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Territorial behaviour, nesting success and brood survival in Barrow's Goldeneye and its congeners Savard, Jean-Pierre L. 1986

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TERRITORIAL BEHAVIOUR, NESTING SUCCESS AND BROOD SURVIVAL IN BARROW'S GOLDENEYE AND ITS CONGENERS . by JeariT-Pierre L. Savard B.Sc. Laval University, Quebec 1974 M.Sc. University of Toronto, Toronto 1978 A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The faculty of graduate studies (Department of Zoology) We accept this thesis as conforming to the required standard The University of Brit i s h Columbia March 1986 © Jean-Pierre L. Savard, 1986 7 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or pu b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of crc^-fyryy. The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date ( X ^ f l , ; mC i i A b s t r a c t I n t h i s s t u d y , I f i r s t d e s c r i b e a n d c h a r a c t e r i z e t h e i n t r a - a n d i n t e r s p e c i f i c t e r r i t o r i a l b e h a v i o u r o f B a r r o w ' s G o l d e n e y e ( B u c e p h a l a  i s l a n d i c a ) a n d c o m p a r e i t t o t h a t o f Common G o l d e n e y e (B. c l a n g u l a ) a n d B u f f l e h e a d (B. a l b e o l a ) . S e c o n d , I examine some f a c t o r s i n f l u e n c i n g t h e u s e o f n e s t b o x e s by B a r r o w ' s G o l d e n e y e a n d t h e i r r e p r o d u c t i v e s u c c e s s . F i n a l l y , I c o m p a r e d u c k l i n g m o r t a l i t y i n B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d . B a r r o w ' s G o l d e n e y e , Common G o l d e n e y e a n d B u f f l e h e a d p a i r s h a v e s i m i l a r t e r r i t o r i a l b e h a v i o u r : t h e y d e f e n d a f i x e d , e x c l u s i v e a r e a a g a i n s t r i v a l s . P a i r s a r e a l s o i n t e r s p e c i f i c a l l y t e r r i t o r i a l d u r i n g t h e b r e e d i n g s e a s o n , a n d i n t e r s p e c i f i c a g g r e s s i o n i s s t r o n g e s t t o w a r d c o n g e n e r s a n d s t r o n g e r t o w a r d d i v i n g d u c k s t h a n t o w a r d d a b b l i n g d u c k s . The degree o f a g g r e s s i o n shown i s c o r r e l a t e d w i t h t h e degree of o v e r l a p i n d i e t a n d f o r a g i n g m o d e s . B a r r o w ' s G o l d e n e y e and B u f f l e h e a d f e m a l e s a r e i n t r a - and i n t e r s p e c i f i c a l l y a g g r e s s i v e a f t e r t h e i r young have h a t c h e d and t h e i r b e h a v i o u r i s s i m i l a r t o t h a t o f t h e d r a k e s i n t h e s p r i n g . B r o o d a m a l g a m a t i o n i s f r e q u e n t i n B a r r o w ' s G o l d e n e y e a n d i s a n a c c i d e n t a l o u t c o m e o f t e r r i t o r i a l e n c o u n t e r s b e t w e e n b r o o d s . B a r r o w ' s G o l d e n e y e p a i r s a l s o d e f e n d i n t r a - a n d i n t e r s p e c i f i c t e r r i t o r i e s o n t h e w i n t e r i n g a r e a s . P h i l o p a t r y t o summer a n d p r o b a b l y a l s o t o w i n t e r t e r r i t o r i e s i s s t r o n g i n B a r r o w ' s G o l d e n e y e . B a r r o w ' s G o l d e n e y e m a i n t a i n monogamous l o n g - t e r m p a i r bonds b u t a r e o c c a s i o n a l l y p o l y g y n o u s . P r o v i s i o n o f n e s t b o x e s r e s u l t e d i n a n i n c r e a s e i n b r e e d i n g d e n s i t i e s o f B a r r o w ' s G o l d e n e y e . F a c t o r s t h a t i n f l u e n c e d t h e use o f n e s t b o x e s b y B a r r o w ' s G o l d e n e y e i n c l u d e d : p r e v i o u s u s e o f t h e n e s t b o x , o u t c o m e o f t h e p r e v i o u s b r e e d i n g a t t e m p t , a g e o f t h e n e s t b o x a n d i t s i i i l o c a tion. Proportions of nest boxes that hatched, were preyed upon and were deserted, averaged respectively 46+4% (S.E.), 31+3% and 23+3% (n=4 years). Minimum estimates of intraspecific nest parasitism ranged between 5% and 20%. The d a i l y mortality rate of Barrow's Goldeneye and Bufflehead ducklings varied with years, duckling age and hatching date. Mortality rates were highest in the f i r s t week following hatching. In years of high mortality, broods that hatched early tended to survive better than l a t e hatching broods. Barrow's Goldeneye ducklings had a higher d a i l y mortality rate than Bufflehead ducklings. The main function of t e r r i t o r i a l i t y in these species seems to be the provision of an exclusive feeding area for the female or the young. I argue that the evolution of i n t e r s p e c i f i c aggression i n the genus Bucephala has been favoured by a high l e v e l of i n t r a s p e c i f i c aggression within the genus and significant feeding advantages obtained from the exclusion of competitors. The genus Bucephala provides one of the best examples of interference competition in a guild of related competitors. i v T a b l e o f C o n t e n t s Page A b s t r a c t i i L i s t o f T a b l e s v i i L i s t o f F i g u r e s x i Acknowledgements x i v C h a p t e r I : G e n e r a l i n t r o d u c t i o n . 1 1) M a n a g e m e n t f r a m e w o r k 2 2) T h e o r e t i c a l f r a m e w o r k 3 a) C o m p e t i t i o n 3 b) I n t r a s p e c i f i c c o m p e t i t i o n 4 c) I n t e r s p e c i f i c c o m p e t i t i o n 7 d) F u n c t i o n s o f t e r r i t o r i a l i t y 10 3) S p e c i e s framework 12 a) D i s t r i b u t i o n and abundance o f B a r r o w ' s Goldeneye . . . 12 b) B e h a v i o u r and e c o l o g y o f B a r r o w ' s Goldeneye . . . . . 13 c ) Common Goldeneye and B u f f l e h e a d 14 4) F o c u s o f t h e s t u d y 14 C h a p t e r I I : G e n e r a l m e t h o d s 17 D S t u d y s i t e s 1 8 a) R i s k e C r e e k 1 8 b) C o l u m b i a V a l l e y 20 c) Vancouver 20 2 ) G e n e r a l m e t h o d s 21 a) C a p t u r e a n d m a r k i n g 21 b) A g e d e t e r m i n a t i o n 21 c) S u r v e y s 22 v Page d ) S t a t i s t i c a l a n a l y s i s 22 C h a p t e r I I I : T e r r i t o r i a l B e h a v i o u r 23 I n t r o d u c t i o n 24 Methods 24 R e s u l t s 26 1) I n t r a s p e c i f i c a g g r e s s i o n 26 a) T e r r i t o r i a l b e h a v i o u r o f p a i r s 26 - B r e e d i n g a r e a s 26 - W i n t e r i n g a r e a s 40 b) T e r r i t o r i a l b e h a v i o u r o f f e m a l e s w i t h b r o o d s . . 40 2) I n t e r s p e c i f i c a g g r e s s i o n 50 a) P a i r s o n t h e b r e e d i n g a r e a s 50 b) F e m a l e s w i t h b r o o d s 64 c) P a i r s o n t h e w i n t e r i n g a r e a s 6 9 3) R e l a t i o n s h i p s between p a i r t e r r i t o r y , b r o o d t e r r i t o r y a n d n e s t s i t e 71 a) P a i r t e r r i t o r y a n d n e s t s i t e 71 b) N e s t s i t e a n d b r o o d t e r r i t o r y 71 c) P a i r t e r r i t o r y and b r o o d t e r r i t o r y 71 d) F i d e l i t y t o t e r r i t o r y 7 5 e) R e m o v a l e x p e r i m e n t s 76 D i s c u s s i o n 76 A) I n t r a s p e c i f i c a g g r e s s i o n 76 B) B r o o d amalgamation 87 C) I n t e r s p e c i f i c a g g r e s s i o n 89 D) T h e t e r r i t o r y 95 Summary 97 v i Page C h a p t e r IV: Use o f n e s t boxes a n d n e s t i n g s u c c e s s 99 I n t r o d u c t i o n 100 Methods 102 R e s u l t s 102 1) N e s t b o x u s e by a l l w i l d l i f e 1 0 2 2) N e s t b o x u s e b y B a r r o w ' s G o l d e n e y e 1 0 5 a) N e s t i n g s u c c e s s 10 9 b) P r o d u c t i v i t y 113 c ) P a r a s i t i c e g g l a y i n g 1 1 9 d) I m p a c t o f n e s t b o x e s o n p o p u l a t i o n s i z e 121 D i s c u s s i o n 126 Summary 129 C h a p t e r V. M o r t a l i t y o f B a r r o w ' s Goldeneye and B u f f l e h e a d b r o o d s . 130 I n t r o d u c t i o n 131 Methods 131 R e s u l t s 133 1) H a t c h i n g c h r o n o l o g y 1 3 3 2) M o r t a l i t y o f b r o o d s 137 a) M a y f i e l d m e t h o d - Unweighted by b r o o d s i z e . . . . 137 b) M a y f i e l d method - W e i g h t e d b y b r o o d s i z e . . . . 137 c) D i r e c t m e t h o d 1 4 9 D i s c u s s i o n 156 Summary 160 v i i Page Chapter VI. General discussion 161 1) T e r r i t o r i a l i t y 162 2) Competition between Barrow's Goldeneye and Bufflehead . . . 165 3) Does t e r r i t o r i a l behaviour limit breeding densities in the genus Bucephala? 168 4) Management implications and research needs 169 Lit e r a t u r e c i t e d 17 2 Appendix 1. Use of a mirror trap to capture t e r r i t o r i a l waterfowl. 195 Appendix 2. Evidence of long-term pair bonds i n Barrow's Goldeneye 199 Appendix 3. Witnessed brood encounters i n Barrow's Goldeneye broods 205 Appendix 4. Polygyny i n Barrow's Goldeneye 211 Appendix 5. Sexual dimorphism i n Barrow's Goldeneye 216 v i i i L I S T OF TABLES Page T a b l e 1 T e r r i t o r i a l d e f e n s e by p a i r e d d r a k e s i n r e l a t i o n t o t h e p r e s e n c e o f t h e i r m a t e s 30 T a b l e 2 C o m p a r i s o n o f a g g r e s s i v e i n t e r a c t i o n s o f t h r e e t e r r i t o r i a l B a r r o w ' s G o l d e n e y e d r a k e s o n c o n t i g u o u s t e r r i t o r i e s o n l a k e 13 (1982) 33 T a b l e 3 Number o f a g g r e s s i v e i n t e r a c t i o n s i n w h i c h e a c h t e r r i t o r y h o l d e r w a s i n v o l v e d d u r i n g 25h o f o b s e r v a t i o n o n l a k e 89 (1981) 34 T a b l e 4 Number o f i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d b e t w e e n t e r r i t o r i a l m a l e Common G o l d e n e y e a n d i n t r u d e r s 38 T a b l e 5 Number o f i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d between t e r r i t o r i a l m a l e B u f f l e h e a d a n d i n t r u d e r s . 