,000 yards (unpublished data). In 1972, t h e i r f i r s t year i n ad u l t plumage, the b i r d s became t e r r i t o r i a l a f t e r t h i s placement and i n 1973, as the age s t r u c t u r e of the removal area approached th a t of the c o n t r o l , the a d u l t t e r r i t o r i a l males on both areas were comparable i n the distance t r a v e l l e d between r e s i g h t i n g s , the m a j o r i t y being r e l i g h t e d w i t h i n 20 to 70 yards of where they were i n i t i a l l y 13 r e c o r d e d . Males which had r e c o l o n i z e d the removal a r e a behaved l i k e t h e r e s i d e n t males on the c o n t r o l a r e a . A l t h o u g h i n 1971 MQL-X was v a c a n t , y e a r l i n g s t h a t moved i n behaved as normal y e a r l i n g s , some b e i n g nomadic i n t h e i r movements and a few showing t e r r i t o r i a l b e h a v i o u r . When t h e same b i r d s , as a d u l t s , were t e r r i t o r i a l on the removal a r e a i n 1972 and 1973 they o c c u p i e d a p p r o x i m a t e l y the same s i z e t e r r i t o r i e s as the b i r d s on the c o n t r o l . B e h a v i o u r o f t e r r i t o r i a l c o cks i n a t e s t a rena Three main r e a c t i o n s were r e c o g n i z e d i n the t e s t a rena: " e x p l o r a t o r y " , " c o u r t i n g " , and " i n t e r a c t i o n " . E x p l o r a t o r y b e h a v i o u r was the r e a c t i o n o f a male t o the whinny c a l l o f a female b l u e grouse ( S t i r l i n g and B e n d e l l , 1970). There was e i t h e r no r e s p o n s e , e v i d e n c e d by no movement o r a l t e r a t i o n i n h i s h o o t i n g r a t e , o r a response which was c h a r a c t e r i z e d by an approach and a n o t i c e a b l e change i n h o o t i n g r a t e (Table 6 ) . There was no s i g n i f i c a n t d i f f e r e n c e i n t h e p e r c e n t a g e o f h o o t i n g t e r r i t o r i a l males t h a t f a i l e d t o respond t o t h e t e s t s i t u a t i o n on the c o n t r o l and removal a r e a s (Table 6, P = .26). The approach by a male t o t h e t e s t arena was by w a l k i n g , r u n n i n g , o r f l y i n g , and was u s u a l l y accompanied by a s l i g h t i n c r e a s e i n the number o f h o o t i n g p h r a s e s and t h e i n t e n s i t y w i t h which they were made. There was a s l i g h t d i f f e r e n c e between the areas i n the r a t e o f approach o f the males, but the d i f f e r e n c e was n o t s i g n i f i c a n t . A p p r o x i m a t e l y 80% o f t h e males on b o t h a r e a s walked o r r a n i n t o t h e t e s t a r e n a . Mossop's (1971) f i g u r e f o r r a t e o f approach was s i g n i f i c a n t l y g r e a t e r t h a n the f i g u r e s I c a l c u l a t e d . However, he d i d n o t s t a t e how the b i r d s approached the arena. A n a l y s i s o f t h e c o u r t i n g phase i n v o l v e d c o u n t i n g t h e number o f f e m a l e - o r i e n t e d b e h a v i o u r s d u r i n g the t e s t and e x p r e s s -i n g them as a c t s o b s e r v e d p e r minute. No s i g n i f i c a n t d i f f e r e n c e was o b s e r v e d i n average f r e q u e n c y o f c o u r t i n g a c t s e x h i b i t e d by t h e b i r d s on the two areas ( P ^ 0.07) . The i n t e r a c t i o n phase was computed i n a s i m i l a r manner t o t h a t f o r the c o u r t i n g phase, a l l