Some ecological aspects of social behaviour in the song sparrow, Melospiza melodia

Knapton, Richard Walter

doi:10.14288/1.0093107

UBC Theses and Dissertations

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UBC Theses and Dissertations

Some ecological aspects of social behaviour in the song sparrow, Melospiza melodia Knapton, Richard Walter 1973

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Title	Some ecological aspects of social behaviour in the song sparrow, Melospiza melodia
Creator	Knapton, Richard Walter
Publisher	University of British Columbia
Date Issued	1973
Description	The purpose of this study is to investigate experimentally some ecological aspects of social behaviour in Song Sparrows, Melospiza melodia, on Reifel Island, British Columbia. Two main questions are asked: A. Does the temporal pattern of settling on territories influence the number of occupied territories, and hence territory size, and the breeding density in a given area? B. Are the juveniles that obtain territories, when the opportunity arises, the dominant individuals in dominance hierarchies established during the pre-breeding season? A necessary pre-requisite for both questions to be answered is that there exists a surplus of birds which are non-territorial and potentially capable of breeding, but which are prevented from taking territories by the resident territory holders. This also is experimentally investigated. Removal experiments were carried but in the fall of 1972 and the spring of 1973. Subsequent replacements and breeding showed that there was a surplus of Song Sparrows on the study area that were physiologically capable of breeding. All but one of the replacement birds were juveniles, and all were probably of local origin. Two types of removal experiments, simultaneous and successive, were carried out in both the spring and fall. On the Simultaneous Removal areas, total replacement took about nine to ten days. Significantly more territories were taken, and the increases in both spring and fall were about 40%. Further, the mean territory size after the removals was significantly smaller than that before. Finally, territory boundaries were completely rearranged following the removals. The replacement on the Successive Removal areas took upto three to four days. There was no significant difference in the number of territories taken, nor in the mean territory size, after the removals. Further, the territorial pattern was retained. Breeding density on all areas, however, remained much the same before and after the experiments. Therefore, there were several unmated males with territories after the removals, and these unmated males proved to have significantly smaller territories than mated ones. Factors which could have accounted for the different results of the simultaneous and the successive removal experiments are discussed, and a proposed explanation is given. Dominance hierarchies were determined in the loose groups of juvenile Song Sparrows that congregated over the winter at certain localities along the hedgerows. Each group tended to be a discrete unit, although some interchange of individuals (both dominant and subordinate) occurred. The hierarchies themselves were stable and essentially linear, with few reversals and the occasional triangle. The removal experiments presented an opportunity for some of the members of the hierarchies to obtain territories. It was found that dominant males in the hierarchies were the successful ones in establishing territories. Further, in the largest hierarchy, out of 12 juvenile males, 4 from the top 5 obtained territories. Factors which could possibly influence the position of the bird in the hierarchy are discussed, and the possible outcomes of the hierarchy are considered.
Subject	Sparrows Birds -- Behavior
Genre	Thesis/Dissertation
Type	Text
Language	eng
Date Available	2011-03-18
Provider	Vancouver : University of British Columbia Library
Rights	For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
DOI	10.14288/1.0093107
URI	http://hdl.handle.net/2429/32589
Degree	Master of Science - MSc
Program	Zoology
Affiliation	Science, Faculty of Zoology, Department of
Degree Grantor	University of British Columbia
Campus	UBCV
Scholarly Level	Graduate
AggregatedSourceRepository	DSpace

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C.I SOME ECOLOGICAL ASPECTS OF SOCIAL BEHAVIOUR IN THE SONG SPARROW, §§lospJLza m e l o d i a by RICHARD WALTER KNAPTON B S c . , L a k e h e a a U n i v e r s i t y , 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OP MASTER OF SCIENCE i n t h e De p a r t m e n t o f Z o o l o g y We a c c e p t t h i s t h e s i s a s 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 September 1973 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada i ABSTRACT The p u r p o s e o f t h i s s t u d y i s t o i n v e s t i g a t e e x p e r i m e n t a l l y some e c o l o g i c a l a s p e c t s o f s o c i a l b e h a v i o u r i n Song S p a r r o w s , H e l o s j a i z a m e l o d i a , on R e i f e l I s l a n d , B r i t i s h C o l u m b i a . Two main q u e s t i o n s a r e a s k e d : A. Does t h e t e m p o r a l p a t t e r n o f s e t t l i n g on t e r r i t o r i e s i n f l u e n c e t h e number o f o c c u p i e d t e r r i t o r i e s , and hence t e r r i t o r y s i z e , and t h e b r e e d i n g d e n s i t y i n a g i v e n a r e a ? B. A r e t h e j u v e n i l e s t h a t o b t a i n t e r r i t o r i e s , when t h e o p p o r t u n i t y a r i s e s , t h e d o m i n a n t i n d i v i d u a l s i n dominance h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n ? ft n e c e s s a r y p r e - r e q u i s i t e f o r b o t h q u e s t i o n s t o be a nswered i s t h a t t h e r e e x i s t s a s u r p l u s o f b i r d s which a r e n o n - t e r r i t o r i a l and p o t e n t i a l l y c a p a b l e o f b r e e d i n g , b u t w h i c h a r e p r e v e n t e d f r o m t a k i n g t e r r i t o r i e s by t h e r e s i d e n t t e r r i t o r y h o l d e r s . T h i s a l s o i s e x p e r i m e n t a l l y i n v e s t i g a t e d . Removal e x p e r i m e n t s were c a r r i e d b u t i n t h e f a l l o f 1972 and t h e s p r i n g o f 1973. S u b s e q u e n t r e p l a c e m e n t s and b r e e d i n g showed t h a t t h e r e was a s u r p l u s o f Song S p a r r o w s on t h e s t u d y a r e a t h a t were p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g . A l l b u t one o f t h e r e p l a c e m e n t b i r d s were j u v e n i l e s , and a l l were p r o b a b l y o f l o c a l o r i g i n . Two t y p e s o f r e m o v a l e x p e r i m e n t s , s i m u l t a n e o u s and i i s u c c e s s i v e , were c a r r i e d o u t i n b o t h t h e s p r i n g and f a l l . On th e S i m u l t a n e o u s Removal a r e a s , t o t a l r e p l a c e m e n t t o o k a b o u t n i n e t o t e n d a y s . S i g n i f i c a n t l y more t e r r i t o r i e s were t a k e n , and t h e i n c r e a s e s i n b o t h s p r i n g and f a l l were a b o u t 40%. F u r t h e r , t h e mean t e r r i t o r y s i z e a f t e r t h e r e m o v a l s was s i g n i f i c a n t l y s m a l l e r t h a n t h a t b e f o r e . F i n a l l y , t e r r i t o r y b o u n d a r i e s were c o m p l e t e l y r e a r r a n g e d f o l l o w i n g t h e r e m o v a l s . The r e p l a c e m e n t on t h e S u c c e s s i v e Removal a r e a s t o o k u p t o t h r e e t o f o u r d a y s . T h e r e 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 number o f t e r r i t o r i e s t a k e n , n o r i n t h e mean t e r r i t o r y s i z e , a f t e r t h e r e m o v a l s . F u r t h e r , t h e t e r r i t o r i a l p a t t e r n was r e t a i n e d . B r e e d i n g d e n s i t y on a l l a r e a s , however, r e m a i n e d much t h e same b e f o r e and a f t e r t h e e x p e r i m e n t s . T h e r e f o r e , t h e r e were s e v e r a l unmated males w i t h t e r r i t o r i e s a f t e r t h e r e m o v a l s , and t h e s e unmated males p r o v e d t o have s i g n i f i c a n t l y s m a l l e r t e r r i t o r i e s t h a n mated o n e s . F a c t o r s w h i c h c o u l d have a c c o u n t e d f o r t h e d i f f e r e n t r e s u l t s o f t h e s i m u l t a n e o u s and t h e s u c c e s s i v e r e m o v a l e x p e r i m e n t s a r e d i s c u s s e d , and a p r o p o s e d e x p l a n a t i o n i s g i v e n . Dominance h i e r a r c h i e s were d e t e r m i n e d i n t h e l o o s e g r o u p s o f j u v e n i l e Song S p a r r o w s t h a t c o n g r e g a t e d o v e r t h e w i n t e r a t c e r t a i n l o c a l i t i e s a l o n g t h e hedgerows. Each g r o u p t e n d e d t o i i i be a d i s c r e t e u n i t , a l t h o u g h some i n t e r c h a n g e o f i n d i v i d u a l s ( b o t h d o m i n a n t and s u b o r d i n a t e ) o c c u r r e d . The h i e r a r c h i e s t h e m s e l v e s were s t a b l e and e s s e n t i a l l y l i n e a r , w i t h few r e v e r s a l s and t h e o c c a s i o n a l t r i a n g l e . The r e m o v a l e x p e r i m e n t s p r e s e n t e d an o p p o r t u n i t y f o r some o f t h e members o f t h e h i e r a r c h i e s t o o b t a i n t e r r i t o r i e s . I t was f o u n d t h a t , d o m i n a n t males i n t h e h i e r a r c h i e s were t h e s u c c e s s f u l o n e s i n e s t a b l i s h i n g t e r r i t o r i e s . F u r t h e r , i n t h e l a r g e s t h i e r a r c h y , o u t o f 12 j u v e n i l e m a l e s , 4 f r o m t h e t o p 5 o b t a i n e d t e r r i t o r i e s . F a c t o r s which c o u l d p o s s i b l y i n f l u e n c e t h e p o s i t i o n o f t h e b i r d i n t h e h i e r a r c h y a r e d i s c u s s e d , and t h e p o s s i b l e o utcomes o f t h e h i e r a r c h y a r e c o n s i d e r e d . i v TABLE OF CONTENTS PAGE ABSTRACT i TABLE OF CONTENTS iv LIST OF TABLES .. v i LIST OF FIGURES > v i i ACKNOWLEDGEMENTS v i i i GENERAL INTRODUCTION 1 1. . AIMS OF THE STUDY .. 1 2. THE STUDY AREA 3 3. LIFE HISTORY 5 U. METHODS 11 PART A. THE EFFECTS OF TEMPORAL SETTLING PATTERNS ON TERRITORY SIZE 16 I INTRODUCTION 16 1. Food supply and t e r r i t o r y s i z e ..... 18 2. Other environmental f a c t o r s and t e r r i t o r y s i z e ..................... 2 2 3. Temporal p a t t e r n s of s e t t l i n g on t e r r i t o r i e s 2 4 I I PROCEDURE 2? I I I RESULTS 32 1. Replacement of removed p a i r s ........ 32 2. Number of occupied t e r r i t o r i e s ...... 33 3. S i z e of t e r r i t o r i e s 35 1. Changes i n number of- t e r r i t o r i e s on the F a l l Removal Area over the winter 40 5. Breeding d e n s i t y i n the s p r i n g of 1973 42 6. D i f f e r e n c e s i n t e r r i t o r y s i z e between mated and unmated males .... 44 7. The replacement b i r d s 47 IV DISCUSSION ... 51 A. The replacement Song Sparrows and the s u r p l u s 51 B. The temporal p a t t e r n s of s e t t l i n g on t e r r i t o r i e s ..................... 55 V 1. F l u c t u a t i n g environmental resource 55 2. Pressure from i n t r u d e r s 57 3. Inexperience of the j u v e n i l e s and the temporal pa t t e r n s of s e t t l i n g 59 1. D i s r u p t i o n of t e r r i t o r i a l boundaries 63 5 . Genetic b a s i s f o r the s i z e of t e r r i t o r y .................. 67 C. Proposed e x p l a n a t i o n f o r the d i f f e r e n t r e s u l t s o f the simultaneous and the s u c c e s s i v e removal experiments ................ 68 PART B"... DOMINANCE HIERARCHIES 7 2 I INTRODUCTION , 72 I I PROCEDURE 75 I I I RESULTS 80 A. The h i e r a r c h i e s 8 0 B. Success i n g a i n i n g t e r r i t o r i e s i n r e l a t i o n to h i e r a r c h y p o s i t i o n ..... 88 IV DISCUSSION 94 a. The f u n c t i o n a l s i g n i f i c a n c e of dominance h i e r a r c h i e s .............. 94 B. F a c t o r s determining p o s i t i o n i n the dominance h i e r a r c h y 95 C. Outcomes of the h i e r a r c h i e s 102 LITERATURE CITED - 106 APPENDIX 1 .-. 118 APPENDIX 2 . , 120 APPENDIX 3 1 2 0 APPENDIX M 123 APPENDIX 5 124 APPENDIX 6 126 APPENDIX 7 . 127 APPENDIX 8 128 APPENDIX 9 129 v i LIST OP TABLES TABLE PAGE 1. Dispersal distances of juveniles from s i t e of b i r t h : f a l l 1972 - , 8 2. Results of removal experiments: numbers of occupied t e r r i t o r i e s , of both mated and unmated males 34 3. Results of removal experiments: differences i n numbers of occupied t e r r i t o r i e s of mated and unmated males 36 4. Results of removal experiments: mean t e r r i t o r y s i z e . F a l l Removal Area • 38 5. Results of removal* experiments: mean t e r r i t o r y s i z e . Spring Removal Area ................................... 39 6. Results of removal experiments: breeding density .... 43 7. Differences i n t e r r i t o r y s i z e between mated and unmated males: spring 1973. Simultaneous Removal areas ........ 46 8 . Vesting data f o r the Controls and the Experimental areas: 1973 49 9. Number of j u v e n i l e s banded, f a l l 1972 to early spring 1973 54 10. Lineage: t e r r i t o r y s i z e s from one generation to the next ^ 11. Numbers of encounters (displacements, avoidances and fights) i n f o u r dominance hierarchies ................. 12. Analysis of the avoidance interactions i n the B-C Hierarchy 84 13. Rank i n h i e r a r c h i e s and sex of Song Sparrows performing intergroup movements 87 14. Analysis of f i g h t s i n the B-C Hierarchy 89 15. Change i n s t a t u s of a juvenile female following the disappearance of an adult t e r r i t o r i a l female 92 16. Feeding order of hierarchy: appearance of f i r s t b i r d at feeding s t a t i o n s of the B-C Hierarchy 1 0 4 v i i LIST OF FIGURES , FIGURE PAGE 1. The study a r e a : R e i f e l I s l a n d and an adjacent p a r t of Mestham I s l a n d 4 2. Numbers of j u v e n i l e Song Sparrows r e s i g h t e d on the S p r i n g Removal Area from mid-December to the end of May ...... 10 3. S i n g l e n g t h s o f male and female Song Sparrows ........ 12 «». Mean weights of male and female Song Sparrows f o r a l l months 13 5. F a l l Removal Area: the movement and expansion of C o n t r o l male C6 a f t e r the removal experiment and d u r i n g the subsequent winter 41 6. S p r i n g Removal Area: Simultaneous Removal area boundaries b e f o r e and a f t e r removals 65 7. The B-C H i e r a r c h y 81 8. Number of i n t e r a c t i o n s versus d i s t a n c e w i t h i n h i e r a r c h y f o r a l l j u v e n i l e s i n the B-C H i e r a r c h y 89 9. P o s i t i o n i n h i e r a r c h y and number of i n t e r a c t i o n s : the B-C H i e r a r c h y 103 1 0 . B u l l d o z e d Area: the arrangement of t e r r i t o r y boundaries b e f o r e the dyke r e b u i l d i n g o c c u r r e d ................... 11*1 11. Cottonwood S t r e t c h H i e r a r c h y 1*9 12. Sedge Patch H i e r a r c h y 1 £ ° 13. B u l l d o z e d Path H i e r a r c h y 131 14. F i r s t B i g A l d e r and Marsh Narrows H i e r a r c h i e s 132 15. No Name C l e a r i n g H i e r a r c h y 1£3 . v i i i aCKNOWLEDGEMEHTS I am most g r a t e f u l t o my s u p e r v i s o r . Dr. J . R. K r e b s , f o r h i s a d v i c e , c r i t i c i s m and g u i d a n c e a t a l l s t a g e s o f t h i s work. Dr. C. J . K r e b s and Dr. N. R. L i l e y c r i t i c a l l y r e a d t h e m a n u s c r i p t , and a d v i c e was r e c e i v e d f r o m Dr. J . F. B e n d e l l a t t h e s t a r t o f t h e s t u d y . I s h o u l d f u r t h e r l i k e t o t h a n k P. T a i t t and W. Z a l e s , who gave v a l u a b l e a s s i s t a n c e d u r i n g t h e r e m o v a l e x p e r i m e n t s , and a l l t h e p e o p l e who a s s i s t e d i n t h e b a n d i n g o p e r a t i o n s and i n n e s t - f i n d i n g . T h e i r h e l p was t r u l y a p p r e c i a t e d . T h a n k s a r e a l s o due t o D. L a u r i e n t e , S. Bor d e n and B. Webb f o r a s s i s t a n c e w i t h t h e co m p u t e r programming. F i n a l l y , I s h o u l d l i k e t o t h a n k my w i f e , w i t h o u t whose p a t i e n c e and t o l e r a n c e t h e s t u d y would n o t have been p o s s i b l e . 1 GENERAL INTRODUCTION 1. Aims o f t h e S t u d y The p u r p o s e o f t h i s s t u d y i s t o i n v e s t i g a t e some e c o l o g i c a l a s p e c t s o f s o c i a l b e h a v i o u r i n Song S p a r r o w s , H e l o s j D i z a m e l o d i a . Song S p a r r o w s show two c l a s s i c a l e x a m ples of s o c i a l i n t e r a c t i o n : t h e t e r r i t o r y and t h e dominance h i e r a r a c h y ( N i c e 1937, 1943; Tompa 1964). T h i s s t u d y c o n s i d e r s a s p e c t s o f b o t h , and i s d i v i d e d i n t o two s e c t i o n s , t h e f i r s t d e a l i n g w i t h t e r r i t o r i a l i t y , and t h e s e c o n d d e a l i n g w i t h dominance h i e r a r c h i e s . T e r r i t o r i a l b e h a v i o u r has been shown t o d e t e r m i n e t h e b r e e d i n g d e n s i t y i n s e v e r a l p o p u l a t i o n s o f a n i m a l s (see Watson and Moss 1970; Klomp 1972). A p e r p l e x i n g p r o b l e m i n b i r d s , however, has been the v a r i a b i l i t y i n mean t e r r i t o r y s i z e , and hence p o p u l a t i o n d e n s i t y , i n a g i v e n a r e a f r o m y e a r t o y e a r . T h e r e a r e s e v e r a l e n v i r o n m e n t a l r e s o u r c e s t h a t c o u l d c o n c e i v a b l y i n f l u e n c e t e r r i t o r y s i z e a n n u a l l y , but t h e e v i d e n c e s u p p o r t i n g any o f them i s n o t u n e q u i v o c a l . T h e r e i s some e v i d e n c e (see K r e b s 1971) t h a t t h e t e m p o r a l p a t t e r n o f s e t t l i n g on t e r r i t o r i e s i s i m p o r t a n t i n d e t e r m i n i n g t h e number o f t e r r i t o r i e s o c c u p i e d i n a g i v e n a r e a . I n t h e f i r s t p a r t o f t h e s t u d y , t h e n , I e x p e r i m e n t a l l y p r o d u c e d two t y p e s o f s e t t l e m e n t p a t t e r n s , s i m u l t a n e o u s and s u c c e s s i v e , i n o r d e r t o t e s t t h i s h y p o t h e s i s . 2 In t h e s e c o n d p a r t o f t h e s t u d y , I l o o k e d a t dominance h i e r a r c h i e s i n t h e l o o s e g r o u p s o f j u v e n i l e Song S p a r r o w s t h a t c o n g r e g a t e d o v e r t h e w i n t e r a t c e r t a i n l o c a l i t i e s i n t h e s t u d y a r e a . The s t r u c t u r e and c o m p o s i t i o n o f t h e h i e r a r c h i e s were d e t e r m i n e d o v e r t h e w i n t e r , and t h e outcomes o f t h e h i e r a r c h i e s were f o l l o w e d d u r i n g t h e s p r i n g when t h e h i e r a r c h i e s began t o d i s i n t e g r a t e . I n p a r t i c u l a r , I i n v e s t i g a t e d t h e h y p o t h e s i s t h a t , g i v e n t h e o p p o r t u n i t y , t h e y e a r l i n g s t h a t o b t a i n t e r r i t o r i e s i n t h e s p r i n g a r e t h e d o m i n a n t i n d i v i d u a l s i n t h e dominance h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n . A n e c e s s a r y p r e - r e q u i s i t e f o r t h e i n v e s t i g a t i o n o f b o t h o f t h e s e p r o b l e m s was t h a t t h e r e e x i s t e d a s u r p l u s o f n o n - t e r r i t o r i a l b i r d s , p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g , b u t p r e v e n t e d f r o m d o i n g s o by t h e t e r r i t o r i a l 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 i n d i v i d u a l s . T h e r e i s good d e s c r i p t i v e e v i d e n c e t h a t t h i s p r o c e s s was o p e r a t i n g i n a n o t h e r p o p u l a t i o n on Song S p a r r o w s i n s o u t h w e s t e r n B r i t i s h C o l u m b i a (Tompa 1962, 1 964). The p r e s e n t s t u d y was i n s t i g a t e d on, (and i n d e e d p r o v i d e d a t e s t f o r ) , t h e a s s u m p t i o n t h a t t h e r e would be s u c h a s u r p l u s o f n o n - t e r r i t o r i a l b i r d s on t h e s t u d y a r e a f r o m t h e f a l l o f 1972 t o t h e s p r i n g o f 1973. F i n a l l y , i t i s worth m e n t i o n i n g t h a t t h e dominance h i e r a r c h y and c l a s s i c a l t e r r i t o r i a l i t y a r e not c o n s i d e r e d t o be i n d e p e n d a n t f e a t u r e s o f a b i r d ' s s o c i a l b e h a v i o u r (Brown 3 1963; D a v i s 1 959). T h e r e f o r e , t h i s t h e s i s i s d i v i d e d i n t o two major p a r t s , w i t h t h e u n d e r s t a n d i n g t h a t t h e two p a r t s need not be m u t u a l l y e x c l u s i v e . 2. The S t u d y A r e a The s t u d y was c a r r i e d o u t on R e i f e l I s l a n d and an a d j a c e n t p a r t o f Westham I s l a n d ( F i g u r e 1 ) . The a r e a i s i n t h e m u n i c i p a l i t y o f D e l t a , B r i t i s h C o l u m b i a , and i s bounded t o t h e n o r t h and e a s t by t h e s o u t h arm o f F r a s e r R i v e r , t o t h e west by G e o r g i a S t r a i t and p a r t o f t h e George C. E e i f e l W a t e r f o w l R e f u g e , and t o t h e s o u t h by a g r i c u l t u r a l f a r m l a n d o f Westham I s l a n d . T o p o g r a p h y i s f l a t , t h e water t a b l e i s c l o s e t o t h e s o i l s u r f a c e f o r most o f t h e y e a r , and t h e l a n d i s o f n e c e s s i t y d y k e d . A l o n g t h e d y k e s , v a r i o u s s p e c i e s o f woody and h e r b a c e o u s p l a n t s have grown t o f o r m hedgerows. A p p e n d i x 1 g i v e s a l i s t o f t h e more common and i m p o r t a n t s p e c i e s . The s t r u c t u r e and c o m p o s i t i o n o f t h e v e g e t a t i o n i s s i m i l a r a l o n g a l l t h e hedgerows, but i s n o t i d e n t i c a l . Beyond t h e d y k e s , t h e marshes b o r d e r i n g t h e F r a s e r R i v e r and G e o r g i a S t r a i t a r e e s s e n t i a l l y f r e s h w a t e r . The water l e v e l v a r i e s w i t h t h e s e a s o n : r i v e r l e v e l s a r e h i g h d u r i n g t h e s p r i n g and e a r l y summer r u n - o f f , b u t d e c r e a s e t o f a i r l y low l e v e l s i n f a l l and w i n t e r . The water i n t h e marshes and s l o u g h s i s t i d a l , r i s i n g and f a l l i n g t w i c e d a i l y . In summer. 4 South Jetty FRASER RIVER FALL R E M O V A L A R E A N SPRING REMOVAL A R E A Figure 1 The Spudy Area: R e i f e l Island and an adjacent part of Westham Island 5 low t i d e s o c c u r i n d a y l i g h t , i n w i n t e r a t n i g h t . The l a n d e n c l o s e d by t h e d y k e s on t h e s t u d y a r e a was used p a r t l y a s p a s t u r e f o r c a t t l e , and p a r t l y as a g r i c u l t u r a l l a n d . The c r o p s grown on t h e a g r i c u l t u r a l l a n d c h anged from s e a s o n t o s e a s o n , and from y e a r t o y e a r , owing t o t h e r o t a t i o n o f c r o p s . The t e r r i t o r i a l Song S p a r r o w s were f o u n d m a i n l y i n t h e v e g e t a t i o n a l o n g t h e hedgerows, o c c a s i o n a l l y f o r a g i n g i n t h e marshes a t low t i d e . The n o n - t e r r i t o r i a l j u v e n i l e s i n t h e f a l l and w i n t e r f o r a g e d e x t e n s i v e l y i n t h e marshes when t h e water l e v e l s were low. No Song Sparrow was s e e n t o use t h e f i e l d s , e i t h e r p a s t u r e o r c r o p s , a t any t i m e . 3. L i f e H i s t o r y Song S p a r r o w s have a wide b r e e d i n g r a n g e i n N o r t h o A m e r i c a , and t h e r e c o g n i t i o n o f more t h a n 30 r a c e s (Dickerman 1963) s u g g e s t s a v e r y h i g h p l a s i c i t y o f t h e s p e c i e s t o v a r y i n g e n v i r o n m e n t a l c o n d i t i o n s . The s t u d i e s on Song S p a r r o w s by B e e r e t a l . ( 1 9 5 6 ) , P h i l l i p s and D i c k e r m a n (1957), N i c e ( 1 9 3 7 ) , J o h n s t o n (1956a,b), and M a r s h a l l (1948a #b) r e v e a l a wide v a r i e t y o f h a b i t a t t y p e s f o r b r e e d i n g , and t h e s t u d i e s o f N i c e (1943) and Tompa (1964) show a h i g h l y d e v e l o p e d a t t a c h m e n t o f t h e s e b i r d s t o t h e s i t e o f b i r t h . I n t h e l o w e r m a i n l a n d o f B r i t i s h C o l u m b i a , t h e Song 6 S p a r r o w s a r e n o n - m i g r a t o r y . The s u b s p e c i e s c o n c e r n e d , H i I i ™2££^BS# O b e r h o l s e r , i s r e s i d e n t i n t h e P u g e t Sound L o w l a n d s , G u l f I s l a n d s , and C o a s t F o r e s t b i o t i c a r e a s (Munro and Cowan, 1947). O t h e r s u b s p e c i e s o c c u r t o t h e n o r t h and e a s t , and a r e m o r p h o l o g i c a l l y d i s t i n c t . A l l b i r d s c a u g h t i n t h i s s t u d y were o f t h e s u b s p e c i e s , nu Jjorphna. The g e n e r a l b e h a v i o u r o f Song S p a r r o w s has been d i s c u s s e d i n d e t a i l by N i c e (1937, 1943). The b i r d s on H e i f e l I s l a n d showed i d e n t i c a l b e h a v i o u r p a t t e r n s i n many r e s p e c t s t o t h o s e d e s c r i b e d by N i c e , and t h e r e f o r e a d e t a i l e d d e s c r i p t i o n i s u n n e c e s s a r y . C e r t a i n a s p e c t s r e l e v a n t t o t h i s s t u d y a r e , however, d i s c u s s e d h e r e . Song S p a r r o w s have Type A t e r r i t o r i e s ( N i c e 1941). The t e r r i t o r y h o l d e r s on H e i f e l I s l a n d r e m a i n e d w i t h i n t h e i r t e r r i t o r y b o u n d a r i e s t h e y e a r r o u n d , i n c o n t r a s t t o t h e f l o c k i n g b e h a v i o u r i n w i n t e r d e s c r i b e d by Tompa (1964) f o r Song S p a r r o w s on Mandarte I s l a n d . The b i r d s on R e i f e l I s l a n d b e h a v e d t e r r i t o r i a l l y f o r a l m o s t t h e whole y e a r , t e r r i t o r i a l b e h a v i o u r c e a s i n g o n l y d u r i n g p e r i o d s o f i n c l e m e n t weather d u r i n g t h e w i n t e r months, and d u r i n g t h e p o s t - b r e e d i n g m o u l t . The i n c e p t i o n and l e n g t h o f t i m e o f m o u l t i n g v a r i e d f r o m b i r d t o b i r d ; p r o b a b l y t h e m o u l t l a s t e d 40 t o 50 d a y s , and t o o k p l a c e i n A u g u s t and September ( c f . N i c e 1937; Tompa 1964). Weather d a t a a r e g i v e n i n A p p e n d i x 2; t h e o n l y s i z e a b l e s n o w f a l l o c c u r r e d i n l a t e December, o t h e r w i s e t h e w i n t e r was v 7 r e l a t i v e l y m i l d . T e r r i t o r y b o u n d a r i e s on R e i f e l I s l a n d were w e l l - d e f i n e d , and were l i n e a r l y a r r a n g e d a l o n g t h e hedgerows. Hence, any one p a i r would have i n g e n e r a l o n l y two n e i g h b o u r i n g p a i r s . From o b s e r v a t i o n s , t h e r e was l i t t l e t r e s p a s s i n g by a d j a c e n t m a l e s i n t o e a c h o t h e r s t e r r i t o r i e s ; b o u n d a r i e s were r e c o g n i z e d and r e s p e c t e d . On b e c o m i n g i n d e p e n d e n t o f t h e i r p a r e n t s , young Song S p a r r o w s p e r f o r m e x p l o r a t o r y movements (Torapa 1964), u n t i l t h e end o f t h e p o s t - j u v e n i l e m o u l t . O b s e r v a t i o n s on young t h a t were banded s h o r t l y a f t e r l e a v i n g t h e n e s t s u g g e s t e d t h a t no l o n g d i s t a n c e s were c o v e r e d . In f a c t , most young were r e s i g h t e d w i t h i n t h e b o u n d a r i e s o f t h e i r p a r e n t ' s t e r r i t o r y a t t h i s t i m e . In t h e f a l l , a f t e r t h e p o s t - b r e e d i n g m o ult, t h e a d u l t s become t e r r i t o r i a l l y a c t i v e o n c e more, and t h i s r e s u l t s i n d i s p e r s a l o f t h e young. T a b l e 1 g i v e s t h e d i s t a n c e s c o v e r e d by i n d i v i d u a l s whose b i r t h p l a c e was known ( s e e Howard 1960, f o r a d i s c u s s i o n on l o n g - and s h o r t - d i s t a n c e d i s p e r s e r s ) . On Mandarte I s l a n d , t h e r i s e i n f a l l t e r r i t o r i a l b e h a v i o u r c o i n c i d e d w i t h t h e e m i g r a t i o n o f many young, 50% o f which were f e m a l e s , t o n e i g h b o u r i n g i s l a n d s . On R e i f e l I s l a n d , a l t h o u g h some o f t h e d i s p e r s a l d i s t a n c e s were q u i t e l a r g e , t h e r e i s some e v i d e n c e t o s u g g e s t t h a t most o f t h e j u v e n i l e s d i d not e m i g r a t e f r o m t h e s t u d y a r e a . F o r example, o u t o f 52 banded 8 TABLE 1 Dispersal distances of juveniles from site of birth; f a l l 1972 Numbers of juveniles Distance (m) 4 0-150 2 150 - 500 1 500 - 750 1 750 - 1000 2 1000 - 1500 1 1500 - 2000 9 j u v e n i l e Song S p a r r o w s t h a t were p r e s e n t on t h e F a l l Removal A r e a d u r i n g A u g u s t and September, 19% were r e s i g h t e d i n O c t o b e r and November, a f t e r t h e peak o f t e r r i t o r i a l a c t i v i t y , w i t h i n t h e s t u d y a r e a . F u r t h e r , o c c a s i o n a l v i s i t s i n t h e f a l l t o a r e a s o u t s i d e t h e s t u d y a r e a f a i l e d t o r e v e a l any banded j u v e n i l e amongst t h e many Song S p a r r o w s p r e s e n t . The young b i r d s t h a t r e m a i n e d a s n o n - t e r r i t o r i a l i n d i v i d u a l s i n t h e f a l l f o r m e d c e n t r e s o f c o n c e n t r a t i o n a t c e r t a i n f a v o u r e d l o c a l i t i e s a l o n g t h e hedgerows. T h e s e c e n t r e s o f young b i r d s p e r s i s t e d t h r o u g h o u t t h e w i n t e r as h i e r a r c h i c a l g r o u p s (see PART B ) . In t h e s p r i n g , t h e h i e r a r c h i c a l g r o u p s began t o b r e a k up, p o s s i b l y as a r e s u l t o f i n c r e a s i n g h o s t i l i t y between t h e y e a r l i n g s t h e m s e l v e s (see Tompa 1964:26). A l s o , i n t h e s p r i n g , t h e t e r r i t o r i a l b i r d s began t o e x c l u d e t h e n o n - t e r r i t o r i a l ones f r o m t h e i r t e r r i t o r i e s . From e a r l y A p r i l t o t h e end o f t h e s t u d y i n l a t e May, 1973, no n o n - t e r r i t o r i a l Song Sparrow was r e c o r d e d on t h e s t u d y a r e a . The R e i f e l W a t e r f o w l R e f u g e and t h e hedgerows a d j o i n i n g t h e s t u d y a r e a on Westham I s l a n d were a l s o s u r v e y e d , i n March and A p r i l 1973, and o n l y one banded b i r d (see A p p e n d i x 3) was l o c a t e d i n t h e two a r e a s . T h e r e seemed t o be, t h e n , a s h a r p d e c l i n e i n t h e numbers of Song S p a r r o w s on t h e s t u d y a r e a i n l a t e March and e a r l y A p r i l . F i g u r e 2 shows t h e numbers o f j u v e n i l e Song S p a r r o w s 10 Each month i s divided i n t o two two-weekly time i n t e r v a l s Figure 2 Numbers of j u v e n i l e Song Sparrows resighted on the Spring Removal Area from mid-December to the end of May 11 r e s i g h t e d i n two-weekly i n t e r v a l s f r o m mid-December t o t h e end o f Hay, s h o w i n g a s h a r p d e c l i n e i n t h e numbers s e e n i n t h e s p r i n g . Tompa (1964) f o u n d t h e same r e s u l t on Mandarte I s l a n d i n Song S p a r r o w s , and s h a r p d e c l i n e s i n numbers i n s p r i n g have been f o u n d i n s e v e r a l o t h e r s p e c i e s o f b i r d s ( e . g . C a r r i c k 1963; Dhondt 1971b; J e n k i n s e t a l , 1963; O r i a n s 1961; S m i t h 1967; Watson 1965). T h u s , a p p a r e n t l y , t h e o n l y Song S p a r r o w s l e f t on t h e s t u d y a r e a i n m i d - A p r i l were t h e t e r r i t o i a l p a i r s . 