39 T a b l e 6 I n t r a s p e c i f i c i n t e r a c t i o n s b e t w e e n t e r r i t o r i a l B a r r o w ' s G o l d e n e y e d r a k e s a n d c o n s p e c i f i c s i n w i n t e r 41 T a b l e 7 Number o f i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d b e t w e e n f e m a l e B a r r o w ' s Goldeneye w i t h young and i n t r u d e r s 42 T a b l e 8 B r o o d a m a l g a m a t i o n i n B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d 45 T a b l e 9 Number o f i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d between f e m a l e B u f f l e h e a d w i t h young a n d i n t r u d e r s 46 T a b l e 10 Number o f i n t r a - a n d 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 i n v o l v i n g t e r r i t o r i a l d r a k e s o b s e r v e d between 1981 a n d 1 9 8 4 51 T a b l e 11 Number o f 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 o b s e r v e d w i t h i n t h e g e n u s B u c e p h a l a 52 T a b l e 12 Number o f i n t r a - and i n t e r g e n e r i c e n c o u n t e r s w i t h a l l i n t r u d e r s t h a t r e s u l t e d i n f i g h t s 56 T a b l e 13 I n t e r a c t i o n s b e t w e e n t e r r i t o r i a l B a r r o w ' s G o l d e n e y e d r a k e s a n d d a b b l i n g d u c k s 58 T a b l e 14 I n t e r a c t i o n s b e t w e e n t e r r i t o r i a l B a r r o w ' s G o l d e n e y e d r a k e s a n d d i v i n g d u c k s 59 ix Page Table 15 Level of aggression i n i n t e r a c t i o n s between Barrow's Goldeneye drakes and other waterfowl . . 63 Table 16 Number of i n t e r s p e c i f i c aggressions by Barrow's Goldeneye drakes i n r e l a t i o n to the presence or absence of t h e i r mates 65 Table 17 Number of interactions observed between female Barrow's Goldeneye and Bufflehead with broods, and other b i r d s 66 Table 18 Intra-generic aggression i n broods of Barrow's Goldeneye and broods of Bufflehead 67 Table 19 Intensity of the interactions observed between females with broods and intra- and interspecific intruders 68 Table 20 Number of cases of i n t r a - and i n t e r s p e c i f i c aggression by t e r r i t o r i a l Barrow's Goldeneye males and females i n winter 70 Table 21 Proportion of t e r r i t o r i e s that were adjacent to the nest s i t e 73 Table 22 Results of the removal experiment on lake 68 i n 1984 77 Table 23 Results of the removal experiment on lake 50 i n 1984 79 Table 24 Dimensions of nest boxes and dates of erection . . 103 Table 25 Number of large boxes used by breeding w i l d l i f e . 104 Table 26 Number of small boxes used by breeding w i l d l i f e . 106 Table 27 Relationship between previous use of a nest box and subsequent use by Barrow's Goldeneye 108 Table 28 Nest box use in relation to abundance of Barrow's Goldeneye on pond i n the previous year 110 Table 29 Comparison of nesting success between cavity nesting ducks 112 Table 30 Egg production in nest boxes in relation to year . 118 Table 31 Egg production i n relation to age of the box . . . 120 X Page Table 32 Summary of counts carried out by Ducks Unlimited i n Central B r i t i s h Columbia and comparison with counts on the study area 125 Table 33 Two-way anova on the e f f e c t of year and species (Barrow's Goldeneye vs Bufflehead) on mean hatching date 136 Table 34 Four-way anova on the effect of species (Barrow's Goldeneye vs Bufflehead), year, age and hatching date on mortality rate of young 138 Table 35 Daily mortality rate of Barrow's Goldeneye and Bufflehead broods in relation to years 139 Table 36 Daily mortality rate of Barrow's Goldeneye and Bufflehead broods in relation to age 140 Table 37 Mortality of Barrow's Goldeneye ducklings . . . . 153 Table 38 Mortality of Bufflehead ducklings 154 Table 39 Distribution of losses between laying and 3 week old young in nests that hatched 155 Table 40 Bird species captured using mirror traps 197 Table 41 Co m p a r i s o n of the number of a g g r e s s i v e interactions observed between polygynous males and monogamous neighbouring males 214 Table 42 Comparison of weight and wing length between male and female Barrow's Goldeneye 218 x i LIST OF FIGURES Page Figure 1 Location of study areas 19 Figure 2 Frequency of types of intraspecif i c interactions between t e r r i t o r i a l male Barrow's Goldeneye and intruders during the breeding season 27 Figure 3 Frequency of threats and attacks by t e r r i t o r i a l male Barrow's Goldeneye toward paired neighbouring males and batchelor males 29 Figure 4 Percentage of time spent by Barrow's Goldeneye males i n various a c t i v i t i e s i n r e l a t i o n to the presence or absence of t h e i r mates 31 Figure 5 L o c a t i o n of t e r r i t o r i e s of p a i r e d Barrow's Goldeneye drakes on lake 13 (1982) and lake 89 (1981) 35 Figure 6 Average % of time spent by male and female Barrow's Goldeneye i n various a c t i v i t i e s within t h e i r t e r r i t o r y 36 Figure 7 Average % of time spent by female and young Barrow's Goldeneye i n various a c t i v i t i e s within t h e i r t e r r i t o r y 44 Figure 8 Average % of time spent by female and young Bufflehead i n various a c t i v i t i e s within t h e i r territory 49 Figure 9 Relative aggressiveness of the three Bucephala species toward intruders 54 Figure 10 Comparison of the proportions'of threats and attacks i n i n t e r s p e c i f i c interactions 55 Figure 11 Aggressive responses of Barrow's Goldeneye drakes toward conspecifics, congeners, diving ducks and dabbling ducks 57 Figure 12 Frequencies of a g g r e s s i v e i n t e r a c t i o n s and tolerances by t e r r i t o r i a l Barrow's Goldeneye drakes toward diving ducks and dabbling ducks . . 61 Figure 13 Distances between pair territories and nest sites i n Barrow's Goldeneye 72 Figure 14 Distances between brood terr i t o r i e s and nest sites i n Barrow's Goldeneye 74 x i i Page F i g u r e 15 T e r r i t o r y b o u n d a r i e s o f B a r r o w ' s G o l d e n e y e p r i o r t o and f o l l o w i n g t h e r e m o v a l e x p e r i m e n t o n l a k e 68 i n 1984 7 8 F i g u r e 16 T e r r i t o r y b o u n d a r i e s o f B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d p r i o r t o a n d f o l l o w i n g t h e r e m o v a l e x p e r i m e n t o n l a k e 50 i n 1984 80 F i g u r e 17 P r o p o r t i o n o f n e s t b o x e s u s e d b y B a r r o w ' s Goldeneye and o t h e r w i l d l i f e i n r e l a t i o n t o age o f t h e n e s t b o x 1 0 7 F i g u r e 18 P r o p o r t i o n o f B a r r o w ' s G o l d e n e y e n e s t s t h a t h a t c h e d , were p r e y e d upon and were d e s e r t e d . . . I l l F i g u r e 1 9 I n f l u e n c e o f v i s i t s b y o b s e r v e r s o n t h e f a t e s o f n e s t s 114 F i g u r e 20 H a t c h i n g s u c c e s s i n r e l a t i o n t o d a t e o f c l u t c h i n i t i a t i o n 115 F i g u r e 21 P r o p o r t i o n s o f n o n - h a t c h i n g n e s t s p r e y e d upon and d e s e r t e d i n r e l a t i o n t o c l u t c h i n i t i a t i o n d a t e . . 116 F i g u r e 22 I n f l u e n c e o f t h e o u t c o m e o f t h e p r e v i o u s r e p r o d u c t i v e a t t e m p t i n a n e s t box on t h e outcome o f f u t u r e n e s t i n g a t t e m p t s i n t h e same n e s t box. . 117 F i g u r e 23 Numbers o f B a r r o w ' s Goldeneye and B u f f l e h e a d p a i r s e s t i m a t e d o n t h e s t u d y a r e a 1 2 2 F i g u r e 24 N u m b e r s o f B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d b r o o d s e s t i m a t e d o n t h e s t u d y a r e a 124 F i g u r e 25 H a t c h i n g d a t e s o f B a r r o w ' s Goldeneye b r o o d s . . . 134 F i g u r e 26 H a t c h i n g d a t e s o f B u f f l e h e a d b r o o d s 135 F i g u r e 27 D a i l y m o r t a l i t y r a t e s ( w e i g h t e d by b r o o d s i z e ) o f B a r r o w ' s G o l d e n e y e d u c k l i n g s 141 F i g u r e 28 D a i l y m o r t a l i t y r a t e s ( w e i g h t e d by b r o o d s i z e ) o f B u f f l e h e a d d u c k l i n g s 1 4 2 F i g u r e 29 D a i l y m o r t a l i t y r a t e s ( w e i g h t e d by b r o o d s i z e ) o f B a r r o w ' s G o l d e n e y e d u c k l i n g s i n r e l a t i o n t o d u c k l i n g a g e 1 4 4 F i g u r e 30 D a i l y m o r t a l i t y r a t e s ( w e i g h t e d by b r o o d s i z e ) o f B u f f l e h e a d d u c k l i n g s i n r e l a t i o n t o d u c k l i n g age . 145 x i i i Page Figure 31 Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings i n r e l a t i o n to hatching period 146 Figure 32 Daily mortality rates (weighted by brood size) of Bufflehead ducklings i n r e l a t i o n to hatching period 147 Figure 33 Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching 148 Figure 34 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1982 150 Figure 35 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1983 151 Figure 36 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1984 152 x i v ACKNOWLEDGEMENTS S e v e r a l p e r s o n s a s s i s t e d me t h r o u g h o u t t h i s r e s e a r c h . I thank G a r y K a i s e r a n d J a m i e S m i t h f o r t h e i r s u p p o r t a n d e n c o u r a g e m e n t d u r i n g t h e c o u r s e o f t h e s t u d y . I w i s h t o acknowledge t h e c o n t r i b u t i o n s o f my f i e l d a s s i s t a n t s , some o f whom w o r k e d s e v e r a l y e a r s on t h i s p r o j e c t w h i l e o t h e r s o f f e r e d t h e i r s e r v i c e s a s v o l u n t e e r s . T h e i r i n t e r e s t and e n t h u s i a s m made t h i s s t u d y a p l e a s a n t one: Thanks t o Dave P o w e l l , J o h n M c L a u g h l i n , Yves T u r c o t t e , A n d r e B r e a u l t , J o n G a r e a u , L e s W i l l i s , B o g u s h a J e d r z e j e w s k a , F a b i a n O s t e n d o r f , S c o t t C r a w f o r d , Pamela W h i t e h e a d and Bob Emery. I thank t h e members o f my s u p e r v i s o r y c o m m i t t e e , J a m i e S m i t h , Tony S i n c l a i r , L e e G a s s , Don M c P h a i l a n d J o h n S m i t h f o r t h e i r c o n s t r u c t i v e c r i t i c i s m s a n d e n c o u r a g e m e n t s . I am g r a t e f u l t o M o i r a L e m o n , P a m e l a W h i t e h e a d and Bob Emery f o r t h e i r a s s i s t a n c e w i t h d r a f t i n g and t