a g g r e s s i v e a c t s d i r e c t e d towards the r e f l e c t i o n i n t h e m i r r o r b e i n g e x p r e s s e d as a c t s p e r minute. The removal a r e a had s i g n i f i c a n t l y l o w e r a g g r e s s i o n r a t e s (P< 0.002). A l t h o u g h t h i s f i g u r e i s s t a t i s t -i c a l l y s i g n i f i c a n t , a d d i t i o n a l t e s t s a r e r e q u i r e d t o r e v e a l the b i o l o g i c a l s i g n i f i c a n c e o f t h i s f i n d i n g . R e s u l t s o f a l l t h e s e t e s t s (Table 6) i n d i c a t e no d i f f e r e n c e i n b e h a v i o u r o f the males l i v i n g i n the two p o p u l a t i o n s . TABLE 6. Response o f males t o are n a t e s t and comparison w i t h d a t a o f Mossop (1969) MQL-X MQL-C MQL-X Mossop (1969) % r esponse 71 (21) 76 (17) average 12.3 (9) 9.0 (7) 21.73 (16) r a t e o f SD = 5.00 SD = .6.38 SD = 4.38 advance average 11.74 (6) 13.1 (5) 11.0 (8) a g g r e s s i v e SD = 5.96 SD = 3.7 a c t s / m i n average 5.85 (4) 5.20 (4) 5.76 (7) r a t e o f SD = 0.57 SD = 0.23 SD = 2.60 c o u r t i n g 15 Grouse a c t i v i t y as r e c o r d e d a t l i s t e n i n g p o sts' ( s p r i n g s o f  1971, 1972, and 1973) L i s t e n i n g a t r e g u l a r p o s t s gave a measure o f e v e n i n g grouse a c t i v i t y t h r o u g h o u t the seasons o f 1972 and 1973, and l i s t e n i n g from roads s u p p l i e d a s i m i l a r i n d e x i n 1971. In a l l t h r e e y e a r s b o t h a r e a s showed s i m i l a r s e a s o n a l peaks and d e c l i n e s i n average numbers o f h o o t i n g males (Table 7) and average numbers o f h o o t s p e r minute, t o t a l number o f hen c a l l s , whoots, and f l u t t e r s . I n 1971, when most males on the removal a r e a were y e a r l i n g s , t hey were s l i g h t l y l e s s v o c a l than were the males on the c o n t r o l a r e a , e s p e c i a l l y a f t e r mid-May (Table 7 ) . I n p a s t s t u d i e s on b l u e g r o u s e , most y e a r l i n g males were thought t o be i n c a p a b l e o f h o o t i n g , w h o o t i n g , and s u c c e s s -f u l f u l c o p u l a t i o n ( B e n d e l l and E l l i o t , 1967). I n the p r e s e n t s t u d y , however, the new y e a r l i n g s on t h e removal a r e a i n 1971 d i d hoot r e g u l a r l y . A c t i v i t i e s c l a s s i f i e d as whoots and hen c a l l s do not g i v e an a c c u r a t e account o f t h e whole p o p u l a t i o n on an a r e a because the b u l k o f t h e s e b r e e d i n g a c t i v i t i e s i n v o l v e o n l y a few i n d i v i d u a l b i r d s which happened t o be v e r y a c t i v e on one o r two e v e n i n g s . Both p o p u l a t i o n s were s i m i l a r i n h o o t i n g t r e n d s t h r o u g h o u t 1972 and 19 73 (Table 7 ) . TABLE 7. Average number o f h o o t i n g males h e a r d p e r even-i n g (40 t o 50 minutes e v e r y d a y , o n e - h a l f hour a f t e r s u n s e t ) E x p e r i m e n t a l C o n t r o l 1971 1972 1973 1971 1972 1973 A p r i l 1.3 1.0 2.0 1.3 1.5 2 . 