4. Methods The Song Sparrow p o p u l a t i o n on t h e s t u d y a r e a was o b s e r v e d c o n t i n u a l l y f r o m F e b r u a r y 1972 t o May 1973. B e c a u s e o f t h e n a t u r e o f t h e e x p e r i m e n t s , i t was n e c e s s a r y t o have a banded p o p u l a t i o n , e a c h b i r d i n d i v i d u a l l y r e c o g n i z a b l e . T h e r e f o r e , each b i r d was banded w i t h one a l u m i n i u m and one o r two c o l o u r e d b a n d s , i n v a r i o u s c o m b i n a t i o n s . D u r i n g t h e s t u d y p e r i o d , 282 Song S p a r r o w s were c a u g h t , m a i n l y i n m i s t n e t s , w i t h a few c a u g h t i n p o r t a b l e s p a r r o w t r a p s . Each b i r d was weighed, and measured f o r l e n g t h o f wing, t a r s u s , and c u l m e n . M a l e s and f e m a l e s c a n be s e x e d b o t h on b e h a v i o u r a l d i f f e r e n c e s and on w i n g l e n g t h ( N i c e 1937). F i g u r e 3 g i v e s t h e w i n g l e n g t h s f o r t h e banded b i r d s ; m ales r a n g e d from 67 t o 72 mm i n w i n g l e n g t h , f e m a l e s from 63 t o 68 mm. A l t h o u g h males on a v e r a g e weighed s l i g h t l y more t h a n f e m a l e s t h r o u g h o u t t h e y e a r ( F i g u r e 4 ) , t h e r e was t o o much o v e r l a p NUMBERS Figure 3 Winglengths of male and female Song Sparrows 13 M E A N WEIGHTS (gm) 4 Figure 4 Mean weights of male and female Song Sparrows f o r a l l months 14 between ' l i g h t * and 'heavy' f e m a l e s f o r t h i s c h a r a c t e r i s t i c t o be u s e f u l i n d e t e r m i n a t i o n o f s e x . T a r s u s and culmen measurements were t a k e n i n c a s e t h e s t u d y a r e a was u s e d a s a w i n t e r i n g ground f o r o t h e r s u b s p e c i e s o f Song S p a r r o w s . As m e n t i o n e d e a r l i e r , no s u b s p e c i e s o t h e r t h a n t h e r e s i d e n t one was i d e n t i f i e d on t h e s t u d y a r e a . J u v e n i l e s l o o s e t h e i r d u s t y , f i n e l y - s t r e a k e d plumage i n l a t e f a l l a f t e r t h e p o s t - j u v e n i l e m o u l t , and t h e n assume a plumage s i m i l a r t o t h e a d u l t s . A u s e f u l d i s t i n g u i s h i n g f e a t u r e i s t h a t a l l j u v e n i l e s have p o i n t e d r e t r i c e s , which a r e r e t a i n e d t h r o u g h t h e w i n t e r , whereas a d u l t males have r o u n d e d r e t r i c e s ( N i c e 1 9 3 7 ) . A c r i t e r i o n which I a l s o used was t h e c o l o u r o f t h e f l e s h y p a r t s a t t h e base o f t h e m a n d i b l e s . In f l e d g e l i n g s , t h e s e f l e s h y p a r t s a r e e x t e n s i v e , and a r e b r i g h t y e l l o w i n c o l o u r . In j u v e n i l e s , t h e f l e s h y p a r t s have d e c r e a s e d i n s i z e , b u t t h e y e l l o w c o l o u r a t i o n i s r e t a i n e d , and p r o v e d t o be an o b v i o u s c h a r a c t e r i s t i c when t h e b i r d was i n fe" t h e hand. C e r t a i n y e a r l i n g s ( p o s s i b l y members o f l a t e b r o o d s i n 1972) r e t a i n e d t h e y e l l o w c o l o u r a t i o n i n t o F e b r u a r y 1973. The f l e s h y p a r t s a t t h e base o f t h e m a n d i b l e s i n a d u l t s a r e dark g r e y . T e r r i t o r y b o u n d a r i e s ! were d e t e r m i n e d by n o t i n g t h e r e s p o n s e o f a t e r r i t o r i a l male t o t h e p l a y b a c k o f a s t r a n g e r Song S p a r r o w ' s s o n g on a t a p e r e c o r d e r (Sony 110A) (method d e s c r i b e d i n Dhondt 1 9 6 6 ) . T h i s method p r o v e d v e r y u s e f u l . 15 M a l e s would r e a c t q u i c k l y t o t h e new song by f l y i n g c l o s e t o t h e t a p e r e c o r d e r , and e i t h e r s i n g o r d i s p l a y . I c o u l d e l i c i t a r e s p o n s e from t e r r i t o r i a l b i r d s by p l a y i n g t h e t a p e r e c o r d e r a t v a r i o u s s p o t s a l o n g t h e hedgerow. M a l e s would n o t c r o s s t e r r i t o r y b o u n d a r i e s , b u t would f l y t o a s o n g p e r c h a l o n g t h e b o u n d a r y and s i n g . In t h i s way, t e r r i t o r y b o u n d a r i e s c o u l d be c l e a r l y d e f i n e d i n a v e r y s h o r t s p a c e o f t i m e , p a r t i c u l a r l y a s any one p a i r u s u a l l y had o n l y two n e i g h b o u r s , owing t o t h e l i n e a r i t y o f t h e hedgerow. T h u s , t h e r e l a t i v e l y c o m p l i c a t e d method o f m e a s u r i n g t e r r i t o r y s i z e i n Song S p a r r o w s a s p r o p o s e d by S u t h e r s (1960) was n o t needed. 16 PART A . T H E EFFECT OT TEMPORAL SETTLING PATTERNS ON TERRITORY S I Z E I . INTRODUCTION T e r r i t o r i a l b e h a v i o u r , and i t s i m p o r t a n c e i n d e t e r m i n i n g b r e e d i n g d e n s i t y i n p o p u l a t i o n s o f a n i m a l s , has been t h e s u b j e c t o f much d i s c u s s i o n i n r e c e n t y e a r s , e. g. Wynne-Edwards 1962; C r o o k 1965; L a c k 1966; Rowan 1966; C h i t t y 1967; Brown 1969; F r e t w e l l and L u c a s 1969; Watson and Moss 1970a; Klomp 1972). T h e r e a r e two main l i n e s o f o p i n i o n on t e r r i t o r i a l b e h a v i o u r ; (a) i t d o e s l i m i t b r e e d i n g p o p u l a t i o n s o f v e r t e b r a t e s , o r (b) i t i s s i m p l y t h e way i n which a n i m a l s , whose b r e e d i n g p o p u l a t i o n s have been l i m i t e d by some o t h e r f a c t o r , s p a c e t h e m s e l v e s o u t . Watson and Moss (1970a) l i s t f i v e c o n d i t i o n s ( Appendix 8) w h i c h t h e y 1 f e e l need t o be s a t i s f i e d i n o r d e r t o show t h a t b e h a v i o u r l i m i t s a b r e e d i n g p o p u l a t i o n . They t h e n p r o c e e d t o show t h a t no s t u d y t o d a t e has so f a r f u l l y s a t i s f i e d a l l f i v e c o n d i t i o n s . Removal e x p e r i m e n t s , i n which r e s i d e n t t e r r i t o r y h o l d e r s a r e removed and s u b s e q u e n t r e p l a c e m e n t , i f any, o c c u r s , a r e means by which c o n d i t i o n s (a) and (b) i n A p p e n d i x 8 can be d e t e r m i n e d . The r a t i o n a l e b e h i n d a r e m o v a l e x p e r i m e n t i s a s f o l l o w s . In a g i v e n a r e a , i f t e r r i t o r i a l i n d i v i d u a l s f r o m a s t a b l e p o p u l a t i o n a r e removed, and new i n d i v i d u a l s I 17 s u b s e q u e n t l y r e p l a c e them, t h e n i t c a n be deduced t h a t t h e s e r e p l a c e m e n t s had been p r e v e n t e d from s e t t l i n g on t e r r i t o r i e s i n t h a t a r e a by t h e p r e s e n c e o f t h e t e r r i t o r i a l i n d i v i d u a l s , p r i o r t o t h e r e m o v a l s . I f t h e h o l d i n g o f a t e r r i t o r y i s n e c e s s a r y f o r b r e e d i n g , t h e n i t c a n be f u r t h e r d educed t h a t t h e p r e s e n c e o f t h e t e r r i t o r y h o l d e r s l i m i t s b r e e d i n g d e n s i t y on t h a t a r e a . Such r e m o v a l e x p e r i m e n t s have been c a r r i e d o u t on a v a r i e t y o f s p e c i e s ; i n i n s e c t s ( e . g . J a c o b s 1955; Moore 1964), i n f i s h ( e . g . C l a r i c e 1 970), i n mammals (e. g. L o c k i e 1966; H e a l e y 1967; Smyth 1968), and p a r t i c u l a r l y i n b i r d s ( e . g . S t e w a r t and A l d r i c h 1951; H e n s l e y and Cope 1951; O r i a n s 1961; Watson 1965, 1967; Watson and J e n k i n s 1968; B e n d e l l and E l l i o t 1967; H a r r i s 1970; Holmes 1970; Young 1970; K r e b s 1971; Peek 1971; Young 1972). The i m p o r t a n c e o f t e r r i t o r i a l b e h a v i o u r would be e a s i e r t o d e m o n s t r a t e i f minimum t e r r i t o r y s i z e were c o n s t a n t , and e q u a l f o r a l l i n d i v i d u a l s . T h i s i s however not s o . T h e r e a r e t h r e e p r o b l e m s w h i c h a r e a s s o c i a t e d w i t h v a r i a t i o n s i n t e r r i t o r y s i z e w i t h i n a s p e c i e s : (a) t h e r e a r e d i f f e r e n c e s between i n d i v i d u a l s w i t h i n one p a r t i c u l a r p o p u l a t i o n and y e a r ; (b) t h e r e a r e d i f f e r e n c e s i n t h e mean t e r r i t o r y s i z e w i t h i n one y e a r between h a b i t a t s ; and (c) t h e r e a r e d i f f e r e n c e s i n t h e mean t e r r i t o r y s i z e w i t h i n a h a b i t a t o v e r s u c c e s s i v e y e a r s . T h i s v a r i a b i l i t y i n t e r r i t o r y s i z e has prompted L a c k 18 (1966) t o r e j e c t t h e h y p o t h e s i s t h a t t e r r i t o r i a l b e h a v i o u r r e g u l a t e s b r e e d i n g d e n s i t y . He p o i n t e d o u t t h a t i f t e r r i t o r i e s have a f i x e d minimum s i z e , t h i s has n o t o p e r a t e d i n l i m i t i n g t h e b r e e d i n g p o p u l a t i o n o f t h e G r e a t T i t s , P a r u s m a j o r , i n B a r l e y Wood, O x f o r d , s i n c e t h e b r e e d i n g d e n s i t y has v a r i e d c o n s i d e r a b l y f r o m y e a r t o y e a r . However, K r e b s (1971) a r g u e s t h a t minimum t e r r i t o r y s i z e need not be c o n s t a n t from y e a r t o y e a r f o r t e r r i t o r i a l b e h a v i o u r t o d e t e r m i n e b r e e d i n g d e n s i t y , My s t u d y was i n t e n d e d t o i n v e s t i g a t e a p o s s i b l e mechanism c a u s i n g t h e d i f f e r e n c e s i n mean t e r r i t o r y s i z e f r o m y e a r t o y e a r w i t h i n an a r e a (problem (c) a b o v e ) . I t i s worth c o n s i d e r i n g now some f a c t o r s w hich c o u l d i n f l u e n c e t h e s i z e o f t e r r i t o r y t a k e n from y e a r t o y e a r . I t s h o u l d however be s t r e s s e d t h a t t h e p o s s i b l e f a c t o r s t o be d i s c u s s e d r e f e r t o p r o x i m a t e mechanisms o n l y , n o t t o u l t i m a t e mechanisms. F u r t h e r , my a p p r o a c h t o t h e s t u d y was n o t i n t e n d e d t o e x p l a i n d i f f e r e n c e s between i n d i v i d u a l s ( p r o b l e m (a) a b o v e ) . 1. Food s u £ £ l y and t e r r i t o r y s i z e T e r r i t o r y s i z e c o u l d f l u c t u a t e a n n u a l l y w i t h f o o d s u p p l y , i f s i z e o f t e r r i t o r y was p r o x i m a t e l y a d j u s t e d t o t h e a v a i l a b i l i t y o f f o o d . The e v i d e n c e h e r e i s f a r from u n e q u i v o c a l . D i f f e r e n c e s i n mean t e r r i t o r y s i z e i n v a r i o u s h a b i t a t s 19 have been r e l a t e d t o d i f f e r e n c e s i n f o o d q u a n t i t y (and, i n some i n s t a n c e s , q u a l i t y ) i n v a r i o u s s p e c i e s , e. g. i n d i r e c t l y i n t h r e e s p e c i e s o f t i t m i c e , P a r u s spp. ( K l u y v e r and T i n b e r g e n 1953), and t h e C h a f f i n c h , F r i n g i l l a c o e l e b s , ( G l a s 1960), and d i r e c t l y (by m e a s u r i n g t h e f o o d ) i n t h e D u n l i n , C a l i d r i s a l p i n a , (Holmes 1970) , t h e Red G r o u s e , Laqppus l - _ S c o t i c u s , ( M i l l e r e t a l . 1966; Moss 1969), t h e T u r n s t o n e , M § £ § l i l lBf® I £ I®s, ( S e t t l e s h i p 1 973), and t h r e e s p e c i e s o f s q u i r r e l s o f t h e genus T a m i a s c i u r u s , (Smith 1968). In f i s h , Mason and Chapman (1965) showed a g r e a t e r b i o m a s s and h i g h e r numbers o f j u v e n i l e Coho Salmon, O n c o r h y n c h u s k i s u t c h , where t h e r e was a g r e a t e r f o o d s u p p l y . E g g l i s h a w ( 1 9 6 7 ) , on t h e o t h e r hand, f o u n d t h a t t h e b i o m a s s o f s a l m o n i d s i n two S c o t t i s h s t r e a m s , one t h r e e t i m e s r i c h e r i n f o o d t h a n t h e o t h e r , h a r d l y d i f f e r e d . E v i d e n c e t h a t d i f f e r e n c e s i n t h e mean t e r r i t o r y s i z e w i t h i n a p o p u l a t i o n o v e r a number o f y e a r s i s r e l a t e d t o f o o d s u p p l y i s f a r from c o n c l u s i v e . H a r r i s (1970) s u g g e s t e d t h a t , f o r t h e O y s t e r - C a t c h e r , Haematopus o s t r a l e g u s , t h e s i z e o f t h e t e r r i t o r y t a k e n was p r o b a b l y a compromise between the a r e a t h e b i r d s needed t o f e e d t h e i r young, and t h e a r e a t h e y c a n d e f e n d , O r i a n s ( 1 9 6 1 ) f o u n d a g e n e r a l c o r r e l a t i o n between t h e s i z e o f a Red-winged B l a c k b i r d , A ^ e l a i us Eljoe n i c e us, t e r r i t o r y , and t h e p r o p o r t i o n o f f o o d o b t a i n e d w i t h i n i t s c o n f i n e s , b u t s u g g e s t s t h a t f o o d i s p r o b a b l y n o t t h e p r o x i m a t e f a c t o r by w h i c h t e r r i t o r y s i z e i s r e g u l a t e d and t h a t 20 t e r r i t o r i a l b e h a v i o u r i n some way i s much more i m p o r t a n t . T h e r e i s some e v i d e n c e t h a t t h e q u a n t i t y o f f o o d i n a g i v e n a r e a can d e t e r m i n e t h e s i z e o f t e r r i t o r y t a k e n by t h e O v e n b i r d , S e ^ u r u s a u r o c a £ i l l u s # w i t h i n one y e a r ( S t e n g e r 1958), a l t h o u g h i n t h i s s t u d y i t i s n o t known i f age o r e x p e r i e n c e was i n f l u e n c i n g t e r r i t o r y s i z e . E v i d e n c e t h a t f o o d s u p p l y c a n i n f l u e n c e t e r r i t o r y s i z e c a n be o b t a i n e d i f m a n i p u l a t i o n o f t h e f o o d s u p p l y c a u s e s t h e t e r r i t o r i a l i n d i v i d u a l s t o change t h e s i z e s o f t h e i r t e r r i t o r i e s . I n f i s h , Symons {1968) s u g g e s t e d t h a t t h e i n c r e a s e i n a g g r e s s i o n a s s o c i a t e d w i t h f o o d d e p r i v a t i o n m ight r e s u l t i n an i n c r e a s e d s i z e i n t h e f e e d i n g t e r r i t o r y i n t h e A t l a n t i c Salmon, Salmo s a l a r . However, he c o u l d n o t d e m o n s t r a t e i n a l a b o r a t o r y e x p e r i m e n t (Symons 1971) t h a t d i f f e r i n g a v a i l a b i l i t y o f f o o d c a u s e d c h a n g e s i n t h e s i z e s o f t h e t e r r i t o r i e s o f d o m i n a n t young salmon (the s u b o r d i n a t e f r y were n o n - t e r r i t o r i a l ) . K e e n l e y s i d e and Yamamoto (1962) showed t h a t f i s h d e p r i v e d o f f o o d were more a g g r e s s i v e t h a n t h o s e r e c e i v i n g an abundance o f f o o d , whereas S m i t h (1970) f o u n d t h e r e v e r s e t o be t r u e i n Brook S t i c k l e b a c k , C u l a e a i n e o n s t a n s , w h i s t Bagnusson (1962) f o u n d t h a t a c o m p l e t e a b s e n c e o r a s u p e r a b u n d a n c e o f f o o d r e d u c e d a g g r e s s i o n i n t h e Medaka, Ory.zias l a t i o e s . I f f o o d and a g g r e s s i o n work t o g e t h e r t o d e t e r m i n e t e r r i t o r y s i z e i n f i s h , t h e n t h e y do so a p p a r e n t l y i n d i f f e r e n t ways f o r d i f f e r e n t s p e c i e s . 21 B u s t a r d (1969) showed t h a t t h e number o f f e m a l e s o f a g e k k o n i d l i z a r d , Gehyjra v a r i e g a t a , i n h a b i t i n g a stump d i d n o t v a r y w i t h d i f f e r i n g s u p p l i e s o f f o o d . He c o n c l u d e d t h a t s o c i a l b e h a v i o u r s e t an u p p e r l i m i t , b u t , as Watson and Moss (1970a) p o i n t o u t , t h e p h y s i c a l s t r u c t u r e o f t h e e n v i r o n m e n t s , and n o t b e h a v i o u r , c o u l d be l i m i t i n g , b e c a u s e a l l t h e s u i t a b l e c r a c k s were u s e d by t h e l i z a r d s . I n t h e G r e a t T i t , t h e y e a r - t o - y e a r f l u c t u a t i o n s i n t e r r i t o r y s i z e have n o t been r e l a t e d t o t h e a v a i l a b i l i t y o f f o o d f o r t h e young (Lack 1966), and K r e b s (1971) showed e x p e r i m e n t a l l y t h a t t e r r i t o r y s i z e i n t h e s p r i n g was n o t r e l a t e d t o t h e f o o d s u p p l y i n t h e p r e v i o u s w i n t e r . P i t e l k a e t a l . (1955) s u g g e s t e d an i n v e r s e r e l a t i o n s h i p between t h e mean t e r r i t o r y s i z e i n t h e P o m a r i n e J a e g e r , S t e r c p r a r i u s £ o m a r i n u s , and t h e d e n s i t y o f lemmings, b u t i t i s n o t known i f t h e b r e e d i n g b i r d s were a d j u s t i n g t h e i r t e r r i t o r y s i z e t o t h e f o o d s u p p l y , o r i f t h e r e was a d i f f e r e n c e i n t h e number o f p o t e n t i a l b r e e d e r s f r o m y e a r t o y e a r , a l l o f which s e t t l e d . I n s m a l l mammals, t h e e v i d e n c e f o r t h e i n f l u e n c e o f f o o d on p o p u l a t i o n d e n s i t y i s a l s o n o t u n e g u i v o c a l . I n P e r o m y s c u s fiSSicuAatus, B e n d e l l (1959) f o u n d t h a t e x c e s s f o o d s u p p o r t e d a p o p u l a t i o n i n a new a r e a and i m p r o v e d t h e s u r v i v a l o f t h e young, w h i l s t Fordham (1970) f o u n d t h a t p o p u l a t i o n s i z e and p r o d u c t i o n o f young i n c r e a s e d w i t h a d d i t i o n a l f o o d . E x c e s s f o o d , however, f a i l e d t o p r e v e n t t h e d e c l i n e o f a p o p u l a t i o n 22 o f M i c r o t u s c a l i f o r n i c u s ( K r e b s and B e l o n g 1965; K r e b s 1966), and o f Mus m u s c u l u s ( D e l o n g 1967; Newsome 1970). F i n a l l y , i n t h e Red G r o u s e , t h e q u a l i t y o f h e a t h e r a p p e a r s t o i n f l u e n c e t h e s i z e o f t e r r i t o r y t a k e n , n o t d i r e c t l y w i t h i n one y e a r , b u t w i t h a one y e a r l a g . T h i s has been a t t r i b u t a b l e t o d e c r e a s e d a g g r e s s i v e n e s s w o r k i n g t h r o u g h h i g h n u t r i t i o n a l l e v e l s o f t h e c h i c k s (Watson and Moss 1970b; Watson and M i l l e r 1971). 2. O t h e r e n v i r o n m e n t a l f a c t o r s and t e r r i t o r y s i z e T h e r e a r e s e v e r a l e n v i r o n m e n t a l f a c t o r s o t h e r t h a n f o o d s u p p l y which might i n f l u e n c e t e r r i t o r y s i z e f r o m y e a r t o y e a r . The n a t u r e o f t h e h a b i t a t has been s u g g e s t e d as b e i n g i m p o r t a n t i n i n f l u e n c i n g t h e numbers o f t e r r i t o r i e s i n a g i v e n a r e a i n some a n i m a l s , b o t h i n v e r t e b r a t e s e.g. D i n g l e and C a l d w e l l ( 1 9 6 8 ) , A l e x a n d e r (1961), and L i n (1963), and v e r t e b r a t e s e . g . D i x o n (1956), Snow (1958), D a v i e s and Snow (1965 ) , B u e c h n e r (1 9 6 1 ) , C a l h o u n (1963), Watson (1964), S n y d e r (1967), Zimmerman (1971), and T e s t e r and Watson (1973). Young (1970) f e l t t h a t t e r r i t o r y s i z e i n t h e S h e l d u c k , T a d o r n a t a d o r n a , was d e t e r m i n e d by t h e immediate t o p o g r a p h y o f t h e a r e a , and by t h e l i m i t s o f t o l e r a n c e o f t h e owner. C a t c h p o l e (1972) s u g g e s t e d t h a t t h e l o c a l t o p o g r a p h y o f r e e d b e d s g r e a t l y i n f l u e n c e d t h e s h a p e , b u t n o t t h e s i z e , o f t h e t e r r i t o r i e s o f Reed W a r b l e r s , A c r o c e P h a l u s s c i r p _ a c e o u s , and Sedge W a r b l e r s , 23 s c h o e n o b a g n u s . F i n a l l y , S a l e (1972) s u g g e s t e d t h a t s h e l t e r and a g o n i s t i c b e h a v i o u r were f a c t o r s r e s p o n s i b l e f o r t h e s p a c i n g p a t t e r n s o v e r c o r a l h e a d s o f a p o m a c e n t r i d f i s h , D a s c y l l u s a r u a n u s . F u r t h e r , a s h o r t a g e o f n e s t s i t e s c a n l i m i t t h e p o p u l a t i o n o f , f o r example, h o l e - n e s t i n g b i r d s , and a s u p p l y o f n e s t boxes can i n c r e a s e d e n s i t y . T h i s has been shown i n t h e G r e a t T i t (Lack 1966), and i n t h e P i e d F l y c a t c h e r , F i c e d u l a LY.£2.1§]J£I» ( V o n Haartman 1956; Enemar and S j o s t r a n d 1972). No s t u d y t o d a t e on Song S p a r r o w s ( r e f s . i n Tompa 1961) s u g g e s t s t h a t t h e n a t u r e o f t h e h a b i t a t o r a s h o r t a g e o f n e s t s i t e s has any i n f l u e n c e on t h e s i z e o f t e r r i t o r y t a k e n ( w i t h i n t h e l i m i t s , o b v i o u s l y , o f t h e t y p e o f h a b i t a t t h a t a Song Sparrow w i l l o c c u p y ) . A f u r t h e r p o s s i b l e f a c t o r which c o u l d i n f l u e n c e t h e d e n s i t y o f a t e r r i t o r i a l a n i m a l , and hence t h e t e r r i t o r y s i z e , i s i n t e r s p e c i f i c c o m p e t i t i o n . T h e r e i s some e v i d e n c e t h a t t h e d e n s i t y o f one s p e c i e s has an e f f e c t on t h e d e n s i t y o f a n o t h e r i n p o p u l a t i o n s o f b o t h i n v e r t e b r a t e s and v e r t e b r a t e s ( e . g . C o n n e l l 1961; I n g e r and G r e e n b e r g 1966; M i c h i e l s o n 1966; A y a l a 1971; Z a r e t and Band 1971; Brown 1971; S h e p p a r d 1971). F o r p a s s e r i n e b i r d s , and p a r t i c u l a r l y Song S p a r r o w s , 8. I . Y e a t o n ( p e r s . comm.) h y p o t h e s i s e d t h a t t h e more s p e c i e s c o m p e t i n g f o r some l i m i t i n g r e s o u r c e i n a g i v e n a r e a , t h e l a r g e r t h e t e r r i t o r i e s o f Song S p a r r o w s w i l l be ( ' h o r i z o n t a l ' 24 r a t h e r t h a n ' v e r t i c a l * ) . H i s h y p o t h e s i s , however, i s b u i l t on c i r c u m s t a n t i a l e v i d e n c e , and no e x p e r i m e n t s have been c o n d u c t e d t o d a t e t o t e s t i t . K r e b s (1971:17) has p r e s e n t e d some t h e o r e t i c a l l y p o s s i b l e ways i n which t e r r i t o r y c o u l d i n f l u e n c e d e n s i t y , and d i s c u s s e s e a c h method a t l e n g t h . He c o n s i d e r s some methods i n which minimum t e r r i t o r y s i z e need n o t be r e l a t e d d i r e c t l y t o t h e e n v i r o n m e n t , and one o f t h e s e methods d e a l s w i t h t h e h y p o t h e s i s t h a t t h e t e m p o r a l p a t t e r n o f s e t t l i n g on t e r r i t o r i e s c a n i n f l u e n c e d e n s i t y . 3. T e m p o r a l p a t t e r n s o f s e t t l i n g on t e r r i t o r i e s F l u c t u a t i n g b r e e d i n g d e n s i t i e s i n d i f f e r e n t y e a r s c o u l d be t h e r e s u l t o f d i f f e r e n t d e g r e e s o f s e t t l i n g i n t h o s e y e a r s . I n t h i s way, an u p p e r l i m i t s e t t o t h e number o f s e t t l e d t e r r i t o r y owners c a n be a v a r i a b l e one. F o r t h e h y p o t h e s i s t h a t t e m p o r a l p a t t e r n s o f s e t t l i n g on t e r r i t o r i e s can i n f l u e n c e d e n s i t y , t h e r e i s some s u p p o r t i n g e v i d e n c e i n work on b i r d s and f i s h . Van den Assem (1967) f o u n d t h a t i n t h e t h r e e - s p i n e d s t i c k l e b a c k , g a s t e r o s t e u s a c u l e a t u s , t e r r i t o r y s i z e s v a r i e d c o n s i d e r a b l y w i t h t h e p a t t e r n o f s e t t l i n g . The number o f t e r r i t o r i a l m a l e s a c c o m o d a t e d i n a t a n k was n e a r l y d o u b l e when t h e males were i n t r o d u c e d s i m u l t a n e o u s l y a s when t h e y were i n t r o d u c e d s u c c e s s i v e l y . He i n t e r p r e t e d t h e r e s u l t s as 25 s u g g e s t i n g t h a t t h e r e l a t i v e d i f f e r e n c e s i n a g g r e s s i v e l e v e l s i n t h e male s t i c k l e b a c k s - a l l o f them i n t h e p r o c e s s o f s e t t l i n g and b u i l d i n g - were t e m p o r a r i l y s m a l l e r t h a n f o u n d i f males were i n t r o d u c e d s u c c e s s i v e l y . Simms (1965) r e l a t e s t h a t f o r t h e E u r o p e a n B l a c k b i r d , T u r d u s m e r u l a , t h e number o f t e r r i t o r i e s i n a s t a b l e p o p u l a t i o n was r e d u c e d by 55% a f t e r a s e v e r e snowstorm. The number o f t e r r i t o r i e s h e l d a f t e r t h e snowstorm was 93 as compared t o a b o u t 200 i n t h e p r e v i o u s y e a r , b u t r o s e t o 244 t h e f o l l o w i n g y e a r , and t h i s i s t a k e n as s u g g e s t i v e e v i d e n c e t h a t t h e p a t t e r n o f s e t t l i n g i n f l u e n c e d t e r r i t o r y s i z e . F o r t h e G r e a t T i t , K r e b s (1971) has put f o r w a r d s u g g e s t i v e e v i d e n c e t h a t i s a t l e a s t c o n s i s t e n t w i t h t h e h y p o t h e s i s . S e t t l i n g on t e r r i t o r i e s by G r e a t T i t s o c c u r s i n F e b r u a r y , and, i f s y n c h r o n y o f s e t t l i n g i n f l u e n c e s t h e c o m p r e s s i b i l i t y o f t e r r i t o r i e s , and a c o n s i s t e n t l y warm F e b r u a r y c a u s e s b o t h a d u l t s and f i r s t y e a r b i r d s t o s e t t l e more s y n c h r o n o u s l y , t h e n t h e b r e e d i n g d e n s i t y might i n c r e a s e . K r e b s showed t h a t t h e r e was a p o s i t i v e c o r r e l a t i o n between mean F e b r u a r y t e m p e r a t u r e and s u b s e q u e n t b r e e d i n g d e n s i t y . C a t c h p o l e (1972) s u g g e s t e d t h a t t e m p o r a l p a t t e r n s o f s e t t l i n g on t e r r i t o r i e s might a c c o u n t f o r t h e v a r i a t i o n s i n mean t e r r i t o r y s i z e he o b s e r v e d i n a t h r e e y e a r s t u d y o f Reed and Sedge W a r b l e r s . He a d m i t s , however, t o h a v i n g no c o n c l u s i v e e v i d e n c e t o s u b s t a n t i a t e t h e h y p o t h e s i s . 