o Susan Garnham f o r t y p i n g t h e t h e s i s . I b e n e f i t e d f r o m p r o d u c t i v e and d y n a m i c d i s c u s s i o n s w i t h J a m i e S m i t h , K i m Cheng, G i l l e s G a u t h i e r , John E a d i e and Bob E m e r y . I am g r a t e f u l t o Ed H e n n a n , R o n B o y c h u c k , R o r i B r o w n a n d Murray C l a r k o f Ducks U n l i m i t e d f o r t h e i r a s s i s t a n c e by g e n e r o u s l y s h a r i n g u n p u b l i s h e d d a t a o n w a t e r f o w l s u r v e y s . I w o u l d l i k e a l s o t o t h a n k t h e l a t e H a r o l d M i t c h e l l o f t h e p r o v i n c i a l F i s h and W i l d l i f e S e r v i c e f o r h i s h e l p a t t h e b e g i n n i n g o f t h e s t u d y . T h i s s t u d y w a s s u p p o r t e d b y t h e f o l l o w i n g o r g a n i z a t i o n s : C a n a d i a n W i l d l i f e S e r v i c e , U n i v e r s i t y o f B r i t i s h C o l u m b i a , D u c k s U n l i m i t e d , C a n a d i a n N a t i o n a l S p o r t s m a n ' s F u n d , N a t u r a l S c i e n c e s a n d E n g i n e e r i n g R e s e a r c h C o u n c i l o f C a n a d a , B r i t i s h C o l u m b i a F i s h a n d W i l d l i f e B r a n c h , B r i t i s h C o l u m b i a F o r e s t S e r v i c e , a n d t h e C a n a d i a n F o r e s t S e r v i c e . F i n a l l y , I w o u l d l i k e t o t h a n k C a r o l e f o r h e r s u p p o r t , a s s i s t a n c e a n d u n d e r s t a n d i n g t h r o u g h o u t t h e w h o l e s t u d y . Chapter 1: General introduction 1 Introduction T h i s t h e s i s a r o s e f r o m t h r e e s e p a r a t e b u t r e l a t e d i n t e r e s t s : a) a n i n t e r e s t i n t h e g e n e r a l n a t u r a l h i s t o r y o f d i v i n g d u c k s , b) a c o n c e r n f o r t h e i r m a n a g e m e n t , a n d c) t h e t h e o r e t i c a l p r o b l e m o f i n t e r f e r e n c e c o m p e t i t i o n w i t h i n a n d b e t w e e n s p e c i e s . D u c k s o f t h e g e n u s B u c e p h a l a , e s p e c i a l l y t h e B a r r o w ' s G o l d e n e y e (Bucephala i s l a n d i c a ) . p r o v e d i d e a l a s s t u d y s u b j e c t s : a) l i t t l e was known o f t h e e c o l o g y o f B a r r o w ' s G o l d e n e y e , b) t h e s p e c i e s f a c e d s e v e r a l t h r e a t s i n B r i t i s h C o l u m b i a ( s e e b e l o w ) , c) i n t e r f e r e n c e c o m p e t i t i o n a p p e a r e d i m p o r t a n t i n t h e e c o l o g y o f t h e w h o l e genus (see b e l o w ) . 1) Management framework B a r r o w ' s Goldeneye b e l o n g s t o t h e genus B u c e p h a l a w h i c h a l s o c o n t a i n s t w o o t h e r b e t t e r s t u d i e d s p e c i e s : B u f f l e h e a d (B. a l b e o l a ) a n d Common G o l d e n e y e (B. c l a n g u l a ) . The B a r r o w ' s G o l d e n e y e h a s a r e s t r i c t e d d i s t r i b u t i o n , w i t h m o r e t h a n 60% o f t h e w o r l d p o p u l a t i o n b r e e d i n g a n d w i n t e r i n g i n B r i t i s h C o l u m b i a , Canada ( B e l l r o s e 1978). There i s a s e r i o u s l a c k o f knowledge on t h e b a s i c e c o l o g y o f B a r r o w ' s G o l d e n e y e i n v i e w o f s e v e r a l t h r e a t s t o t h e w e s t e r n N o r t h A m e r i c a n p o p u l a t i o n : 1 . The g r o w t h o f m a r i t i m e t r a f f i c and o f f s h o r e o i l e x p l o r a t i o n i n B r i t i s h C o l u m b i a a n d A l a s k a h a s g r e a t l y i n c r e a s e d t h e r i s k s o f m a j o r o i l s p i l l s w h i c h c o u l d a d v e r s e l y a f f e c t w i n t e r i n g b i r d s and t h e i r m a j o r f o o d s u p p l y , M u s s e l s ( M y t i l u s ) ( C a r t h y a n d A r t h u r 1 9 6 8 , V e r m e e r a n d V e r m e e r 1975). 2 2 . I n t h e l a s t d e c a d e , l o g g i n g a c t i v i t i e s h a v e i n t e n s i f i e d i n c e n t r a l B r i t i s h C o l u m b i a w h e r e t h e h i g h e s t b r e e d i n g d e n s i t i e s o f B a r r o w ' s G o l d e n e y e a r e f o u n d , r e d u c i n g t h e a v a i l a b i l i t y o f n e s t i n g s i t e s a t an i n c r e a s i n g r a t e . 3 . H u n t i n g p r e s s u r e i s h i g h i n some a r e a s , n e g a t i v e l y a f f e c t i n g l o c a l r e c r u i t m e n t (Savard 1 9 8 2 a ) . 2) T h e o r e t i c a l framework a) C o m p e t i t i o n C r o m b i e (1947) d e f i n e d c o m p e t i t i o n a s t h e demand b y t w o o r m o r e o r g a n i s m s f o r t h e same r e s o u r c e s i n e x c e s s o f i m m e d i a t e s u p p l y . B i r c h (1957) f u r t h e r s t a t e d t h a t i f t h e r e s o u r c e s a r e n o t i n s h o r t s u p p l y , c o m p e t i t i o n o c c u r s when t h e o r g a n i s m s s e e k i n g t h o s e r e s o u r c e s n e v e r t h e l e s s h a r m one a n o t h e r i n t h e p r o c e s s . M i l l e r (1967) d i s t i n g u i s h e d b e t w e e n i n t e r f e r e n c e and e x p l o i t a t i o n a s c o m p o n e n t s o f t h e c o m p e t i t i o n p r o c e s s , e x p l o i t a t i o n b e i n g t h e d o m i n a n t f o r m o f c o m p e t i t i o n whenever i n t e r f e r e n c e mechanisms a r e p o o r l y d e v e l o p e d . C o m p e t i t i o n b y d i r e c t e x p l o i t a t i o n i s p r e s u m a b l y t h e p r i m i t i v e f o r m o f i n t e r a c t i o n . E x p l o i t a t i o n c o m p e t i t i o n i s common among i n v e r t e b r a t e s ( C r o m b i e 1947) a n d i s o f t e n f o u n d b e t w e e n u n r e l a t e d o r g a n i s m s f e e d i n g on t h e same r e s o u r c e : r o d e n t s and a n t s (Brown a n d D a v i d s o n 1 9 7 7 ) , n e c t a r f e e d i n g b i r d s a n d i n s e c t s ( C a r p e n t e r 1 9 7 9 , Brown £ t a l . 1 9 8 1 ) , w a t e r f o w l and f i s h e s ( E r i k s s o n 1979a, A n d e r s s o n 1 9 8 1 , E a d i e a n d K e a s t 1 9 8 2 ) , u n g u l a t e s a n d g r a s s h o p p e r s ( S i n c l a i r 1 9 7 5 ) . I n t e r f e r e n c e c o m p e t i t i o n i s b e s t e x e m p l i f i e d by t e r r i t o r i a l i t y . T e r r i t o r y d e f e n s e h a s been r e p o r t e d i n a v a r i e t y o f a n i m a l g r o u p s : i n s e c t s (Moore 1 9 5 7 , O t t e a n d J o e r n 197 5 , J o h n s o n 1 9 6 4 , B a k e r 1 9 8 3 , F i t z p a t r i c k a n d W e l l i n g t o n 1 9 8 3 ) , a r a c h n i d s ( R i e c h e r t 1981) c r u s t a c e a n s ( D i n g l e a n d C a l d w e l l 196 8 ) , a m p h i b i a n s ( M a r t o f 1 9 5 3 , J a e g e r e ± a l . 1 9 8 2 ) , r e p t i l e s 3 (Rand 1967), f i s h e s (Van Den Assem 1967, Katzir 1981a, Sammarco and Williams 1982), birds (Howard 1920, Hinde 1956, Brown 1964) and mammals (Buechner 1961, Lockie 1966, Armitage 1974, Floody and Arnold 1975). b) Intraspecific competition Brown (1964) stated that intraspecific aggressiveness i s primarily a behavioural response to competition for e c o l o g i c a l r e q u i s i t e s i n short supply and that the predominant single factor tending to increase aggressiveness through n a t u r a l s e l e c t i o n should be c o m p e t i t i o n . Competition, coupled with economic defendability of the limiting resource, should lead to t e r r i t o r i a l i t y . D e f i n i t i o n s of t e r r i t o r y vary among authors. Noble (193 9) defined a t e r r i t o r y as "any defended area". Pitelka (1959) simplified the definition to "an exclusive area". The most encompassing d e f i n i t i o n was given by Davies i n 197 8: " T e r r i t o r i a l i t y occurs whenever i n d i v i d u a l animals or groups are spaced out more than would be expected from a random occupation of suitable habitats". Morse (1980) and Wittenberger (1981) give a detailed overview of the different definitions of t e r r i t o r i a l i t y . Here I shall adopt the definition of Brown and Orians (197 0) who defined t e r r i t o r i a l i t y as the defense of a f i x e d , exclusive area against rivals. This definition encompasses most of the proposed definitions. In most passerine birds, t e r r i t o r i e s are established before pa i r i n g , and thus may play a r o l e i n pair formation (Hinde 1956, Welty 1962). In waterfowl, te r r i t o r i e s are established after pair formation and are not a factor i n pair formation. McKinney (1965) reviewed the spacing behaviour of several species of North American ducks and observed that in general, aggressive behaviour by males was associated with the presence of 4 a s t r o n g p a i r - b o n d . He s u g g e s t e d t h a t t h e r e s t r i c t i o n o f t h e m a l e ' s a g g r e s s i o n t o a c e r t a i n a r e a w a s a r e s u l t o f t h e f e m a l e ' s a t t a c h m e n t t o t h e a r e a she s e l e c t s f o r b r e e d i n g . T i t m a n and Seymour (1981) compared t h e s p a c i n g b e h a v i o u r o f s i x N o r t h A m e r i c a n s p e c i e s o f d a b b l i n g d u c k s a n d c o n f i r m e d M c K i n n e y ' s o b s e r v a t i o n s . T h e r e w a s a c l e a r g r a d i e n t o f m a l e t e r r i t o r i a l i t y among t h e s p e c i e s t h e y s t u d i e d r a n g i n g f r o m t h e n o n -t e r r i t o r i a l N o r t h e r n P i n t a i l (Anas a c u t a ) t o t h e s t r o n g l y t e r r i t o r i a l N o r t h e r n S h o v e l e r (A. c l y p e a t a ) . N o r t h e r n S h o v e l e r a r e a t t a c h e d t o a p h y s i c a l s i t e d u r i n g t h e b r e e d i n g s e a s o n / d e f e n d i t a c t i v e l y a n d f o r m s t r o n g a n d l o n g - l a s t i n g p a i r b o n d s ( S e y m o u r 1974 a , b ) . T i t m a n (1983) showed t h a t M a l l a r d s defended t e r r i t o r i e s t h a t w e r e e s s e n t i a l l y e x c l u s i v e a r e a s f r o m a t e m p o r a l p o i n t o f v i e w , a l t h o u g h t h e y o f t e n o v e r l a p p e d p h y s i c a l l y . B a l l e_t sX. (197 8) s h o w e d t h a t t h e A f r i c a n B l a c k Duck (A. s p a r s a ) m a i n t a i n s t e r r i t o r i e s t h a t s a t i s f y t h e c l a s s i c a l d e f i n i t i o n o f t e r r i t o r i a l i t y , i . e . d e f e n s e o f a f i x e d a r e a and e x c l u s i o n o f c o n s p e c i f i c s vcrown and O r i a n s 1970). S i m i l a r l y , a t l e a s t t h r e e s p e c i e s of s h e l d u c k s ( T a d o r n a ) h a v e w e l l d e v e l o p e d t e r r i t o r i a l b e h a v i o u r ( H o r i 1 9 6 4 a , 1 9 6 9 , Y o u n g 1 9 7 0 , R i g g e r t 1 9 7 7 , W i l l i a m s 1 9 7 9 , P a t t e r s o n 1 9 8 2 ) . I n d i v i n g d u c k s , t e r r i t o r i a l i t y h a s been r e p o r t e d i n S t e a m e r - D u c k s (Tacjhyeres spp.) ( P e t t i n g i l l 1 9 6 5 , W e l l e r 1 9 7 6 ) , O l d s q u a w ( C l a n g u l a h y e m a l i s ) ( A l i s o n 1975), and B u f f l e h e a d (Munro 1942, Donaghey 1 9 7 5 , G a u t h i e r 1985). I n t h e genus B u c e p h a l a . 