0 May 1.6 2.5 2.1 2.2 2.75 3.25 June 0.7 1.6 1.7 2.1 2.0 1.6 17 DISCUSSION P r e v i o u s s t u d i e s on b l u e g r o u s e , f o c u s i n g on d i s e a s e s , p a r a s i t e s , p r e d a t o r s , f o o d , and v e g i t a t i o n have f a i l e d t o e x p l a i n what d e t e r m i n e s t h e numbers o f grouse l i v i n g i n an a r e a . (Ben-d e l l , 1967; B e n d e l l and E l l i o t , 1967; and Z w i c k e l and B e n d e l l , 1972). S t u d y i n g the b e h a v i o u r o f a n i m a l s i s a r e l a t i v e l y new approach t o t h e s t u d y o f p o p u l a t i o n r e g u l a t i o n . A number o f a u t h o r s have r e c e n t l y r e p o r t e d changes i n b e h a v i o u r w h i c h are c o r r e l a t e d w i t h changes i n p o p u l a t i o n d e n s i t y (Healey, 1967; J e n k i n s , 1961; K i n g , 1968; S a d l e i r , 1965; Watson, 1965). S o c i a l i n t e r a c t i o n , e x h i b i t e d t h r o u g h p o s s i b l e a g o n i s t i c b e h a v i o u r , t a k e s p l a c e i n b l u e grouse i n the s p r i n g when t h e y f i r s t appear on t h e i r b r e e d i n g range ( B e n d e l l and E l l i o t , 1967). F o r t h i s b e h a v i o u r t o r e g u l a t e a p o p u l a t i o n i t s e x p r e s s i o n must be d e n s i t y - r e l a t e d . P r e v i o u s b l u e and r e d grouse removal e x p e r i m e n t s i n d i c a t e d t h a t i n e v e r y i n s t a n c e , r e g a r d l e s s o f a r e a o r d e n s i t y o f b r e e d i n g s t o c k , complete r e c r u i t m e n t always o c c u r r e d by the f o l l o w i n g s p r i n g . ( B e n d e l l e t a l 1972; Watson and J e n k i n s , 1968; Z w i c k e l , 1972). However, no f o l l o w - u p s t u d i e s have m o n i t o r e d the r e c r u i t m e n t p o p u l a t i o n f o r l a t e n t changes i n p o p u l a t i o n t r e n d s o r d i f f e r e n c e s i n the new s t o c k . P o p u l a t i o n t r e n d i n the new p o p u l a t i o n A g e n e r a l d e c l i n i n g t r e n d o f grouse p o p u l a t i o n s i n t h e 18 Campbell R i v e r a r e a was r e v e a l e d t h r o u g h a l o n g - t e r m s t u d y p r i o r t o t h e removal e x p e r i m e n t . I n 1971, t h e r e c o l o n i z i n g p o p u l a t i o n e s t a b l i s h e d t h e same d e n s i t y as t h e o l d p o p u l a t i o n , and i n 1972 and 1973 c o n t i n u e d t o d e c l i n e , p a r a l l e l i n g t h e t r e n d i n the s u r r o u n d i n g c o n t r o l a r e a . The appearance and p e r s i s t e n c e o f t h e s e new b i r d s on t h e removal a r e a d i d not r e s u l t i n a lower r e c r u i t m e n t r a t e on s u r r o u n d i n g a r e a s , hence t h i s s u p p o r t e d the c o n c l u s i o n t h a t t h e s e new r e c r u i t s were s u r p l u s ( B e n d e l l e t a l , 1972), and t h a t t h e g e n e r a l d e c l i n e d i d not a r i s e from t h e r e b e i n g an i n s u f f i c i e n t number o f p o t e n t i a l r e c r u i t s . Three outcomes might have been e x p e c t e d from t h e removal experiment i f b e h a v i o u r i s i n v o l v e d i n the l i m i t a t i o n o f d e n s i t y i n an e s t a b l i s h e d grouse p o p u l a t i o n . Replacement i n d i v i d u a l s c o u l d be more o r l e s s a g g r e s s i v e t h a n t h o s e removed, i n wh i c h case t h e y might s e t t l e more o r l e s s c l o s e l y and numbers would change a c c o r d i n g l y . T h i r d l y , t hey c o u l d be o f s i m i l a r , a g g r e s s i v e -ness and s e t t l e a t the same d e n s i t y . T h i s i s i n d e e d what the experiment r e v e a l e d . These d a t a a re e v i d e n c e a g a i n s t a b e h a v i o u r -a