26 P o s s i b l y t h e example which b e s t s u p p o r t s t h e h y p o t h e s i s i n b i r d s i s f r o m Song S p a r r o w s on M a n d a r t e I s l a n d (Tompa 1964; 1 9 7 1). The number o f t e r r i t o r i e s f o r t h e f i r s t two y e a r s o f t h e s t u d y was c o n s t a n t , b u t i n c r e a s e d s u b s t a n t i a l l y i n t h e t h i r d y e a r o f t h e s t u d y f o l l o w i n g a c a t a s t r o p h i c m o r t a l i t y , c a u s e d by a f r e a k snowstorm i n March, o f t e r r i t o r i a l b i r d s . The s t o r m o c c u r r e d i n t h e s p r i n g a t t h e peak o f t e r r i t o r i a l b e h a v i o u r , and a p p a r e n t l y c a u s e d l i t t l e m o r t a l i t y amongst t h o s e y e a r l i n g s t h a t were no t t e r r i t o r i a l l y a c t i v e . A f t e r t h e s t o r m , t h e s e n o n - t e r r i t o r i a l b i r d s were a l l o w e d t o s e t t l e , now t h a t t h e r e s i s t a n c e f r o m t h e e s t a b l i s h e d t e r r i t o r i a l b i r d s had gone, and t h e number o f o c c u p i e d t e r r i t o r i e s i n c r e a s e d . The number o f t e r r i t o r i e s a l s o r e m a i n e d h i g h f o r t h e f o u r t h y e a r o f t h e s t u d y . I t h e r e f o r e s e t o u t t o e x p e r i m e n t a l l y i n v e s t i g a t e t h e f o l l o w i n g q u e s t i o n : i n Song S p a r r o w s , d o e s t h e t e m p o r a l p a t t e r n o f s e t t l i n g on t e r r i t o r i e s i n a g i v e n a r e a i n f l u e n c e t h e number o f t e r r i t o r i e s o c c u p i e d , and hence t e r r i t o r y s i z e , and> t h e b r e e d i n g d e n s i t y ? 27 I I . PROCEDURE In o r d e r t o t e s t e x p e r i m e n t a l l y t h e h y p o t h e s i s t h a t t e m p o r a l p a t t e r n s o f s e t t l i n g on t e r r i t o r i e s c a n i n f l u e n c e t h e number o f t e r r i t o r i e s t a k e n i n a g i v e n a r e a , i t was n e c e s s a r y t o c a r r y o u t r e m o v a l s o f t h e t e r r i t o r i a l p a i r s . The r e m o v a l e x p e r i m e n t s t h e m s e l v e s would show t h a t , i f r e p l a c e m e n t o c c u r r e d , t h e r e e x i s t e d a s u r p l u s o f Song S p a r r o w s on t h e s t u d y a r e a . I f t h e r e p l a c e m e n t b i r d s came from t h e l o o s e g r o u p s o f n o n - t e r r i t o r i a l j u v e n i l e s , t h e n i t c a n be deduced t h a t t h e r e s i d e n t t e r r i t o r y h o l d e r s were p r e v e n t i n g c e r t a i n j u v e n i l e s f r o m t a k i n g t e r r i t o r i e s on t h e s t u d y a r e a . As h o l d i n g a t e r r i t o r y f o r a Song Sparrow i s a n e c e s s a r y p r e - r e q u i s i t e f o r b r e e d i n g , t h e n i t can be f u r t h e r d e d u c e d t h a t , i f t h e r e p l a c e m e n t j u v e n i l e s were c a p a b l e o f b r e e d i n g , t h e t e r r i t o r i a l b e h a v i o u r o f t h e r e s i d e n t b i r d s l i m i t e d t h e b r e e d i n g d e n s i t y . Two t y p e s o f r e m o v a l e x p e r i m e n t s were c a r r i e d o u t : • S i m u l t a n e o u s ' and ' S u c c e s s i v e ' . A S i m u l t a n e o u s Removal i n v o l v e d t h e r e m o v a l o f t h e t e r r i t o r i a l b i r d s , b o t h males and f e m a l e s , i n as s h o r t a s p a c e o f t i m e a s p o s s i b l e , t h u s c r e a t i n g an a r e a o f s u i t a b l e h a b i t a t which was c o m p l e t e l y empty o f t e r r i t o r i a l Song S p a r r o w s . T h i s was i n t e n d e d t o a l l o w s i m u l t a n e o u s s e t t l i n g o f some o f t h e n o n - t e r r i t o r i a l Song S p a r r o w s . T h i s t y p e o f r e m o v a l was i n t e n d e d t o s i m u l a t e 28 a c a t a s t r o p h i c m o r t a l i t y o f n o n - m i g r a t o r y t e r r i t o r i a l b i r d s , b u t i t c o u l d e q u a l l y w e l l be a p p l i e d t o o t h e r i n s t a n c e s c f a v o i d o f t e r r i t o r i a l b i r d s i n an a r e a o f s u i t a b l e h a b i t a t , a s f o r example when m i g r a t o r y b i r d s r e t u r n i n t h e s p r i n g a t t h e same t i m e t o a n o n - o c c u p i e d a r e a . T h e s e t y p e s o f o c c u p a n c y a r e h e r e t r e a t e d a s e q u i v a l e n t . A S u c c e s s i v e Removal i n v o l v e d t h e r e m o v a l o f t e r r i t o r i a l p a i r s a t r e g u l a r i n t e r v a l s , s i m u l a t i n g t h e more n o r m a l s i t u a t i o n o f t h e p e r i o d i c d i s a p p e a r a n c e o v e r a l o n g e r p e r i o d of t i m e o f t e r r i t o r i a l i n d i v i d u a l s . T h i s was i n t e n d e d t o a l l o w s u c c e s s i v e s e t t l i n g o f some n o n - t e r r i t o r i a l Song S p a r r o w s . S i m u l t a n e o u s and S u c c e s s i v e r e m o v a l s were c o n d u c t e d i n the f a l l o f 1972 and i n t h e s p r i n g o f 1973. T h e s e two t i m e s c o i n c i d e d w i t h t h e two p e a k s o f t e r r i t o r i a l b e h a v i o u r o f Song S p a r r o w s ( N i c e 1943; Tompa 1964). Two d i f f e r e n t hedgerows were used f o r e a c h s e t o f r e m o v a l e x p e r i m e n t s (see F i g u r e 1 ) . Each s e t was a r r a n g e d s u c h t h a t a C o n t r o l a r e a was s a n d w i c h e d between t h e S i m u l t a n e o u s and t h e S u c c e s s i v e Removal a r e a s . B i r d s were removed e i t h e r by m i s t n e t t i n g o r by s h o o t i n g . The most s u c c e s s f u l means p r o v e d t o be t h e use o f a t a p e d song o f a s t r a n g e r Song S p a r r o w , and a m i s t n e t s t r u n g o v e r t h e t a p e r e c o r d e r . B o t h males and f e m a l e s were c a u g h t i n t h e m i s t n e t s as t h e y r e s p o n d e d t o t h e t a p e . The o n l y major p r o b l e m c o n c e r n e d t h e r e m o v a l o f f e m a l e s i n t h e f a l l (see b e l o w ) . 29 Appendix 4 g i v e s some p o s s i b l e r e a s o n s a c c o u n t i n g f o r t h e d i f f i c u l t y i n l o c a t i n g f e m a l e s a t t h i s t i m e . The F a l l Removal A r e a T h i s hedgerow c o n t a i n e d 24 t e r r i t o r i e s i n t h e f a l l o f 1972. 8 t e r r i t o r i e s were u s e d f o r t h e S u c c e s s i v e Removal, 6 f o r t h e C o n t r o l , and 10 f o r t h e t h e S i m u l t a n e o u s Removal. The 10 t e r r i t o r i e s on t h e S i m u l t a n e o u s Removal a r e a c o n t a i n e d 8 a d u l t males f r o m t h e summer, and 2 j u v e n i l e m a l e s , w i t h o u t mates, t h a t had e s t a b l i s h e d t e r r i t o r i e s f o r t h e m s e l v e s by i n t r u s i o n d u r i n g t h e e a r l y f a l l . S i m i l a r l y , t h e 8 t e r r i t o r i e s on t h e S u c c e s s i v e Removal a r e a c o n t a i n e d 1 j u v e n i l e male, m a t e l e s s , w i t h a t e r r i t o r y e s t a b l i s h e d by i n t r u s i o n e a r l y i n t h e f a l l . 9 o u t o f t h e 10 m a l e s on t h e S i m u l t a n e o u s Removal a r e a were removed i n t h e p e r i o d O c t o b e r 4 t o 7; t h e l a s t male was removed on O c t o b e r 12. T h i s l a s t male was n o t r e c o r d e d from O c t o b e r 1 t o 11, and i t i s p o s s i b l e t h a t t h e d i f f i c u l t y i n l o c a t i n g him c o u l d be due t o t h e f a c t t h a t he had n o t c o m p l e t e d t h e p o s t - b r e e d i n g m o u l t u n t i l t h e s e c o n d week o f O c t o b e r . A l s o , on t h e S i m u l t a n e o u s Removal a r e a , o u t o f a p o s s i b l e 8 f e m a l e s , o n l y 4 were removed. Some p o s s i b l e e x p l a n a t i o n s f o r t h i s d i s c r e p a n c y a r e g i v e n i n Ap p e n d i x 4. 30 The 8 males on t h e S u c c e s s i v e Removal a r e a were removed from O c t o b e r 3 t o 27, a t i n t e r v a l s o f t h r e e and f o u r days a l t e r n a t e l y . Once a g a i n , f e m a l e s p r o v e d d i f f i c u l t t o l o c a t e . Out o f a p o s s i b l e 7 f e m a l e s , o n l y one was removed (see Ap p e n d i x 4 a g a i n f o r p o s s i b l e e x p l a n a t i o n s ) . The S p r i n g Removal A r e a T h i s hedgerow c o n t a i n e d 19 t e r r i t o r i e s i n t h e s p r i n g o f 1973. 7 t e r r i t o r i e s were t a k e n f o r t h e S i m u l t a n e o u s Removal, 6 f o r t h e C o n t r o l , and 6 f o r t h e S u c c e s s i v e Removal. 7 males and 5 f e m a l e s were removed f r o m t h e S i m u l t a n e o u s Removal a r e a on March 7. Two f e m a l e s were a p p a r e n t l y m i s s i n g on t h e day o f t h e e x p e r i m e n t . One t e r r i t o r i a l male, a y e a r l i n g t h a t had t a k e n o v e r a t e r r i t o r y i n t h e f a l l o f 1972 a f t e r an a d u l t male had d i s a p p e a r e d , d i d n o t a p p e a r t o have a f e m a l e ( s i x h o u r s o f w a t c h i n g from a h i d e i n t h i s male's t e r r i t o r y f a i l e d t o r e v e a l a p a i r e d f e m a l e ) . The s e c o n d f e m a l e d i s a p p e a r e d f r o m h e r mate's t e r r i t o r y between J a n u a r y 29 and F e b r u a r y 2. The male i s t h o u g h t t o have t a k e n a j u v e n i l e f e m a l e as h i s mate; t h i s i n c i d e n t i s c o n s i d e r e d more a t l e n g t h i n PART B. 6 males and 4 f e m a l e s were removed i n p a i r s f r o m t h e S u c c e s s i v e Removal a r e a , a t i n t e r v a l s o f t h r e e and f o u r d a ys a l t e r n a t e l y , between March 3 and 23. Two f e m a l e s were a p p a r e n t l y m i s s i n g on t h e d a y s o f t h e e x p e r i m e n t a l r e m o v a l s . 31 One f e m a l e d i s a p p e a r e d s h o r t l y b e f o r e t h e r e m o v a l e x p e r i m e n t s , and was n o t s e e n a f t e r w a r d s . The s e c o n d f e m a l e d e s e r t e d h e r mate b e f o r e t h e e x p e r i m e n t s , and remated w i t h a C o n t r o l male i n e a r l y March. The C o n t r o l s C o n t r o l s i n b o t h S p r i n g and F a l l Removal A r e a s r e m a i n e d u n d i s t u r b e d d u r i n g t h e r e m o v a l e x p e r i m e n t s . 32 I I I . RESULTS 1. R e p l a c e m e n t Of Removed P a i r s The Sparing Removal A r e a On t h e S i m u l t a n e o u s Removal a r e a , 7 males and 5 f e m a l e s were removed. W i t h i n 9 d a y s , 10 males and 7 f e m a l e s had s e t t l e d . T h u s , 17 b i r d s had r e p l a c e d t h e 12 removed. On t h e S u c c e s s i v e Removal a r e a , 6 males and 4 f e m a l e s were removed. R e p l a c e m e n t p a i r s s e t t l e d on v a c a n t t e r r i t o r i e s I, d u r i n g t h e t h r e e o r f o u r day i n t e r v a l s between t h e s u c c e s s i v e :\ r e m o v a l s . By H a r c h 27, 5 p a i r s s e t t l e d . T h u s , 10 b i r d s had r e p l a c e d t h e 10 removed. The F a l l Removal A r e a On t h e S i m u l t a n e o u s Removal a r e a , 10 males and 4 f e m a l e s were removed. W i t h i n 10 d a y s a f t e r t h e r e m o v a l o f t h e n i n t h male on O c t o b e r 7, 14 males had s e t t l e d . A l t h o u g h s e v e r a l f e m a l e s were c a u g h t i n t h e f a l l o f 1972, i t was n o t known i f t h e y were p a i r e d w i t h t h e r e p l a c e m e n t b i r d s o r n o t . T h e r e f o r e , a s s e s s m e n t o f t h e number o f f e m a l e s was n o t done u n t i l t h e s p r i n g o f 1973. On t h e S u c c e s s i v e Removal a r e a , 8 males and 1 f e m a l e were removed. As i n t h e S u c c e s s i v e Removal i n t h e s p r i n g e x p e r i m e n t , r e p l a c e m e n t b i r d s s e t t l e d on v a c a n t t e r r i t o r i e s d u r i n g t h e t h r e e o r f o u r day i n t e r v a l s between t h e s u c c e s s i v e 33 r e m o v a l s . By O c t o b e r 30, 9 males had e s t a b l i s h e d t e r r i t o r i e s . Once a g a i n , s e v e r a l f e m a l e s were c a u g h t i n t h e f a l l o f 1972, bu t t h e i r r e l a t i o n t o t h e t e r r i t o r i a l males was n o t known. A s s e s s m e n t o f t e r r i t o r i a l f e m a l e s t h e r e f o r e was d e f e r r e d u n t i l t h e s p r i n g o f 1973. A f t e r r e s e t t l i n g had o c c u r r e d , t e r r i t o r i e s c o v e r e d t h e e n t i r e l e n g t h o f t h e hedgerows i n b o t h S p r i n g and F a l l Removal A r e a s (see F i g u r e 6 as an e x a m p l e ) . Some e x p a n s i o n o c c u r r e d i n i n s t a n c e s where a C o n t r o l and an E x p e r i m e n t a l a r e a met (see b e l o w ) , s u g g e s t i n g t h a t b e f o r e t h e r e m o v a l s , t h e r e was p r e s s u r e p r e v e n t i n g e x p a n s i o n (Watson 1967; K r e b s 1971). Thus, t h e r e p l a c e m e n t e x p e r i m e n t s showed t h e e x i s t e n c e o f a s u r p l u s o f p o t e n t i a l b r e e d e r s who were p r e v e n t e d f r o m s e t t l i n g on t h e s t u d y a r e a by t h e r e s i d e n t t e r r i t o r y h o l d e r s . 2. Numbers Of O c c u p i e d T e r r i t o r i e s T a b l e 2 g i v e s t h e r e s u l t s o f t h e r e m o v a l e x p e r i m e n t s f o r b o t h S p r i n g and F a l l Removal A r e a s . Numbers o f t e r r i t o r i e s o c c u p i e d by m a l e s , b o t h mated and unmated, a r e g i v e n . On b o t h S i m u l t a n e o u s Removal a r e a s , t h e r e was an i n c r e a s e i n t h e number o f o c c u p i e d t e r r i t o r i e s a f t e r t h e r e m o v a l s . I n c r e a s e s i n b o t h s p r i n g and f a l l were i n t h e r e g i o n o f 40%. On t h e S u c c e s s i v e Removal a r e a s and on t h e C o n t r o l s , t h e r e were o n l y s l i g h t c h a n g e s i n t h e numbers o f o c c u p i e d 34 TABLE 2 Results of removal experiments: numbers of occupied territories of both mated and unmated males Spring Removal Area Before After Percentage change i n number of territories Simultaneous: 7 10 +42% Successive: 6 -16.7% Control: 6 +16.7% F a l l Removal Area Simultaneous: 10 14 +40% Successive: 8 +12.5% Control: -16.7% 35 t e r r i t o r i e s (see b e l o w ) . The d i f f e r e n c e s i n t h e numbers o f t e r r i t o r i e s b e f o r e and a f t e r t h e r e m o v a l e x p e r i m e n t s a r e compared i n T a b l e 3. The d i f f e r e n c e s between t h e S i m u l t a n e o u s and t h e S u c c e s s i v e Removal a r e a s , and between t h e S i m u l t a n e o u s Removal a r e a s and t h e C o n t r o l s , i n b o t h S p r i n g and F a l l Removal A r e a s , a r e compared. The d i f f e r e n c e s i n o c c u p i e d t e r r i t o r i e s on t h e S i m u l t a n e o u s Removal a r e a s a r e s i g n i f i c a n t l y h i g h e r (P<0.05) t h a n t h o s e on t h e S u c c e s s i v e Removal a r e a s and on t h e C o n t r o l s . T h e s e d a t a s u g g e s t t h e s i m u l t a n e o u s s e t t l i n g r e s u l t s i n more t e r r i t o r i e s t a k e n t h a n i f t h e s e t t l i n g o c c u r s s u c c e s s i v e l y . 3 • S i z e Of T e r r i t o r i e s An i n c r e a s e i n numbers o f t e r r i t o r i e s i n a f i x e d a r e a n e c e s s a r i l y i m p l i e s t h a t t h e mean t e r r i t o r y s i z e d e c r e a s e s . I n t h e p r e s e n t s t u d y , t h e a r e a s were n o t e x a c t l y t h e same b e f o r e and a f t e r t h e e x p e r i m e n t s , p a r t i c u l a r l y t h e S p r i n g Removal A r e a . T h i s was due t o t h e e x p a n s i o n o f t h e t e r r i t o r i a l b o u n d a r i e s o f t h o s e C o n t r o l males t h a t had t e r r i t o r i e s a d j a c e n t t o t h e r e m o v a l a r e a s . Hence a more a c c u r a t e measure o f t h e d i f f e r e n c e s b e f o r e and a f t e r t h e r e m o v a l e x p e r i m e n t s i s t o compare mean t e r r i t o r y s i z e s . 36 TABLE 3 Results of removal experiments: differences i n numbers of occupied t e r r i t o r i e s of both mated and unmated males Simultaneous Successive Spring: +3 -1 F a l l : +4 +1 t = 3.13 P < 0.05 (one-tail) Simultaneous Control Spring: +3 +1 F a l l : +4 -1 t = 3.13 P < 0.05 (one-tail) 37 T a b l e s 4 and 5 g i v e t h e mean t e r r i t o r y s i z e s i n t h e S i m u n t a n e o u s and t h e S u c c e s s i v e Removal a r e a s , and t h e C o n t r o l s , f o r b o t h s p r i n g and f a l l r e m o v a l e x p e r i m e n t s . On t h e S i m u l t a n e o u s Removal a r e a s , t h e d i f f e r e n c e s between t h e mean t e r r i t o r y s i z e s b e f o r e and a f t e r t h e r e m o v a l s a r e s i g n i f i c a n t ; P<0.01 f o r t h e S p r i n g Removal A r e a , P<0.05 f o r t h e F a l l Removal A r e a . The mean t e r r i t o r y s i z e s on t h e S i m u l t a n e o u s Removal a r e a s a r e much s m a l l e r a f t e r t h e e x p e r i m e n t s t h a n b e f o r e . T h e r e a r e d i f f e r e n c e s i n mean t e r r i t o r y s i z e s b e f o r e and a f t e r t h e r e m o v a l s on b o t h S u c c e s s i v e Removal a r e a s , and on t h e C o n t r o l s , b u t i n no i n s t a n c e a r e t h e d i f f e r e n c e s s i g n i f i c a n t . T h e s e d a t a f u r t h e r s u p p o r t t h e h y p o t h e s i s t h a t s i m u l t a n e o u s s e t t l i n g r e s u l t s i n more t e r r i t o r i e s o c c u p i e d , w i t h s m a l l e r mean t e r r i t o r y s i z e , t h a n i f t h e s e t t l i n g i s s u c c e s s i v e . So f a r , t h e a n a l y s e s have d e a l t w i t h t h e numbers o f t e r r i t o r i e s , and t h e s i z e s o f t e r r i t o r i e s , b e f o r e and a f t e r t h e r e m o v a l e x p e r i m e n t s . I t i s n e c e s s a r y , however, t o compare t h e b r e e d i n g d e n s i t y b e f o r e and a f t e r t h e r e m o v a l s , a s some mal e s r e m a i n e d unmated d u r i n g t h e s p r i n g o f 1973. B e f o r e d o i n g s o , however, c e r t a i n c h a n g e s i n numbers o f t e r r i t o r i e s t h a t t o o k p l a c e o v e r t h e w i n t e r on t h e F a l l Removal A r e a need t o be c o n s i d e r e d . 38 TABLE 4 Results of the removal experiments: mean t e r r i t o r y s i z e . F a l l Removal Area. 2 2 N Mean T e r r i t o r y Size (m ) S(m ) Simultaneous: Before 10 2323 972 A f t e r 14 1659 652 * t = 2.01 P < 0.05 Successive: Before 8 3238 969 A f t e r 9 2878 548 t = o.96 0.2 > p y 0.1 Control: Before 6 1745 406 A f t e r 5 2094 520 t = 1.25 0.2 > P > 0.1 * S t a t i s t i c a l l y s i g n i f i c a n t 39 TABLE 5 R e s u l t s o f removal experiments: mean t e r r i t o r y s i z e . Spring Removal Area 2 2 N Mean T e r r i t o r y Size (m ) S(m ) Simultaneous: Before A f t e r 10 3638 2572 370 887 * t = 2.69 P < 0.01 ( o n e - t a i l ) Successive: Before 1890 766 A f t e r 2143 608 t = 0.60 0.45 > P > 0.3 ( o n e - t a i l ) C o n t r o l : Before 3956 611 A f t e r 3480 1229 t = 0.86 0.25 > P ^ 0.2 ( o n e - t a i l ) * S t a t i s t i c a l l y s i g n i f i c a n t \ 40 4. Changes In Numbers Of T e r r i t o r i e s On The F a l l Removal Area Over The Winter In the preceding a n a l y s e s , numbers of replacement males on the F a l l Removal Area were determined during the f a l l a f t e r the removal experiments. Changes i n the numbers of t e r r i t o r i e s on the F a l l Removal Area however occ u r r e d over the winter. By October 17, 14 j u v e n i l e males had r e p l a c e d 10 t e r r i t o r i a l males on the Simultaneous Removal area. In mid-December, the 14 replacements were s t i l l present. From mid-December to mid-March, I d i d not survey t h i s area as time was spent l o o k i n g at the dominance h i e r a r c h i e s on the S p r i n g Removal Area. (See PART B). In mid-March, i t was apparent from surveys of the breeding p o p u l a t i o n t h a t a ' n a t u r a l ' removal had taken p l a c e . Only 10 males had t e r r i t o r i e s along the hedgerow; 9 of these males were ' o r i g i n a l s ' from the f a l l , and one was a newcomer t h a t had taken over one of the ' o r i g i n a l ' s ' t e r r i t o r i e s . Of the f o u r t e r r i t o r i e s t h a t had been occupied i n the f a l l and were now n o n - e x i s t e n t , two had been expanded i n t o , and p a r t i t i o n e d , by neighbouring males, and two had been i n c o r p o r a t e d i n t o the t e r r i t o r y of a C o n t r o l male. Figure 5 g i v e s the sequence of events l e a d i n g t o the l a t t e r i n c o r p o r a t i o n . The p a r t i c u l a r male i n v o l v e d (C6), i n the s p r i n g of 1973, defended a p p a r e n t l y s u c c e s s f u l l y a t e r r i t o r y Figure 5 F a l l Removal Area: the Simultaneous Removal Area - Control. The movement and expansion of Control male (C6) a f t e r the removal experiments and during the subsequent winter 42 whose s i z e was an u n p r e c e d e n t e d 8755 s q u a r e m e t r e s , f a r l a r g e r t h a n any o t h e r Song S p a r r o w s t e r r i t o r y on R e i f e l I s l a n d . T hus, t h e 10 r e p l a c e m e n t m a l e s t h a t o c c u p i e d t e r r i t o r i e s i n t h e s p r i n g o f 1973 a c t u a l l y c o v e r e d much l e s s a r e a t h a n t h e 14 i n t h e f a l l o f 1972. I n f a c t , t h e i r combined t e r r i t o r i e s c o v e r e d an a r e a t h a t s u p p o r t e d 12 r e p l a c e m e n t males i n t h e f a l l a f t e r t h e r e m o v a l , and 8 a d u l t males i n t h e f a l l b e f o r e t h e r e m o v a l . On t h e S u c c e s s i v e Removal a r e a , 2 males o u t o f 9 r e p l a c e m e n t s d i s a p p e a r e d o v e r t h e w i n t e r . B o t h o f t h e t e r r i t o r i e s were expanded i n t o , and i n c o r p o r a t e d , by n e i g h b o u r i n g m a l e s . T h e r e f o r e , i n t h e s p r i n g o f 1973, 7 m a l e s , a l l p a i r e d , h e l d t e r r i t o r i e s . 5- Breeding. D e n s i t y I n The S p r i n g . Of ,1973 T a b l e 6 g i v e s t h e number o f b r e e d i n g p a i r s , and t h e number o f t e r r i t o r i a l unmated m a l e s , f o r a l l a r e a s . On t h e F a l l Removal A r e a , t h e b r e e d i n g d e n s i t i e s between t h e s p r i n g o f 1972 and t h e s p r i n g o f 1973 a r e compared. D e s p i t e t h e f a c t t h a t t h e number o f t e r r i t o r i e s i n c r e a s e d a f t e r t h e e x p e r i m e n t s on t h e S i m u l t a n e o u s Removal a r e a s on b o t h S p r i n g and F a l l Removal A r e a s , t h e number o f b r e e d i n g p a i r s r e m a i n e d e s s e n t i a l l y t h e same - 14 p a i r s b e f o r e , 15 a f t e r . T h e r e were t h e r e f o r e s e v e r a l (5) unmated t e r r i t o r i a l 43 TABLE 6 Results of the removal experiments: breeding density Spring Removal Area T e r r i t o r i a l Number of Breeding p a i r s unmated males t e r r i t o r i e s Simultaneous: Before 6 1 7 A f t e r 7 3 10 Successive: Before 6 0 6 A f t e r 5 0 5 Control: Before 6 0 6 A f t e r 7 0 7 F a l l Removal Area Simultaneous: Before 8 0 8 A f t e r 8 2 10 Successive: Before 7 0 7 A f t e r 7 0 7 Control: Before 5 1 6 A f t e r 5 0 5 44 ma l e s p r e s e n t . I t i s o f i n t e r e s t t h a t Tompa (1964; 1971) f o u n d much t h e same r e s u l t on Mandarte I s l a n d . F o l l o w i n g t h e c a t a s t r o p h i c m o r t a l i t y o f t e r r i t o r i a l Song S p a r r o w s i n March 1962, t h e number o f o c c u p i e d t e r r i t o r i e s r o s e by n e a r l y 401 t o 69, w h i l s t t h e b r e e d i n g d e n s i t y r e m a i n e d r o u g h l y a t t h e same l e v e l as p r e v i o u s y e a r s - 47 p a i r s i n 1960 and 1961, 44 i n 1962. I t was not u n t i l t h e f a l l o f 1962 t h a t t h e s e t t l i n g o f j u v e n i l e f e m a l e s on t h e t e r r i t o r i e s o f unmated males r a i s e d t h e number o f t e r r i t o r i e s w i t h p a i r s t o 69. As t h e p r e s e n t s t u d y t e r m i n a t e d i n t h e summer o f 1973, t h e r e i s no e v i d e n c e t h a t t h e b r e e d i n g d e n s i t y a c h i e v e d a b a l a n c e d s e x r a t i o , e i t h e r t h r o u g h t h e d i s a p p e a r a n c e o f t h e unmated males o r t h r o u g h t h e s e t t l i n g o f f e m a l e s on t h e s e unmated m a l e s ' t e r r i t o r i e s . 1 The number o f b r e e d i n g p a i r s on t h e S u c c e s s i v e Removal a r e a s , and on t h e C o n t r o l s , r e m a i n e d e s s e n t i a l l y the same b e f o r e and a f t e r t h e r e m o v a l e x p e r i m e n t s . The s l i g h t d i f f e r e n c e s on t h e C o n t r o l s c a n be a c c o u n t e d f o r by t h e e x p a n s i o n o f t h e t e r r i t o r y b o u n d a r i e s o f c e r t a i n C o n t r o l m a l e s , a s e x p l a i n e d e a r l i e r . 6. D i f f e r e n c e s I n T e r r i t o r y S i z e Between Mated And Unmated M a l e s 45 An i n t e r e s t i n g s i d e l i g h t on t h e s i z e o f t e r r i t o r i e s i n t h e S i m u l t a n e o u s Removal a r e a s i s t h a t males t h a t d i d n o t a t t r a c t a mate had s i g n i f i c a n t l y s m a l l e r t e r r i t o r i e s t h a n t h o s e t h a t d i d ( T a b l e 7 ) . B oth N i c e (1943) and Tompa (1964) s t a t e t h a t t h e f e m a l e Song S p a r r o w s does not d i s c r i m i n a t e i n h e r c h o i c e o f male o r t e r r i t o r y , b u t s e t t l e s w h e r e v e r t h e r e i s a v a c a n t t e r r i t o r y w i t h an unmated male. F o r t h e Song S p a r r o w s on R e i f e l I s l a n d , e i t h e r t h e r e was an o v e r a l l s h o r t a g e o f f e m a l e s i n March 1973, as s e v e r a l males d i d not o b t a i n mates, o r e l s e t h e f e m a l e s d i s c r i m i n a t e d a g a i n s t males w i t h s m a l l e r t e r r i t o r i e s . T a b l e 9 g i v e s t h e number o f n o n - t e r r i t o r i a l f e m a l e s banded from f a l l 1972 t o e a r l y F e b r u a r y 1973. Of t h e 57 banded i n t h i s p e r i o d , 32 were known t o be a l i v e i n m i d - F e b r u a r y . The e v i d e n c e h e r e i s b o t h s p e c u l a t i v e and c i r c u m s t a n t i a l . A l t h o u g h i t a p p e a r s t h a t t h e r e were s e v e r a l f e m a l e s a v a i l a b l e i n t h e s p r i n g o f 1973 and t h a t t h e y d i d d i s c r i m i n a t e a g a i n s t m a l e s w i t h s m a l l e r t e r r i t o r i e s , i t i s i n t e r e s t i n g t o n o t e t h a t , on M a n d a r t e I s l a n d , t h o s e males (25) t h a t d i d n o t have f e m a l e s i n t h e s p r i n g o f 1962 o b t a i n e d mates i n t h e f a l l , a p p a r e n t l y t h r o u g h t h e p a s s i v e s e t t l i n g o f new f e m a l e s (Tompa 1964). Tompa c o n c l u d e d t h a t t h e r e was an o v e r a l l s h o r t a g e o f f e m a l e s i n t h e s p r i n g o f 1962. Y e t , even i n t h e o t h e r y e a r s o f h i s s t u d y , t h e r e were 46 TABLE 7 Differences i n territory size between mated and unmated males: spring 1973. Simultaneous Removal areas. Simultaneous Removal Areas 2 2 N Mean Territory Size (m ) S(m ) Te r r i t o r i a l males: mated 15 2828 1401 unmated 5 1736 867 * t = 1.75 P < 0.05 (one-tail) * S t a t i s t i c a l l y significant 47 unmated males w i t h t e r r i t o r i e s . He a l s o shows ( I b i d : 1 8 , T a b l e 7) t h a t unmated males had s m a l l e r t e r r i t o r i e s t h a n mated m a l e s . The s i t u a t i o n r e q u i r e s f u r t h e r i n v e s t i g a t i o n t o s u b s t a n t i a t e o r r e f u t e t h e p r e c e d i n g s p e c u l a t i o n s . 