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 B u f f l e h e a d h a s b e e n w e l l d o c u m e n t e d (Munro 1 9 4 2 , E r s k i n e 197 2 a n d D o n a g h e y 197 5 ) . The d r a k e d e f e n d s a w e l l - d e f i n e d a r e a a l o n g t h e s h o r e o f a pond f r o m w h i c h i t e x c l u d e s a l l c o n s p e c i f i c s b u t i t s m a t e . S i m i l a r l y , a f t e r t h e young h a t c h t h e f e m a l e d e f e n d s a n a r e a o f w a t e r f r o m w h i c h s h e e x c l u d e s a l l c o n s p e c i f i c s . D e s c r i p t i o n o f t e r r i t o r i a l i t y i n t h e B a r r o w ' s Goldeneye i s 5 l i m i t e d to short q u a l i t a t i v e accounts (Munro 1918, 1939, Harris et a l . 1954, Myres 1957, Bengtson 1971, 1972, Palmer 1976). These indicate that i t s behaviour i s s i m i l a r to that of the Bufflehead. The t e r r i t o r i a l behaviour of Common Goldeneye i s poorly understood. Bruggemann (1876) observed two captive pairs defending f i x e d t e r r i t o r i e s on a pond and described a r i t u a l i z e d display occurring at the t e r r i t o r y boundaries s i m i l a r to one used by Bufflehead during t e r r i t o r i a l defense (Donaghey 197 5). Cramp and Simmons (1977) reported that, i n Europe, Common Goldeneye defend territories on their breeding grounds, but they did not describe the behaviour or cite any references. Nilsson (1969) describes behaviour that resembles t e r r i t o r i a l defense but explains i t simply as mate defense. Carter (1958) and Gibbs (1961) mentioned that Common Goldeneye drakes do not e s t a b l i s h f i x e d t e r r i t o r i e s , but only defend an area around their mate. Several other studies on Common Goldeneye (Munro 1939, Siren 1952, Prince 196 5, Rajala and Ormio 1971, Eriksson 1976, 1979a, Dow 1982, Fredga and Dow 1984) do not mention t e r r i t o r i a l i t y . T e r r i t o r i a l i t y may not be r e s t r i c t e d to the breeding grounds. Barrow's Goldeneye have been observed defending t e r r i t o r i e s on t h e i r w i n t e r i n g ground (Ian Robertson personal communication; personal observation). Also, Sayler and Afton (1981) suggested that some Common Goldeneye defended territories on their wintering area. Comparison of winter and summer t e r r i t o r i a l i t y of Barrow's Goldeneye and of any differences between the three species of Bucephala should therefore provide i n s i g h t into the evolution and functions of t e r r i t o r i a l behaviour in this group. 6 c ) 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 f i r s t t h i r d o f t h e c e n t u r y , V o l t e r r a , L o t k a a n d G a u s e d e v e l o p e d a s i m p l e m a t h e m a t i c a l m o d e l t o d e s c r i b e p o p u l a t i o n g r o w t h i n t w o - s p e c i e s s y s t e m s ( r e v i e w s i n M i l l e r 1 9 6 7 , P i a n k a 1 9 7 8 ) . T h i s l e d t o t h e e l a b o r a t i o n of t h e c o m p e t i t i v e e x c l u s i o n p r i n c i p l e , w h i c h s t a t e s t h a t two s p e c i e s w i t h s i m i l a r n i c h e s c a n n o t l i v e t o g e t h e r a t t h e same p l a c e a t t h e same t i m e . However, t h e model and t h e subsequent t h e o r y b u i l t on i t d e a l o n l y w i t h e q u i l i b r i u m c o n d i t i o n s , w h i c h a r e r a r e i n n a t u r e (Pianka 197 8 ) . F u r t h e r , m o s t o f t h e a s s u m p t i o n s o f t h e m o d e l do n o t h o l d i n n a t u r a l s y s t e m s . C o m p e t i t i v e e x c l u s i o n i s now r e g a r d e d a s o n l y a s m a l l s e g m e n t o f a b r o a d e r c l a s s o f i n t e r s p e c i f i c p h e n o m e n a ( P a t t e n 1 9 6 1 ) , c o e x i s t e n c e o f c l o s e l y r e l a t e d s p e c i e s b e i n g more common t h a n e x c l u s i o n (Den Boer 1 ? 8 0 ) . Some have even d e b a t e d i f t h e p r i n c i p l e o f c o m p e t i t i v e e x c l u s i o n h a s s e r v e d any u s e f u l p u r p o s e (Diamond 1978, J a c k s o n 1981). 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 s o f t e n h a r d t o o b s e r v e i n n a t u r e ( M i l l e r 1 9 6 7 , P i a n k a 197 8 ) , b u t i s p r o b a b l y q u i t e common ( S c h o e n e r 1 9 8 2 , 1 9 8 3 , C o n n e l l 1983). The most o b v i o u s c a s e s o f n a t u r a l l y o c c u r r i n g c o m p e t i t i o n a r e t h o s e i n v o l v i n g i n t e r s p e c i f i c t e r r i t o r i a l i t y . I n t e r s p e c i f i c t e r r i t o r i a l i t y i s common among b i r d s ( S i m m o n s 1 9 5 1 , O r i a n s a n d W i l l s o n 1 9 6 4 , M u r r a y 1971) a n d h a s a l s o b e e n r e p o r t e d i n f i s h e s (Low 1 9 7 1 , E b e r s o l e 1 9 7 7 , M y r b e r g a n d T h r e s h e r 1 9 7 4 , H i x o n 197 9 ) , i n s e c t s ( J o h n s o n a n d H u b b e l l 1974) Crustacea ( D i n g l e £ t a 2 . 1 9 7 3 ) , a n d m a m m a l s ( W o l f f e_t fll. 1 9 8 3 ) . Simmons (1951) s t a t e d t h a t i n t e r s p e c i f i c t e r r i t o r i a l i t y o c c u r s when a s p e c i e s e x h i b i t s p e r s i s t e n t a g g r e s s i v e b e h a v i o u r t o a n i n t r u d i n g b i r d o f a n o t h e r s p e c i e s , s h o w i n g i t s o m e , i f n o t a l l , o f t h e r e a c t i o n s u s u a l l y f o r t h c o m i n g i n i n t r a s p e c i f i c e n c o u n t e r s . He a l s o h y p o t h e s i z e d t h a t i n t e r s p e c i f i c t e r r i t o r i a l i t y s e r v e d t o r e d u c e o r e l i m i n a t e c o m p e t i t i o n 7 between c l o s e l y a l l i e d species with a s i m i l a r ecology. This view was l a t e r shared by Lanyon (1956), Orians and Willson (1964), Grant (1966), and M i l l e r (1967). Cody (196 9) stated that species may converge i n appearance or voice because s i m i l a r i t i e s i n c r e a s e i n t e r s p e c i f i c aggressiveness, which leads to the individuals of two species maintaining mutually exclusive territories i n a common habitat. This results i n the exclusion of competitors for food from the individuals' territories, and i s therefore adaptive. Murray (1971) disagreed with the previous adaptive interpretations of i n t e r s p e c i f i c t e r r i t o r i a l i t y and proposed t h a t i n t e r s p e c i f i c t e r r i t o r i a l i t y resulted most often from misdirected i n t r a s p e c i f i c t e r r i t o r i a l i t y , that i t was not an adaptive characteristic, and therefore should even be selected against. Murray (1976) later c r i t i c i z e d the paper by Cody (1969) on the grounds that the cases Cody presented i n support of his convergence hypothesis did not link any case of convergence with any case of interspecific t e r r i t o r i a l i t y ; hence the hypotheses do not explain any real situation, much less a substantial body of fact. Several recent studies i n f i s h e s suggest t h a t i n t e r s p e c i f i c t e r r i t o r i a l i t y i s not a result of misidentification (Low 1971, Myrberg and Thresher 1974, Katzir 1981b). Ebersole (1977) found a s i g n i f i c a n t c o r r e l a t i o n between the frequency that a t e r r i t o r i a l pomacentrid f i s h attacked trespassers of other species and an index of competitive overlap. S i m i l a r l y , Moore (1978) found a r e l a t i o n s h i p between degree of interspecific aggression by t e r r i t o r i a l Mockingbirds (Mimus polyglottos) and the percentage of dietary overlap with birds competing for f r u i t s on Mockingbird territories. 8 Davies (1978) r e j e c t e d Murray's view t h a t i n t e r s p e c i f i c t e r r i t o r i a l i t y i s not adaptive and occurs through mistaken identity, i n view of the great v a r i a b i l i t y i n appearance and behaviour of the species that e l i c i t aggression i n the pomacentrid fishes, and the very distinctive songs that e l i c i t i n t e r s p e c i f i c aggression i n some birds (Catchpole 1977). He concluded that the evidence suggests that i n t e r s p e c i f i c t e r r i t o r i a l i t y i s b e a u t i f u l l y adapted to the amount of overlap i n resource requirements. Wittenberger (1981) remarked that, according to the m i s i d e n t i f i c a t i o n hypothesis, interspecific t e r r i t o r i a l i t y should evolve among similar species regardless of whether they compete with one another. Instead, i t has evolved among competing species regardless of whether they are similar to one another. Murray's (1971) intention was to caution against the attribution of adaptive advantages to any behaviour without examining alternatives. He presented the misidentification hypothesis as an alternative hypothesis to the adaptationist view and showed with success that i t could explain many cases of i n t e r s p e c i f i c aggression. In a recent review of interspecific t e r r i t o r i a l i t y (Murray 1981), he c l a r i f i e d h i s views and stated that interspecific t e r r i t o r i a l behaviour may originate either as an adaptation to the presence of competitors, or as a fo r t u i t o u s consequence of two species possessing common c h a r a c t e r i s t i c s that normally stimulate i n t r a s p e c i f i c aggression. He maintained, however, that i t can only be adaptive i n the dominant species, and that i t results i n segregation, not coexistence. The o r i g i n and sig n i f i c a n c e of i n t e r s p e c i f i c t e r r i t o r i a l behaviour i s s t i l l the focus of debate (Morse 1980, Murray 1981, Wittenberger 1981). I n t e r s p e c i f i c t e r r i t o r i a l i t y has not yet been described i n waterfowl, although many cases of i n t e r s p e c i f i c c o m p e t i t i o n by 9 e x p l o i t a t i o n (Erskine I960, Myres 1957, Donaghey 197 5, Eriksson 1979a, Nudds 1980, and Eadie and Keast 1982) and i n t e r s p e c i f i c aggression (McKinney et a l . 