l d i f f e r e n c e i n the repl a c e m e n t s t o c k . Were t h e new b i r d s b e h a v i o u r a l l y d i f f e r e n t from the o l d s t o c k ? A g g r e s s i o n , one f a c t o f a g o n i s t i c b e h a v i o u r , i s known t o a f f e c t l i t t e r s u r v i v a l i n mice (Southwick, 1955) and t o be c o r r e l a t e d w i t h changes i n p o p u l a t i o n d e n s i t y i n r e d grouse (Watson and Moss, 1969), b l u e grouse (Mossop, 1971), and mice (Krebs, 1970). The r e c o l o n i z i n g grouse on t h e e x p e r i -me-ntal a r e a had s i m i l a r s u r v i v a l r a t e s and w e i g h t s when when compared w i t h the grouse on the c o n t r o l a r e a . R e s u l t s from l i s t e n i n g p o s t s and are n a t e s t i n g y i e l d e d no e v i d e n c e o f b e h a v i o u r a l d i f f e r e n c e s between a r e a s . I f t h e r e had been any o u t s t a n d i n g d i f f e r e n c e s between p o p u l a t i o n s , they would have emerged as a g e n e r a l t r e n d i n t h e p o p u l a t i o n i n 19 72 and 1973. Fu r t h e r m o r e , d i f f e r e n t l y behaved i n d i v i d u a l s would have r e c o l o n i z e d t h e a r e a a t a d i f f e r e n t d e n s i t y o r i n some way t y p i f i e d a d i f f e r e n t l y behaved p o p u l a t i o n . One o f the d i f f e r e n c e s found between a r e a s concerned the w i l d n e s s o f c e r t a i n b i r d s on the removal a r e a i n 1971 and 1972 such t h a t i t was d i f f i c u l t t o o b t a i n b e h a v i o u r a l i n f o r m a -t i o n from t h e s e i n d i v i d u a l s i n the f i e l d o r i n t h e t e s t a r e n a . However, a n a l y s i s o f u n d i s t u r b e d a c t i v i t y a t t h e l i s t e n i n g p o s t s near t h e s e i n d i v i d u a l s d i d not expose any r e c o g n i z a b l y h i g h e r o r lo w e r e v e n i n g a c t i v i t y r a t e s when compared w i t h t h o s e i n the c o n t r o l p o p u l a t i o n . I f t h e s e u n c a t c h a b l e b i r d s r e p r e s e n t a p o r t i o n o f the p o p u l a t i o n t h a t i s g e n e t i c a l l y d i f f e r e n t t h e r e s h o u l d be a d i f f e r e n c e i n s e t t l i n g p a t t e r n o r s i g h t i n g s i n the areas o c c u p i e d by the s e c l u s i v e b i r d s . T h i s however was not o b s e r v e d . T h e r e f o r e , the pr e s e n c e o f c e r t a i n w i l d b i r d s i n grouse p o p u l a t i o n s may be the r e s u l t o f r e p e a t e d u n s u c c e s s f u l c a p t u r e a t t e m p t s and o f t h e grouse l e a r n i n g t o a v i o d t h e o b s e r v e r s . The b i r d s appeared w i l d t o human o b s e r v e r s ; they d i d not n e c e s s a r i l y appear w i l d t o o t h e r grouse. The o t h e r d i f f e r e n c e i n the r e c r u i t m e n t p o p u l a t i o n was 20 the production of chicks on the areas i n 1972 and 1973. The new population produced what appeared to be more broods and chicks than the c o n t r o l p o p u l a t i o n , but a l l f i e l d observers recorded no v i s i b l e d i f f e r e n c e i n behaviour of hens g i v i n g brood-defense or hen-chick i n t e r a c t i o n when d i s t u r b e d i n the f i e l d . In 19 71, Mossop found that areas c o n t a i n i n g high d e n s i t i e s of grouse a l s o had high success i n production of c h i c k s . With no d