7. The R e p l a c e m e n t B i r d s F i n a l l y , i t i s w o r t h c o n s i d e r i n g some a s p e c t s o f t h e r e p l a c e m e n t b i r d s . A l l b u t one (see A p p e n d i x 3) o f t h e r e p l a c e m e n t b i r d s on b o t h r e m o v a l a r e a s were j u v e n i l e s ( o r , more a c c u r a t e l y i n t h e s p r i n g , y e a r l i n g s ) . Some o f t h e r e p l a c e m e n t b i r d s (5 m a l e s , 3 f e m a l e s ) had been banded on t h e s t u d y a r e a a s d e p e n d e n t j u v e n i l e s , and hence t h e i r p a r e n t a g e was known ( t h e q u e s t i o n o f l i n e a g e i s c o n s i d e r e d more a t l e n g t h i n t h e D i s c u s s i o n g . v . ) . A young b i r d i s d e f i n e d as d e p e n d e n t d u r i n g t h e t i m e a f t e r i t has l e f t t h e n e s t , and b e f o r e i t g a i n s i n d e p e n d e n c e from i t s p a r e n t s . I n Song S p a r r o w s , t h i s t i m e i n t e r v a l i s a b o u t 20 days ( U i c e 1943). The j u v e n i l e s t h a t r e p l a c e d t h e t e r r i t o r i a l b i r d s removed d u r i n g t h e f a l l r e m o v a l e x p e r i m e n t were p r o b a b l y a l l o f l o c a l o r i g i n . T a b l e 1 shows t h a t , d u r i n g t h e f a l l , most j u v e n i l e s do n o t d i s p e r s e more t h a n 1000 m e t r e s f r o m t h e i r b i r t h p l a c e , and t h a t t h e m a j o r i t y d i s p e r s e l e s s t h a n 500 m e t r e s . F u r t h e r , t h e y were p r o b a b l y a l l n o n - t e r r i t o r i a l , as j u v e n i l e males Song S p a r r o w s do n o t a t t e m p t t o e s t a b l i s h t e r r i t o r i e s f o r 48 t h e m s e l v e s u n t i l a f t e r t h e p o s t - j u v e n i l e moult i n t h e f a l l , and c o i n c i d e n t a l l y d u r i n g t h e r e c r u d e s c e n c e o f t e r r i t o r i a l b e h a v i o u r o f t h e r e s i d e n t b i r d s ( N i c e 1937, 1943; Tompa 1964), a t which t i m e t h e r e m o v a l e x p e r i m e n t was c a r r i e d o u t . On t h e S p r i n g Removal A r e a , o u t • o f 15 r e p l a c e m e n t y e a r l i n g m ales (10 f r o m t h e S i m u l t a n e o u s Removal, 5 from t h e S u c c e s s i v e Removal ) , 11 had been banded d u r i n g t h e p r e c e d i n g f a l l o r e a r l y w i n t e r , and 2 had been banded as d e p e n d e n t young d u r i n g t h e summer o f 1972, om t h e s t u d y a r e a . S e v e r a l o f t h e r e p l a c e m e n t y e a r l i n g s were i n v o l v e d i n dominance h i e r a r c h i e s , and hence were f o l l o w e d c l o s e l y o v e r t h e w i n t e r (see PART B ) . I t i s t e n t a t i v e l y s u g g e s t e d t h a t , c o n s i d e r i n g d i s p e r s a l d i s t a n c e s ( T a b l e 1) and t h e b e h a v i o u r o f t h e n o n - t e r r i t o r i a l j u v e n i l e s d u r i n g t h e w i n t e r (see G e n e r a l I n t r o d u c t i o n ) , t h e s e r e p l a c e m e n t m a l e s were a l l l o c a l b i r d s . I n t e r e s t i n g l y enough, o u t o f 12 f e m a l e s t h a t p a i r e d w i t h some o f t h e t e r r i t o r i a l m a l e s , o n l y 5 had been banded d u r i n g t h e p r e c e d i n g f a l l o r e a r l y w i n t e r , and one as a d e p e n d e n t young i n t h e summer o f 1972, on t h e s t u d y a r e a . The r e m a i n i n g 6 were a l l unhanded. F i n a l l y , b r e e d i n g s u c c e s s f o r t h e s p r i n g o f 1973 was compared between t h e E x p e r i m e n t a l a r e a s and t h e C o n t r o l s . R e s u l t s a r e g i v e n i n T a b l e 8. The p a i r s on t h e C o n t r o l s l a i d s l i g h t l y more eggs s l i g h t l y e a r l i e r , and had a h i g h e r r a t e o f s u c c e s s f u l n e s t s , t h a n t h e p a i r s on t h e E x p e r i m e n t a l s . The d i f f e r e n c e s however 49 TABLE 8 Nesting data f o r the Controls and the Experimental areas: 1973 N Nest success Experimental: 10 40% Control: 11 46% N Clutch s i z e Experimental: Control: 3.50 3.66 t = 0.683 P y 0.5 N Mean l a y i n g date ( s t a r t of f i r s t brood) Experimental: A p r i l 19 Control: A p r i l 17 50 a r e n o t s t a t i s t i c a l l y s i g n i f i c a n t . Tompa (1964) f o u n d t h a t , when t h e s e x r a t i o was h i g h l y u n b a l a n c e d , a s i n 1962 f o l l o w i n g t h e c a t a s t r o p h i c m o r t a l i t y o f Song S p a r r o w s on Mandarte I s l a n d , t h e r e was much i n t e r f e r e n c e i n t h e b r e e d i n g a c t i v i t i e s by t h e unmated m a l e s . Y e a r l i n g s however a r e r e p o r t e d t o have s m a l l e r c l u t c h e s , and , t o l a y t h e i r f i r s t c l u t c h l a t e r , i n some s p e c i e s o f b i r d s ( e . g . C o u l s o n 1966; Snow 1958; R i c h d a l e 1957; P e r r i n s 1965). T h e r e f o r e , t h e d i f f e r e n c e s between t h e C o n t r o l s and t h e E x p e r i m e n t a l s i n c l u t c h s i z e and i n t h e mean d a t e o f l a y i n g i n t h e Song S p a r r o w s on R e i f e l I s l a n d c o u l d be a t t r i b u t e d t o t h e i n e x p e r i e n c e o f t h e new b i r d s , r a t h e r t h a n i n t e r f e r e n c e from t h e unmated t e r r i t o r i a l m a l e s . I n summary, t h e n , i t was f o u n d t h a t t h e r e p l a c e m e n t b i r d s were a l l ( e x c e p t one) j u v e n i l e s , and were p r o b a b l y a l l n o n - t e r r i t o r i a l b e f o r e t h e r e m o v a l e x p e r i m e n t s . T h o s e r e p l a c e m e n t j u v e n i l e s t h a t were banded as d e p e n d a n t young were o b v i o u s l y o f l o c a l o r i g i n . The e v i d e n c e f o r t h e o r i g i n o f t h e r e m a i n i n g r e p l a c e m e n t b i r d s i s c i r c u m s t a n t i a l , b u t i s s t r o n g l y s u g g e s t i v e t h a t t h e y t o o were o f l o c a l s t o c k . 51 IV DISCUSSION &. The R e p l a c e m e n t Song S p a r r o w s And The S u r p l u s I t was s t a t e d i n t h e G e n e r a l I n t r o d u c t i o n t h a t a n e c e s s a r y p r e - r e q u i s i t e f o r t h e i n v e s t i g a t i o n o f s e t t l e m e n t p a t t e r n s on t e r r i t o r i e s was t h e e x i s t e n c e o f a s u r p l u s o f Song S p a r r o w s , p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g b u t p r e v e n t e d from d o i n g s o by t h e t e r r i t o r i a l b e h a v i o u r o f t h e b r e e d i n g b i r d s . The r e m o v a l e x p e r i m e n t s and t h e s u b s e q u e n t r e p l a c e m e n t s show t h a t t h e r e i n d e e d e x i s t e d a s u r p l u s o f Song S p a r r o w s on t h e s t u d y a r e a , and t h e f a c t t h a t b r e e d i n g t o o k p l a c e on t h e r e m o v a l a r e a s a f t e r t h e e x p e r i m e n t s shows t h a t t h e r e p l a c e m e n t s were p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g . However, a l t h o u g h t h e r e m o v a l e x p e r i m e n t s and t h e s u b s e q u e n t r e p l a c e m e n t s show t h e e x i s t e n c e o f a s u r p l u s o f Song S p a r r o w s on t h e s t u d y a r e a , t h e y do n o t r u l e o u t t h e p o s s i b i l i t y t h a t t h e r e p l a c e m e n t b i r d s would n o t have b r e d e l s e w h e r e i f t h e r e m o v a l s had n o t been c a r r i e d o u t . The d e m o n s t r a t i o n by r e m o v a l e x p e r i m e n t s t h a t a s u r p l u s o f p o t e n t i a l b r e e d e r s e x i s t s i s n o t new. Removal e x p e r i m e n t s have been c a r r i e d o u t on a v a r i e t y o f a n i m a l s ( r e f e r e n c e s i n K r e b s 1971) s i n c e t h e f i r s t l a r g e s c a l e e x p e r i m e n t s on t h e r e m o v a l o f t e r r i t o r i a l b i r d s was c o n d u c t e d i n t h e s p r i n g and summer o f 1949 and 1950 by S t e w a r t and A l d r i c h (1951) and H e n s l e y and Cope (1 9 5 1 ) . Many o f t h e r e m o v a l e x p e r i m e n t s have 52 shown c o n c l u s i v e l y t h a t a s u r p l u s o f p o t e n t i a l b r e e d e r s e x i s t s . The p r e s e n t f i n d i n g s on Song S p a r r o w s on R e i f e l I s l a n d f u r t h e r add t o t h e m a t e r i a l on t h e e x i s t e n c e o f s u c h s u r p l u s e s . The age o f t h e r e p l a c e m e n t i n d i v i d u a l s has a l s o been d e t e r m i n e d i n a few o f t h e r e m o v a l e x p e r i m e n t s . L i k e t h e Song Sparrow on R e i f e l I s l a n d , t h e r e p l a c e m e n t s have been f o u n d t o be p r i m a r i l y y e a r l i n g s i n some b i r d s , e.g. t h e B l u e G r o u s e , 2§£dracjapus o b s c u r u s , ( B e n d e l l and E l l i o t 1967) , t h e Red G r o u s e (Watson and Boss 1970b), t h e Red-winged B l a c k b i r d , A g ; e l a i u s p h g e n i c e u s , ( O r i a n s 1961), and t h e G r e a t T i t (Krebs 1971). I n s m a l l mammals, t h e s i t u a t i o n i s l e s s c l e a r ; H e a l e y (1967) c l a i m e d t h a t , f o r j?eromv.scus m a n i c u l a t u s , young p r e d o m i n a t e d i n d i s p e r s a l o n t o an empty p l o t , b u t Myers and K r e b s (1971) c o u l d n o t s u p p o r t t h i s from d a t a on d i s p e r s i n g M i c r p t u s spp. Few r e m o v a l e x p e r i m e n t s have e s t a b l i s h e d t h e o r i g i n o f t h e r e p l a c e m e n t i n d i v i d u a l s . Some r e m o v a l s have shown t h a t r e p l a c e m e n t s a r e drawn f r o m a n o n b r e e d i n g s u r p l u s p o p u l a t i o n w hich e x i s t s a t t h e p e r i p h e r y o f t h e b r e e d i n g p o p u l a t i o n ( O r i a n s 1961; Watson and J e n k i n s 1968; Young 1970; H a r r i s 1970), and a s i m i l a r s i t u a t i o n has been shown t o e x i s t i n some d e s c r i p t i v e s t u d i e s ( e . g . D e l i u s 1965; C a r r i c k 1963; and i n Song S p a r r o w s on Mandarte I s l a n d by Tompa 1964). T h i s i s n o t t h e c a s e i n t h e G r e a t T i t i n Bean Wood ( K r e b s 1971) , where 53 v a c a n t woodland t e r r i t o r i e s were o c c u p i e d m a i n l y by b i r d s t h a t a l r e a d y had t e r r i t o r i e s i n a d j a c e n t hedgerows. In t h e Song S p a r r o w s on R e i f e l I s l a n d , t h e r e i s a s u r p l u s o f a p p a r e n t l y l o c a l b i r d s , f r o m which r e p l a c e m e n t s a r e d e r i v e d , and which a p p a r e n t l y d i s a p p e a r s by t h e s e c o n d week o f A p r i l ( F i g u r e 2; a l s o Tompa 1964). A f u r t h e r n e c e s s a r y p r e - r e g u i s i t e f o r t h e i n v e s t i g a t i o n o f s e t t l e m e n t p a t t e r n s was t h a t t h e s u r p l u s o f Song S p a r r o w s on t h e s t u d y a r e a s h o u l d n u m e r i c a l l y e x c e e d t h o s e t e r r i t o r i a l b i r d s t h a t were t o be removed. T a b l e 9 shows t h e number o f n o n - t e r r i t o r i a l j u v e n i l e s banded o v e r t h e w i n t e r i n a l l a r e a s . A l t h o u g h w i n t e r m o r t a l i t y a n d / o r e m i g r a t i o n a c c o u n t e d f o r some o f t h e s e b i r d s , o u t o f 82 j u v e n i l e s banded on t h e S p r i n g Removal A r e a , 63 were known t o be a l i v e i n m i d - F e b r u a r y . T a b l e 9 r e q u i r e s some f u r t h e r e x p l a n a t i o n . T h e r e a p p e a r t o be more b i r d s p o t e n t i a l l y a v a i l a b l e t o s e t t l e on b o t h S i m u l t a n e o u s Removal a r e a s , b u t t h i s may not n e c e s s a r i l y be so f o r t h e f o l l o w i n g r e a s o n s . P r o p o r t i o n a t e l y more t i m e was s p e n t t r a p p i n g on t h e S i m u l t a n e o u s Removal a r e a s ( p a r t i c u l a r l y on t h e S p r i n g Removal Area) t h a n on e i t h e r t h e S u c c e s s i v e Removal a r e a s o r t h e C o n t r o l s . A l s o , some b i r d s moved a r o u n d t h e hedgerows, a l t h o u g h t h e m a j o r i t y t e n d e d t o r e m a i n i n c e r t a i n l o c a l i t i e s . The p r o b l e m o f i n d i v i d u a l s moving from one dominance h i e r a r c h y i n one a r e a t o a n o t h e r e l s e w h e r e i s c o n s i d e r e d i n PART B. F i n a l l y , j u v e n i l e s t e n d e d t o c o n g r e g a t e 54 TABLE 9 Number of juveniles banded, f a l l 1972 to early spring 1973 Spring Removal Area Males Females Undetermined Total Simultaneous: 29 20 1 50 Successive: 7 1 2 10 Control: 11 10 1 22 Totals: 47 31 4 82 Fall Removal Area Males Females Undetermined Total Simultaneous: 22 18 1 41 Successive: 11 7 1 19 Control: 4 1 0 5 Totals: 37 26 2 65 55 a t c e r t a i n f a v o u r e d l o c a l i t i e s a l o n g t h e hedgerows. On t h e S p r i n g Removal A r e a , t h e s i n g l e most f a v o u r e d l o c a l i t y was a t t h e j u n c t i o n o f t h e S i m u l t a n e o u s Removal a r e a and t h e C o n t r o l . Out o f 82 j u v e n i l e s banded on t h e S p r i n g Removal A r e a , no l e s s t h a n 34 were c a u g h t and banded a t t h i s l o c a l i t y . T h us, t h e r e a p p e a r e d t o be a l a r g e number o f p o t e n t i a l r e p l a c e m e n t s on b o t h r e m o v a l a r e a s . The r e s u l t s o f t h e r e m o v a l e x p e r i m e n t s show t h a t s e v e r a l o f t h e s e b i r d s were a b l e t o e s t a b l i s h t e r r i t o r i e s . The f a t e o f t h e r e s t o f t h e s u r p l u s i s n o t known. B The T e m p o r a l P a t t e r n s Of S e t t l i n g On T e r r i t o r i e s The r e m o v a l e x p e r i m e n t s and t h e s u b s e q u e n t r e p l a c e m e n t s show t h a t a g r e a t e r number o f t e r r i t o r i e s , w i t h a s m a l l e r mean t e r r i t o r y s i z e , can be a c c o m o d a t e d i n a g i v e n a r e a a f t e r a s i m u l t a n e o u s r e m o v a l . They a l s o show t h a t a s u c c e s s i v e r e m o v a l does n o t r e s u l t i n more t e r r i t o r i e s , o r a s i g n i f i c a n t l y s m a l l e r mean t e r r i t o r y s i z e , i n a g i v e n a r e a . I t i s now n e c e s s a r y t o e n g u i r e i n t o f a c t o r s which c o u l d have r e s u l t e d i n t h e s m a l l e r mean t e r r i t o r y s i z e on t h e S i m u l t a n e o u s Removal a r e a s , and i n no s i g n i f i c a n t d i f f e r e n c e s on t h e S u c c e s s i v e Removal a r e a s . 1. F l u c t u a t i n g E n v i r o n m e n t a l R e s o u r c e The s m a l l e r mean t e r r i t o r y s i z e on t h e S i m u l t a n e o u s 56 Removal area could be related to some fluctuating environmental resource, on the argument that t e r r i t o r y sizes are adjusted annually to some environmental variable. If t h i s were the case, then the t e r r i t o r y sizes on the Controls and Successive Removal areas should have fluctuated i n accordance with the Simultaneous Removal areas. This did not happen. The mean t e r r i t o r y s i z e s on the Successive Removal areas and on the Controls fluctuated i n opposite directions i n the spring and f a l l removals, although i n no case was a difference in t e r r i t o r y s i z e before and after a removal experiment s i g n i f i c a n t . It i s possible that some resource changed along only part of the hedgerow, i n both Simultaneous Removal areas. The hedgerows are not homogeneous i n vegetational structure, and there are substantial differences i n mean t e r r i t o r y s i z e between, and within, the Spring and F a l l Removal Areas (Tables 4 and 5 ) . A subjective assessment of the vegetation along the hedgerows suggested that smaller mean t e r r i t o r y size was related to a higher incidence of brambles, although no further, analysis of the vegetation was carried out. However, a reasonable assumption would be that a resource would fluctuate i n p a r a l l e l along the whole hedgerow. Thus, i t seems j u s t i f i a b l e to rej e c t the argument that a resource changed along only part of the hedgerow from 1972 to 1973. The observed r e s u l t s on mean t e r r i t o r y s i z e , therefore, 57 / c a n n o t e a s i l y be e x p l a i n e d on t h e b a s i s o f a f l u c t u a t i n g e n v i r o n m e n t a l r e s o u r c e , s u c h a s f o o d s u p p l y o r a change i n t h e n a t u r e o f t h e h a b i t a t . F u r t h e r , c a s u a l o b s e r v a t i o n s d u r i n g t h e s t u d y p e r i o d on s p e c i e s o f b i r d s c o - e x i s t i n g w i t h t h e Song S p a r r o w s a l o n g t h e hedgerows d i d n o t r e v e a l any major c h a n g e s i n numbers i n t h o s e s p e c i e s ( e . g . B e w i c k ' s Wren, Thryomanes b e w i c k i i ) t h a t m ight compete f o r some e n v i r o n m e n t a l r e s o u r c e . T h e r e f o r e , i n t e r s p e c i f i c c o m p e t i t i o n was a l s o a p p a r e n t l y u n i m p o r t a n t . 2- P r e s s u r e From I n t r u d e r s I n h i s d i s c u s s i o n on f a c t o r s t h a t might d e t e r m i n e t e r r i t o r y s i z e , K r e b s (1971) s u g g e s t s t h a t a p o s s i b l e f a c t o r m i g h t be t h e p r e s s u r e f r o m p o t e n t i a l s e t t l e r s a t t h e t i m e when t e r r i t o r i e s a r e b e i n g e s t a b l i s h e d . The r a t i o n a l e b e h i n d t h i s s u g g e s t i o n i s g i v e n i n A p p e n d i x 7. F o r t h e G r e a t T i t i n M a r l e y Wood, t h e r e a p p e a r s t o be a r e l a t i o n s h i p between w i n t e r p o p u l a t i o n o f j u v e n i l e s and s u b s e q u e n t b r e e d i n g d e n s i t y ( P e r r i n s 1965; L a c k 1966). A r e l a t i o n s h i p between number o f b i r d s i n t h e s p r i n g and b r e e d i n g d e n s i t y has a l s o been f o u n d i n t h e Wheatear, Oenanthe o e n a n t h e , (Conder 1956) and t h e T r e e S p a r r o w , S p i z e l l a a r b o r e a , (Weeden 1 9 6 5 ) . Tompa (1964) however f o u n d t h a t t h e number o f young Song S p a r r o w s t h a t s u r v i v e d t h e w i n t e r d i d n o t i n f l u e n c e t h e b r e e d i n g d e n s i t y o f t h e n e x t s p r i n g on M a n d a r t e I s l a n d . 58 F o r t h e Song S p a r r o w s on R e i f e l I s l a n d , t h e w i n t e r p o p u l a t i o n o f banded n o n - t e r r i t o r i a l j u v e n i l e s was l a r g e , and i t was l a r g e s t on t h e S i m u l t a n e o u s Removal a r e a s (see T a b l e 9 ) . F o r example, 82 j u v e n i l e s were banded on t h e S p r i n g Removal A r e a , and, o f t h e s e , 50 were banded on t h e S i m u l t a n e o u s Removal a r e a . T h u s , i t a p p e a r s t h a t t h e r e were more b i r d s p o t e n t i a l l y a v a i l a b l e t o s e t t l e on b o t h S i m u l t a n e o u s Removal a r e a s , b u t a s e x p l a i n e d e a r l i e r , t h i s may n o t n e c e s s a r i l y be s o , f o r t h e r e a s o n s g i v e n . I f an i n c r e a s e i n t e r r i t o r i e s on t h e S i m u l t a n e o u s Removal a r e a s was c a u s e d by t h e p r e s s u r e o f a l a r g e number o f p o t e n t i a l s e t t l e r s , t h e n one might s u p p o s e t h a t a s i m i l a r s o r t o f p r e s s u r e would have been e x e r t e d on b o t h t h e S u c c e s s i v e Removal a r e a s and t h e C o n t r o l s . No s i g n i f i c a n t d i f f e r e n c e s o c c u r r e d i n any o f t h e s e l a t t e r a r e a s , t h e r e f o r e one c a n c o n c l u d e t h a t , f o r t h e s e a r e a s , p r e s s u r e from i n t r u d e r s was not i m p o r t a n t . I t may be w o r t h m e n t i o n i n g t h a t t h e n o n - t e r r i t o r i a l b i r d s f o r m e d dominance h i e r a r c h i e s (see PART B) i n t h e l a t e f a l l , and r e t a i n e d them t h r o u g h t h e w i n t e r . I t i s c o n c l u d e d t h a t a c o n s e q u e n c e o f t h e dominance h i e r a r c h y i s t h a t t h e d o m i n a n t i n d i v i d u a l has p r e c e d e n c e t o a v a c a n t t e r r i t o r y o v e r s u b o r d i n a t e s i n t h e s p r i n g . The y e a r l i n g m a l e s do n o t a p p a r e n t l y c o l l e c t i n a g r o u p and t r y t o f o r c e an e x i s t i n g t e r r i t o r y h o l d e r t o s h r i n k t h e b o u n d a r i e s o f h i s t e r r i t o r y , t o 59 accomodate one o r more o f t h e g r o u p . ( I t s h o u l d be s t r e s s e d , however, t h a t ' p r e s s u r e f r o m i n t r u d e r s ' does n o t i m p l y t h a t t h e b i r d s gang up i n g r o u p s - s e e A p p e n d i x 7 ) . A l t h o u g h most d o m i n a n t Song S p a r r o w s i n t h e h i e r a r c h i e s o b t a i n e d t e r r i t o r i e s (PAST B ) , i t i s n o t known i f a l l males competed f o r t e r r i t o r i e s , o r j u s t t h e dominant i n d i v i d u a l s competed. A l t h o u g h t h e h y p o t h e s i s t h a t t h e p r e s s u r e r e s u l t i n g from a l a r g e number o f p o t e n t i a l s e t t l e r s c a u s e d a r e d u c t i o n i n t h e mean t e r r i t o r y s i z e t a k e n on t h e S i m u l t a n e o u s Removal a r e a s (but n o t t h e S u c c e s s i v e Removal a r e a s , o r t h e C o n t r o l s ) , c a n n o t be e l i m i n a t e d , i t a l o n e i s n o t c o n s i d e r e d n e a r l y s u f f i c i e n t t o e x p l a i n t h e r e s u l t s . 3- Inexperience Of The J u v e n i l e s And The T e m p o r a l P a t t e r n s Of S e t t l i n g I f c h a n g e s i n an e n v i r o n m e n t a l r e s o u r c e , o r p r e s s u r e from p o t e n t i a l s e t t l e r s , c a n n o t f u l l y e x p l a i n t h e o b s e r v e d r e s u l t s , t h e n t h e i n e x p e r i e n c e o f t h e r e p l a c e m e n t b i r d s and t h e p a t t e r n o f s e t t l i n g ( s i m u l t a n e o u s and s u c c e s s i v e ) on t e r r i t o r i e s c o u l d be a f a c t o r . Y e a r l i n g s have been shown t o t a k e s m a l l e r t e r r i t o r i e s t h a n a d u l t s i n t h e Marsh T i t , P a r u s p a l u s t r i s , ( S o u t h e r n and M o r l e y 1950), t h e G r e a t T i t (Dhondt and H u b l e 1968; Dhondt 1 9 7 1 a ) , t h e White-crowned S p a r r o w , Z o n o t r i c h i a l§M£2£llH2* ( R a l p h and P e a r s o n 1971) , and t h e B l a c k - c a p p e d ' C h i c k a d e e , P a r u s a t r i c a p i l l u s , ( S t e f a n s k i 1967). N i c e (1937) 60 and Tompa (1964) , however, c o u l d n o t show f o r Song S p a r r o w s t h a t t h e r e was a s i g n i f i c a n t d i f f e r e n c e between t h e mean t e r r i t o r y s i z e s o f f i r s t y e a r b i r d s , and t h o s e o f o l d e r b i r d s , and weeden (1965) f o u n d s i m i l a r r e s u l t s i n t h e T r e e Sparrow i n A l a s k a . I t i s p o s s i b l e t h a t i n e x p e r i e n c e o f t h e s e t t l i n g b i r d s was p l a y i n g a p a r t i n t h e s m a l l e r t e r r i t o r i e s t a k e n on t h e S i m u l t a n e o u s Removal a r e a s , a s a l l t h e r e p l a c e m e n t b i r d s were y e a r l i n g s . on t h e S u c c e s s i v e Removal a r e a s , however, i n e x p e r i e n c e was a p p a r e n t l y u n i m p o r t a n t , a s mean t e r r i t o r y s i z e s were much t h e same b o t h b e f o r e and a f t e r t h e r e m o v a l s , a l t h o u g h o n c e a g a i n t h e r e p l a c e m e n t b i r d s were a l l y e a r l i n g s ( e x c e p t one; s e e A p p e n d i x 3 ) . The r e t e n t i o n o f t h e t e r r i t o r i a l s y s t e m on t h e S u c c e s s i v e Removal a r e a s i s p r o b a b l y v e r y i m p o r t a n t i n t h i s r e s p e c t , and i s c o n s i d e r e d a t l e n g t h i n t h e s e c t i o n on d i s r u p t i o n o f t e r r i t o r i a l b o u n d a r i e s . However, one e x p l a n a t i o n c o u l d be t h a t , i n g e n e r a l , j u v e n i l e s do have a t e n d e n c y t o t a k e up a s m a l l e r t e r r i t o r y t h a n an a d u l t , b u t t h a t t h i s i s n o t a p p a r e n t when o n l y a s i n g l e v a c a n c y a p p e a r s i n t h e t e r r i t o r i a l p a t t e r n . The v a c a n c y may i n i t i a l l y be l a r g e r t h a n t h e r e p l a c e m e n t j u v e n i l e i s r e a d y t o d e f e n d , b u t i t i s n o t l a r g e enough t o be d i v i d e d i n two between two r e p l a c e m e n t b i r d s . T h i s i n i t i a l t e n d e n c y would be masked i f t h e d i s a p p e a r a n c e o f t e r r i t o r y h o l d e r s , w i t h s u b s e q u e n t r e p l a c e m e n t s , o c c u r r e d p e r i o d i c a l l y , a s 61 happened i n t h e s t u d i e s on Song S p a r r o w s o f N i c e and Tompa ( c a t a s t r o p h i c m o r t a l i t y a p a r t ) , and i n t h e s u c c e s s i v e r e m o v a l e x p e r i m e n t s i n t h e p r e s e n t s t u d y . The t e n d e n c y might not be masked i f a l a r g e s t r e t c h o f s u i t a b l e hedgerow c o m p l e t e l y empty o f t e r r i t o r i a l Song S p a r r o w s was p r e s e n t , a s i n t h e s i m u l t a n e o u s r e m o v a l e x p e r i m e n t s . From r e s u l t s on t h e S u c c e s s i v e Removal a r e a s , however, a f t e r a p e r i o d o f t h r e e o r f o u r d a y s ( t h e t i m e i n t e r v a l ( s ) between e a c h s u c c e s s i v e r e m o v a l ) , t h e r e p l a c e m e n t j u v e n i l e male a p p a r e n t l y had e s t a b l i s h e d t h e o r i g i n a l b o u n d a r i e s w i t h h i s n e i g h b o u r s , i n d i c a t i n g t h a t p e r h a p s t h e i n i t i a l t e n d e n c y ( i f p r e s e n t ) t o t a k e a s m a l l e r t e r r i t o r y had d i s a p p e a r e d . The t e n d e n c y t h e n t o t a k e a s m a l l e r t e r r i t o r y m i ght be c o n n e c t e d w i t h l e v e l s o f a g g r e s s i o n . The r e p l a c e m e n t j u v e n i l e s might be l e s s a g g r e s s i v e i n i t i a l l y , p o s s i b l y b e c a u s e t h e y a r e on u n f a m i l i a r g r o u n d , and t h e r e f o r e i n c l i n e d t o t a k e a s m a l l e r t e r r i t o r y . I f a l l t h e r e p l a c e m e n t s have t h i s i n i t i a l low l e v e l o f a g g r e s s i o n , a s i n a s i m u l t a n e o u s r e m o v a l e x p e r i m e n t , t h e n a s e t o f s m a l l e r t e r r i t o r i e s c o u l d r e s u l t . I f j u s t one r e p l a c e m e n t j u v e n i l e i s i n v o l v e d , as i n a s u c c e s s i v e r e m o v a l , t h e n a f t e r t h r e e o r f o u r d a y s h i s l e v e l o f a g g r e s s i o n might have r i s e n t o t h e p o i n t where he c a n c l a i m t h e whole o f t h e 62 t e r r i t o r y he has a c q u i r e d 1 . Van den Assent (1967) f o r t h e t h r e e - s p i n e d s t i c k l e b a c k e x p l a i n e d h i s o b s e r v a t i o n s , t h a t s i m u l t a n e o u s i n t r o d u c t i o n s i n t o a t a n k r e s u l t e d i n a l a r g e r number o f t e r r i t o r i e s t h a n d i d s u c c e s s i v e i n t r o d u c t i o n , i n a s i m i l a r manner; p r o b a b l y , t h e r e l a t i v e d i f f e r e n c e s i n a g g r e s s i v e l e v e l s o f t h e male s t i c k l e b a c k s - a l l o f them s i m u l t a n e o u s l y i n t h e p r o c e s s o f s e t t l i n g and b u i l d i n g - were t e m p o r a r i l y s m a l l e r t h a n f o u n d i f m ales were i n t r o d u c e d s u c c e s s i v e l y . I n Song S p a r r o w s on Mandarte I s l a n d , Tompa (1964) showed t h a t t h e s e t t l i n g i n l a r g e numbers o f s u b o r d i n a t e , p r e v i o u s l y n o n - t e r r i t o r i a l j u v e n i l e s r e s u l t e d i n a l a r g e r number o f t e r r i t o r i e s t a k e n a f t e r t h e c a t a s t r o p h i c m o r t a l i t y . F u r t h e r , t h e r e i s some e v i d e n c e ( e . g . B r i a n 1949; Brown 1963; D i x o n 1965; P h i l l i p s 1971) t h a t t h e l e s s f a m i l i a r an a n i m a l i s w i t h an a r e a , t h e more l i k e l y t h a t a n i m a l w i l l be s u b o r d i n a t e ( t h i s i s c o n s i d e r e d i n g r e a t e r d e t a i l i n PART B under p r i o r o c c u p a n c y and e x p e r i e n c e and p o s i t i o n i n t h e h i e r a r c h y ) . T h e r e i s no c o n c l u s i v e e v i d e n c e from t h e s t u d y t o 1. An i n d e p e n d a n t measure o f ' l e v e l o f a g g r e s s i o n ' s h o u l d be t a k e n i n o r d e r t o v e r i f y t h i s h y p o t h e s i s . One p o s s i b l e method would be t o m o n i t o r a b i r d ' s r e s p o n s e t o a t a p e p l a y b a c k - a method which might be p a r t i c u l a r l y u s e f u l i n t h e c a s e o f Song S p a r r o w s , w h i c h p r o v e d t o be v e r y r e s p o n s i v e t o a s t r a n g e r Song S p a r r o w ' s s o n g . 