1978, Weller 1976, Nuechterlein and Storer 1985a, Livezey and Humphrey 1985a) have been documented. The s i g n i f i c a n c e of interspecific aggression i s s t i l l unclear (Murray 1985, Nuechterlein and Storer 1985b, Livezey and Humphrey 1985b). The breeding distributions of Barrow's Goldeneye, Common Goldeneye and Bufflehead overlap i n B r i t i s h Columbia (Bellrose 1978, Palmer 1976). Erskine (1959, 1960) and McLaren (1963, 196 9) have reported competition between Barrow's Goldeneye and Bufflehead for nesting cavities. Other descriptive accounts indicate that competition may not be restricted to nest sites (Munro 1939, Myres 1957, Robertson and Stelfox 1969, Palmer 1976). Myres (1957) observed aggressive interactions between Barrow's Goldeneye and Common Goldeneye. Myres (1957) and Donaghey (1975) reported aggression of Bufflehead toward Common Goldeneye. Barrow's Goldeneye and Bufflehead also e x h i b i t aggression toward other waterfowl species (Myres 1957, 1959a, Andrew 1960, Sugden 1960, Robertson and Stelfox 196 9, Bengtson 1972, Erskine 1972, Donaghey 1975). This indicates that competition on the breeding grounds may be strong. A study of i n t e r s p e c i f i c competition i n the genus Bucephala should provide new perspectives on the causes and consequences of i n t e r s p e c i f i c t e r r i t o r i a l i t y , and shed l i g h t on the controversial phenomenon of interspecific competition (Connor and Simberloff 1979, 1984, Gilpin and Diamond 1984). d) Functions of T e r r i t o r i a l i t y Many publications have focused on the functions of t e r r i t o r i a l i t y since Howard's (1920) book emphasized the concept (Alexander 1921, 10 Jourdain 1921, Lack and Lack 1933, Nice 1941, Hinde 1956, Tinbergen 1957, Carpenter 1958, Brown 1964, Davies 1978). These reviews have stressed the d i v e r s i t y of t e r r i t o r i a l behaviour i n birds and suggested several functions of t e r r i t o r i a l i t y , including: protection of nest s i t e s , attracting or protecting mates, protecting food, spacing out of pairs to reduce predation, disease and exploitation competition, and prevention of overpopulation. Whether t e r r i t o r i a l behaviour l i m i t s population density has been widely debated (Lack and Lack 1933, Brown 1969, Klomp 1972, 1980, Patterson 1980). A few recent studies indicate strongly that t e r r i t o r i a l behaviour can and does l i m i t local population density (Watson and Jenkins 1968, Krebs 1971, Fjeldsa 1973 b, Verner 1977, Hilden 1979, Charles 1972 (in Patterson 1980), Watson and Moss 1980, Klomp 1980, Dhondt e i a l . 1982, V i l l a g e 1983). There are i n d i c a t i o n s that t e r r i t o r i a l i t y may have a similar role in some waterfowl species: Bufflehead successfully exclude other pairs from small ponds (Donaghey 1975, Gauthier 1985), African Black Ducks are strongly t e r r i t o r i a l and must hold a territory to breed (Ball e± aJL. 1978) and t e r r i t o r i a l behaviour during the breeding season may regulate Mountain Duck (Tadorna tadornoides) and Shelduck populations (Riggert 1977, Evans and Pienkowski 1982, Patterson 1982). In Barrow's Goldeneye, t e r r i t o r i a l i t y could have a density-dependent effect on the population during three periods of the year: 1. During spring; when paired drakes defend t e r r i t o r i e s early i n the breeding season, pairs may be excluded from breeding, or at l e a s t excluded from the better feeding areas. 2. During summer; when females with young defend territories, broods can be excluded from productive or safe ponds, and young can be k i l l e d by aggressive females. 11 3. During winter; when paired drakes defend t e r r i t o r i e s on the wintering ground, some pairs may f a i l to obtain a productive territory and the female may not be as f i t when the spring migration a r r i v e s . Pair bonds may break because the male cannot defend a territory. Whether t e r r i t o r i a l behaviour l i m i t s Barrow's Goldeneye density or not i s not known as few studies have been done on the species. An answer to this question would greatly enhance our a b i l i t y to manage the species. 3) Species framework a) Distribution and abundance of Barrow's Goldeneye The d i s t r i b u t i o n of Barrow's Goldeneye i s discontinuous, with two small populations associated with the North A t l a n t i c Ocean and a comparatively large population associated with the Pacific Ocean (Bellrose 197 8). The two A t l a n t i c populations are i s o l a t e d , one i n Iceland estimated at 2,000 in d i v i d u a l s (Gardarsson 1978, 1979a,b) and one i n Quebec estimated at 2,500 individuals (Reed and Bourget 1977). More than 90% of the world population of Barrow's Goldeneye breed west of the Rocky Mountains and winter on the P a c i f i c Ocean from Alaska to C a l i f o r n i a . Current population estimates are crude. Bellrose (197 8) reported 45,000 birds in Alaska, and 70,000 to 100,000 birds i n British Columbia whereas Munro and Goodchild (1981) reported 186,000 birds for B r i t i s h Columbia. Estimates for Washington, Oregon and California indicate less than 8,000 birds (Anonymous 1979, Bellrose 1978, Harris £t a l . 1954). A few other studies have described the d i s t r i b u t i o n of Barrow's Goldeneye in British Columbia (Swarth 1926, Munro 1939), in Yellowstone National Park (Skinner 1937), in Alaska (Gabrielson and Lincoln 1959, King 1963) and i n the eastern United States (Griscom 1945, Hasbrouck 1944). Although the population estimates are questionable, British Columbia 12 appears to be the center of abundance of the species. Barrow's Goldeneye i s the only species of waterfowl i n Canada that has most of the world population breeding and wintering within a single province. This r e s t r i c t e d d i s t r i b u t i o n makes the species p a r t i c u l a r l y susceptible to environmental threats. b) Behaviour and ecology of Barrow's Goldeneye The elaborate courtship behaviour of Barrow's Goldeneye has been thoroughly described (Sawyer 1928, Myres 1957, 1959a, 1959b, Nickell 1966, Palmer 1976, Cramp and Simmons 1977, Pourtois 197 8). Some authors have described the aggressive behaviour of the drake (Myres 1957, Palmer 1976), but the causes and consequences of such aggression have not been investigated. Brief reports (Andrew 196 0, Sugden 1960, Robertson and Stelfox 196 9) suggest that females become highly aggressive after the young have hatched. Only a few studies have documented the breeding biology of Barrow's Goldeneye. Palmer (1976) reported the work of Mary Jackson i n B r i t i s h Columbia. Her work complemented the earlier observations of Munro (1918, 1939), Brooks (1920) and Bent (1923), and provided basic information on clutch size and breeding success for the species. Work on the small Icelandic population by Bengtson (1971, 1972) provides the only other a v a i l a b l e information on the breeding ecology of Barrow's Goldeneye. Barrow's Goldeneye nest p r i m a r i l y i n tree c a v i t i e s i n B r i t i s h Columbia (Brooks 1903, Munro 1939) but occasionally use crows' nests (Edwards 1953, Sugden 196 3) and marmot burrows (Munro 1935). In Iceland they nest i n c a v i t i e s on the ground among basalt rocks, (Bengtson 197 0). S i m i l a r l y , they use holes i n basalt c l i f f s i n eastern Washington (Harris a l . 1954) . 13 Barrow's Goldeneye feed on invertebrates during the breeding season, especially on damselfly and dragonfly larvae, chironomids, and amphiphods (Cottam 1939, Munro 1939). In winter, they are found along rocky shores where they feed on mussels and crustaceans (Cottam 1939, Munro 1923, 1939, Mitchell 1952, Vermeer 1982, Koehl e t a l . 1984). This short review l i s t s most of the published literature on Barrow's Goldeneye at the time my study was initiated. c) Common Goldeneye and Bufflehead By 1980, several d e t a i l e d studies had been published on the congeners of Barrow's Goldeneye. Works by Munro (1942), Erskine (1972) and Donaghey (1975) provided a thorough overview of the breeding biology and t e r r i t o r i a l behaviour of Bufflehead. Common Goldeneye had been widely studied i n Europe and North America (Munro 1939, Siren 1952, Carter 1958, Gibbs 1961, t r i n c e 1965, 1968, Rajala and Ormio 1971, Eriksson 197 9b). During the course of this study, new studies have furthered our knowledge of the genus Bucephala. Gauthier (1985) presented a detailed analysis of t e r r i t o r i a l i t y in the Bufflehead, and Dow (1982) summarized a long-term study of the breeding biology of Common Goldeneye. She also published several papers on the facto r s influencing their reproductive success i n nest boxes (Dow and Fredga 1983, 1984, 1985, Fredga and Dow 1983, 1984). 4) Focus of the study The main questions I asked were: 1. Is the t e r r i t o r i a l behaviour of Barrow's Goldeneye similar to that of Bufflehead? 2. Are CoiMi.on Goldeneye t e r r i t o r i a l i n North America and, i f so, i s their behaviour similar to that of Barrow's Goldeneye and Bufflehead? 14 3 . A r e t h e t h r e e s p e c i e s i n t e r s p e c i f i c a l l y t e r r i t o r i a l ? 