i f f e r e n c e i n behaviour.of hens or chicks evident between the removal and c o n t r o l areas the b e t t e r production observed on the removal area, although not s t a t i s t -i c a l l y s i g n i f i c a n t , i s a t t r i b u t e d to the age s t r u c t u r e of the breeding hens. Where does t h i s leave us i n e x p l a i n i n g r e g u l a t i o n of animal numbers? The removal experiment demonstrated t h a t r e s i d e n t b i r d s r e s t r i c t e d new b i r d s from s e t t l i n g on t h e i r t e r r i t o r y or nearby. The new r e c r u i t s , freed of suppression from e s t a b l i s h e d b i r d s , might have s e t t l e d to a higher population d e n s i t y than e x i s t e d there before. In f a c t , though they wandered more widely and showed l e s s tendency t o e s t a b l i s h t e r r i t o r i e s , t h e i r o v e r a l l d e n s i t y d i d not d i f f e r * f r o m t h a t of the male po p u l a t i o n removed. The new b i r d s a l s o appeared t o be regulated from- the. year they r e c o l o n i z e d . S e t t l i n g i n even s e x - r a t i o i s evidence of r e g u l a t i o n . Since blue grouse do not form p a i r bonds there seems to be no reason why i n i t i a l l y there would have not been unequal sex r a t i o , that i s assuming t h a t i n any year there may be more surplus of one sex than the other. I t i s not known how much i s surplus nor how the new population a t t a i n e d 21 sexual e q u a l i t y . However, i t appears t h a t sexual maturity and the presence of experienced b i r d s are not necessary f o r a population to r e g u l a t e i t s e l f . The r e s u l t s of t h i s study r a t e d the r e c o l o n i z e r s as aggressive and i n no way b e h a v i o u r a l l y d i f f e r e n t from grouse i n surrounding areas. The c h a r a c t e r i s t i c behaviour of the grouse i n t h a t area has not changed since Mossop (1971) conducted m i r r o r t e s t s on the o l d r e s i d e n t s on the removal area i n 1969. Therefore, the i n d i v i d u a l s r e c r u i t e d t o the Campbell R i v e r area are b e h a v i o u r a l l y c h a r a c t e r i s t i c of the surrounding r e s i d e n t s . Future research i n t o r e g u l a t i o n of grouse populations should concentrate on s t u d i e s at d i f f e r e n t p o p ulation d e n s i t i e s conducting manipulation experiments of the h a b i t a t and stocks of grouse. More understanding of s o c i a l i n t e r a c t i o n w i t h i n a population would be achieved through experimenting to f i n d out how much surplus i s a v a i l a b l e i n the s p r i n g . Female grouse, because of t h e i r s e c l u s i v e behaviour, are the l e a s t known popu l a t i o n component i n the springtime. Females are capable of d i s p l a y i n g aggression, p a r t i c u l a r l y p r i o r to egg-laying season ( S t i r l i n g , 1962; Theberge, unpublished Ph.D. t h e s i s , 1971), and s e v e r a l i n c i d e n t s i n v o l v i n g aggression amongst females have been recorded i n the f i e l d and i n the a v i a r y . Research on females would be v a l u a b l e i n e x p l a i n i n g equal sex r a t i o , the v a r i a b l e compensation f o r m o r t a l i t y w i t h i n the sexes, and i n general would r e s u l t i n a broader outlook ~on-"population r e g u l a t i o n . 