63 s u b s t a n t i a t e t h e h y p o t h e s i s t h a t t h e s e t t l i n g b i r d s a r e i n i t i a l l y l e s s a g g r e s s i v e , and hence more i n c l i n e d t o t a k e a s m a l l e r t e r r i t o r y . S u g g e s t i v e e v i d e n c e s u p p o r t i n g t h e h y p o t h e s i s i s ; (a) a l l t h e r e p l a c e m e n t s were young, n o n - t e r r i t o r i a l b i r d s , and (b) most were s u b o r d i n a t e t o a d u l t s i n t h e dominance h i e r a r c h i e s (PART B ) . A f u r t h e r f a c t o r i s t h e r e t e n t i o n , o r d i s r u p t i o n , o f t h e t r a d i t i o n a l t e r r i t o r y b o u n d a r i e s , t o be d i s c u s s e d n e x t . B e f o r e l e a v i n g t h i s s e c t i o n , however, i t may be w o r t h c o n s i d e r i n g t h e p r o b l e m o f t i m e o f r e p l a c e m e n t . On t h e S u c c e s s i v e Removal a r e a s , a t i m e i n t e r v a l o f t h r e e t o f o u r d a y s i s s u g g e s t e d a s b e i n g t h e l e n g t h o f t i m e needed f o r t h e r e p l a c e m e n t b i r d s t o r e - e s t a b l i s h t h e t e r r i t o r y b o u n d a r i e s w i t h n e i g h b o u r s . The v e r y f a c t t h a t t h e r e were n e i g h b o u r s w i t h f i x e d t e r r i t o r y b o u n d a r i e s p r e s e n t m i g h t have a i d e d t h e s e t t l i n g b i r d i n q u i c k l y e s t a b l i s h i n g h i s b o u n d a r i e s . On t h e S i m u l t a n e o u s Removal a r e a s , t h e r e were no s u c h g u i d e l i n e s t o f o l l o w , and t h u s b o u n d a r i e s may have t a k e n much l o n g e r t o f i x . T h i s may p a r t l y e x p l a i n t h e n i n e o r t e n d a y s needed f o r t o t a l r e p l a c e m e n t . 4. D i s r u p t i o n Of T e r r i t o r i a l B o u n d a r i e s i Both Simms (1965) and Tompa (1964) n o t e d t h a t t h e i n c r e a s e i n number o f o c c u p i e d t e r r i t o r i e s f o l l o w i n g a c a t a s t r o p h i c m o r t a l i t y was a c c o m p a n i e d by t h e t o t a l 64 r e a r r a n g e m e n t o f t e r r i t o r y b o u n d a r i e s . The t r a d i t i o n a l t e r r i t o r i a l s y s t e m o f t h e Song S p a r r o w s on t h e s t u d y a r e a b r o k e down c o m p l e t e l y on t h e S i m u l t a n e o u s Removal a r e a s , and t h e hedgerows were d i v i d e d up i n t o t e r r i t o r i e s e n t i r e l y anew. The S i m u l t a n e o u s Removal a r e a on t h e S p r i n g Removal a r e a i s g i v e n i n F i g u r e 6, w i t h t h e o l d and new t e r r i t o r y b o u n d a r i e s shown. I t i s a p p a r e n t f r o m F i g u r e 6 t h a t t h e r e p l a c e m e n t b i r d s were n o t i n f l u e n c e d by t h e t e r r i t o r i a l s y s t e m b e f o r e t h e r e m o v a l s . T h e 1 o n l y s i m i l a r i t i e s i n t h e t e r r i t o r y b o u n d a r i e s o c c u r a l o n g t h e n a r r o w e s t s e c t i o n o f t h e hedgerow. The g e n e r a l l i n e a r i t y o f t h e t e r r i t o r y a r r a n g e m e n t i s p r e s e r v e d . The t e r r i t o r y b o u n d a r i e s a l o n g t h e S u c c e s s i v e Removal a r e a s r e m a i n e d much t h e same b e f o r e and a f t e r t h e e x p e r i m e n t s . A l t h o u g h new b i r d s s e t t l e d a f t e r t h e r e m o v a l s , t h e t r a d i t i o n a l t e r r i t o r y p a t t e r n was r e t a i n e d , i n c o n t r a s t t o t h e S i m u l t a n e o u s Removal a r e a s . I t i s worth c o n s i d e r i n g some o f t h e e x p l a n a t i o n s t h a t might a c c o u n t f o r t h e r e t e n t i o n o f t h e t e r r i t o r i a l p a t t e r n i n t h e S u c c e s s i v e Removal a r e a s . I t i s p o s s i b l e t h a t t h e s t a b i l i t y o f t h e t e r r i t o r y p a t t e r n i s due t o t o p o g r a p h i c f e a t u r e s ; t h e h a b i t a t i s s t r u c t u r e d s u c h t h a t t h e t e r r i t o r i a l b i r d s f i x t h e i r b o u n d a r i e s a c c o r d i n g t o c e r t a i n l a n d m a r k s . The s t a b i l i t y i n t e r r i t o r i e s f r o m y e a r t o y e a r i n t h e Song T h r u s h , T u r d u s p h i l g m e l g s , ( D a v i e s and Snow 1965) and t h e E u r o p e a n B l a c k b i r d , Figure 6 Spring Removal Area: boundaries before and a f t e r the removal . experiments on the Simultaneous Removal area 66 T_«. m e r u l a , (Snow 1958) have been a t t r i b u t e d t o f e a t u r e s o f t h e h a b i t a t . Song Sparrow t e r r i t o r i e s a r e c l e a r l y d e f i n e d , and p r e s u m a b l y t h e b i r d s r e c o g n i z e t h e b o u n d a r i e s between t h e m s e l v e s and t h e i r n e i g h b o u r s . The r e c o g n i t i o n o f b o u n d a r i e s , however, i s most l i k e l y a p r o d u c t o f t h e i n t e r a c t i o n s between t h e b i r d s t h e m s e l v e s , and i s n o t r e l a t e d d i r e c t l y t o f e a t u r e s o f t h e h a b i t a t . A s e c o n d e x p l a n a t i o n i s t h a t t h e t r a d i t i o n a l t e r r i t o r y p a t t e r n i s r e s p e c t e d by t h e t e r r i t o r i a l i n d i v i d u a l s . When a v a c a n c y o c c u r s , a new r e p l a c e m e n t b i r d c a n s e t t l e b e f o r e n e i g h b o u r i n g b i r d s b e g i n t o e n c r o a c h i n t o t h e v a c a t e d a r e a . I n t h e p r e s e n t s t u d y , a r e p l a c e m e n t male Song Sparrow would have t o c o n t e n d w i t h o n l y two n e i g h b o u r i n g males a l o n g t h e S u c c e s s i v e Removal a r e a s , owing t o t h e l i n e a r i t y o f t h e hedgerow. I t i s n o t known how l o n g i t t a k e s f o r t h e r e p l a c e m e n t b i r d t o ,become f a m i l i a r w i t h t h e e x i s t i n g t e r r i t o r y b o u n d a r i e s , o r how l o n g t h e a d j a c e n t males w a i t b e f o r e a t t e m p t i n g t o expand t h e i r b o u n d a r i e s i n t o t h e v a c a t e d a r e a . From t h e f a c t t h a t t h e t e r r i t o r y b o u n d a r i e s d i d n o t change a f t e r t h e e x p e r i m e n t s on t h e S u c c e s s i v e Removal a r e a s , and t h a t t h e r e m o v a l s were c o n d u c t e d on a t h r e e and f o u r day s c h e d u l e , t h e n one c a n deduce t h a t t e r r i t o r y b o u n d a r i e s had been d e t e r m i n e d i n an i n t e r v a l o f a maximum o f f o u r d a y s . In some s e d e n t a r y p a s s e r i n e s t h a t , l i k e t h e Song S p a r r o w , r e t a i n t h e i r t e r r i t o r i e s t h r o u g h o u t t h e y e a r , as i n t h e 67 E u r o p e a n R o b i n , E r i t h a c u s r u b e c u l a , (Lack 194 3) and t h e W r e n - t i t , Chamaea f a s c i a t a , ( E r i c k s o n 1938), one o f t h e f i r s t a c t i v i t i e s o f t h e newly s e t t l e d b i r d s i s t o e x p l o r e t h e t e r r i t o r y b o u n d a r i e s , l e a d i n g t o t h e r e - e s t a b l i s h m e n t o f t h e f o r m e r b o u n d a r i e s w i t h n e i g h b o u r s . S i m i l a r e x p l o r a t o r y b e h a v i o u r has been d e s c r i b e d i n M c c o r m i c k ' s Skua, C a t h a r a c t a M££2£ f i i £ K i # (Young 1972). I t seems r e a s o n a b l e t o a r g u e t h a t t h e newly s e t t l e d Song S p a r r o w s on R e i f e l I s l a n d would a l s o show s u c h b e h a v i o u r a l p a t t e r n s . On t h e S i m u l t a n e o u s Removal a r e a s , however, any one r e p l a c e m e n t male, on e x p l o r i n g t h e t e r r i t o r y b o u n d a r i e s , would f i n d o t h e r r e p l a c e m e n t males d o i n g t h e same t h i n g a t t h e same t i m e , w i t h no g u i d e l i n e s t o f o l l o w . T h i s c o u l d f u r t h e r e x p l a i n t h e l e n g t h o f t i m e t a k e n t o f i x t h e b o u n d a r i e s . 5. G e n e t i c B a s i s F o r The S i z e Of T e r r i t o r y I t i s n o t known how f a r t e r r i t o r i e s c a n be c o m p r e s s e d . Klomp (1972) d i s c u s s e s t h e p r o b l e m o f an optimum s i z e o f t e r r i t o r y t h a t i s g e n e t i c a l l y f i x e d , and g i v e s c i r c u m s t a n t i a l e v i d e n c e t h a t l e n d s s u p p o r t t o t h e e x i s t e n c e o f an optimum s i z e t h a t i s g e n e t i c a l l y f i x e d f r o m S c h o e n e r (1968) and G i b b ( 1 9 6 2 ) . However, Klomp s t a t e s t h a t , a l t h o u g h i t i s h i g h l y p r o b a b l e t h a t t e r r i t o r y s i z e has a g e n e t i c b a s i s , t h e r e a r e no i n d i c a t i o n s t h a t t h e v a r i a t i o n s o f t h i s a t t r i b u t e among i n d i v i d u a l s o f t h e same s p e c i e s a r e b a s e d on d i f f e r e n c e s i n t h e i r g e n e t i c make-up. Most o f t h e d i f f e r e n c e s seem t o be o f 68 a m o d i f i c a t o r y n a t u r e . a t e r r i t o r y o f a p a r t i c u l a r s i z e may be p a s s e d on f r o m one g e n e r a t i o n t o t h e n e x t . T a b l e 10 g i v e s t h e o n l y e x a m p l e s o f l i n e a g e f r o m t h e s t u d y a r e a , i n which t h e p a r e n t s o f a p a r t i c u l a r male a r e known, and t h a t p a r t i c u l a r male o b t a i n e d a t e r r i t o r y t h e f o l l o w i n g y e a r . The d a t a a r e t o o few t o be t e s t e d s t a t i s t i c a l l y , b u t t h e g e n e r a l i m p r e s s i o n i s t h a t t h e t a k i n g o f a l a r g e o r s m a l l t e r r i t o r y i s p a s s e d on f r o m one g e n e r a t i o n t o t h e n e x t . However, s m a l l t e r r i t o r i e s a p p e a r t o be t a k e n where t h e r e i s a h i g h i n c i d e n c e o f b r a m b l e s , and t h e r e f o r e a v e g e t a t i o n a l f a c t o r c o u l d a l s o be i n v o l v e d . The d a t a a r e n o t s u f f i c i e n t f o r any f i r m c o n c l u s i o n s t o be drawn, and t h e m a t t e r i s n o t p u r s u e d f u r t h e r h e r e . C. P r o p o s e d E x p l a n a t i o n F o r The D i f f e r e n t R e s u l t s Of The S i m u l t a n e o u s And The S u c c e s s i v e Removal E x p e r i m e n t s The S u c c e s s i v e Removal a r e a s d i d n o t show a s i g n i f i c a n t c hange i n t h e number o f t e r r i t o r i e s , o r i n mean t e r r i t o r y s i z e , a f t e r t h e r e m o v a l s b e c a u s e r e p l a c e m e n t o c c u r r e d s u c c e s s i v e l y on a o n e - t o - o n e b a s i s , and t h e t r a d i t i o n a l t e r r i t o r i a l p a t t e r n was r e t a i n e d . Each r e p l a c e m e n t j u v e n i l e may i n i t i a l l y have been p r e p a r e d t o d e f e n d o n l y a p a r t o f t h e v a c a n t t e r r i t o r y , b u t , p e r h a p s b e c a u s e o f t h e r e l u c t a n c e o f n e i g h b o u r i n g t e r r i t o r y h o l d e r s t o expand t h e i r b o u n d a r i e s i m m e d i a t e l y i n t o t h e v a c a n t a r e a , and p o s s i b l y b e c a u s e o f t h e 6 9 TABLE 10 Lineage: t e r r i t o r y s i z e s from one generation to the next 2 2 Generation 1 T e r r i t o r y s i z e (m ) Generation 2 T e r r i t o r y s i z e (m ) W/0 2708 R/BL 1824 W/0 2708 LP/BL 1444 W/DP 1625 Y/LP 2166 DP/M 1264 M/W 722 G/R 5054 B/B 3249 70 p r o p o s e d e x p l o r a t o r y b e h a v i o u r o f t h e new b i r d , t h e s i z e and b o u n d a r i e s o f t h e t e r r i t o r y o f t h e removed b i r d were t a k e n by t h e r e p l a c e m e n t b i r d , p r o b a b l y i n a m a t t e r o f t h r e e t o f o u r d a y s . The S i m u l t a n e o u s Removal a r e a s , on t h e o t h e r hand, showed s i g n i f i c a n t c h a n g e s i n number o f t e r r i t o r i e s , and i n mean t e r r i t o r y s i z e s . The t r a d i t i o n a l t e r r i t o r i a l s y s t e m was c o m p l e t e l y b r o k e n down, and t e r r i t o r y b o u n d a r i e s were fo r m e d e n t i r e l y anew, w i t h o u t a p p a r e n t g u i d e l i n e s . I n c o m p a r i s o n w i t h t h e S u c c e s s i v e Removal a r e a s , t h e t i m e t a k e n t o f i x t h e t e r r i t o r y b o u n d a r i e s t o o k much l o n g e r ( n i n e t o t e n d a y s ) . A l l t h e r e p l a c e m e n t s were young b i r d s , and i t seems r e a s o n a b l e t o a r g u e t h a t i n e x p e r i e n c e a n d / o r u n f a m i l i a r i t y w i t h t h e a r e a were p o s s i b l e f a c t o r s a f f e c t i n g t h e s i z e o f t e r r i t o r y t a k e n . I t i s p o s t u l a t e d t h a t t h e r e p l a c e m e n t b i r d s i n i t i a l l y had l o w e r l e v e l s o f a g g r e s s i o n , and hence were l e s s l i k e l y t o i m m e d i a t e l y c l a i m a s i z e o f t e r r i t o r y e q u i v a l e n t t o t h a t o f t h e removed a d u l t s . T h u s , t h e t e m p o r a r y low l e v e l o f a g g r e s s i o n o f t h e r e p l a c e m e n t b i r d s , a l l s i m u l t a n e o u s l y a t t e m p t i n g t o s e t t l e , c o u l d have r e s u l t e d i n a l a r g e r number o f t e r r i t o r i e s t a k e n , w i t h a s m a l l e r mean t e r r i t o r y s i z e . I n summary, t h e n , t h e r e m o v a l e x p e r i m e n t s showed t h a t , on t h e s t u d y a r e a , t h e r e was a s u r p l u s o f b i r d s t h a t were p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g . The r e p l a c e m e n t b i r d s 71 were a l m o s t a l l j u v e n i l e s , and were p r o b a b l y a l l o f l o c a l o r i g i n . The s u c c e s s i v e p a t t e r n o f s e t t l i n g on t e r r i t o r i e s d i d n o t show s i g n i f i c a n t c h a n g e s i n numbers o f t e r r i t o r i e s , o r i n mean t e r r i t o r y s i z e s . The s i m u l t a n e o u s p a t t e r n o f s e t t l i n g on t e r r i t o r i e s r e s u l t e d i n h i g h e r numbers o f t e r r i t o r i e s , and s m a l l e r mean t e r r i t o r y s i z e s . P o s s i b l e f a c t o r s which might a c c o u n t f o r t h e s e r e s u l t s a r e d i s c u s s e d , and a p r o p o s e d e x p l a n a t i o n i s g i v e n . 72 PART B DOMINANCE HIERARCHIES I INTRODUCTION Schelder'up-Ebbe (1922) i s c r e d i t e d as b e i n g t h e f i r s t b i o l o g i s t t o r e c o g n i z e t h e i m p o r t a n c e o f dominance h i e r a r c h i e s i n g r o u p s o f a n i m a l s . He d i s c o v e r e d t h e e x i s t e n c e o f a l i n e a r p e c k - o r d e r i n d o m e s t i c f o w l , s u c h t h a t e a c h b i r d was e i t h e r d o m i n a n t o r s u b o r d i n a t e t o any o t h e r , and t h a t t h e d y a d i c s i t u a t i o n was e s s e n t i a l l y i r r e v e r s a b l e . S i n c e t h e n , dominance h i e r a r c h i e s have been o b s e r v e d i n numerous s p e c i e s o f a n i m a l s , b o t h d o m e s t i c ( e . g . G u h l 1953; Wood-Gush 1965) and w i l d . F o r w i l d a n i m a l s , h i e r a r c h i e s have been documented i n i n v e r t e b r a t e s , e.g. t h e C o c k r o a c h , Nauphoeta c i n e r e a , (Ewing 1970), and t h e M a n t i s S h r i m p , G o n g d a c t y l u s b r e d i n i , ( D i n g l e and C a l d w e l l 1969); i n l o w e r v e r t e b r a t e s , e . g . t h e L e o p a r d F r o g , Rang p i p i e n s , ( B o i c e and W i t t e r 1969); i n h i g h e r v e r t e b r a t e s , e.g. t h e P r a i r i e Dog, Cynomys l u d o y i c i a n u s , (Anthony 1955), t h e B o t t l e - n o s e d D o l p h i n , T u r s i o p s t r u n c a t u s , ( M c B r i d e and Hebb 1948), and l a b o r a t o r y m i c e , Mus m u s c u l u s , ( L e v i c k and B e i l h a r z 1973); i n p r i m a t e s , e.g. l e m u r s . Lemur s p p . , ( J o l l y 1966), and baboons, P a p i o s p p . , ( H a l l and D e v o r e 1965); and i n man, (Sommer 1967; K r e b s 1973). I n d e e d , t h e h i e r a r c h y i s c o n s i d e r e d by some ( e . g . I t o 1970) t o be one o f t h e most i m p o r t a n t c o n c e p t s i n 73 a n i m a l s o c i a l b e h a v i o u r . ^ v T h e r e i s a w e a l t h o f o b s e r v a t i o n a l m a t e r i a l on h i e r a r c h i c a l r e l a t i o n s h i p s i n b i r d s . T h e s e r e l a t i o n s h i p s have been f o u n d i n s u c h d i v e r s e g r o u p s a s c o l o n i a l t r e e - n e s t i n g h e r o n s ( N o b l e , Worm and S c h m i d t 1938), l e k s p e c i e s (Watts and S t o k e s 1971; B r u l l , c i t e d by K r u i j t and Hogan 1967), p i g e o n s (Bennet 1 9 3 9 ) , p a r r o t s (Masure and A l l e e 1934b), and v a r i o u s p a s s e r i n e s ; i n c o r v i d s (Brown 1963; L o r e n z 1952; L o c k i e 1956), i n p a r i d s ( B r i a n 1949; D i x o n 1966; Odum 1942), and i n f r i n g i l l i d s ( T o r d o f f 1954; Tompkins 1933; Tompa 1964; S a b i n e 1959; W e s s e l l and L e i g h 1941; Shoemaker 1939). A l m o s t h a l f o f t h e s e b i r d s t u d i e s , however, were done u n d e r u n n a t u r a l c o n d i t i o n s , i n l a b o r a t o r i e s , a f a c t o r which c o u l d p o s s i b l y have i n f l u e n c e d t h e a n i m a l ' s b e h a v i o u r (see Brown 1963:460). G a r t l a n (1968) a l s o e x p r e s s e s s i m i l a r s e n t i m e n t s when he s t r e s s e s t h a t c a r e s h o u l d be t a k e n i n i m p o s i n g s o c i a l models on what a r e n o t s o c i a l u n i t s . S e v e r a l o f t h e s t u d i e s c o n d u c t e d i n t h e w i l d were o f w i n t e r f l o c k s o f b i r d s t h a t . b r e e d i n a d i f f e r e n t g e o g r a p h i c a r e a f r o m t h a t i n which t h e y w i n t e r . Hence, t h e r e i s no i n f o r m a t i o n on t h e f i n a l outcome o f t h e h i e r a r c h y . I n d e e d , a l t h o u g h t h e f u n c t i o n o f t h e dominance h i e r a r c h y has been t h e s u b j e c t o f much d i s c u s s i o n (e.g. L a c k 1954, 1966; Wynne-Edwards 1962), t h e c o n s e q u e n c e s a r e n o t w e l l u n d e r s t o o d . ( 74 A few s t u d i e s i n b i r d s have f o l l o w e d t h e dominance h i e r a r c h y t h r o u g h t h e w i n t e r u n t i l i t s breakdown i n t h e s p r i n g . Odum (1942) r e p o r t e d t h a t t h e t o p t h r e e males i n a f l o c k o f B l a c k - c a p p e d C h i c k a d e e s e s t a b l i s h e d t e r r i t o r i e s i n t h e s p r i n g , and D i x o n (1965) f o u n d s i m i l a r r e s u l t s i n C a r o l i n a C h i c k a d e e s , P a r u s c a r o l i n e n s i s . Tompa (1964) d e t e r m i n e d t h e s t a t u s o f e i g h t j u v e n i l e m ales i n a group o f Song S p a r r o w s on Man d a r t e I s l a n d , and f o u n d t h a t t h e grou p was composed o f two a l p h a , f o u r b e t a , and two gamma b i r d s , a l t h o u g h no d a t a on how t h e r e l a t i o n s h i p s were d e t e r m i n e d a r e g i v e n . In t h e s p r i n g , t h e two a l p h a b i r d s a p p a r e n t l y had no d i f f i c u l t y i n e s t a b l i s h i n g t e r r i t o r i e s , b u t o n l y two o f t h e b e t a and n e i t h e r o f t h e gamma b i r d s s u c c e e d e d i n o b t a i n i n g t e r r i t o r i e s . I t h e r e f o r e i n v e s t i g a t e d t h e f o l l o w i n g q u e s t i o n ; when t h e o p p o r t u n i t y a r i s e s , a r e t h e j u v e n i l e s t h a t o b t a i n t e r r i t o r i e s t h e dominant i n d i v i d u a l s i n dominance h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n ? The p o p u l a t i o n o f Song S p a r r o w s on R e i f e l I s l a n d p r e s e n t e d an e x c e l l e n t o p p o r t u n i t y t o l o o k a t t h e n a t u r e o f t h e h i e r a r c h i e s , and t h e i r c o n s e q u e n c e s . The j u v e n i l e s f o r m e d l o o s e a s s o c i a t i o n s i n t h e f a l l , and c o n g r e g a t e d a t s p e c i a l f a v o u r e d l o c a l i t i e s a l o n g t h e hedgerows. A l a r g e p r o p o r t i o n o f t h e Song S p a r r o w s i n t h e a r e a had been c o l o u r - b a n d e d by l a t e f a l l , e n a b l i n g i n d i v i d u a l r e c o g n i t i o n . F i n a l l y , t h e r e m o v a l e x p e r i m e n t i n t h e s p r i n g would p r e s e n t a c h a n c e f o r s e v e r a l y e a r l i n g s t o o b t a i n t e r r i t o r i e s . 75 I I PROCEDURE The S p r i n g Removal A r e a was t h e o n l y hedgerow a l o n g which t h e h i e r a r c h i e s were d e t e r m i n e d . F e e d i n g s t a t i o n s ( t a b l e s ) were s e t up i n each a d u l t m a l e ' s t e r r i t o r y i n t h e f a l l o f 1972. N i n e t e e n t a b l e s were s e t up; t h e y were made o u t o f f l a t p i e c e s o f plywood, m e a s u r i n g 60cm by 40cm. B a i t (a m i x t u r e o f y e l l o w and w h i t e m i l l e t , b a r l e y and o a t s ) was put o u t a t i r r e g u l a r i n t e r v a l s a t e a c h s t a t i o n t h r o u g h o u t t h e w i n t e r , m a i n l y a f t e r December, and a f t e r t h e p e r i o d o f t h e w i n t e r ' s w o r s t weather (see monthly weather summary. A p p e n d i x 2 ) . O n l y a s m a l l amount o f b a i t (about t h r e e h a n d f u l s ) was put o u t a t a s t a t i o n on any one day. Song S p a r r o w s were r e a d i l y a t t r a c t e d t o t h e f e e d i n g s t a t i o n s , a s were a number o f o t h e r s e e d - e a t i n g p a s s e r i n e s , p r i n c i p a l l y J u n c o s , J u n c g s p p., Towhees, P i p i l o e r y t h r o p h t h a l m u s , and Fox S p a r r o w s , P a s s e r e l l a i l i a c a . Any f o o d l e f t a t t h e s t a t i o n a t t h e end o f t h e day had gone by e a r l y m o r n i n g , p r e s u m a b l y e a t e n by r o d e n t s . i A h i d e was e r e c t e d c l o s e t o a f e e d i n g s t a t i o n when t h a t s t a t i o n was u n d e r o b s e r v a t i o n . The b i r d s d i d n o t a p p e a r t o be e f f e c t e d by t h e p r e s e n c e o f t h e h i d e . A c a s s e t t e t a p e r e c o r d e r (Sony 110a) and a m i c r o p h o n e were u s e d t o r e c o r d t h e a c t i v i t i e s a t t h e s t a t i o n ; i n t h i s way, f u l l a t t e n t i o n was g i v e n t o t h e i n t e r a c t i o n s between t h e b i r d s . 76 A l l i n t e r a c t i o n s between Song S p a r r o w s were r e c o r d e d . I n t e r a c t i o n s between Song S p a r r o w s and o t h e r b i r d s a t t h e f e e d i n g s t a t i o n s were a l s o n o t e d (see A p p e n d i x 5 ) . A l l e n c o u n t e r s i n v o l v i n g Song S p a r r o w s i n v a r i a b l y t o o k p l a c e between o n l y two b i r d s a t a t i m e , and i n a l l e n c o u n t e r s a wi n n e r and a l o s e r c o u l d be c l e a r l y d e t e r m i n e d . The i n d i v i d u a l c a u s i n g t h e o t h e r t o r e t r e a t was n o t e d as dominant; t h e r e t r e a t i n g i n d i v i d u a l was n o t e d as s u b o r d i n a t e . E n c o u n t e r s were d i v i d e d i n t o t h r e e c a t e g o r i e s : d i s p l a c e m e n t s , a v o i d a n c e s , and f i g h t s . (a) D i s p l a c e m e n t s B i r d A i s f e e d i n g a t t h e b i r d t a b l e o r on t h e gr o u n d below. B i r d B a p p e a r s , and e i t h e r makes a r a p i d d e t e r m i n e d f l i g h t a t B i r d A, o r q u i c k l y hops i n t h r e a t p o s t u r e ( N i c e 1943:156) d i r e c t l y a t B i r d ft. B i r d B has wings • o u t - o f - p o c k e t * , body f e a t h e r s f l u f f e d o u t , head l o w e r e d , and beak p o i n t i n g a t B i r d A, who i n v a r i a b l y f l i e s o f f b e f o r e c o n t a c t i s made. On b e i n g d r i v e n o f f , and p r o v i d i n g a n o t h e r d o m i n a n t b i r d i s n o t a l r e a d y p r e s e n t . B i r d A would u s u a l l y f l y e i t h e r t o t h e t a b l e o r t o t h e g r o u n d below, d e p e n d i n g on where i t had j u s t been d i s p l a c e d . S h o u l d a s u b o r d i n a t e be p r e s e n t , t h e n i t would be d r i v e n o f f by B i r d A. D i s t a n c e s between t h e b i r d s v a r i e d f r o m o n e - h a l f t o one 77 m etre, and a p p e a r e d t o i n c r e a s e a s s p r i n g a p p r o a c h e d . (b) A v o i d a n c e s B i r d A i s f e e d i n g a t t h e t a b l e o r , more o f t e n , on t h e g r o u n d below. B i r d B a p p e a r s and hops t o w a r d s t h e f e e d i n g a r e a , w h i l s t a d o p t i n g a m i l d t h r e a t e n i n g p o s t u r e , w i t h wings • o u t - o f - p o c k e t * . B i r d A assumes an a l a r m p o s t u r e ( N i c e 1943:225), w i t h r a i s e d c r e s t f e a t h e r s , body f e a t h e r s s l e e k e d down, and neck s t r e t c h e d o u t and up. As B i r d B a p p r o a c h e s , B i r d A hops away from t h e f e e d i n g a r e a . D i s t a n c e s o nce a g a i n between b i r d s v a r i e d , but were r o u g h l y one m e t r e . (c) F i g h t s Two b i r d s ' s q u a r e o f f * , d i r e c t l y f a c i n g e a c h o t h e r . B o t h have t a i l s f a n n e d and g e n e r a l l y d e p r e s s e d , wings • o u t - o f - p o c k e t ' , body c l o s e t o t h e g r o u n d , f e a t h e r s p u f f e d o u t , and f r e q u e n t l y b i l l open. The two b i r d s g e n e r a l l y a r e q u i t e c l o s e t o e ach o t h e r , a b o u t 20 t o 30 c e n t i m e t r e s a p a r t , and o f t e n r e m a i n m o t i o n l e s s i n t h e s e p o s t u r e s f o r s e v e r a l s e c o n d s . Two p o s s i b l e outcomes a r e d i s t i n g u i s h a b l e : (1) one b i r d c l o s e s i t s b i l l , t u r n s i t s head, and t h e n f l i e s o f f w i t h t h e o t h e r i n c l o s e p u r s u i t . T h e r e t h e n f o l l o w s a p r o l o n g e d c h a s e t h r o u g h t h e s h r u b b e r y , and (2) t h e b i r d s p h y s i c a l l y f i g h t . They s p r i n g i n t o t h e a i r t o g e t h e r , p e c k i n g , and 78 a t t e m p t i n g t o c l e n c h c l a w s , e a c h t r y i n g t o surmount the o t h e r . The two b i r d s c a n r i s e a s much as t w e l v e f e e t above t h e g r o u n d , b e f o r e one g i v e s way and f l i e s o f f , w i t h t h e a c c o m p a n y i n g c l o s e p u r s u i t by t h e v i c t o r and a p r o l o n g e d c h a s e t h r o u g h t h e u n d e r b r u s h . Each t y p e o f e n c o u n t e r ( d i s p l a c e m e n t , a v o i d a n c e , and f i g h t ) was g i v e n e q u a l w e i g h t i n t h e a n a l y s i s , and a l l t h r e e t y p e s o f e n c o u n t e r s were combined. T h i s seemed j u s t i f i a b l e on t h e g r o u n d s t h a t i n t e r a c t i o n s d i d n o t i n v o l v e more t h a n two Song S p a r r o w s a t a t i m e , and t h a t t h e d e c i s i o n a s t o who was t h e v i c t o r i n an e n c o u n t e r was n o t i n d o u b t . T h i s i s i n c o n t r a s t t o t h e i n t e r a c t i o n s i n some o t h e r f r i n g i l l i d s ( e . g . S a b i n e 1959). As m e n t i o n e d e a r l i e r , t h e j u v e n i l e Song S p a r r o w s c o n g r e g a t e d a t s p e c i a l f a v o u r e d l o c a l i t i e s a l o n g t h e hedgerow. T h e s e l o c a l i t i e s f r e q u e n t l y encompassed more t h a n one a d u l t m ale's t e r r i t o r y , and t h e r e f o r e o b s e r v a t i o n s a t d i f f e r e n t f e e d i n g s t a t i o n s i n v o l v e d t h e same g r o u p o f j u v e n i l e s . T h e s e o b s e r v a t i o n s were combined i n t h e a n a l y s i s . F u r t h e r , t h e same g r o u p o f i n d i v i d u a l s r a n g i n g o v e r more t h a n one t e r r i t o r y would i n e v i t a b l y i n t e r a c t w i t h more t h a n one a d u l t t e r r i t o r i a l male and f e m a l e . I n t e r a c t i o n s i n v o l v i n g d i f f e r e n t a d u l t males and t h e g r o u p o f j u v e n i l e s were combined, a s were i n t e r a c t i o n s i n v o l v i n g d i f f e r e n t a d u l t f e m a l e s and t h e j u v e n i l e s . A l s o , c e r t a i n f e e d i n g s t a t i o n s a t t r a c t e d o n l y t h e a d u l t male and h i s 1 79 f e m a l e d u r i n g t h e o b s e r v a t i o n p e r i o d , and hence no h i e r a r c h y was r e s o l v e d . M a t r i c e s were c o n s t r u c t e d f o r e a c h h i e r a r c h i c a l g r o u p (see R e s u l t s ) . The outcomes o f t h e h i e r a r c h i e s were f o l l o w e d d u r i n g t h e s p r i n g a s t h e h i e r a r c h i e s began t o b r e a k - u p , and p a r t i c u l a r l y t h e y were f o l l o w e d i n t h e r e m o v a l a r e a s where t h e r e m o v a l e x p e r i m e n t s p r e s e n t e d an o p p o r t u n i t y f o r some o f t h e members o f t h e h i e r a r c h i e s t o o b t a i n t e r r i t o r i e s . 