4 . What a r e t h e f u n c t i o n s o f t e r r i t o r i a l i t y i n B a r r o w ' s G o l d e n e y e ? To e v a l u a t e t h i s , I q u a n t i f i e d some f a c t o r s a f f e c t i n g t h e r e p r o d u c t i v e s u c c e s s o f B a r r o w ' s G o l d e n e y e and a d d r e s s e d t h e f o l l o w i n g q u e s t i o n s : 5 . What a r e t h e s i m i l a r i t i e s between 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 m a l e s i n t h e s p r i n g and w i n t e r and t h a t o f t h e f e m a l e i n t h e summer? 6 . I s t h e b r e e d i n g d e n s i t y o f B a r r o w ' s G o l d e n e y e l i m i t e d b y n e s t s i t e a v a i l a b i l i t y ? 7 . What i s t h e n e s t i n g s u c c e s s o f B a r r o w ' s G o l d e n e y e a n d w h a t f a c t o r s a f f e c t i t ? 8 . What f a c t o r s i n f l u e n c e b r o o d s u r v i v a l i n B a r r o w ' s G o l d e n e y e ? 9 . W i l l an i n c r e a s e i n B a r r o w ' s Goldeneye d e n s i t y n e g a t i v e l y i n f l u e n c e B u f f l e h e a d d e n s i t y ? 1 0 . C a n t e r r i t o r i a l b e h a v i o u r i n B a r r o w ' s G o l d e n e y e l i m i t b r e e d i n g d e n s i t y ? Q u e s t i o n s 1 t o 5 a r e a d d r e s s e d i n C h a p t e r I I I , q u e s t i o n s 6-7 i n C h a p t e r I V , q u e s t i o n s 8 - 9 i n C h a p t e r V , and q u e s t i o n 10 i n C h a p t e r V I . E a c h o f t h e s e q u e s t i o n s h a s b o t h t h e o r e t i c a l a n d p r a c t i c a l a p p l i c a t i o n s b e c a u s e no d e t a i l e d s t u d i e s h a v e e v e r b e e n d o n e o n t h e b r e e d i n g e c o l o g y o f B a r r o w ' s G o l d e n e y e i n N o r t h A m e r i c a . The e m p h a s i s o f t h e s t u d y , h o w e v e r , was o n t h e d e s c r i p t i o n and c h a r a c t e r i z a t i o n o f i n t r a -and i n t e r s p e c i f i c t e r r i t o r i a l b e h a v i o u r o f B a r r o w ' s Goldeneye and o n t h e s i g n i f i c a n c e and f u n c t i o n s o f t e r r i t o r i a l i t y w i t h i n t h e genus B u c e p h a l a . I i n s t a l l e d n e s t b o x e s t o i n c r e a s e b r e e d i n g d e n s i t i e s o f B a r r o w ' s G o l d e n e y e a n d t h u s f a c i l i t a t e t h e s t u d y o f t e r r i t o r i a l i t y . M o n i t o r i n g o f n e s t b o x e s p r o v i d e d d a t a o n t h e f a c t o r s a f f e c t i n g t h e n e s t i n g s u c c e s s o f B a r r o w ' s G o l d e n e y e and t h e i r use of n e s t b o x e s . I m o n i t o r e d s u r v i v a l o f 1 5 B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d b r o o d s t o d e t e r m i n e a n y e f f e c t o f t e r r i t o r i a l i t y o n r e p r o d u c t i v e s u c c e s s . I d e v o t e d s p e c i a l a t t e n t i o n t o t h e i n t e r a c t i o n s between B a r r o w ' s G o l d e n e y e and B u f f l e h e a d . I h a v e o r g a n i z e d t h e r e m a i n d e r o f t h e t h e s i s a s f o l l o w s : I n C h a p t e r I I , I d e s c r i b e t h e s t u d y a r e a s and t h e g e n e r a l methods u s e d . I n C h a p t e r I I I , I d e s c r i b e , a n a l y s e , a n d d i s c u s s t e r r i t o r i a l b e h a v i o u r o f B a r r o w ' s G o l d e n e y e a n d i t s c o n g e n e r s . I n C h a p t e r I V , I i d e n t i f y a n d q u a n t i f y some o f t h e f a c t o r s a f f e c t i n g n e s t box use b y B a r r o w ' s Goldeneye a n d t h e i r n e s t i n g s u c c e s s . I n C h a p t e r V , I a n a l y s e a n d c o m p a r e b r o o d s u r v i v a l i n B a r r o w ' s Goldeneye and B u f f l e h e a d . I n C h a p t e r V I I r e v i e w t h e m a j o r f i n d i n g s o f t h e s t u d y i n r e l a t i o n t o t h e q u e s t i o n s I have a s k e d . I n A p p e n d i x 1 , I d e s c r i b e t h e e f f i c i e n c y o f m i r r o r t r a p s t o c a p t u r e t e r r i t o r i a l w a t e r f o w l . I n A p p e n d i x 2 , I p r e s e n t e v i d e n c e s u g g e s t i n g t h e e x i s t e n c e o f l o n g t e r m p a i r bonds i n B a r r o w ' s G o l d e n e y e . I n A p p e n d i x 3 I d e s c r i b e f o u r o b s e r v a t i o n s w h i c h shed l i g h t on t h e c a u s e s and mechanism o f b r o o d a m a l g a m a t i o n i n B a r r o w ' s G o l d e n e y e , and i n A p p e n d i x 4 , I document f o u r c a s e s o f p o l y g y n y i n B a r r o w ' s G o l d e n e y e . P o r t i o n s o f C h a p t e r I I I and C h a p t e r I V h a v e a l r e a d y b e e n p u b l i s h e d ( S a v a r d 1 9 8 2 b , c , 1 9 8 4 ) . A p p e n d i c e s 1 , 2 a n d 4 h a v e b e e n p u b l i s h e d s e p a r a t e l y (Savard 1 9 8 5 a , b , 1986). 16 Chapter II: General methods 17 1) STUDY SITES a) Riske Creek (summer) T h i s i s t h e m a i n s t u d y a r e a . I t c o v e r s a b o u t 1 0 0 k m ^ n e a r R i s k e C r e e k i n c e n t r a l B r i t i s h C o l u m b i a . I t i s l o c a t e d o n t h e C h i l c o t i n P l a t e a u , 1000 m above s e a l e v e l ( F i g . 1 ) . The s t u d y a r e a i s i n c l u d e d i n t h e C a r i b o o - A s p e n - L o d g e p o l e P i n e - D o u g l a s F i r P a r k l a n d B i o g e o c l i m a t i c Zone o f K r a j i n a (1969, 1973). The t e r r a i n i s r o l l i n g savannah u p l a n d d o m i n a t e d b y A g r o p y r o n s p i c a t u m a n d s t a n d s o f P o p u l u s t r e m u l o i d e s , P s e u d o t s u g a  m e n z i e s i i , a n d P i n u s c o n t o r t a ( C a n n i n g s a n d S c u d d e r 197 8 ) . T h e m o s t i m p o r t a n t i n f l u e n c e o n t h e c l i m a t e of t h e a r e a i s t h e r a i n s h a d o w e f f e c t o f t h e C o a s t M o u n t a i n s ( B e i l 1974). P r e c i p i t a t i o n a v e r a g e s 35 cm a n n u a l l y , w i t h J u n e h a v i n g t h e h i g h e s t m o n t h l y p r e c i p i t a t i o n . A v e r a g e a n n u a l t e m p e r a t u r e s a r e l o w w i t h mean d a i l y t e m p e r a t u r e s o f -11.6 and 1 3 . 7 ° C f o r J a n u a r y a n d J u l y , r e s p e c t i v e l y . F l u c t u a t i o n s i n d a i l y t e m p e r a t u r e s a r e l a r g e (Cannings and Scudder 1978). L a k e s w i t h i n t h e s t u d y a r e a r a n g e i n s i z e f r o m 0.1 t o 5 4 . 0 h a (n=117). C o n d u c t i v i t y m e a s u r e m e n t s v a r y g r e a t l y b e t w e e n t h e s e l a k e s r a n g i n g b e t w e e n 42 m i c r o m h o s / c m ( a t 2 5 ° C ) a n d 1 7 , 0 5 0 m i c r o m h o s / c m ( a t 2 5 ° C ) . Most w a t e r b o d i e s l a c k i n l e t and o u t l e t s t r e a m s and a r e d e v o i d o f f i s h e s (Scudder 1969). S e a s o n a l and a n n u a l v a r i a t i o n s i n c o n d u c t i v i t y a r e i m p o r t a n t , a n d may a f f e c t t h e a q u a t i c f a u n a ( S c u d d e r 196 9 , L a n c a s t e r 1 9 8 5 ) . C a n n i n g s ( 1 9 7 3 ) , T o p p i n g a n d S c u d d e r (1977) a n d S p e n c e (1979) p r e s e n t d e t a i l e d a n a l y s i s o f t h e c h e m i c a l c o m p o s i t i o n of s e v e r a l l a k e s i n t h e s t u d y a r e a . I n t h i s s t u d y a r e a , I l o o k e d a t i n t r a - and i n t e r s p e c i f i c a g g r e s s i o n o f B a r r o w ' s G o l d e n e y e , a n d s t u d i e d t h e i r b r e e d i n g b i o l o g y i n d e t a i l . 1 8 F i g . 1 L o c a t i o n o f s t u d y a r e a s . b) Columbia Valley (summer) This study s i t e was located i n the upper section of the Columbia valley near Invermere, British Columbia, Canada (Fig. 1). The valley i s part of the Rocky Mountain Trench and i s bordered on the west by the Selkir k Range and on the east by various ranges of the Rocky Mountains. The valley can be divided into two habitats: (1) the flood plain contains several ponds created by the flooding of the Columbia River each spring. The s a l i n i t y of these ponds i s low. A sample of 8 ponds averaged 619+67 (S.E.) micromhos/cm and ranged from 449 to 900 micromhos/cm; (2) the benches, 300 m above the flood p l a i n , contain small, i s o l a t e d lakes and ponds that vary greatly i n conductivity. A sample of 12 upland ponds averaged 147 9+371 micromhos/cm i n conductivity and ranged from 220 to 4,200 micromhos/cm. The ponds on the benches are therefore s i m i l a r to those found near Riske Creek. This site was chosen to look at the t e r r i t o r i a l behaviour of Common Goldeneye and at the spacing behaviour of the three species of Bucephala in a zone of aympatry. c) Vancouver (winter) This study site was located along the shores of Burrard Inlet in and near Vancouver, British Columbia (Fig. 1). The shoreline consisted of a mixture of sandy beaches and rocky shores. Goldeneye fed along the rocky shores, where they mainly took mussels (Vermeer 1982). At t h i s s i t e , I studied the wintering ecology of Barrow's Goldeneye, e s p e c i a l l y t h e i r t e r r i t o r i a l behaviour. 20 2) GENERAL METHODS a) C a p t u r e and M a r k i n g B a r r o w ' s Goldeneye w e r e c a p t u r e d o n t h e b r e e d i n g a r e a s i n t w o w a y s : 1) F e m a l e s were c a p t u r e d o n t h e n e s t d u r i n g t h e l a s t week o f i n c u b a t i o n . 