22 SUMMARY The purpose o f t h i s s t u d y was to a n a l y z e a r e c o l o n i z i n g p o p u l a t i o n o f b l u e grouse. D i f f e r e n t t e c h n i q u e s r a n g i n g from p o p u l a t i o n census t o m i r r o r - i m a g e s t i m u l a t i o n were used t o t r y t o e v a l u a t e the a g g r e s s i v e b e h a v i o u r o f t h e r e c o l o n i z e r s a f t e r t h e removal o f r e s i d e n t grouse. The new b i r d s r e c o l o n i z e d t o the same d e n s i t y as tho s e i n the s u r r o u n d i n g a r e a s and i n even sex r a t i o . The p o p u l a t i o n i n the a r e a was g e n e r a l l y d e c l i n i n g , and c o n t i n u e d t o d e c l i n e t h r o u g h o u t t h e s t u d y . The a n n u a l m o r t a l i t y r a t e o f a d u l t s was s i m i l a r on the c o n t r o l and e x p e r i m e n t a l a r e a s ( a p p r o x i m a t e l y 3 0 % ) . I n the f i r s t y e a r t h e e x p e r i m e n t a l a r e a was c o l o n i z e d by 90% y e a r l i n g b i r d s . In o t h e r y e a r s the r e c r u i t m e n t r a t e s on the e x p e r i m e n t a l and c o n t r o l a r e a s were l e s s than 30%. P r o d u c t i o n o f c h i c k s i n 1972 and 1973 was s l i g h t l y b e t t e r on the e x p e r i m e n t a l a r e a than on the c o n t r o l a r e a , b u t t h i s was not s t a t i s t i c a l l y s i g n i f i c a n t . No d i f f e r e n c e i n l i v e w e i g h t s o f b i r d s caught on the two areas was found r e g a r d l e s s o f age o r sex o f b i r d s sampled. B e h a v i o u r a l t e s t s on r e s i d e n t males i n an ar e n a showed no d i f f e r e n c e i n r a t e o f approach, c o u r t i n g , o r a g g r e s s i o n between the a r e a s . R e s u l t s o b t a i n e d from the t e s t were s i m i l a r t o t h o s e found i n 1971 by Mossop, who conducted arena t e s t s on t h e o l d r e s i d e n t p o p u l a t i o n . The grouse t h a t now occupy t h e e x p e r i m e n t a l a r e a a r e e s s e n t i a l l y the same t y p e o f grouse found i n s u r r o u n d i n g a r e a s and i n t h e o l d p o p u l a t i o n . The new p o p u l a t i o n appeared t o be l i m i t e d and r e g u l a t e d from the f i r s t y e a r o f r e c o l o n i z a t i o n d e s p i t e the absence o f mature and e x p e r i e n c e d b i r d s . I n b l u e grouse, r e g u l a t i o n t a k e s p l a c e i n e a r l y s p r i n g on the b r e e d i n g range, where d i s p u t e o v e r t e r r i t o r i e s ^ i n v o l v e s b o t h r e s i d e n t s and p o t e n t i a l r e c r u i t s . 24 LITERATURE CITED B e n d e l l , J . F . , 1955. Age, b r e e d i n g b e h a v i o u r and m i g r a t i o n o f so o t y g r o u s e , Dendragapus o b s c u r u s f u l i g i n o s u s (Ridgway). T r a n s . N. Am. W i l d l . Conf., 20:367-381. B e n d e l l , J . F . , and P.W. E l l i o t , 1967. B e h a v i o u r and r e g u l a t i o n o f numbers i n b l u e g r o u s e . Can. W i l d l . S e r v . Report Ser . No. 4, 76 pp. B e n d e l l , J.F., D.G. K i n g , and D.H. Mossop, 19 72. Removal and r e p o p u l a t i o n o f b l u e grouse i n a d e c l i n i n g p o p u l a t i o n . J . W i l d l . Mgmt. 36. No. 4,pp. 1153-1165. Boag, D.A., 1965. I n d i c a t o r s o f sex , age and b r e e d i n g phenology i n b l u e g r o u s e . J . W i l d l . Mgmt. 29:103-108. G a l l u p , G.G., and S t u a r t A. Capper, 1970. P r e f e r e n c e f o r m i r r o r -image s t i m u l a t i o n i n f i n c h e s and p a r a k e e t s . Anim. Behav., 18:621-624. Healey, M.C., 1967. A g g r e s s i o n and s e l f - r e g u l a t i o n o f p o p u l a t i o n s i z e i n deermice. E c o l . , 48:377-392. J e n k i n s , D., 1963. P o p u l a t i o n c o n t r o l i n r e d g r o u s e . P r o c . 