80 I I I RESULTS (A) The H i e r a r c h i e s Seven h i e r a r c h i e s were d e t e r m i n e d a l o n g t h e hedgerows, and m a t r i c e s were c o n s t r u c t e d f o r each one. The B-C H i e r a r c h y i s r e p r e s e n t e d i n t h e t e x t ( F i g u r e 7 ) , and t h e r e m a i n i n g s i x a r e i n c l u d e d i n t h e A p p e n d i c e s . The number o f Song S p a r r o w s i n v o l v e d i n t h e h i e r a r c h i e s r a n g e d from t w e n t y - s e v e n down t o f i v e i n d i v i d u a l s . The amount o f t i m e s p e n t w i t h e a c h g r o u p o f b i r d s i s g i v e n . The heavy b i a s i n amount o f t i m e s p e n t on t h e B-C H i e r a r c h y i s p a r t l y due t o t h e f a c t t h a t t h e g r o u p o f b i r d s c o n c e r n e d wandered o v e r an a r e a i n c o r p o r a t i n g t h r e e t e r r i t o r i e s , and hence t h r e e f e e d i n g s t a t i o n s . As n o t e d e a r l i e r , o b s e r v a t i o n s a t d i f f e r e n t s t a t i o n s i n v o l v i n g t h e same g r o u p o f b i r d s were combined i n t h e a n a l y s i s . In a l l h i e r a r c h i e s , t h e m a j o r i t y o f i n t e r a c t i o n s i n v o l v e d d i s p l a c e m e n t s . T a b l e 11 shows t h e numbers o f e n c o u n t e r s ( d i s p l a c e m e n t s , a v o i d a n c e s , and f i g h t s ) i n f o u r h i e r a r c h i e s . As an example, t h e B-C H i e r a r c h y was b a s e d on a g r a n d t o t a l o f 1153 i n t e r a c t i o n s , o f w h i c h o n l y 9% were a v o i d a n c e s , l e s s t h a n ^% f i g h t s , and t h e r e s t d i s p l a c e m e n t s . On t h e whole, males t e n d e d t o be i n v o l v e d i n more e n c o u n t e r s t h a n f e a a l e s . I n t h e B-C H i e r a r c h y , b i r d s a t t h e t o p o f t h e h i e r a r c h y ( m o s t l y males) were i n v o l v e d i n more i n t e r a c t i o n s t h a n b i r d s l o w e r 81 Figure 7 B - C HIERARCHY LOSER 5 \ G B Bl \ R Y R 9 W R R DB <f B 8 tf Y LP tt G Y tf w ® tf 0 • G tf R Y tf w BG tf B BG 11 tf BY BY tf w © 9 R ® tf B RW 1 9 LP 80 tf y<B 9 B BY 9 B ® 9 G © 9 B © 9 G DB 9 JL. DB 9 LO R 9 B © G B8I R Y R 4 5 7 22 13 7 6 3 6 11 4 11 1 6 13 2 13 4 2 W R ROB 3 6 2 7 7 4 4 1 2 5 5 16 4 6 5 3 4 8 B 3 6 5 4 c 13 11 5 ' 6 8 2 8 1 10 6 2 8 1 3 Y LP 6 8 3 4 5 2 2 1 5 1 3 7 3 4 6 2 9 2. Y 1 1 1 2 5 5 3 1 1 W ® 1 34 3 14 10 11 2 22 2 3 24 1 6 18 1 12 2 1 5 £ OG 1 9 17 1 5 17 3 1 15 3 18 4 20 1 3 1 R T \ 5 6 5 5 9 3 10 2 6 6 2 6 w BG 2 1 \ 11 9 9 16 6 6 3 10 12 1 14 2 8 BS 4 1 2 \ 10 2 16 6 7 5 1 2 20 1 3 BY BY 2 \ 5 2 6 1 3 1 1 1 W © \ 1 2 1 3 2 3 1 R ® 1 1 \ 1 7 10 4 3 8 9 1 B RW 1 \ 2 1 4 LP BO 6 5 1 1 \ 2 1 1 2 Y ® 3 1 \ 2 4 16 7 B BY 1 \ 2 1 4 B ® \ 7 2 6 3 Q © 2 \| 1 7 1 8 © 1 1 1 G OB 1 2 1 B 08 1 \ IS. R \ 8 © \ 1153 INTERACTIONS , 0 1 AVOIDANCES 80 MAN HOURS 7 F I G H T S 82 TABLE 11 Numbers of encounters (displacements, avoidances and f i g h t s ) i n four dominance h i e r a r c h i e s Hierarchies Displacements Avoidances Fights T o t a l B-C 1043 101 7 1153 Sedge Patch 142 41 3 186 Bulldozed Path 160 11 3 174 Cottonwood Stretch 153 17 0 170 83 down ( m o s t l y f e m a l e s ) (see F i g u r e 9 b e l o w ) . Of t h e s e v e n f i g h t s i n t h e B-C H i e r a r c h y , s i x were male-male e n c o u n t e r s , and t h e s e v e n t h m a l e - f e m a l e . However, males were o n l y s l i g h t l y more i n v o l v e d i n a v o i d a n c e i n t e r a c t i o n s t h a n f e m a l e s ( T a b l e 12). A l l s e v e n h i e r a r c h i e s a r e s t r i k i n g l y l i n e a r . T h e r e a r e v e r y few r e v e r s a l s 1 ; O n l y 4% o f a l l i n t e r a c t i o n s i n t h e B-C H i e r a r c h y i n v o l v e d r e v e r s a l s . T h i s t y p e o f a r r a n g e m e n t c o r r e s p o n d s w i t h t h e c l a s s i c a l * p e c k - r i g h t * o f S c h e l d e r u p - E b b e ( 1 9 2 2 ) , and n o t t h e •peck-dominance* o f Masure and a l l e e ( 1 9 3 4 a ) . N i c e ( 1 9 4 3 ) , f r o m o b s e r v a t i o n s on young Song S p a r r o w s she was r a i s i n g , c o n c l u d e d t h a t j u v e n i l e Song S p a r r o w s p a s s from s u p e r c e d e n c e t h r o u g h p e c k - d o m i n a n c e t o a c l e a r - c u t p e c k - o r d e r by t h e t i m e t h e y a r e t h r e e months o l d . E x t r a p o l a t i n g t h i s t i m e p e r i o d t o t h e j u v e n i l e Song S p a r r o w s on R e i f e l I s l a n d , t h e n , s t a b l e l i n e a r ' p e c k - r i g h t * r e l a t i o n s h i p s s h o u l d have been e s t a b l i s h e d amongst the g r o u p s o f j u v e n i l e s by e a r l y w i n t e r . As o b s e r v a t i o n s on t h e h i e r a r c h i e s s t a r t e d a f t e r December, t h e n one might n o t e x p e c t many r e v e r s a l s . I t seems l i k e l y t h a t more r e v e r s a l s would 1. In e n c o u n t e r s between any two b i r d s (a and B ) , a would p r e d o m i n a n t l y be t h e w i n n e r o v e r B. O c c a s i o n a l l y , B would win s u c h an e n c o u n t e r , and t h i s would be c l a s s e d as a r e v e r s a l . I n t h e m a t r i c e s , numbers o f r e v e r s a l s a p p e a r below th e d i a g o n a l l i n e s . 84 TABLE 12 Analysis of the avoidance interactions i n the B-C Hierarchy Won Lost Total Males: 83 26 109 Females: 18 75 93 Total: 101 101 - % 2 = 64.74 P < 0.001 85 have been recorded e a r l i e r i n the winter, as the rank of each bird was being decided. Reversals did not involve i n d i v i d u a l s that were seen less often. In the B-C Hierarchy, those individuals (9) that were involved i n more than one reversal were a l l prominent, d a i l y members of the hierarchy, when under observation. Also, reversals did not tend to occur l a t e r than e a r l i e r during the observation period. Out of 43 reversals on the B-C Hierarchy, 40 man hours before February 12 showed 24 reversals, 40 man hours after February 12 showed 19 reversals. •Triangles', where A dominates B, B dominates C, and C dominates A, the rela t i o n s h i p remaining stable, are a frequently observed phenomena of dominance hierarchies, e. g. in domestic fowl (Masure and Allee 1934b); in Oregon Juncos (Sabine 1956); in Black-capped Chickadees (Odum 1942); and i n White-eyes, Zosterops l a t e r a l i s , (Kikkawa 1961). Brown (1963) found that t r i a n g l e s i n the S t e l l e r ' s Jay, Cyanositta s t e l l e r i , were transient, the l i n e a r s i t u a t i o n soon asserting i t s e l f . In Song Sparrows, tr i a n g l e s occurred only in the B-C Hierarchy, and remained stable during the observation period. It was found that t r i a n g l e s involved birds i n the middle of the hierarchy only, with both sexes involved. In a l l hierarchies, the adult male and his female were the dominant birds at the feeding station located in t h e i r t e r r i t o r y . The only time that pairs from adjoining 86 t e r r i t o r i e s f e d a t t h e same s t a t i o n was when t h e t a b l e was p l a c e d o n , o r v e r y c l o s e t o , t h e b o u n d a r y s e p a r a t i n g t h e two p a i r s , a s h a p p e n e d i n t h e C o t t o n w o o d S t r e t c h H i e r a r c h y . O t h e r w i s e , a d u l t s r e s p e c t e d t e r r i t o r y b o u n d a r i e s , and t r e s p a s s i n g d i d n o t o c c u r . The r e m a i n d e r o f e a c h h i e r a r c h y was composed o f j u v e n i l e s , r a n g i n g i n numbers f r o m two t o t w e n t y - t w o . F a c t o r s w h i c h m i g h t d e t e r m i n e t h e d o m i n a n t o r s u b o r d i n a t e s t a t u s i n t h e h i e r a r c h y a r e i n c l u d e d i n t h e d i s c u s s i o n . A l t h o u g h t h e g r o u p s o f j u v e n i l e s r e m a i n e d r e l a t i v e l y i n t a c t , some i n t e r c h a n g e o f i n d i v i d u a l s b e t w e e n h i e r a r c h i e s d i d o c c u r . Some 14% o f a l l j u v e n i l e s i n v o l v e d i n t h e h i e r a r c h i e s p e r f o r m e d i n t e r g r o u p movements. I n O r e g o n J u n c o s ( S a b i n e 1 9 5 9 ) , C a r o l i n a C h i c k a d e e s ( D i x o n 1 9 6 5 ) , and Wood P i g e o n s , C o l u m b a p a l u m b u s , ( f i u r t o n e t a l . 1 9 6 6 ) , g r o u p i n t e r c h a n g e s i n v o l v e d b i r d s o f l o w r a n k o n l y , and t h e s e b i r d s m a i n t a i n e d t h e i r l o w p o s i t i o n i n t h e new g r o u p t h e y j o i n e d . Tompa (1964) m e n t i o n e d t h a t o n l y s u b o r d i n a t e Song S p a r r o w s were i n v o l v e d i n i n t e r c h a n g e s b e t w e e n g r o u p s on M a n d a r t e I s l a n d . T h i s was n o t t h e c a s e f o r Song S p a r r o w s on R e i f e l I s l a n d . Not o n l y d i d i n d i v i d u a l s o f l o w r a n k p e r f o r m i n t e r g r o u p movements, b u t a l s o i n d i v i d u a l s o f m i d d l e and e v e n u p p e r r a n k s ( T a b l e 1 3 ) . T h e s e w a n d e r i n g b i r d s assumed t h e same s t a t u s i n t h e new g r o u p a s t h a t w h i c h t h e y had h e l d i n t h e o l d one. M o s t e x a m p l e s a r e o f l o w r a n k e d b i r d s , and o f 87 TABLE 13 Rank i n hierarchy and sex of Song Sparrows performing intergroup movements Sex Hierarchy p o s i t i o n Male Female T o t a l Top t h i r d 2 0 2 Middle t h i r d 2 1 3 Bottom t h i r d 0 5 5 T o t a l 4 6 10 Each hierarchy was divided i n t o three sections i n order to eliminate the differences i n numbers of j u v e n i l e s i n each hierarchy. The adult males and females were not used i n the a n a l y s i s ; hence only the j u v e n i l e s were numerically divided i n t o the three categories, top, middle, and bottom. 88 f e m a l e s i n p a r t i c u l a r , but t h e d o m i n a n t male {Red/Yellow) i n t h e B u l l d o z e d P a t h H i e r a r c h y i n l a t e J a n u a r y , was f o u n d i n e a r l y F e b r u a r y h i g h i n t h e s c a l e i n t h e B-C H i e r a r c h y , and i n m i d - F e b r u a r y was f o u n d as t h e d o m i n a n t male i n t h e Cottonwood S t r e t c h H i e r a r c h y , a d i s t a n c e o f a b o u t 1000 m e t r e s . T h i s male, i n t e r e s t i n g l y enough, was t h e o n l y d o m i n a n t j u v e n i l e male i n t h e h i e r a r c h i e s n o t t o o b t a i n a t e r r i t o r y (see (B) The C o n s e q u e n c e s o f t h e H i e r a r c h i e s ) . An a n a l y s i s o f t h e f i g h t s i n t h e B-C H i e r a r c h y ( T a b l e 14) shows t h a t i n d i v i d u a l s t h a t a r e c l o s e r t o g e t h e r i n t h e h i e r a r c h y a r e s i g n i f i c a n t l y more l i k e l y t o be i n v o l v e d i n f i g h t s t h a n t h o s e t h a t a r e f a r t h e r a p a r t . T h e r e f o r e , a c o m p l e t e a n a l y s i s was r u n on a l l i n t e r a c t i o n s ( d i s p l a c e m e n t s , a v o i d a n c e s , and v f i g h t s ) i n t h e B-C H i e r a r c h y t o i n v e s t i g a t e f u r t h e r t h e p o s s i b i l i t y t h a t b i r d s c l o s e r t o g e t h e r i n t h e h i e r a r c h y i n t e r a c t more t h a n t h o s e f a r t h e r a p a r t . F i g u r e 8 g i v e s t h e r e s u l t s o f t h e a n a l y s i s . T h e r e i s no c o r r e l a t i o n between d i s t a n c e i n h i e r a r c h y and "numbers o f i n t e r a c t i o n s . T h u s , b i r d s which a r e c l o s e r t o g e t h e r i n t h e h i e r a r c h y a r e n o t n e c e s s a r i l y more l i k e l y t o i n t e r a c t t h a n a r e b i r d s which a r e f a r t h e r a p a r t . (B) S u c c e s s i n G a i n i n g T e r r i t o r i e s i n r e l a t i o n t o H i e r a r c h y P o s i t i o n Of t h e s e v e n h i e r a r c h i e s ( F i g u r e 7 and A p p e n d i x 8) NUMBER OF INTERACTIONS 10 o _1_ CO o —I— J>0 Oo o o • >• • MOOo DO D X 4^ J>t> >&•• • ipt> O D D C J O o • J>o oo o • > " • • a a o • oo-Jpaa • > ( t O O O oa o J>a oo o o <J> Oa o o o o • o d> • o o o JI o o o <po o o o o o $ 0 0 o o o a * N)JP O D O "D a p ro co -< 11 1 p b 00 x + CD CO > X o • mm> > 2 s r r > > m rn mm .< .< < 5: "n 2 • m > 5 > > m ? r r " > m m r~ m Figure 8 Number of i n t e r a c t i o n s versus distance w i t h i n hierarchy fo I a l l j u v e n i l e s i n the B-C Hierarchy 89 TABLE 14 Analysis of fights i n the B-C Hierarchy Number of juveniles i n the B-C Hierarchy = 22 Number of fights observed = 7 Random sample size ('pairs' from Random Digits Tables) = 70 Distance i n hierarchy* 1 2 3 4 5 6 7-22 Numbers of 'pairs' of birds: Observed 1 0 1 2 2 1 0 Expected .3 .5 .2 .3 .7 .4 4.6 D = 0.76 P 0.01 Kolmogorov-Smirnov one-sample test * Distance i n the hierarchy refers to how far apart i n numbers one member was from the other member of a 'pair'. Thus, i f the distance in the hierarchy i s 1, then the two birds involved i n a fight were next to each other i n the hierarchy. If the distance was 5, then there were 4 other birds i n the hierarchy between the 'pair'. 90 d e t e r m i n e d , f o u r ( B i g A l d e r , B u l l d o z e d P a t h , No-Name, and Sedge Path) were i n t h e S i m u l t a n e o u s Removal a r e a , one (Marsh Narrows) was i n t h e S u c c e s s i v e Removal a r e a , and one (Cottonwood S t r e t c h ) was on t h e C o n t r o l . The s e v e n t h (B-C) was where t h e S i m u l t a n e o u s Removal a r e a and t h e C o n t r o l met, and i n c o r p o r a t e d two t e r r i t o r i e s i n t h e S i m u l t a n e o u s Removal a r e a and one on t h e C o n t r o l . (1) S i m u l t a n e o u s Removal A r e a As e x p l a i n e d i n PART A, t e n males e s t a b l i s h e d t e r r i t o r i e s i n the S i m u l t a n e o u s Removal a r e a a f t e r t h e r e s i d e n t t e r r i t o r y h o l d e r s had been removed. Of t h e s e t e n , s e v e n had f i g u r e d i n t h e h i e r a r c h i e s . The d o m i n a n t males i n t h e f o l l o w i n g h i e r a r c h i e s o b t a i n e d t e r r i t o r i e s : No-Name, Sedge P a t c h , B i g A l d e r , and B-C. The s e c o n d males i n t h e B u l l d o z e d P a t h and B-C H i e r a r c h i e s a l s o o b t a i n e d t e r r i t o r i e s , and f i n a l l y t h e f i f t h male i n t h e B-C H i e r a r c h y o b t a i n e d a t e r r i t o r y . The d o m i n a n t male (Red/Yellow) i n t h e B u l l d o z e d P a t h H i e r a r c h y was t h e o n l y t o p b i r d i n t h e h i e r a r c h i e s on t h e S i m u l t a n e o u s Removal a r e a n ot t o o b t a i n a t e r r i t o r y a l o n g t h i s s t r e t c h o f hedgerow. As e x p l a i n e d e a r l i e r , t h i s p a r t i c u l a r male was c o n s p i c u o u s by i t s w a n d e r i n g b e h a v i o u r , h a v i n g been a p r o m i n e n t member o f t h r e e h i e r a r c h i e s . I t i s c o n c e i v a b l e t h a t t h i s male was n o t p r e s e n t a l o n g t h e S i m u l t a n e o u s Removal a r e a when t h e r e m o v a l t o o k p l a c e . 91 T h r e e males t h a t e s t a b l i s h e d t e r r i t o r i e s d i d n o t t a k e p a r t i n t h e h i e r a r c h i e s . One o f t h e s was banded i n x D e c e m b e r on t h e C o n t r o l , and was n o t r e s i g h t e d u n t i l t h e week o f t h e s i m u l t a n e o u s r e m o v a l e x p e r i m e n t . The s e c o n d was s e e n o c c a s i o n a l l y t h r o u g h o u t t h e w i n t e r a l o n g t h e S i m u l t a n e o u s Removal a r e a , b u t was n o t r e c o r d e d a t any f e e d i n g s t a t i o n d u r i n g t h e t i m e t h a t o b s e r v a t i o n s were made. The l a s t was an unbanded male t h a t e s t a b l i s h e d a t e r r i t o r y i n t h e r e g i o n where hedgerows from flestham I s l a n d j o i n t h e s t u d y a r e a , and i t i s q u i t e p o s s i b l e t h a t t h i s i n d i v i d u a l s p e n t t h e w i n t e r o u t s i d e t h e s t u d y a r e a . Of t h e s e v e n f e m a l e s t h a t p a i r e d w i t h t h e new t e r r i t o r i a l m a l e s a f t e r t h e r e m o v a l s , o n l y one had ^ e e n a p r o m i n e n t member i n t h e h i e r a r c h i e s . T h i s f e m a l e ( B l a c k / B l u e ) had a low p o s i t i o n i n t h e Sedge P a t c h and B u l l d o z e d P a t h H i e r a r c h i e s b e f o r e F e b r u a r y 3. A f t e r t h i s d a t e , she r a p i d l y moved up t h e s c a l e . T a b l e 15 shows a 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 number of i n t e r a c t i o n s won and l o s t a f t e r F e b r u a r y 3. The a d u l t f e m a l e i n t h e a r e a o f t h e B u l l d o z e d P a t h H i e r a r c h y was l a s t s e e n on J a n u a r y 29, and i t i s t h o u g h t t h a t B l a c k / B l u e assumed t h e a d u l t f e m a l e ' s p o s i t i o n i n e a r l y F e b r u a r y . On t h e d e a t h o f t h e a d u l t male d u r i n g t h e r e m o v a l s , s h e p a i r e d w i t h one o f t h e r e p l a c e m e n t m a l e s . (2) S u c c e s s i v e Removal A r e a s O n l y one h i e r a r c h y was d e t e r m i n e d a l o n g t h e S u c c e s s i v e 92 TABLE 15 Change i n status of a j u v e n i l e female following the disappearance of an adult t e r r i t o r i a l female Before Feb.3 A f t e r Feb.3 T o t a l I n t e r a c t i o n s : Win 2 23 25 Lo*se 11 5 16 Totals 13 28 41 X 2 = 17.09 P < 0.005 The adult female was l a s t seen on January 29. Juvenile female (Black/Blue) presumably assumes the adult female's r o l e i n e a r l y February. The j u v e n i l e female wins s i g n i f i c a n t l y more i n t e r a c t i o n s , not only with b i r d s below her, but p r i m a r i l y with b i r d s above her; hence her change i n status. 93 Removal a r e a . I t c o n s i s t e d o f f i v e b i r d s , o f which o n l y two were j u v e n i l e s , and b o t h f e m a l e s . One o f t h e s e f e m a l e s s u c c e e d e d i n p a i r i n g w i t h a new male a f t e r t h e r e m o v a l , t h e o t h e r f e m a l e d i s a p p e a r e d . I t i s p o s s i b l e t h a t t h e r e p l a c e m e n t b i r d s , most o f which were unbanded, c o u l d have s p e n t t h e w i n t e r a c r o s s Ewen S l o u g h i n t h e F a l l Removal Area ( F i g u r e 1 ) . (3) C o n t r o l Of 11 j u v e n i l e s t h a t t o o k p a r t i n t h e Cottonwood S t r e t c h H i e r a r c h y , none were s e e n a f t e r t h e r e m o v a l e x p e r i m e n t s . I n e a r l y May, however, one o f t h e a d u l t males d i e d ( t h e c o r p s e was f o u n d on May 4). On May 5, a male had t a k e n e v e r t h i s t e r r i t o r y , and a p p a r e n t l y a l s o t h e a d u l t f e m a l e . T h i s r e p l a c e m e n t male had been t h i r d b i r d i n t h e B-C H i e r a r c h y . The B-C H i e r a r c h y was t h e l a r g e s t o f t h e h i e r a r c h i e s , and was t h e o n l y one s u p p l y i n g more t h a n one t e r r i t o r i a l male amongst t h e r e p l a c e m e n t s . A n a l y s i n g t h i s h i e r a r c h y , o u t o f 12 j u v e n i l e m a l e s t h a t t o o k p a r t i n t h e h i e r a r c h y , f o u r f r o m t h e t o p f i v e o b t a i n e d t e r r i t o r i e s . T h i s i s h i g h l y u n l i k e l y t o have o c c u r r e d by c h a n c e (P = 0.01). The e v i d e n c e , t h e n , s t r o n g l y s u p p o r t s t h e h y p o t h e s i s t h a t , g i v e n t h e o p p o r t u n i t y , t h e j u v e n i l e s t h a t o b t a i n t e r r i t o r i e s a r e t h e d o m i n a n t i n d i v i d u a l s i n dominance h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n . 94 IV DISCUSSION (a) The Functional Significance of Dominance Hierarchies Gartlan (1968) suggests that the primary function of the s o c i a l dominance hierarchy i s to relate population size to available resources. Wynne-Edwards (1962) suggests that hierarchies can function as a s o c i a l g u i l l o t i n e for subordinate i n d i v i d u a l s during times of food shortage, although Lack (1966), whilst concurring that the few in d i v i d u a l s near the bottom of the peck-order starve or emigrate when the numbers of the species are up against the food l i m i t , regarded t h i s as a consequence, not a function. Lack argues that the hierarchy arises as a response to scarce food resources, and not as an a n t i c i p a t i o n of them. Wynne-Edwards, however, maintains that the hierarchy i s pre-adaptive for conditions of privation. There i s evidence that can be put forward supporting both arguments; however, i t i s frequently d i f f i c u l t to d i f f e r e n t i a t e between cause and e f f e c t of the dominance hierarchies i n most instances. I t i s even more d i f f i c u l t to relate the food shortage hypothesis with the hierarchies in Song Sparrows, where a l l the bottom, hence subordinate birds, are females! The g u i l l o t i n i n g of subordinates i n times of food shortage, then, would presumably ef f e c t females far more than males. 95 A f u r t h e r argument i s t h a t h i e r a r c h i e s f u n c t i o n i n r e d u c i n g a g g r e s s i v e e n c o u n t e r s between i n d i v i d u a l s , t h u s c o n s e r v i n g e n e r g y , b u t a g a i n i t c a n be a r g u e d t h a t t h i s i s a c o n s e q u e n c e , and n o t a f u n c t i o n , o f t h e h i e r a r c h y . T h e r e i s good e v i d e n c e t h a t h i e r a r c h i e s a r e i m p o r t a n t i n r e d u c i n g a g g r e s s i v e e n c o u n t e r s i n work on mammals (e.g. Anthony 1955; C a l h o u n 1971; K i n s e y 1971), and on d o m e s t i c b i r d s (e. g. G u h l 1956). Lack (1954) a l s o a r g u e d a l o n g s i m i l a r l i n e s when he s t a t e s t h a t t h e p e c k - o r d e r has s u r v i v a l v a l u e f o r b o t h s t r o n g e r and weaker i n d i v i d u a l s , f o r t h o s e h i g h e r b e c a u s e t h e y o b t a i n f o o d w i t h v e r y l i t t l e f i g h t i n g , and f o r t h o s e l o w e r b e c a u s e i t s a v e s them w a s t i n g t i m e on f i g h t s w hich t h e y would l o s e anyway, and t h e i r e n e r g i e s c a n be c o n s e r v e d f o r s e a r c h i n g e l s e w h e r e . I t seems r e a s o n a b l e t o a r g u e t h a t a g g r e s s i o n between i n d i v i d u a l Song S p a r r o w s has been r e d u c e d b e c a u s e o f t h e h i e r a r c h i e s , p a r t i c u l a r l y a s f i g h t s a r e r a r e , r e v e r s a l s a r e few, and t h e h i e r a r c h y i s s t a b l e . Dominance h i e r a r c h i c a l b e h a v i o u r , l i k e t e r r i t o r i a l b e h a v i o u r , c o u l d f u n c t i o n i n v a r i o u s ways f o r d i f f e r e n t a n i m a l s . F o r Song S p a r r o w s , t h e f u n c t i o n a l s i g n i f i c a n c e o f t h e h i e r a r c h y c o u l d be t o r e d u c e a g g r e s s i v e i n t e r a c t i o n s , t o i d e n t i f y a s u r p l u s , o r t o d e t e r m i n e t h e dominant i n d i v i d u a l s t h a t m i g h t o b t a i n a t e r r i t o r y g i v e n t h e o p p o r t u n i t y . D a t a f o r any one o f them a r e n o t u n e q u i v o c a l . (b) F a c t o r s d e t e r m i n i n g p o s i t i o n i n t h e Dominance H i e r a r c h y 96 I t has a l r e a d y been shown t h a t t h e h i e r a r c h y i n Song S p a r r o w s i s e s s e n t i a l l y l i n e a r and s t a b l e . I t i s worth now c o n s i d e r i n g some o f t h e f a c t o r s which might d e t e r m i n e t h e dominance o r s u b o r d i n a n c e o f t h e i n d i v i d u a l s c o m p r i s i n g t h e h i e r a r c h y . Sex and p o s i t i o n i n h i e r a r c h y I n Song S p a r r o w s , j u v e n i l e m ales were dom i n a n t o v e r j u v e n i l e f e m a l e s . In t h e B-C H i e r a r c h y , f o r example, o u t o f 22 j u v e n i l e s , 12 f r o m t h e t o p 14 were m a l e s . A l t h o u g h t h i s a r r a n g e m e n t c a n be f o u n d i n some o t h e r p a s s e r i n e s p e c i e s (e. g. Red C r o s s b i l l , L o x i a c u r y i . r o s t r a , ( T o r d o f f 1 9 5 5 ) ) , i t i s n o t t h e c a s e i n P a r u s s p e c i e s ( D i x o n 1966; Odum 1942; B r i a n 1949), o r i n S t e l l e r » s J a y (Brown 1964), where t h e f e m a l e t a k e s t h e r a n k o f t h e male she p a i r s w i t h . In c e r t a i n i n s t a n c e s , a s i n B l a c k - c r o w n e d N i g h t - H e r o n s , N y c t i c o r a x M£ii£2ia2[» ( N o b l e , Worm and S c h m i d t 1939) , males and f e m a l e s a r e g r a d e d w i t h o u t r e g a r d t o s e x , s u g g e s t i n g an a s e x u a l s i t u a t i o n . , G u h l (1956) f o u n d f o r d o m e s t i c f o w l t h a t c o c k s do n o t n o r m a l l y peck hens, and t h e r e f o r e a b r e e d i n g f l o c k u s u a l l y has two h i e r a r c h i e s , one f o r ea c h s e x . The h i e r a r c h i e s i n Song S p a r r o w s c a n n o t be d i v i d e d i n t h i s manner, as b o t h s e x e s were i n v o l v e d i n t h e i n t e r a c t i o n s . An i n d i v i d u a l c a n c l i m b t h e s o c i a l l a d d e r by p a i r i n g w i t h 97 a d o m i n a n t b i r d o f t h e o p p o s i t e s e x . Brown (1963) r e l a t e s an i n s t a n c e o f a male moving up t h e s c a l e o f dominance a f t e r p a i r i n g w i t h a d o m i n a n t a d u l t f e m a l e . I n t h e Song S p a r r o w s , a j u v e n i l e f e m a l e ( B l a c k / B l u e ) moved up t h e h i e r a r c h y a f t e r t h e a d u l t f e m a l e had d i s a p p e a r e d i n t h e p e r i o d J a n u a r y 29 t o F e b r u a r y 3. Her s u c c e s s i n i n t e r a c t i o n s i n c r e a s e d s i g n i f i c a n t l y a f t e r t h i s p e r i o d (see T a b l e 1 4 ) . She a p p a r e n t l y p a i r e d w i t h t h e a d u l t male on t h e d i s a p p e a r a n c e o f h i s mate, and, a f t e r t h e s p r i n g r e m o v a l e x p e r i m e n t , she p a i r e d w i t h t h e r e p l a c e m e n t young male. S i z e and p o s i t i o n i n h i e r a r c h y f S i z e has been f o u n d t o be a f a c t o r i n d e t e r m i n i n g h i e r a r c h i c a l p o s i t i o n i n B o t t l e - n o s e d D o l p h i n s ( M c B r i d e and Hebb 1948), and i n New F o r e s t P o n i e s ( T y l e r 1972). F r e t w e l l (1969) f o u n d t h a t , i n t h e Oregon J u n c o , d o m i n a n t s had l o n g e r wings t h a n s u b o r d i n a t e s . Song S p a