2) M a l e s and f e m a l e s w e r e c a p t u r e d i n m i r r o r t r a p s e a r l y i n t h e b r e e d i n g s e a s o n ( s e e A p p e n d i x 1 f o r d e t a i l s o f t h e t r a p a n d i t s e f f i c i e n c y ) . A l l c a p t u r e d b i r d s w e r e w e i g h e d , banded and f i t t e d w i t h n y l o n n a s a l d i s k s o f v a r i o u s c o l o u r s ( r e d , w h i t e , y e l l o w , g r e e n , g r a y , b l u e , b l a c k ) and shapes ( c i r c l e , o v a l , s q u a r e , c r o s s , Y) (Lokemoen and S h a r p 1979). The speculum o f t h e b i r d s was a l s o p a i n t e d v a r i o u s c o l o u r s w i t h a i r p l a n e s p r a y p a i n t , t o f a c i l i t a t e i d e n t i f i c a t i o n o f i n d i v i d u a l s . B i r d s r a p i d l y b e c a m e a c c u s t o m e d t o t h e d i s k s and no o b v i o u s d e l e t e r i o u s e f f e c t s were o b s e r v e d . b) Age d e t e r m i n a t i o n The age o f each b r o o d was d e t e r m i n e d i n t h e f i e l d u s i n g t h e c r i t e r i a o f G o l l o p and M a r s h a l l (1954). They c l a s s i f i e d d u c k l i n g s i n t o s e v e r a l age c l a s s e s b a s e d o n plumage g r o w t h . The c o r r e s p o n d e n c e o f t h o s e age c l a s s e s w i t h t h e a g e o f t h e d u c k l i n g s i n d a y s w a s d e r i v e d f r o m S c h n e i d e r (1965) a n d E r s k i n e (197 2) f o r B u f f l e h e a d . B e c a u s e S c h n e i d e r ' s (196 5) a n d E r s k i n e ' s (197 2) d a t a d i f f e r e d , I u s e d t h e a g e c l a s s e s g i v e n f o r L e s s e r S c a u p ( A y t h y a a f f i n i s ) a s a n a p p r o x i m a t i o n o f B u f f l e h e a d a g e c l a s s e s (Taber 1971). E r s k i n e (1972) i n d i c a t e d t h a t B u f f l e h e a d a n d L e s s e r S c a u p h a d s i m i l a r g r o w t h p a t t e r n s . S u c h d a t a a r e n o t a v a i l a b l e f o r B a r r o w ' s G o l d e n e y e ; I t h e r e f o r e a s s u m e d t h e i r g r o w t h t o be s i m i l a r t o t h a t o f Common G o l d e n e y e (Gibbs 1961). G o l d e n e y e f e m a l e s w i t h orange b i l l s w e r e assumed t o be a d u l t s w h e r e a s t h o s e w i t h p r e d o m i n a n t l y dark b i l l s were c l a s s i f i e d a s s u b a d u l t s . T h i s d i s t i n c t i o n h o l d s u n t i l t h e o n s e t of i n c u b a t i o n , when t h e b i l l s o f a d u l t 21 females darken. Subadult drakes were characterized by the presence of an incomplete white crescent on the side of the face (Palmer 1976). c) Surveys Each year from 1980 to 1984, four pair counts were done within a 2-week period. Birds were counted from the shore with a spotting scope and the observations were recorded on data sheets by an assistant or on a tape recorder. It took from 2 to 2 1/2 days to complete a survey of the 117 ponds on the Riske Creek study area. After broods had hatched, the ponds were surveyed from 3 to 4 times to determine the number of broods on the study area. Because hatching i s spread over several weeks, only an estimate can be obtained for numbers of broods. d) S t a t i s t i c a l analysis Means are presented throughout the text + S.E. unless otherwise s p e c i f i e d . Chi-square test s were done on the observed frequencies. Student's T-test was used to detect significant differences between means. Data were log transformed when the variance of the two samples was unequal. Mulciple comparisons were performed using the Student Newman-Keuls test (Zar 1974). Because some aspects were studied i n only one year whereas others were studied during several years, t o t a l s vary between tables. 22 Chapter III: T e r r i t o r i a l behaviour 23 Introduction My a i m i n t h i s c h a p t e r i s t o d e s c r i b e and q u a n t i f y t h e phenomenon o f t e r r i t o r i a l i t y i n B a r r o w ' s G o l d e n e y e , and t o c o n s i d e r i t s f u n c t i o n s . The c h a p t e r i s d i v i d e d i n t o t h r e e p a r t s . I n t h e f i r s t p a r t , I d e s c r i b e a n d q u a n t i f y t h e i n t r a s p e c i f i c t e r r i t o r i a l b e h a v i o u r of p a i r s on t h e b r e e d i n g and w i n t e r i n g a r e a s , and o f f e m a l e s d u r i n g b r o o d r e a r i n g . I n t h e second p a r t , I d e s c r i b e a n d q u a n t i f y i n t e r s p e c i f i c a g g r e s s i o n . F i n a l l y , I a n a l y s e v a r i o u s a s p e c t s o f t h e t e r r i t o r y i t s e l f . Throughout I compare t h e b e h a v i o u r o f B a r r o w ' s Goldeneye t o t h a t o f Common G o l d e n e y e and B u f f l e h e a d t o o b t a i n a n o v e r v i e w o f t e r r i t o r i a l i t y i n t h e genus. METHODS I n 1 9 8 2 I e s t i m a t e d t h e t i m e b u d g e t s o f s e v e r a l t e r r i t o r i a l p a i r s d u r i n g 141 h o u r s o f o b s e r v a t i o n . O b s e r v a t i o n p e r i o d s l a s t e d f r o m 1 t o 4 h o u r s . A t 2 m i n u t e i n t e r v a l s , I o b s e r v e d e a c h member o f a p a i r f o r s e v e r a l s e c o n d s a n d r e c o r d e d t h e i r d o m i n a n t a c t i v i t y . I u s e d t h e f o l l o w i n g c a t e g o r i e s : f e e d i n g , r e s t i n g ( i n c l u d i n g s l e e p i n g and s w i m m i n g ) , p r e e n i n g , t e r r i t o r i a l d e f e n s e ( a g g r e s s i o n ) , and d i s p l a y i n g ( n o n - a g g r e s s i v e d i s p l a y s ) . T h i s s a m p l i n g p r o c e d u r e p r o v i d e d a n e s t i m a t e o f t h e t i m e b u d g e t o f e a c h b i r d u n d e r o b s e r v a t i o n . P r e l i m i n a r y s a m p l i n g h a d s h o w n t h a t most a c t i v i t i e s o c c u r r e d i n b o u t s o f s e v e r a l m i n u t e s d u r a t i o n . F o r e x a m p l e , i f a b i r d f e d i t w o u l d do s o f o r 15 t o 40 m i n . s t r e t c h e s . T o t a l s a m p l i n g e f f o r t w a s d i s t r i b u t e d a s f o l l o w s : 56 h b e f o r e 0 900 h , 4 9 h between 0900 h and 1200 h , 36 h a f t e r 1800 h . A l l a g g r e s s i v e i n t e r a c t i o n s o b s e r v e d d u r i n g p a i r a n d b r o o d c o u n t s (see G e n e r a l Methods) w e r e r e c o r d e d . I n t e n s i v e b e h a v i o u r a l o b s e r v a t i o n s w e r e made on some ponds t o e s t i m a t e t h e f r e q u e n c y o f i n t e r a c t i o n s between t e r r i t o r i a l p a i r s . I made b e h a v i o u r a l o b s e r v a t i o n s o f p a i r s (264 h) a n d 24 o f f e m a l e s w i t h b r o o d s (410 h ) . D u r i n g t h e s e o b s e r v a t i o n s , I o b s e r v e d b i r d s f r o m a d i s t a n t v a n t a g e p o i n t a n d r e c o r d e d a c o m m e n t a r y o n a l l i n t e r a c t i o n s on a u d i o t a p e . For each i n t e r a c t i o n , I r e c o r d e d t h e i d e n t i t y o f t h e a g g r e s s o r and t h e v i c t i m , and t h e outcome of t h e i n t e r a c t i o n . I c l a s s i f i e d t h e r e a c t i o n s o f t e r r i t o r i a l b i r d s t o i n t r u d e r s a c c o r d i n g t o t h e i r i n t e n s i t y a n d g r o u p e d t h e m i n t o t h r e e c a t e g o r i e s : t h r e a t , a t t a c k and f i g h t . A t h r e a t c o n s i s t e d o f t h e b i r d e l o n g a t i n g i t s neck a l o n g t h e w a t e r and f l a t t e n i n g i t s b o d y , p o i n t i n g t o w a r d t h e i n t r u d e r o r t u r n i n g s i d e w a y s . A t t a c k s w e r e o f t h r e e t y p e s : 1) u n d e r w a t e r d i v e t o w a r d t h e v i c t i m , 2) r u s h o v e r t h e w a t e r , a n d 3) a e r i a l p u r s u i t . F i g h t s s o m e t i m e s o c c u r r e d b e t w e e n n e i g h b o u r i n g m a l e s . Those c a t e g o r i e s a r e c u m u l a t i v e i n t h a t a f i g h t w a s u s u a l l y p r e c e d e d b y a t h r e a t a n d a n a t t a c k . For each i n t e r a c t i o n , h o w e v e r , I o n l y r e c o r d e d t h e h i g h e s t l e v e l r e a c h e d . I n 1 9 8 2 , I q u a n t i f i e d i n t e r s p e c i f i c a g g r e s s i o n i n B a r r o w ' s G o l d e n e y e . I r e c o r d e d t h e number o f t i m e s a g i v e n s p e c i e s was o b s e r v e d w i t h i n 3 m o f a t e r r i t o r i a l B a r r o w ' s G o l d e n e y e d r a k e w i t h o u t b e i n g t h r e a t e n e d o r a t t a c k e d , a n d d e f i n e d t h i s a s a c a s e o f t o l e r a n c e . To e n s u r e t h a t t h e r e c o r d s w e r e i n d e p e n d e n t o b s e r v a t i o n s , a g i v e n i n d i v i d u a l was r e c o r d e d a s t o l e r a t e d o n l y o n c e , e v e n i f i t s t a y e d f o r s e v e r a l m i n u t e s n e a r t h e g o l d e n e y e d r a k e . I f t w o o r t h r e e b i r d s w e r e t o l e r a t e d s i m u l t a n e o u s l y , t h e y w e r e r e c o r d e d a s a g r o u p . G r o u p s c o n t a i n i n g s e v e r a l s p e c i e s w e r e r e c o r d e d a s 1 t o l e r a n c e p e r s p e c i e s . The f r e q u e n c y o f t o l e r a t e d b i r d s was u s u a l l y l o w b e c a u s e most b i r d s a v o i d e d t e r r i t o r i a l B a r r o w ' s G o l d e n e y e a n d r a r e l y swam c l o s e t o them. B e f o r e each o b s e r v a t i o n p e r i o d I c o u n t e d t h e number o f b i r d s p r e s e n t o n t h e p o n d , i t ie number o f b i r d - h o u r s was u s e d when e x a m i n i n g t h e number 2 5 of interactions recorded for each species. I divided waterfowl into three groups: 1) dabbling ducks, which included Mallard (Anas platyrhynchos), Gadwall (A. strepera), American Wigeon (A. americanus), Northern Pi n t a i l (A., acuta), Green-winged Teal (A. crecca), Blue-winged Teal discors), Northern Shoveler (A_. cjypeata) ? 2) diving ducks, which included Redhead (Aythya americana), Ring-necked Duck (&. c o l l a r i s ) , Canvasback (A. v a l i s i n e r i a ) , Scaup (A. maxila. and A., a f f i n i s ) (not distinguished i n the f i e l d , marila i s a migrant in the area whereas a f f i n i s breed in the study area); Surf Scoter (Melanitta p e r s p i c i l l a t a ) and Ruddy Duck (Oxyura  jamaicensis): 3) Congeners, Bufflehead (Bucephala albeola) and Common Goldeneye (B. Clangula). A l l these species except the Surf Scoter and Greater Scaup breed in the study area. RESULTS 1) Intraspecific Aggression a) T e r r i t o r i a l behaviour of pairs Breeding areas - Barrow's Goldeneye drakes maintained well-defined t e r r i t o r i e s (0.70+0.07 ha i n size) from which they excluded a l l other goldeneyes but t h e i r mate. A t e r r i t o r i a l male t y p i c a l l y reacted to intruders by adopting a threat posture, flattening and slightly submerging h i s body, and elongating h i s neck on the water (see Myres 1959b, Palmer 1976). If the intruder persisted, the t e r r i t o r i a l male then swam toward him i n the threat posture and attacked him either by diving and resurfacing underneath or by rushing at the intruder flapping his wings on the water. Usually the intruder took f l i g h t but in some cases fights and even a e r i a l pursuit ensued. Confrontations between males resulted i n proportionally fewer attacks (42%) than confrontations with either pairs (63%), females (83%) or subadults (76%) (Fig. 2). This i s because 26 T Y P E O F I N T E R A C T I O N M A L E P A I R F E M A L E S U B - A D U L T " = 9 9 7 n = 2 2 4 n = i i 2 n = 2 4 C O N S P E C I F I C I N T R U D E R F i g . 