13th I n t e r n . O r n i t h . Congr., pp. 690-700. Krebs, C.J., 1970. B e h a v i o u r a l changes a s s o c i a t e d w i t h the p o p u l a t i o n c y c l e i n v o l e s . E c o l , 51, No. 1. Mossop, D. H. 1971. A r e l a t i o n between a g g r e s s i v e b e h a v i o u r and p o p u l a t i o n dynamics i n b l u e g r o u s e . Unpubl. M.Sc. t h e s i s , U n i v e r s i t y o f B.C., 119 pp. R e d f i e l d , J.A., F.C. Z w i c k e l , and J.F. B e n d e l l , 1971. E f f e c t s o f f i r e on numbers o f b l u e g r o u s e . P r o c . T a l l Timbers F i r e E c o l . Conf. 10:63-83. R e d f i e l d , J.A., 1972. V a r i a t i o n s i n w e i g h t o f b l u e g r o u s e , (Dendragapus o b s c u r u s ) , Condor, 75:312-321. S a d l e i r , R.M.S., 1965. The r e l a t i o n s h i p between a g o n i s t i c behav-i o u r and p o p u l a t i o n changes i n the deermouse, P e r o -myscus m a n i c u l a t u s . J . Anim. E c o l . , 14:331-352. Southwick, C.H., 1955. R e g u l a t o r y mechanisms o f house mouse p o p u l a t i o n s : s o c i a l b e h a v i o u r a f f e c t i n g l i t t e r s u r v i v a l . E c o l o g y , 36:627-634. 25 S t i r l i n g , I.G., 1968. Aggressive behaviour and the d i s p e r s i o n of female blue grouse. Can. J . Zoology, 46:405. S t i r l i n g , I.G., and J.F. B e n d e l l , 1970. The reproductive behaviour of blue grouse. S y e s i s , 3:161-171. Svendsen, G.E., and K.B. Armitage, 1973. Mirror-image s t i m u l a t i o n a p p l i e d to f i e l d behavioural s t u d i e s . E c o l . , V o l . 54, No. 3, pp. 623-627. Theberge, J . , 1971. Population f l u c t u a t i o n and changes i n the q u a l i t y of Rock Ptarmigan i n Alas k a . Unpubl. Ph.D. t h e s i s , U n i v e r s i t y of B.C. Watson, A., 1964. Aggression and population r e g u l a t i o n i n red grouse. Nature, 202 (4931) :506-507. Watson, A., and Jen k i n s , D., 1968. Experiments on Population C o n t r o l by T e r r i t o r i a l Behaviour i n Red Grouse. J . Anim. E c o l . 37, 595-614. Watson, A., and R. Moss, 1969. Dominance, spacing behaviour and aggression i n r e l a t i o n to population l i m i t a t i o n i n ve r t e b r a t e s . In: Animal Populations i n R e l a t i o n to Their Food Resources. The B r i t i s h E c o l o g i c a l S o c i e t y , Aberdeen, March 1969. pp. 167-222. Zwickel, F.C., 1965. E a r l y m o r t a l i t y and the numbers of blue grouse. Unpubl. PhD. t h e s i s , U n i v e r s i t y of B.C. 153 pp. Zwickel, F.C., and J.F. B e n d e l l , 1967a. A snare f o r cap t u r i n g blue grouse. J . W i l d l . Mgmt., 31:202-204. Zwickel, F.C., and J.F. B e n d e l l , 1967b. E a r l y m o r t a l i t y and the r e g u l a t i o n of numbers i n blue grouse. Can. J . Zool., 45:815-851. Zwickel, F.C., 1972. Removal and repop u l a t i o n of blue grouse i n an i n c r e a s i n g p o p u l a t i o n . J . W i l d l . Mgmt. 36, pp. 1141-1152. 

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