r r o w s v a r y c o n s i d e r a b l y i n w e i g h t ( F i g u r e 4) and i n w i n g l e n g t h ( F i g u r e 3) , but no r e l a t i o n s h i p between w e i g h t o r w i n g l e n g t h and p o s i t i o n i n h i e r a r c h y was f o u n d . Thus, i t c a n n o t be a r g u e d t h a t t h e l a r g e s t o r h e a v i e s t b i r d s were t h e ones t h a t o b t a i n e d t e r r i t o r i e s . Age and p o s i t i o n i n h i e r a r c h y Age and dominance have been f o u n d t o c o r r e l a t e i n d o m e s t i c f o w l (Shoemaker 1939), b u t n o t i n s h o r t - l i v e d p a s s e r i n e s (R. I. S t e w a r t p e r s coram). A more s u b t l e 98 r e l a t i o n s h i p between age and dominance o c c u r s i n t h e Sage G r o u s e , C e n t r o c e r c u s u r o p h a s i a n u s , ( W i l e y 1970), where t h e r e i s a c e n t r i p e t a l movement o f t e r r i t o r i a l males t o w a r d s a m a t i n g c e n t r e o f t h e ^ Lek^)as v a c a n c i e s a r i s e o v e r t h e y e a r s . In Song S p a r r o w s , any one h i e r a r c h i c a l g r o u p i s c o m p r i s e d o f a t most two a d u l t b i r d s i n any one t e r r i t o r y , and t h e r e s t j u v e n i l e s . Age t h e n c o u l d o n l y be i m p o r t a n t w i t h r e s p e c t t o t h e j u v e n i l e s t h e m s e l v e s , f o r example i f t h e i n d i v i d u a l s f r o m t h e f i r s t b r o o d s were dominant o v e r t h o s e from s e c o n d o r t h i r d b r o o d s . R e s u l t s , however, c o u l d be c o n f u s e d w i t h t h e i d e a s o f p r i o r o c c u p a n c y and e x p e r i e n c e , t o be d i s c u s s e d n e x t . T h e r e i s some e v i d e n c e , a l b e i t meagre, t o s u g g e s t t h a t , f o r j u v e n i l e s , age i s n o t i m p o r t a n t i n d e t e r m i n i n g p o s i t i o n i n t h e h i e r a r c h y . The age o f t h e two t o p j u v e n i l e m ales i n t h e B-C H i e r a r c h y a r e known, as t h e y were banded i n t h e summer o f 1972, a t a s t a g e o f d e v e l o p m e n t when t h e i r age c o u l d be d e t e r m i n e d (see A p p e n d i x 6 f o r c a l c u l a t i o n s o f a g e ) . The s e c o n d b i r d was a p r o d u c t o f a f i r s t b r o o d , b u t t h e t o p b i r d was t h e p r o d u c t o f e i t h e r a s e c o n d o r t h i r d b r o o d , and was c a l c u l a t e d t o be a b o u t 60 d a y s younger t h a n t h e s e c o n d b i r d . N e v e r t h e l e s s , he was t h e d o m i n a n t j u v e n i l e i n t h e l a r g e s t h i e r a r c h y . P r i o r o c c u p a n c y and e x p e r i e n c e and p o s i t i o n i n t h e h i e r a r c h y E x p e r i e n c e a n d / o r p r i o r o c c u p a n c y ( p r i o r r e s i d e n c y , f a m i l i a r i t y w i t h t e r r i t o r y ) and t h e r e l a t i o n s h i p w i t h 99 h i e r a r c h y r a n k h a s r e c e i v e d much a t t e n t i o n i n r e c e n t y e a r s . T h e s e r e l a t i o n s h i p s have been f o u n d i n f i s h , e. g. P h i l l i p s ( 1 9 7 1 ) ; i n b i r d s , e. g. Brown (1964); and even i n man, e. g. K r e b s (1973). I n t h e G r e a t T i t ( B r i a n 1949), C a r o l i n a C h i c k a d e e (Dixon 1965), B l u e T i t , P a r u s c a e r u l e u s , ( C o l g u h o u n 1942), and S t e l l e r ' s J a y (Brown 1963), t h e p o s i t i o n o f t h e b i r d i n t h e dominance o r d e r c o r r e s p o n d s w i t h t h e d i s t a n c e o f i t s t e r r i t o r y f r o m th e f e e d i n g p l a c e ; t h e r a n k o f t h e i n d i v i d u a l v a r i e d i n v e r s e l y w i t h i t s d i s t a n c e f r o m i t s t e r r i t o r y . I n Song S p a r r o w s , t h i s phenomenon p r o b a b l y does n o t a p p l y . T e r r i t o r i a l a d u l t s c o u l d n o t be e n t i c e d f r o m t h e i r t e r r i t o r i e s even when f o o d was s u p p l i e d i n t h e i r n e i g h b o u r ' s t e r r i t o r y . I t seems u n l i k e l y t h a t t h e y were n o t aware o f t h e p r e s e n c e o f t h e f o o d , p a r t i c u l a r l y by t h e n o i s y f e e d i n g b e h a v i o u r of j u n c o s a t t h e f e e d i n g s t a t i o n s . The i n c e n t i v e t h e n t o l e a v e t h e i r t e r r i t o r i e s was a p p a r e n t l y n o t s t r o n g enough t o overcome t h e r e c o g n i t i o n o f , and r e s p e c t f o r , t e r r i t o r i a l b o u n d a r i e s . The j u v e n i l e s c o m p r i s i n g t h e r e s t o f t h e h i e r a r c h y were n o n - t e r r i t o r i a l , and t h e r e f o r e would n o t be i n v o l v e d i n t h i s i d e a . S a b i n e (1959) s u g g e s t e d t h a t t h o s e j u n c o s t h a t a r r i v e d f i r s t on t h e w i n t e r i n g g r o u n d s were i n , g e n e r a l d ominant t o g r o u p s t h a t a r r i v e d l a t e r . P r i o r r e s i d e n c y , however, was n o t t h o u g h t by Kikkawa (1961) t o be a f a c t o r i n d e t e r m i n i n g 100 h i e r a r c h y p o s i t i o n i n W h i t e - e y e s ; he s u g g e s t e d t h a t any a d v a n t a g e c o n f e r r e d on b i r d s w i t h p r e v i o u s f a m i l i a r i t y w i t h an a r e a was masked by t h e l a r g e number o f b i r d s p r e s e n t , The s i t u a t i o n r e g a r d i n g p r i o r o c c u p a n c y and h i e r a r c h i c a l p o s i t i o n i n Song S p a r r o w s i s c o m p l i c a t e d by t h e f a c t t h a t o n l y ' j u v e n i l e s can be c o n s i d e r e d . a l l a d u l t s were t o p b i r d s i n t h e i r own t e r r i t o r i e s . The j u v e n i l e g r o u p s a r e most l i k e l y f o rmed a b o u t t h e same t i m e i n c e r t a i n a r e a s a l o n g t h e hedgerow, d u r i n g t h e r e c r u d e s c e n c e o f f a l l t e r r i t o r i a l 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 a d u l t s . I f t h i s s u g g e s t i o n i s t h e c a s e , t h e n t h e j u v e n i l e s a p p e a r t o a r r a n g e t h e h i e r a r c h i c a l p o s i t i o n s w i t h o u t r e g a r d f o r p r e v i o u s f a m i l i a r i t y w i t h an a r e a , b e c a u s e no i n d i v i d u a l would have t h a t f a m i l i a r i t y . One c o u l d p o s s i b l y a r g u e t h a t t h o s e j u v e n i l e s t h a t happened t o a r r i v e f i r s t , d u r i n g t h e d i s p e r s a l phase (see G e n e r a l I n t r o d u c t i o n ) , a t one o f t h e c e n t r e s o f c o n c e n t r a t i o n would have an a d v a n t a g e o v e r l a t e r a r r i v a l s . No d a t a s u p p o r t i n g o r r e f u t i n g t h i s i d e a a r e a v a i l a b l e . I t seems, t h e r e f o r e , t h a t l o n g - t e r m p r i o r o c c u p a n c y i s n o t a f a c t o r i n d e t e r m i n i n g t h e p o s i t i o n o f a j u v e n i l e Song Sparrow i n t h e h i e r a r c h y . S h o r t - t e r m p r i o r o c c u p a n c y , however, c a n n o t be r u l e d o u t as a p o s s i b l e f a c t o r . O t h e r f a c t o r s and t h e p o s i t i o n i n h i e r a r c h y The t o p b i r d s may be g e n e t i c a l l y d i f f e r e n t from b i r d s o f l o w e r r a n k . F u r t h e r , s o c i a l r a n k c o u l d be g e n e t i c a l l y 101 i n h e r i t e d . Sade (1967) however has a r g u e d t h a t dominance i s n o t an i n t r i n s i c f e a t u r e o f an i n d i v i d u a l , b u t a ' r o l e * a c q u i r e d by him. I have no e v i d e n c e s u p p o r t i n g o r r e f u t i n g a h y p o t h e s i s b a s e d on g e n e t i c f e a t u r e s t h a t might d e t e r m i n e a j u v e n i l e Song S p a r r o w ' s p o s i t i o n i n t h e dominance h i e r a r c h i e s on R e i f e l I s l a n d . A l t h o u g h t h e dominance h i e r a r c h i e s a r e based on a g g r e s s i v e e n c o u n t e r s , i t i s f r e q u e n t l y d i f f i c u l t t o d e t e r m i n e i f t h e most a g g r e s s i v e b i r d i s t h e dominant b i r d . F i g u r e 9 shows t h a t t h e r e i s a s i g n i f i c a n t p o s i t i v e c o r r e l a t i o n between p o s i t i o n i n h i e r a r c h y and t h e number o f i n t e r a c t i o n s i n which e a c h b i r d was i n v o l v e d . However, as K r e b s (1973) p o i n t s o u t , an a l p h a i n d i v i d u a l need n o t show t h e h i g h e s t f r e g u e n c y o f a g g r e s s i v e b e h a v i o u r , b e c a u s e h i s p o s i t i o n i s s t a b l e . The f a c t t h a t t h e h i e r a r c h i e s i n Song S p a r r o w s a r e s t a b l e , and y e t t h e r e i s a h i g h e r i n c i d e n c e o f i n t e r a c t i o n s c o n c e r n i n g b i r d s a t t h e t o p end o f t h e h i e r a r c h y , r e q u i r e s f u r t h e r i n v e s t i g a t i o n . In summary, t h e n , t h e r e a p p e a r s t o be l i t t l e c o n c l u s i v e e v i d e n c e i n t h i s s t u d y s u p p o r t i n g any f a c t o r (s) t h a t might d e t e r m i n e t h e r a n k t h a t an i n d i v i d u a l Song Sparrow h e l d i n t h e h i e r a r c h y . M a l e s d o m i n a t e d f e m a l e s . S i z e , age, and l o n g - t e r m p r i o r o c c u p a n c y were n o t t h o u g h t t o be i m p o r t a n t , b u t s h o r t - t e r m p r i o r o c c u p a n c y and p o s s i b l y g e n e t i c o r a g g r e s s i o n 102 f e a t u r e s were n o t r u l e d o u t . F i n a l l y , i t i s worth l o o k i n g a t t h e outcomes o f t h e h i e r a r c h i e s , and i n p a r t i c u l a r t h e i d e a t h a t t h e dominant i n d i v i d u a l s i n t h e h i e r a r c h i e s were t h e s u c c e s s f u l ones i n o b t a i n i n g t e r r i t o r i e s when t h e o p p o r t u n i t y a r o s e . (c) Outcomes o f t h e H i e r a r c h i e s In c e r t a i n h i e r a r c h i c a l g r o u p s o f a n i m a l s , t h e r e i s a p r o n o u n c e d f e e d i n g o r d e r (e. g. Anthony 1955; G u h l 1956; Dix o n 1965). The dominant i n d i v i d u a l f e e d s f i r s t , f o l l o w e d by s u b o r d i n a t e s i n d e s c e n d i n g o r d e r . The a p p e a r a n c e o f t h e f i r s t Song Sparrow a t t h e f e e d i n g s t a t i o n was n o t r e l a t e d t o i t s p o s i t i o n i n t h e dominance h i e r a r c h y . T a b l e 16 g i v e s t h e p o s i t i o n o f t h e f i r s t b i r d t h a t a p p e a r e d on t h e t e n days t h a t were s p e n t i n o b s e r v i n g t h e B-C H i e r a r c h y . I n f a c t , s u b o r d i n a t e s a r r i v e d f i r s t j u s t a s o f t e n a s d o m i n a t e s , and f e m a l e s a s o f t e n a s m a l e s . Shoemaker (1939) f o u n d t h a t , i n a l a b o r a t o r y p o p u l a t i o n o f c a n a r i e s , S e r i n u s s e r i n u s , t h e d o m i n a n t males had a much h i g h e r b r e e d i n g s u c c e s s t h a n s u b o r d i n a t e s . T h e r e i s no e v i d e n c e f r o m t h e p r e s e n t s t u d y t o s u p p o r t o r r e f u t e t h i s s u g g e s t i o n . In c e r t a i n l e k s p e c i e s , (e. g. Sage G r o u s e , W i l e y 1970), not o n l y i s i t i m p o r t a n t f o r males t o o b t a i n a t e r r i t o r y t o 103 P O S I T I O N IN H I E R A R C H Y Figure 9 P o s i t i o n i n h i e r a r c h y and number of i n t e r a c t i o n s : the B-C Hierarchy The l i m i t a t i o n s o f t h i s a n a l y s i s are acknowledged. Each b i r d d i d not spend an equivalent amount o f time at the feeding s t a t i o n . Some b i r d s fed without an i n t e r a c t i o n o c c u r i n g . The manifestations of aggressive behaviour are discussed i n the t e x t . 104 mate, b u t i t i s a l s o i m p o r t a n t t o o b t a i n c e r t a i n f a v o u r e d t e r r i t o r i e s t o e n s u r e s u c c e s s f u l m a t i n g s . T h e r e a r e s e v e r a l s p e c i e s o f b i r d s i n which t h e a c q u i s i t i o n o f a t e r r i t o r y i s a p r e - r e q u i s i t e f o r o b t a i n i n g a mate, and hence b r e e d i n g . I n many o f t h e s e s p e c i e s , t h e p r e s e n c e o f a dominance h i e r a r c h y i n t h e p r e - b r e e d i n g s e a s o n has been d e t e r m i n e d . The c o r r e l a t i o n between dominance i n t h e h i e r a r c h y and s u c c e s s v i n o b t a i n i n g a t e r r i t o r y has been shown i n o n l y a few p o p u l a t i o n s . Odum (1942) r e p o r t e d t h a t t h e t o p t h r e e males i n a w i n t e r f l o c k o f B l a c k - c a p p e d C h i c k a d e e s e s t a b l i s h e d t e r r i t o r i e s i n t h e s p r i n g . D i x o n (1965) f o u n d s i m i l a r r e s u l t s i n C a r o l i n a C h i c k a d e e s , as d i d Tompa (1964) i n Song S p a r r o w s . The r e s u l t s i n t h e p r e s e n t s t u d y f u r t h e r s t r e n g t h e n t h i s c o r r e l a t i o n , t h a t t h e i n d i v i d u a l s t h a t o b t a i n t e r r i t o r i e s a r e t h e d o m i n a n t o n e s i n dominance h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n . I n summary, t h e n , g r o u p s o f j u v e n i l e Song S p a r r o w s c o n g r e g a t e d i n t h e f a l l a t c e r t a i n f a v o u r e d l o c a l i t i e s a l o n g t h e hedgerow. H i e r a r c h i e s were f o r m e d , which by m i d - w i n t e r were l i n e a r s t a b l e , w i t h few r e v e r s a l s . In t h e h i e r a r c h i e s , males d o m i n a t e d f e m a l e s . S i z e , age, and l o n g - t e r m p r i o r o c c u p a n c y were n o t t h o u g h t t o be i m p o r t a n t i n d e t e r m i n i n g th e r a n k t h a t an i n d i v i d u a l h e l d i n t h e 1 0 4 TABLE 16 Feeding order of hierarchy: appearance of f i r s t b i r d at feeding s t a t i o n s of the B-C Hierarchy Sex P o s i t i o n of b i r d i n hierarchy Number of days Male Female F i r s t seven 3 3 0 Middle eight 4 2 2 Last seven 3 0 3 T o t a l s : 22 b i r d s 10 105 h i e r a r c h y . S h o r t - t e r m p r i o r o c c u p a n c y and p o s s i b l y g e n e t i c o r a g g r e s s i o n f e a t u r e s were n o t r u l e d o u t . The r e m o v a l e x p e r i m e n t s and s u b s e q u e n t r e p l a c e m e n t s showed t h a t t h o s e y e a r l i n g s t h a t o b t a i n e d t e r r i t o r i e s i n t h e s p r i n g on t h e S p r i n g Removal A r e a were t h e d o m i n a n t i n d i v i d u a l s i n t h e h i e r a r c h i e s e s t a b l i s h e d d u r i n g t h e p r e - b r e e d i n g s e a s o n . 106 LITERATURE CITED A l e x a n d e r , R. D. 1961. A g g r e s s i v e n e s s , t e r r i t o r i a l i t y , and s e x u a l b e h a v i o u r i n f i e l d c r i c k e t s ( O r t h o p t e r a r G r y l l i d a e ) . B e h a v i o u r 17: 130-223. A n t h o n y , A. 1955. B e h a v i o u r p a t t e r n s i n a l a b o r a t o r y c o l o n y o f P r a i r i e Dogs, Cynomis l u d o y i c i a n u s . J . Mammal. 36: 69-78. Van den Assem, J . 1967. T e r r i t o r y i n t h e t h r e e - s p i n e d s t i c k l e b a c k G a s t e r o s t e u s a c u l e a t u s . B e h a v i o u r S u p p l . 16: 1-164. A y a l a , F. J . 1971. C o m p e t i t i o n between s p e c i e s : f r e q u e n c y d e p e n d e n c e . S c i e n c e 171:820-4. B e e r , J . R., F r e n z e l , L. D., and N. Hansen. 1956. Minimum s p a c e r e q u i r e m e n t s o f some n e s t i n g p a s s e r i n e b i r d s . W i l s o n B u l l . 6 8 : 200-9. B e n d e l l , J . F. 1959. Food a s a c o n t r o l o f a p o p u l a t i o n o f W h i t e - f o o t e d M i c e , P e r o m y s c u s l e u c o p u s n o y e b g r a c e n s i s . Can. J . Z o o l . 37: 173-209. B e n d e l l , J . F. and P. W. E l l i o t . B e h a v i o u r and t h e r e g u l a t i o n o f numbers i n t h e B l u e G r o u s e . Canad. W i l d l i f e Rep. S e r . 4: 1-76. B e n n e t t , M. A. 1939. The s o c i a l h i e r a r c h y i n R i n g Doves. E c o l o g y 20: 337 -57. B o i c e , R. and D. W. W i t t e r . 1969. H i e r a r c h i c a l f e e d i n g b e h a v i o u r i n t h e L e o p a r d F r o g , Rana p i p i e n s . Anim. Behav. 17: 474-79. B r i a n , A. D. 1949. Dominance i n t h e G r e a t T i t , P a r u s m ajor. S c o t . H a t . 61: 144-55. Brown, J . H. 1971. Mechanisms o f c o m p e t i t i v e e x c l u s i o n between two s p e c i e s o f chipmunks. E c o l o g y 52: 305-11. Brown, J . V L . 1963. A g g r e s s i v e n e s s , dominance and s o c i a l o r g a n i z a t i o n i n t h e S t e l l e r ' s J a y . C ondor 65: 460-84. Brown, J . L. 1969. T e r r i t o r i a l b e h a v i o u r and p o p u l a t i o n 107 r e g u l a t i o n i n b i r d s . W i l s o n B u l l . 8 1 : 293-329. B u e c h n e r , H. K. 1963. T e r r i t o r i a l i t y a s a b e h a v i o u r a l a d a p t a t i o n t o e n v i r o n m e n t i n Uganda Kob. P r o c . 16th I n t . C o n g r . Z o o l . 3: 59-60. B u s t a r d , H. R. 1969. The p o p u l a t i o n e c o l o g y o f t h e g e k k o n i d l i z a r d G e h y r a v a r j . e g a t a i n e x p l o i t e d f o r e s t s i n n o r t h e r n New S o u t h W a l e s 7 ~ J . Anim. E c o l . 38: 35-51. C a l h o u n , J . B. 1963. The e c o l o g y and s o c i o l o g y o f t h e Norway R a t . B e t h e s d a , M a r y l a n d . C a l h o u n , J . B. 1971. Space and t h e s t r a t e g y o f l i f e . IN: B e h a v i o u r and e n v i r o n m e n t : t h e use o f s p a c e by a n i m a l s and men. A. H. E s s e r (ed) Plenum P r e s s , New York -London: 329-87. C a r r i c k , R. 1963. E c o l o g i c a l s i g n i f i c a n c e o f t e r r i t o r y i n t h e A u s t r a l i a n Magpie, Gy_mnprhina t i b i c e n . P r o c . I n t . Orn. C o n g r . 13: 740-53. C a t c h p o l e , C. K. 1972. A c o m p a r a t i v e s t u d y o f t e r r i t o r y i n t h e Reed W a r b l e r , A c r g c e p h a l u s s c i r p a c e u s , and t h e Sedge W a r b l e r , A. s c h o e n g b a e n u s . J . Z o o l . L o n d . 166: 213-31. C h i t t y , D. 1967. The n a t u r a l s e l e c t i o n o f s e l f - r e g u l a t o r y b e h a v i o u r i n a n i m a l p o p u l a t i o n s . P r o c . v E c o l . S oc. A u s t , 2: 51-78. C l a r k e , T. A. 1970. T e r r i t o r i a l b e h a v i o r and p o p u l a t i o n d y n a m i c s o f a p o m a c e n t r i d f i s h , t h e G a r i b a l d i , Hypsypops r u b i c u n d a * E c o l . Monogr. 40: 182 -212. C o l q u h o u n , M. K. 1942. N o t e s on t h e s o c i a l b e h a v i o u r o f B l u e T i t s . B r i t . B i r d s 35: 234-40. C o n d e r , P. J . 1956. The t e r r i t o r y o f t h e Wheatear, Oenanthe g e n a n t h e . I b i s 98: 453-59. C o n n e l l , J . H. 1961. The i n f l u e n c e o f i n t e r s p e c i f i c c o m p e t i t i o n and o t h e r f a c t o r s on t h e d i s t r i b u t i o n o f t h e b a r n a c l e , C h t h a m a l u s s t e l l a t u s . E c o l o g y 42: 710-23. C o u l s o n , J . C. 1966. The i n f l u e n c e o f t h e p a i r - b o n d and age on t h e b r e e d i n g b i o l o g y o f t h e K i t t i w a k e , R i s s a t r i d a c t y l a . J . Anim. E c o l . 29: 251-71. C r o o k , J . H. 1965. The a d a p t i v e s i g n i f i c a n c e o f a v i a n s o c i a l o r g a n i z a t i o n s . Symp. Z o o l . S o c . Lond. 14: 181-218. 108 D a v i e s , P. W. and D. W. Snow. 1965. T e r r i t o r y and f o o d i n t h e Song T h r u s h . B r i t . B i r d s 58: 161-75. D e l i u s , J . D. 1965. A p o p u l a t i o n s t u d y o f S k y l a r k s , A l a u d a a r y e n s i s . I b i s 107: 466-92. D e l o n g , K. T. 1967. P o p u l a t i o n e c o l o g y o f f e r a l house mice. E c o l o g y 48: 61 1-34. Dhondt, A. A. 1966. A method t o e s t a b l i s h t h e b o u n d a r i e s o f b i r d t e r r i t o r i e s . Le Ger.fau.lt 56: 404-8. Dhondt, A. A. 1971a. Some f a c t o r s i n f l u e n c i n g t e r r i t o r y i n th e G r e a t T i t , P a r u s major. L e G e r f a u l t 61: 125-35. Dhondt, A. A. 1971b. The r e g u l a t i o n o f numbers i n B e l g i a n p o p u l a t i o n s o f G r e a t T i t s . I H : Dynamics o f p o p u l a t i o n s . P. J . den B o e r and G. R. G r a d w e l l (eds) Pudoc, Wageningen ; 532-44. Dhondt, A. A. and J . H u b l e . 1968. F l e d g i n g d a t e and sex i n r e l a t i o n t o d i s p e r s a l i n young G r e a t T i t s . B i r d S t u d y 15: 127-34. D i c k e r m a n , R. W. 1963. The Song S p a r r o w s o f t h e M e x i c a n P l a t e a u . O c c a s . P a p e r s Minn. Mus. Nat. H i s t . No. 11: 413 pp. D i n g l e , H. and R. I . C a l d w e l l . 1969. The a g g r e s s i v e and t e r r i t o r i a l b e h a v i o u r o f t h e M a n t i s S h r i m p , G o n o d a c t y l u s b r e d i n i ( M a n n i n g ) , ( C r u s t a c e a : S t o m a t o p a ) . Behav. 33: 115-36. D i x o n , K. L. 1956. T e r r i t o r i a l i t y and s u r v i v a l i n t h e P l a i n T i t m o u s e . Condor 58: 169-82. D i x o n , K. L. 1963. Some a s p e c t s o f s o c i a l o r g a n i z a t i o n i n th e C a r o l i n a C h i c k a d e e . P r o c . ' X I I I I n t e r n . O r n i t h . C o ngr. 240-58. E g g l i s h a w , H. J . 1967. The f o o d , g r o w th and p o p u l a t i o n s t r u c t u r e o f salmon and t r o u t i n two s t r e a m s i n t h e S c o t t i s h H i g h l a n d s . F r e s h w a t . Salm. F i s h . Res. 38: 1-32. Enemar, A. and B. S j o s t r a n d 1972. E f f e c t s o f t h e i n t r o d u c t i o n o f P i e d F l y c a t c h e r s , F i c e d u l a h y p p l e u c a on t h e c o m p o s i t i o n o f a p a s s e r i n e ' b i r d community. O r n i s S c a n . 3: 79-90. E r i c k s o n , M. M. 1938. T e r r i t o r y , a n n u a l c y c l e and numbers 109 i n a population of Wren-tits. Univ. C a l i f . Publ. Zool. 42: 247-333. Ewing, L. S. 1970. Hierarchy and i t s r e l a t i o n to t e r r i t o r y in the Cockroach, Nauphoeta cigerea. Behaviour 37: 152-73. Fordham, B. A. 1970. F i e l d populations of deermice with supplemental food. Ecology 52: 138-46. Fretwell, S. 1969. Dominance behavior and winter habitat d i s t r i b u t i o n i n juncos, Junco hyemalis. Bird Banding 40: 1-25. Fretwell, S. D and H. L. Lucas, Jr. 1969. On t e r r i t o r i a l behaviour and other factors influencing habitat d i s t r i b u t i o n i n birds. I. Theoretical development. Acta Biotheoret. 19: 16-36. Gartlan, J. S. 1968. Structure and function in primate society. F o l i a Primat. 8: 89-120. Gibb, J. 1956. T e r r i t o r y i n the genus Parus. Ibis 98: 420-29. Gibb, J. 1962. The importance of t e r r i t o r y and food supply in the natural control of a population of birds. S c i . Rev. 20: 20-1. Glas, P. 1960. Factors governing density i n the Chaffinch, F r i n g i l l a coelebs in d i f f e r e n t types of woods. Arch.~neerl.~ Zool. 13: 466-72. Guhl, a . M. 1953. The s o c i a l behaviour of the domestic fowl. Tech. B u l l . Kans. State C o l l . Agric. Exp. Sta. 73. Guhl, A. M. 1956. The s o c i a l order of chickens. Scient. Amer. 194 (2): 42-6 . Von Haartman, L. 1956. T e r r i t o r y in the" Pied Flycatcher, Muscicapa f i c e d u l a . Ibis 98: 460-75. Ha l l , K. R. L. and I. Devore. 1965. Baboon s o c i a l behaviour. IN: Primate Behaviour: F i e l d studies of monkeys and apes. I. Devore (ed) New York: 53-110. Harris, M. P. 1970. T e r r i t o r y l i m i t i n g the size of the breeding population of the Oystercatcher, Haematopus ostralegus - a removal experiment. J. Anim. Ecol. 39: 707-13. 110 H e a l e y , 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 d e e r m i c e . E c o l o g y 48: 377-92. H e n s l e y , M. M. and J . B. Cope. 1951. F u r t h e r d a t a on r e m o v a l and r e p o p u l a t i o n o f t h e b r e e d i n g b i r d s i n a s p r u c e - f i r f o r e s t community. Auk 68: 488-93. Holmes, R. T. 1970. D i f f e r e n c e s i n p o p u l a t i o n d e n s i t y , t e r r i t o r i a l i t y , and f o o d s u p p l y o f D u n l i n on a r c t i c and s u b a r c t i c t u n d r a . IN: A n i m a l p o p u l a t i o n s i n r e l a t i o n t o t h e i r f o o d r e s o u r c e s . A. Watson (ed) B l a c k w e l l , O x f o r d : 303-17 . I n g e r , R. F. and B. G r e e n b e r g . 1966. E c o l o g i c a l and c o m p e t i t i v e r e l a t i o n s among t h r e e s p e c i e s o f f r o g s (genus R a n a ) . E c o l o g y 47: 746-59. I t o , Y, 1970. Group and f a m i l y bonds i n a n i m a l s i n r e l a t i o n t o t h e i r h a b i t a t s . IN: Development and e v o l u t i o n o f b e h a v i o u r : e s s a y s i n memory o f T. C. S c h n e i r l a . L. R. A r o n s o n (ed) New Y o r k : 389-415. J a c o b s , M. E. 1955. S t u d i e s on t e r r i t o r i a l i s m and s e x u a l s e l e c t i o n i n d r a g o n f l i e s . E c o l o g y 36: 566-86. J e n k i n s , D., A. Watson and G. R. M i l l e r . 1963. P o p u l a t i o n s t u d i e s on Red G r o u s e , Lagojaus l . _ s c o t i c u s . j . Anim. E c o l . 32: 317-76. J o h n s t o n , R. F. 1956a. P o p u l a t i o n s t r u c t u r e i n s a l t marsh Song S p a r r o w s . P a r t I . E n v i r o n m e n t and a n n u a l c y c l e . Condor 56: 22-44. J o h n s t o n , R. F. 1956b. P o p u l a t i o n s t r u c t u r e i n s a l t marsh Song S p a r r o w s . P a r t I I . D e n s i t y , age s t r u c t u r e , and m a i n t e n a n c e . C o n dor 56: 254-72. * J o l l y , A. 1966. Lemur b e h a v i o u r : a M a d a g a s c a r F i e l d S t u d y . C h i c a g o and London: 187 pp. K e e n l e y s i d e , M. H. A. and F. T. Yamamoto. 1962. T e r r i t o r i a l b e h a v i o u r o f j u v e n i l e A t l a n t i c s almon, Salmo s a l a r . B e h a v i o u r 19: 139-69. ~ Kikkawa, J . 1961. S o c i a l b e h a v i o u r o f t h e W h i t e - e y e , Z o s t e r o p s l a t e r a l i s , i n w i n t e r . I b i s 103a: 428-42. K i n s e y , K. P. 1971. S o c i a l o r g a n i z a t i o n i n a l a b o r a t o r y c o l o n y o f Wood R a t s , Meotoma f u s c i p . e s . IN: B e h a v i o u r and e n v i r o n m e n t : t h e use o f s p a c e by a n i m a l s and men. A. H. E s s e r (ed) Plenum P r e s s , New York and L o ndon: 40 - 5 . 111 Klomp, H. 1972. R e g u l a t i o n o f t h e s i z e o f b i r d p o p u l a t i o n s by means o f t e r r i t o r i a l b e h a v i o u r . Neth. J . Z o o l . 22: 456-88. K l u y v e r , H. N. and L. T i n b e r g e n . 1953. T e r r i t o r y and t h e r e g u l a t i o n o f d e n s i t y i n t i t m i c e . A r c h . N e e r l . Z o o l . 10: 265-86. K r e b s , C. J . 1966. Demographic c h a n g e s i n f u c t u a t i n g p o p u l a t i o n s o f M i c r o t u s c a l i f o r n i c u s . E c o l . Honogr. 36: 239-73. K r e b s , C. J . and K. T. D e l o n g . 1965. A M i c r o t u s p o p u l a t i o n w i t h s u p p l e m e n t a l f o o d . J . Hammal. 46: 566-73. K r e b s , J . B. 1971. T e r r i t o r y and b r e e d i n g d e n s i t y i n t h e G r e a t T i t , P a r u s m ajor. E c o l o g y 52: 2-22. K r e b s , K. A. 1973. An e t h o l o g i c a l s t u d y o f dominance b e h a v i o u r i n young c h i l d r e n . D. P h i l . T h e s i s , O x f o r d U n i v . K r u i j t , J , P. and J . A. Hogan. 1967. S o c i a l b e h a v i o u r on t h e l e k i n t h e B l a c k g r o u s e , L;yurus t e t r i x t e t r i x . A r d e a 55: 203-40. L a c k , D. 1943. The l i f e o f t h e R o b i n . London. L a c k , D. 1954. The n a t u r a l r e g u l a t i o n o f a n i m a l numbers. C l a r e n d o n P r e s s , O x f o r d . L a c k , D. 1966. P o p u l a t i o n s t u d i e s o f b i r d s . C l a r e n d o n P r e s s , O x f o r d . L e v i c k , J . and R. G. B e i l h a r z . 1973. S o c i a l dominance and r e p r o d u c t i v e p e r f o r m a n c e ( i n l a b o r a t o r y m ice. Z. T i e r p s y c h o l . 32: 147-52. L i n , N. 1963. T e r r i t o r i a l b e h a v i o u r i n t h e c i c a d a k i l l e r wasp, S p h e c i u s s p e c i o s u s ( H y m e n o p t e r a : S p h e c i d a e ) . P t . 1. B e h a v i o u r ~ 2 0 : 115-33. L o c k i e , J . D. 1956. W i n t e r f i g h t i n g i n f e e d i n g f l o c k s o f Rooks, Jackdaws , and C a r r i o n Crows. B i r d S t u d y 3: 180-90. L o c k i e , J . D. 1966. T e r r i t o r y i n s m a l l c a r n i v o r e s . Symp. Z o o l . S o c . Lond. 18: 143-65. L o r e n z , K. Z. 1952. K i n g Solomon's R i n g . London. 112 M c B r i d e , A. F. and D. 0. Hebb, 1948. B e h a v i o u r o f t h e c a p t i v e B o t t l e - n o s e d D o l p h i n , T u r s i o p s t r u n c a t u s . J . Comp. P h y s i o l . P s y c h o l . 41: 11T-2 3. ~ ~ Magnuson, J . J . 1962. An a n a l y s i s o f a g g r e s s i v e b e h a v i o u r , g r o w t h , and c o m p e t i t i o n f o r f o o d and s p a c e i n medaka, O r y z i a s l a t i p . e s ( P i s c e s : C y p r i n o d o n t i d a e ) . Can. J . Z o o l . ~407 3"l3-63. M a r s h a l l , J . T. 1948a. E c o l o g i c a l r a c e s o f Song S p a r r o w s i n t h e San F r a n c i s c o Bay r e g i o n . P a r t I . H a b i t a t and abundance. Condor 50: 193-215. M a r s h a l l , J . T. 1948b. E c o l o g i c a l r a c e s o f Song S p a r r o w s i n t h e San F r a n c i s c o Bay r e g i o n . P a r t I I . G e o g r a p h i c v a r i a t i o n . Condor 50: 233-56. Mason, J . C. and D. W. Chapman. 1965. S i g n i f i c a n c e o f e a r l y emergence, e n v i r o n m e n t a l r e a r i n g c a p a c i t y , and b e h a v i o u r a l e c o l o g y o f j u v e n i l e coho salmon i n s t r e a m c h a n n e l s . J . F i s h . Res. Bd. Can. 22: 173-90. Masure, R. H. and w. C. A l l e e . 1934a. The s o c i a l o r d e r i n f l o c k s o f t h e common c h i c k e n and t h e p i g e o n . Auk 51: 306-27. Masure, R. H. and W. C. A l l e e . 1934b. F l o c k o r g a n i z a t i o n o f t h e S h e l l P a r a k e e t , M e l o p s i t t a c u s u n d u l a t u s . E c o l o g y 15: 388-98. M i c h i e l s o n , A. 1966. I n t r a s p e c i f i c and i n t e r s p e c i f i c c o m p e t i t i o n i n t h e shrews S o r e x a r a n e u s and S. m i n u t u s . A r c h . N e e r l . Z o o l . 17: 73-1947 M i l l e r , G. R., D. J e n k i n s and A. Watson. 1966. H e a t h e r p e r f o r m a n c e and Red G r o u s e p o p u l a t i o n s . I V i s u a l e s t i m a t e s o f h e a t h e r p e r f o r m a n c e . J . A p p l . E c o l . 3: 313-26. Moore, N. W. 1964. I n t r a - and i n t e r s p e c i f i c c o m p e t i t i o n among d r a g o n f l i e s . J . Anim. E c o l . 33: 49-71. Moss, R. 1969. A c o m p a r i s o n o f Red Grouse s t o c k s w i t h t h e p r o d u c t i o n and n u t r i t i v e v a l u e o f t h e h e a t h e r C a l l u n a v u l g a r i s . J . Anim. E c o l . 38: 103 -22. Mur t o n , R. K., A. J . I s a a c s o n and N. J . Westwood. 1966. The r e l a t i o n s h i p s between Wood P i g e o n s and t h e i r c l o v e r f o o d s u p p l y and t h e mechanism o f p o p u l a t i o n c o n t r o l . J . A p p l . E c o l . 3: 55-96." Myres, J . H. and C. J . K r e b s . 1971. G e n e t i c , b e h a v i o r a l 113 and r e p r o d u c t i v e a t t r i b u t e s o f d i s p e r s i n g F i e l d V o l e s M i c r o t u s p e n n s v j . a n i c u s and fl. p c h r o _ g a s t e r . E c o l . Monogr. 41: 53-787 N e t t l e s h i p , D. N. 1973. B r e e d i n g e c o l o g y o f T u r n s t o n e s , A r e n a r i a i n t e r p r e s , a t Hazen Camp, E l l e s m e r e I s l a n d . I b i s Tl5: 202-7. Newsome, A. E. 1970. An e x p e r i m e n t a l a t t e m p t t o p r o d u c e a mouse p l a g u e . J . Anim. E c o l . 39: 299-311. N i c e , M. M. 1937. S t u d i e s i n t h e l i f e h i s t o r y o f t h e Song Sparrow. P a r t I . T r a n s . L i n n . S o c . N, Y. IV. 247pp. N i c e , M. M. 1941. The r o l e o f t e r r i t o r y i n b i r d l i f e . Amer. M i d i . Nat. 26: 441-87. N i c e , , M. M. 1943. S t u d i e s i n t h e l i f e h i s t o r y o f t h e Song Sparrow. P a r t I I . T r a n s . L i n n . S o c. N. Y. V I . 329pp. N o b l e , G. K., M. Worm and A. S c h m i d t . 1938. S o c i a l b e h a v i o u r o f t h e B l a c k - c r o w n e d N i g h t - H e r o n . Auk 55: 7-40. Odum, E. P. 1942. A n n u a l c y c l e o f t h e B l a c k - c a p p e d C h i c k a d e e . P t . 3. Auk 59: 499-531. O r i a n s , G. H. 1961. The e c o l o g y o f b l a c k b i r d ( A g e l a i u s ) s o c i a l s y s t e m s . E c o l . Monogr. 31: 285-312. Peek, F. W. 1971. S e a s o n a l c hange i n t h e b r e e d i n g b e h a v i o u r o f t h e male Red-winged B l a c k b i r d . W i l s o n B u l l . 83: 383-95. P e r r i n s , C. M. 1965. P o p u l a t i o n f l u c t u a t i o n s and c l u t c h - s i z e i n t h e G r e a t T i t , P a r u s m a j o r . J . Anim. E c o l . 34: 601-47. P h i l l i p s , A. R. and R. W. D i c k e r m a n . 1957. N o t e s on Song S p a r r o w s o f t h e M e x i c a n P l a t e a u . Auk 74: 376-82. P h i l l i p s , R. R. 1971. The r e l a t i o n s h i p between s o c i a l b e h a v i o u r and t h e use o f s p a c e i n t h e B e n t h i c f i s h Chasmodes b o s a u i a n u s L a c e p e d e . Z. T i e r p s y c h o l . 29: 3 8 9 - 4 0 8 ™ P i t e l k a , F. A., P. Q. T o m i c h and G. W. T r e i c h e l . 1955. E c o l o g i c a l r e l a t i o n s o f j a e g e r s and owls as lemming p r e d a t o r s n e a r Barrow, A l a s k a . E c o l , Monogr . 25: 85-117. 1 14 R a l p h , C. J . and C. A. P e a r s o n . 1971. C o r r e l a t i o n o f age, s i z e o f t e r r i t o r y , plumage and b r e e d i n g s u c c e s s i n W h i t e - c r o w n e d S p a r r o w s . Condor 73: 77-80. R i c h d a l e , L. E. 1957. A p o p u l a t i o n s t u d y o f p e n g u i n s . O x f o r d . Rowan, M. K. 1966. T e r r i t o r y as a d e n s i t y - r e g u l a t i n g mechanism i n some S o u t h A f r i c a n b i r d s . O s t r i c h S u p p l . 6: 397-408. S a b i n e , W. S. 1959. The w i n t e r s o c i e t y o f t h e O r e g o n J u n c o : i n t o l e r a n c e , dominance and t h e p e c k i n g o r d e r . Condor 61: 110-35. Sade, D. S. 1967. D e t e r m i n a n t s o f dominance i n a g r o u p o f f r e e - r a n g i n g r h e s u s monkeys. IN: S o c i a l c o m m u n i c a t i o n s among p r i m a t e s . S. A. Altmann (ed) C h i c a g o . S a l e , P. F. 1972. I n f l u e n c e o f c o r a l s i n t h e d i s p e r s i o n o f t h e p o m a c e n t r i d f i s h , D a s c y j L l u s a r u a n u s . E c o l o g y 53: 741-44. S c h j e l d e r u p - E b b e , T. 1922. B e i t r a g e z u r S o c i a l p s y c h o l o g i e d e s Haushuhns . Z. P s y c h o l . 88: 226-52. S c h o e n e r , T. W. 1968. S i z e s o f f e e d i n g t e r r i t o r i e s among b i r d s . E c o l o g y 49 : 123-41. S h e p p a r d , D. H. 1971. C o m p e t i t i o n between two chipmunk s p e c i e s ( E u t a m i a s ) . E c o l o g y 52: 320-29. Shoemaker, H. H. 1939. S o c i a l h i e r a r c h y i n f l o c k s o f t h e c a n a r y . Auk 56: 381-406. Simms, E. 1965. E f f e c t s o f t h e c o l d weather o f 1962-63 on t h e B l a c k b i r d p o p u l a t i o n o f D o l l i s H i l l , L ondon. B r i t . B i r d s 58: 33-43. S m i t h , C. C. 1968. The a d a p t i v e n a t u r e o f s o c i a l o r g a n i z a t i o n i n t h e genus o f t r e e s q u i r r e l s T a m i a s c i u r u s . E c o l monogr. 38: 31-63. S m i t h , R. F. J . 1970. E f f e c t s o f f o o d a v a i l a b i l i t y on a g g r e s s i o n and n e s t b u i l d i n g i n Brook S t i c k l e b a c k , C u l a e a i n c o n s t a n s . J . F i s h . Res. Bd. Can. 27: 2350-55. S m i t h , S. M. 1967. S e a s o n a l c h a n g e s i n t h e s u r v i v a l o f t h e B l a c k - c a p p e d C h i c k a d e e . Condor 69: 344-59. Smyth, M. 1968. The e f f e c t s o f r e m o v a l o f i n d i v i d u a l s f r o m a 115 p o p u l a t i o n o f Bank V o l e s , C l e t h r i o n y m u s g l a r e o l u s . J . Anim. E c o l . 37: 167-83. Snow, D. W. 1958. A s t u d y o f b l a c k b i r d s . London. S n y d e r , W. D. 1967. E x p e r i m e n t a l h a b i t a t improvement f o r s c a l e d q u a i l . T e c h . P u b l . C o l o . Game F i s h Pks. Dep. 19. Sommer, R. 1967. S m a l l g r o u p e c o l o g y . P s y c h c l . B u l l . 67: 145-52. S t e f a n s k i , R. A. 1967. U t i l i z a t i o n o f t h e b r e e d i n g t e r r i t o r y i n t h e B l a c k - c a p p e d C h i c k a d e e . C o n d o r 69: 259-67. S t e n g e r , J . 1958. Food h a b i t s and a v a i l a b l e f o o d o f O v e n b i r d s i n r e l a t i o n t o t e r r i t o r y s i z e . Auk 75: 335-46. S t e w a r t , R. E. and J . W. A l d r i c h . 1951. Removal and r e p o p u l a t i o n o f b r e e d i n g b i r d s i n a s p r u c e - f i r f o r e s t community. Auk 68: 471-82. S u t h e r s , R. A. 1960. Measurement o f some l a k e s h o r e t e r r i t o r i e s o f t h e Song Sparrow. W i l s o n B u l l . 72: 232-37. Symons, P. E. K. 1968. I n c r e a s e i n a g g r e s s i o n and i n s t r e n g t h o f t h e s o c i a l h i e r a r c h y among j u v e n i l e A t l a n t i c s a l m o n d e p r i v e d o f f o o d . J . F i s h . Res. Bd, Can. 25: 2387-401. Symons, P. E. K. 1971. B e h a v i o r a l a d j u s t m e n t o f p o p u l a t i o n d e n s i t y t o a v a i l a b l e f o o d by j u v e n i l e A t l a n t i c s a l m o n . J . F i s h . Res. Bd. Can. 28: 569-87. ° T e s t e r , J . R. and A. Watson. 1973. S p a c i n g and t e r r i t o r i a l i t y o f Woodcock, S c o l o p a x r u s t i c o l a b a s e d on r o d i n g b e h a v i o u r . I b i s 115: 135-7. Tompa, F. S. 1962. T e r r i t o r i a l b e h a v i o u r : t h e main c o n t r o l l i n g f a c t o r o f a l o c a l p o p u l a t i o n o f Song S p a r r o w s . Auk 79: 687-97. Tompa, F. S. 1964. F a c t o r s d e t e r m i n i n g t h e numbers o f Song S p a r r o w s , M e l o s p i z a m e l o d i a , on M a n d a r t e I s l a n d , B. C , Canada. A c t a Z o o l . Fenn. 109: 1-73. Tompa, F. S. 1971. C a t a s t r o p h i c m o r t a l i t y and i t s p o p u l a t i o n c o n s e q u e n c e s . Auk 88: 753-59. Tompkins, G. 1933. I n d i v i d u a l i t y and t e r r i t o r i a l i t y as 116 d i s p l a y e d by t h r e e p a s s e r i n e s p e c i e s . C o n d o r 35: 98-106, T o r d o f f , H. B, 1954. S o c i a l o r g a n i z a t i o n and b e h a v i o u r i n a f l o c k o f c a p t i v e , n o n - b r e e d i n g Red C r o s s b i l l s . Condor 56: 346-58. T y l e r , S. J . 1972. The b e h a v i o u r and s o c i a l o r g a n i z a t i o n o f t h e New F o r e s t P o n i e s . Anim. Behav. Monogr. 5: 187-94. Watson, A. 1964. A g g r e s s i o n and p o p u l a t i o n r e g u l a t i o n i n Red G r o u s e . N a t u r e 202: 506-7. Watson, A. 1965. A p o p u l a t i o n s t u d y o f P t a r m i g a n , Laggpus mutus , i n S c o t l a n d . J . Anim. E c o l . 34: 135-72. Watson, A. 1967. T e r r i t o r y and p o p u l a t i o n r e g u l a t i o n i n t h e Red G r o u s e . N a t u r e 215: 1274-75. Watson, A. and D. J e n k i n s . 1968. E x p e r i m e n t s on p o p u l a t i o n c o n t r o l by t e r r i t o r i a l b e h a v i o u r i n t h e Red G r o u s e . J . Anim. E c o l . 3: 595-614. Watson, A. and G. R. M i l l e r . 1971. T e r r i t o r y s i z e and a g g r e s s i o n i n a f l u c t u a t i n g Red G r o u s e p o p u l a t i o n . J . Anim. E c o l . 40: 367-83. Watson, A. and R. Moss. 1970a. Dominance, s p a c i n g b e h a v i o u r and a g g r e s s i o n i n r e l a t i o n t o p o p u l a t i o n l i m i t a t i o n s i n v e r t e b r a t e s . IN: A n i m a l p o p u l a t i o n s i n r e l a t i o n t o t h e i r f o o d r e s o u r c e s . A. Watson (ed) B l a c k w e l l , O x f o r d : 167-218. Watson, A. and R. Moss. 1970b. S p a c i n g a s a f f e c t e d by t e r r i t o r i a l b e h a v i o u r , h a b i t a t , and n u t r i t i o n i n Red G r o u s e . IN: B e h a v i o u r and e n v i r o n m e n t : t h e use o f s p a c e by a n i m a l s and men. A. H. E s s e r (ed) Plenum P r e s s , New Y o r k - London. Watts, C. R. and A. W. S t o k e s . 1971, The s o c i a l o r d e r o f T u r k e y s . S c i e n t . Amer. 224 ( 6 ) : 112-8. Weeden, J . S. 1965. T e r r i t o r i a l b e h a v i o u r o f t h e T r e e S p a r row. Condor 67: 193-209. W e s s e l l , J . P. and H. L e i g h . 1941. S t u d i e s o f t h e f l o c k o r g a n i z a t i o n o f t h e W h i t e - t h r o a t e d S p a rrow. W i l s o n B u l l . 53: 222-30. Wood-Gush, D. G. M. 1965. The s o c i a l o r g a n i z a t i o n o f d o m e s t i c b i r d c o m m u n i t i e s . Symp. Z o o l . S o c. Lond. 14: 219-31. 1 17 W i l e y , R. H. J r . 1970. T e r r i t o r i a l i t y and non-random m a t i n g i n t h e Sage G r o n s e , C e n t r o c e r c u s u r o p h a s i a n u s . O n p u b l . Ph. D. T h e s i s , The R o c k e f e l l e r U n i v e r s i t y , New Y o r k . Wynne-Edwards, V. C. 1962. A n i m a l d i s p e r s i o n i n r e l a t i o n t o s o c i a l b e h a v i o u r . O l i v e r and Boyd. E d i n b u r g h . Young, C. W. 1970. T e r r i t o r i a l i t y i n t h e Common S h e l d u c k T a d o r n a t a d o r n a . I b i s 112: 330-5. Young, E. C. 1972. T e r r i t o r y e s t a b l i s h m e n t and s t a b i l i t y i n M c c o r m i c k ' s Skua. I b i s 114: 234-44. Z a r e t , T. M. and A. , S. Rand. 1971. C o m p e t i t i o n i n t r o p i c a l s t r e a m f i s h e s : s u p p o r t f o r t h e c o m p e t i t i v e e x c l u s i o n t h e o r y . E c o l o g y 52: 336-42. Zimmerman, J . L. 1971. The t e r r i t o r y and i t s d e n s i t y d e p e n d a n t e f f e c t i n S p i z a a m e r i c a n a . Auk 88: 590-612. 118 APPENDIX 1. L i s t o f s p e c i e s o f most common and most i m p o r t a n t p l a n t s a l o n g t h e hedgerows and a d j o i n i n g marsh. The hedgerow was c o m p r i s e d o f a t h i c k , f r e q u e n t l y i m p e n e t r a b l e t a n g l e o f s m a l l t r e e s and s h r u b s , w i t h t h e o c c a s i o n a l s t a n d o f mature t r e e s . The main s p e c i e s o f s m a l l t r e e s were AInus r u b r a , S a l i x h o o k e r i a n a , Sambucus r a c e m g s a , C r a t a e g u s d o u g l a s i i , and P r u n u s s p p . S h r u b s c o n s i s t e d m a i n l y o f C o r n u s s t o l o n i f e r a , Rubus s p e c t a b i l i s , R.. l a c i n i a t u s , J * i m a c r o p h y l l u s , Rosa s p p . , S y m p h o r i c a r p o s a l b u s , and L o n i c e r a s p p . F i n a l l y , t h e s t a n d s o f mature t r e e s were p r i n c i p a l l y P o p u l u s t r e m u l o i d e s , P.. t r i c h o c a r p a , A I n us r u b r a , and P s e u d o t s u g a m e n z i e s i i . A c o m p l e t e and d e t a i l e d v e g e t a t i o n a l s u r v e y o f t h e h e r b a c e o u s p l a n t s was n o t a t t e m p t e d . The most common and i m p o r t a n t o n e s , however; a r e l i s t e d h e r e : H e r a c l g u m l a n a t u m , V i c i a s p p . , C i r s i u m l a n c e o l a t u m , U r t i c a l y a l i i , P e t a s i t g s s p e c i o s a , A n a p h o l i s m a r g a r i t a c e a , E g u i s e t u m a r y e n s e , P t e r i d i u r a a g u i l i n u m , and s e v e r a l s p e c i e s o f g r a s s i n c l e a r e d a r e a s . The marsh a d j a c e n t t o t h e hedgerow was c o m p r i s e d m a i n l y o f : S a l i x s p p . , H y r i c a g a l e , T y p h a 1 a t i f o l i a , S c i r p u s S E ® r i c a n u s , C a r e x l y n g b y e i , I ^ y s i c h i t o n ka rots h a t c e n s e . 119 APPENDIX 2 Weather data from the Meteorological Office, Vancouver International Airport Mean monthly temperatures Jan. Feb. Mar. Apr. May June July Aug.- Sep. Oct. Nov. Dec. 1972: — 39.0 44.6 44.6 54.7 58.3 62.3 64.0 54.3 46.1 43.0 35.2 1973: 36.0 40.5 43.2 47.4 53.7 Normal (37 y r ) : 36.3 40.0 42.5 48.1 54.3 59.5 63.4 62.7 57.6 50.1 42.9 38.9 Monthly temperature : ranges Jan. Feb. Mar. Apr. May June July ft Aug. Sep.- Oct. Nov. Dec. 1972 Max. — 56.0 62.0 60.9 75.0 73.4 81.4 80.7 77.9 62.1 56.6 51.8 Min. ~ 17.4 30.0 30.8 41.1 45.9 47.9 48.0 35.0 30.2 25.4 12.0 1973 Max. 52.9 58.1 53.2 60.6 76.6 Min. 13.1 24.3 28.1 33.9 36.8 Precipitation - Jan. Feb. Mar. Apr. May_ June July Aug. Sep. Oct. Nov. Dec. R a i n f a l l : 1972: — 5.25 6.98 45.1 1.17 1.84 3.20 0.92 3.14 2.09 4.61 11.34 1973: 5.43 2.69 2.69 0.51 1.91 Normal: A.95 4.29 3.51 2.39 1.87 1.78 1.17 1.46 2.41 4.81 5.47 5.96 Snowfall: 1972: — 0.3 0.4 1.9 TR 6.4 1973: 4.7 TR 0.1 TR Normal: 8.8 3.1 2.1 TR 0.9 5.7 Totals: 1972: — 5.28 7.05 4.70 1.27 1.84 3.20 0.92 3.14 2.09 4.61 11.82 1973: 5.92 2.69 2.70 0.51 1.91 Normal: 5.80 4.57 3.69 2.40 1.87 1.78 1.17 1.46 2.41 4.81 5.56 6.51 120 APPENDIX 3 D e s t r u c t i o n o f a s t r e t c h o f dyke ( , B u l l d o z e d A r e a ' ) . I n J u n e , 1972, 800 f e e t o f dyked hedgerow on t h e F a l l R emoval A r e a was r e b u i l t . T h i s e n t a i l e d t h e t o t a l d e t r u c t i o n o f t h e v e g e t a t i o n , and r e p l a c i n g i t w i t h g r a v e l and r o c k . T h i s s t r e t c h o f hedgerow s u p p o r t e d a number o f Song S p a r r o w s ; F i g u r e 10 g i v e s t h e t e r r i t o r y b o u n d a r i e s t h a t e x i s t e d b e f o r e t h e b u l l d o z i n g s t a r t e d . 3 m a l e s and 1 f e m a l e were known a l o n g t h i s s t r e t c h . A l l 4 b i r d s d i s a p p e a r e d i n l a t e J u n e . However, no l e s s t h a n 3 o f t h e s e 4 were r e l o c a t e d . One male ( B l a c k / O r a n g e ) must have s p e n t t h e summer a s a c r y p t i c n o n - t e r r i t o r i a l b i r d a l o n g t h e hedgerow c l o s e t o t h e B u l l d o z e d A r e a , as he t o o k o v e r a t e r r i t o r y a d j a c e n t t o t h e B u l l d o z e d A r e a when t h e r e s i d e n t male was removed on O c t o b e r 3/1972 d u r i n g t h e f a l l r e m o v a l e x p e r i m e n t s . A s e c o n d male (Green/Green) was l o c a t e d i n e a r l y March 1973 a s a s t r o n g l y t e r r i t o r i a l b i r d i n a s t r e t c h o f s h r u b b e r y a b o u t 2000 m e t r e s t o t h e s o u t h on Westham I s l a n d . The t h i r d b i r d , t h e f e m a l e (LP/White) , p a i r e d w i t h a C o n t r o l male a b o u t 300 m e t r e s from h e r d e s t r o y e d t e r r i t o r y , a p p a r e n t l y a f t e r t h i s m ale's f e m a l e d i s a p p e a r e d i n e a r l y s p r i n g . Figure 10 Bulldozed Area: before the dyke the arrangement of t e r r i t o r y boundaries r e b u i l d i n g occurred 122 T h e s e d a t a s u g g e s t t h a t a d u l t s c an s u r v i v e as n o n - b r e e d i n g , n o n - t e r r i t o r i a l b i r d s t h r o u g h t h e summer, i n s p i t e o f t h e f a c t t h a t t h e s u r p l u s o f b i r d s on t h e s t u d y a r e a seemed t o be composed o n l y o f j u v e n i l e s . \ 7 123~ APPENDIX 4 P o s s i b l e r e a s o n s why f e m a l e s were d i f f i c u l t t o l o c a t e i n t h e f a l l o f 1972. Some p o s s i b l e r e a s o n s why f e m a l e s were d i f f i c u l t t o l o c a t e i n t h e f a l l o f 1972 a r e g i v e n h e r e . 1. I t i s p o s s i b l e t h a t n o t a l l f e m a l e s were o u t o f moult by e a r l y O c t o b e r , when t h e r e m o v a l s t o o k p l a c e . M o u l t i n g i n d i v i d u a l s a r e e x t r e m e l y d i f f i c u l t t o f i n d . N i c e (1937) f o u n d t h a t t h e Song S p a r r o w s i n O h i o m o u l t e d i n A u g u s t and S e p t e m b e r , w i t h t h e o c c a s i o n a l b i r d n o t f i n i s h i n g u n t i l m i d - O c t o b e r . C a s u a l o b s e r v a t i o n s o f m o u l t i n g b i r d s on B e i f e l I s l a n d were made i n 1972, and September seemed t o be t h e month i n w h i c h m o u l t i n g most o c c u r r e d . However, one male removed on O c t o b e r 4 f r o m t h e S i m u l t a n e o u s Removal a r e a was s t i l l i n p a r t i a l m o u l t . 2. F e m a l e s a r e g e n e r a l l y more d i f f i c u l t t o l o c a t e t h a n m a l e s , and a p p a r e n t l y a r e l e s s r e s p o n s i v e i n t h e f a l l t h a n i n t h e s p r i n g ( N i c e 1943; Tompa 1964). 3. F e m a l e s d e s e r t t h e i r mates most o f t e n i n t h e l a t e summer and e a r l y f a l l . N i c e (1943) showed t h a t i n o n l y 31% o u t o f 55 p o s s i b l e i n s t a n c e s d i d f e m a l e s r e t u r n t o t h e i r f o r m e r t e r r i t o r i e s . 3056 went t o a d j a c e n t t e r r i t o r i e s , and 33^ t o t e r r i t o r i e s 100-700 m e t r e s d i s t a n t . T h u s , i t seems q u i t e l i k e l y t h a t s e v e r a l o f t h e t e r r i t o r i a l m a l e s d i d n o t have f e m a l e s i n t h e f a l l o f 1972. 124 APPENDIX 5 I n t e r s p e c i f i c i n t e r a c t i o n s between t s o n g S p a r r o w s and o t h e r s e e d - e a t i n g p a s s e r i n e s a t t h e f e e d i n g s t a t i o n s . Song S p a r r o w s i n t e r a c t e d w i t h most o f t h e o t h e r s p e c i e s o f b i r d s t h a t f e d a t t h e f e e d i n g s t a t i o n s . T h e r e were t h r e e common s p e c i e s , Oregon J u n c o , Fox S p a r r o w , and Towhee, t h a t f r e q u e n t e d t h e s t a t i o n s , o f which t h e j u n c o was by f a r t h e most abundant.. O c c a s i o n a l l y , o t h e r s e e d - e a t e r s s u c h as House F i n c h , Carjgodacus m e x i c a n u s , and L i n c o l n ' s S p a r r o w , H e l g s p i z a l i n c o l n i i , o c c u r r e d a t t h e s t a t i o n s . From o b s e r v a t i o n s , a v e r y g e n e r a l l i s t i n o r d e r o f i n e t r s p e c i f i c d o minance c o u l d be c o m p i l e d t h u s : Towhee Fox Sparrow Song Sparrow L i n c o l n ' s Sparrow House F i n c h O regon J u n c o however, c e r t a i n Song S p a r r o w s would t h r e a t e n b o t h Towhees and Fox S p a r r o w s . On o c c a s i o n , a Song Sparrow would d r i v e o f f a Fox S p a r r o w , b u t t h i s was r a r e , and u s u a l l y Fox S p a r r o w s t o o k p r e c e d e n c e o v e r Song S p a r r o w s . Towhees t e n d e d t o r e m a i n i n d i f f e r e n t t o t h e t h r e a t e n i n g b e h a v i o u r o f t h e Song S p a r r o w , and would f e e d and l e a v e i n d e p e n d e n t l y o f s u c h b e h a v i o u r . J u n c o s were r e a d i l y d r i v e n o f f by a l l t h e o t h e r 125 / s e e d - e a t e r s , b u t o f t e n s h e e r numbers a l l o w e d them t o f e e d r e l a t i v e l y c l o s e t o p o t e n t i a l a n t a g o n i s t s w i t h o u t i n d u c i n g r e t a l i a t i o n . 126. APPENDIX 6 Age and p o s i t i o n i n h i e r a r c h y : t h e t o p two b i r d s i n t h e B-C H i e r a r c h y The age o f t h e t o p two j u v e n i l e m ales i n t h e B-C H i e r a r c h y a r e known. The f i r s t d o m i n a n t j u v e n i l e ( B l u e / B l u e ) was banded on J u l y 25, w i t h no s i g n s o f p o s t - j u v e n i l e m o u l t , and i t had p r o b a b l y j u s t g a i n e d i n d e p e n d e n c e f r o m i t s p a r e n t s (s e e N i c e 1 9 ^ 3 ) . I t s . a g e on J u l y 25 was p u t t e n t a t i v e l y a t 35-40 d a y s . The s e c o n d male on t h e dominance s c a l e ( Y e l l o w / L P ) was banded on May 25, a t t h e f l u t t e r i n g s t a g e o f d e v e l o p m e n t ( S t a g e 4 o f N i c e 1943).. T h e r e f o r e i t was between 10 and 16 d a y s o l d . T h u s , i n J a n u a r y , when t h e p o s i t i o n s o f t h e s e two b i r d s were d e t e r m i n e d , B l u e / B l u e would be a b o u t 200 d a y s o l d , and Y e l l o w / L P would be a b o u t 260 d a y s o l d . B l u e / B l u e would be a p r o d u c t o f most l i k e l y a s e c o n d b r o o d , and Y e l l o w / LP a p r o d u c t o f a f i r s t b r o o d . Y e t , B l u e / B l u e was t h e t o p j u v e n i l e o f t h e l a r g e s t h i e r a r c h y . 127 APPENDIX 7. P r e s s u r e f r o m i n t r u d e r s : E x p l a n a t i o n . I f e a c h p o t e n t i a l s e t t l e r makes x i n t r u s i a n s p e r day on t o a r e s i d e n t ' s t e r r i t o r y , t h e t o t a l number o f i n t r u s i o n s = Nx (N = n o s . o f p o t e n t i a l s e t t l e r s ) . The v a l u e o f Nx i s p r o p o r t i o n a l t o t h e t i m e t h e r e s i d e n t s p e n d s i n d e f e n c e ( T ) . T i s a l s o p r o p o r t i o n a l t o t e r r i t o r y a r e a , s o i n o r d e r t o keep T c o n s t a n t , ,when Nx goe s up, t e r r i t o r y s i z e g o e s down - t h e a s s u m p t i o n b e i n g t h a t t h e b i r d d o e s n o t have much s p a r e t i m e t o i n c r e a s e T. 128 APPENDIX 8 The f i v e c o n d i t i o n s o f Watson and Moss. Watson and Moss (1970a) put f o r w a r d t h e f o l l o w i n g f i v e c o n d i t i o n s w h i c h need t o be met t o show t h a t b e h a v i o u r l i m i t s a b r e e d i n g p o p u l a t i o n . A. A s u b s t a n t i a l p a r t o f t h e p o p u l a t i o n d o e s n o t b r e e d , e i t h e r b e c a u s e a n i m a l s d i e ; o r b e c a u s e t h e y a r e i n h i b i t e d f r o m b r e e d i n g e v e n t h o u g h t h e y s u r v i v e , and may b r e e d i n l a t e r y e a r s . B. Such n o n - b r e e d e r s a r e p h y s i o l o g i c a l l y c a p a b l e o f b r e e d i n g i f t h e more d o m i n a n t o r t e r r i t o r i a l ( i . e. b r e e d i n g ) a n i m a l s a r e removed. C The b r e e d i n g a n i m a l s a r e n o t c o m p l e t e l y u s i n g up some r e s o u r c e , s u c h a s f o o d , s p a c e , o r n e s t s i t e s . I f t h e y a r e , t h e r e s o u r c e i t s e l f i s l i m i t i n g . D. The m o r t a l i t y o r d e p r e s s e d r e c r u i t m e n t due t o t h e l i m i t i n g f a c t o r ( s ) c h a n g e s i n an o p p o s i t e s e n s e t o , and a t t h e same r a t e a s , o t h e r c a u s e s o f m o r t a l i t y o r d e p r e s s e d r e c r u i t m e n t . E. I f (A) , (B) , (C) , and (D) a r e f u l f i l l e d , and t h e numbers c h a n g e f o l l o w i n g c h a n g e s i n f o o d , t h e n f o o d and b e h a v i o u r a r e b o t h l i m i t i n g t h e b r e e d i n g p o p u l a t i o n . 129 C O T T O N W O O D S T R E T C H L O S E R \ 6 LP \ L P LP 2 jjBUnt) 6" R Y Y © o" G G d* LP RW d1 w © 2 Black © - 11 9 G ® ? LP L -D ? B 0 0 B 2 BO B G LP LP LP \ 14 « 1 9 3 2 5 3 5 1 M LpUnb \ 5 2 5 7 10 1 3 4 5 R Y \ 2 2 1 4 3 2 1 4 Y © 1 2 3 1 1 1 G G 1 2 11 1 1 2 2 LP RW 11 7 1 1 w © 5 2 1 2 Black <D \ 2 1 RW RW 1 G ® 1 LP L-D 1 BO OB 1 BO B 170 I N T E R A C T I O N S 13 M A N H O U R S Figure 12 S E D G E PATH (W) DC LU it \ cf GB GB cf G BY cf R Y ? Black B cf 0 Y LO cf R G SEF ? R B ? Y B ? Y DG '? W Y ? BO RW cf W DG ? B © ? B BY cf LD BY GB GB \ 2 15 1 1 3 6 9 4 9 8 G BY \ 1 4 2 1. 1 4 R Y 1 2 3 7 6 Black B 2 1 3 3 1 4 2 O Y 11 2 2 7 5 2 R G 1 \ 2 1 2 8 R B 1 1 3 1 Y B 2 2 2 Y DG 1 2 1 2 W Y 1 1 \ 3 2 BO RW \ 4 W DG 1 4 B © 2 B BY 1 LD BY \ 186 INTERACTIONS 15 MAN HOURS 121 Figure 13 B U L L D O Z E D P A T H S L O S E R oc LU 5 . cf \ M s _o_ R cf R Y cf L P ® cf Black 2 Black 2 Y DG 2 w 2 B ® 2 RW D P DG B Y BY M DP 10 « 5 2 10 1 0 R \ 11 1 5 1 2 0 6 R Y 9 2 6 34 1 6 5 L P ® 1 2 1 3 Black D G 1 10 3 Black B \ 4 2 2 1 Y DG 2 3 W Y 3 B ® \ 1 RW BY \ 174 INTERACTIONS 22 MAN H O U R S 1g2 Figure 14 FIRST BIG A L D E R L O S E R cr LU z \ 1 © LD LD R © B W 0_ Y Y DG Bl BO 1 9 5 2 1 1 L D LD 6 2 6 1 R © 9 5 3 1 B W 4 1 0 Y 2 1 Y DG \ 1 Bl BO \ 61 INTERACTIONS; 6 MAN HOURS M A R S H N A R R O W S L O S E R 4 ? ? ? \ Y i f © UNB BO O B B l © M B ^ 2 4 UNB 1 BO O B 1 B l © 8 INTERACTIONS; 5 MAN HOURS 1 ^ Figure 15 N O - N A M E C L E A R I N G L O S E R 42 INTERACTIONS 11 MAN HOURS

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UBC Theses and Dissertations

UBC Theses and Dissertations

Some ecological aspects of social behaviour in the song sparrow, Melospiza melodia Knapton, Richard Walter 1973

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UBC Theses and Dissertations

Some ecological aspects of social behaviour in the song sparrow, Melospiza melodia Knapton, Richard Walter 1973

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