2 Frequency o f t y p e s o f i n t r a s p e c i f i c i n t e r a c t i o n s b e t w e e n t e r r i t o r i a l male B a r r o w ' s G o l d e n e y e and i n t r u d e r s d u r i n g t h e b r e e d i n g s e a s o n . (Based o n 264 h o f o b s e r v a t i o n . ) 27 i n t e r a c t i o n s between neighbouring t e r r i t o r i a l paired males tended to be more ritualized and less violent, resulting in proportionally more threats than attacks (Fig. 3). Strange pairs intruding into a t e r r i t o r y e l i c i t e d the strongest reaction from t e r r i t o r i a l drakes. They were immediately attacked and chased o f f the t e r r i t o r y . This i s not r e f l e c t e d i n Fig. 2 because interactions with neighbouring pairs and strange pairs were not recorded separately. Although less intense, interactions between neighbours lasted longer. Drakes often made lengthy displays at the boundaries of their territories. They faced each other 3 to 10 m apart i n threat posture, diving to resurface at the same loca t i o n . Males also swam p a r a l l e l to each other along the boundary of the t e r r i t o r y . Most of these "boundary displays" l a s t e d l e s s than 1 min. but some laste d f o r 20 minutes. These displays occurred almost exclu s i v e l y between neighbouring t e r r i t o r i a l drakes (Fig. 2). Te r r i t o r i a l drakes were dominant to a l l intruders on their territory. On over 20 occasions I saw males chase a trespassing neighbouring male back into h i s t e r r i t o r y to be chased i n turn by the l a t t e r , the confrontation ending with both males doing boundary displays. Males defended the t e r r i t o r y even when t h e i r mate was absent (Table 1). Lone males even attacked females that trespassed into t h e i r territory. There was no obvious effect of the presence of the female on the t e r r i t o r i a l aggressiveness of the male. Time budgets of males were not affected s i g n i f i c a n t l y o v e r a l l by the presence or absence of t h e i r mate (Fig. 4). The proportion of time spent i n t e r r i t o r i a l defense was 11% when the female was present and 13% when she was absent. 28 P A I R E D M A L E U B A C H € L - O R n B87 n B 4 8 I N T R U D E R Pig. 3 • Frequency of threats and attacks by territorial male Barrow's Goldeneye toward paired neigh-bouring males and bachelor males. (x2=23.28, df=l, P<0.001; n=number of interactions) 29 Table 1. T e r r i t o r i a l defense (number of interactions) by paired drakes in relation to the presence of their mates1. Females present Females absent (35 h ) 2 (60 h) Intruder Threat Attack Boundary Display Total Threat Attack Boundary Display Total Male 14 34 18 66 13 18 19 50 Pair - 3 - 3 1 3 4 8 Female - - - - 1 11 - 12 Total 14 37 18 69 15 32 23 70 No. of interactions/hour 1.97 1.18 Two neighbouring paired males were observed with and without their mates. Number of hours of observation. R E 8 T I N Q P R E E N I N G A G Q R E 8 8 I O N D I S P L A Y I N G M A L E A C T I V I T Y : Percentage of time spent by Barrow's Goldeneye males in various activities in relation to the presence or absence of their mates. 31 Some t e r r i t o r i a l d r a k e s w e r e i n v o l v e d i n m o r e i n t e r a c t i o n s t h a n o t h e r s ( T a b l e s 2 - 3 ) . The number and t y p e s o f i n t e r a c t i o n s depended upon t h e l o c a t i o n o f t h e t e r r i t o r y a n d t h e d i s t r i b u t i o n o f n e i g h b o u r i n g t e r r i t o r i e s . P a i r B ( T a b l e 2) w a s t h e c e n t r a l p a i r ( F i g . 5a) a n d t h e r e f o r e was t h e v i c t i m o f t w i c e a s many i n t e r a c t i o n s a s t h e two o t h e r p a i r s . P a i r s A and D (Table 3) h a d more i n t e r a c t i o n s w i t h B u f f l e h e a d t h a n B o r C , b e c a u s e t h e i r t e r r i t o r i e s b o r d e r e d B u f f l e h e a d t e r r i t o r i e s ( F i g . 5 b ) . A l s o d r a k e s B a n d C h a d f e w e r i n t e r a c t i o n s w i t h o t h e r g o l d e n e y e t h a n d r a k e A . T h e s p a c e o c c u p i e d b y p a i r s A , E a n d F w a s m o d i f i e d d a i l y b y t h e a r r i v a l o r d e p a r t u r e o f o t h e r p a i r s w h e r e a s t h e t e r r i t o r i e s o f B a n d C r e m a i n e d c o n s t a n t t h r o u g h o u t t h e o b s e r v a t i o n p e r i o d . P a i r e d f e m a l e s r a r e l y p a r t i c i p a t e d i n t e r r i t o r i a l d e f e n s e a n d s p e n t t h e i r t i m e f e e d i n g a n d r e s t i n g w i t h i n t h e i r m a t e ' s t e r r i t o r y . F e m a l e s s p e n t o n a v e r a g e t w i c e a s much t i m e f e e d i n g w i t h i n t h e t e r r i t o r y a s d i d m a l e s ( F i g . 6 ) . B o t h m a l e s a n d f e m a l e s s p e n t s i m i l a r a m o u n t s o f t i m e p r e e n i n g a n d d i s p l a y i n g . T h i s d i v i s i o n o f t i m e s u g g e s t s t h a t i n t h e s p r i n g a f e m a l e ' s f o o d r e q u i r e m e n t i s much h i g h e r t h a n a m a l e ' s , a n d t h a t t e r r i t o r i a l d e f e n s e a l t h o u g h o c c u p y i n g a f i f t h o f t h e m a l e ' s t i m e , may n o t b e a s d e m a n d i n g a s e g g l a y i n g i s f o r t h e f e m a l e . I n f a c t , t h e m o s t f r e q u e n t a c t i v i t y o f m a l e s was r e s t i n g . The a v e r a g e p r o p o r t i o n o f t i m e s p e n t f e e d i n g b y m a l e s a n d f e m a l e s r e s p e c t i v e l y d i d n o t d i f f e r s i g n i f i c a n t l y b e t w e e n t h e t h r e e sampled p e r i o d s (0500-0900 h ; 0900-1200 h ; 1700-2100 h) (P=0.9 f o r m a l e s a n d P=0.7 f o r f e m a l e s ) . E a r l y i n t h e s e a s o n when t e r r i t o r i e s a r e e s t a b l i s h e d , f e m a l e s s o m e t i m e s i n c i t e d t h e i r m a l e s t o a t t a c k i n t r u d e r s , and o c c a s i o n a l l y a t t a c k e d o t h e r b i r d s , e s p e c i a l l y o t h e r f e m a l e s . 3 2 Table 2. C o m p a r i s o n o f a g g r e s s i v e i n t e r a c t i o n s o f t h r e e t e r r i t o r i a l Barrow's Goldeneye d r a k e s on c o n t i g u o u s t e r r i t o r i e s on l a k e 13 (1 982) ( a l l p a i r s were o b s e r v e d s i m u l t a n e o u s l y f o r 22 h). Aggressor V i c t i m P a i r A P a i r B 1 P a i r C T o t a l P a i r A — 19 7 26 P a i r B 22 — 51 73 P a i r C 2 32 — 34 T o t a l 24 51 58 133 P a i r B had the c e n t r a l t e r r i t o r y (see F i g . 5 ) . 33 Table 3. Number o f a g g r e s s i v e i n t e r a c t i o n s i n w h i c h e a c h t e r r i t o r y h o l d e r was i n v o l v e d d u r i n g 25 h o u r s o f o b s e r v a t i o n on lake 89 (1981). T e r r i t o r y h o l d e r Barrow's Goldeneye B u f f l e h e a d Aggressor or v i c t i m A B C D E F T o t a l Barrow's Goldeneye 39 23 21 27 13 7 130 B u f f l e h e a d 6 2 4 13 8 8 41 Other 2 3 8 0 0 6 19 T o t a l 47 28 33 40 21 21 190 see F i g . 5 f o r t e r r i t o r y l o c a t i o n s . 34 L A K E 1 3 L A K E 8 8 100 meters A B C D - B A R R O W ' S G O L D E N E Y E T E R R I T O R I E S E F - B U F F L E H E A D TERRITORIES Fig. 5 Location of t e r r i t o r i e s of paired Barrow's Goldeneye drakes on Lake 13 (1982) and Lake 89 (1981) . 3 5 6 0 -FEEDING RESTING PREENING AGGRESSION DISPLAYING MALE AND FEMALE ACTIVITY F i g . 6 A v e r a g e % o f t i m e ( ± S . E . ) s p e n t b y m a l e a n d f e m a l e B a r r o w ' s Goldeneye i n v a r i o u s a c t i v i t i e s w i t h i n t h e i r t e r r i t o r y . ( N i n e p a i r s w e r e o b s e r v e d a n d o b s e r v a t i o n t i m e p e r p a i r r a n g e d between 7 h and 28 h a v e r a g i n g 1 6 . 3 h . ) 36 The sex ratio of Barrow's Goldeneyes was biased toward males. Males outnumbered females by a factor of 1.43+0.03 (n=8 counts over 4 years, each estimate based on more than 500 birds). The r a t i o i s even more skewed i f only unpaired birds are considered: unpaired males outnumbered unpaired females by a factor of 3.0+0.2 (n=8) counts). Thus, competition for females i s strong between males. Common Goldeneye and Bufflehead also maintained i n t r a s p e c i f i c territories (Tables 4-5). The t e r r i t o r i a l behaviour of Common Goldeneye was s i m i l a r to that of the Barrow's Goldeneye: fewer confrontations between males resulted i n attacks (30%) (X2=31.21, df=3, P<0.001) than confrontations with p a i r s (65%), females (68%) and yearlings (90%). The l a s t three classes of i n d i v i d u a l s did not d i f f e r s i g n i f i c a n t l y i n t h e i r l i k e l i h o o d of being attacked (X2=2.23, df=2, p=0.33). Bufflehead also behaved similarly, excluding a l l conspecifics but th e i r mate. However, contrary to Barrow's Goldeneye, attacks were as prominent towards males (in 86% of confrontations) as towards pairs (75%) (X2=1.25, df=l, P=0.26). This i s because few contiguous Bufflehead t e r r i t o r i e s were observed. Therefore, most of the i n t e r a c t i o n s involving males were with bachelor males, whereas i n Barrow's Goldeneye, most in t e r a c t i o n s with males involved neighbouring t e r r i t o r i a l drakes and ra r e l y resulted i n attacks (Fig. 3). Female Common Goldeneye and Bufflehead, l i k e female Barrow's Goldeneye, rarely took part i n t e r r i t o r i a l defense. Boundary displays were frequent between neighbouring pairs of Common Goldeneye. They averaged 6 min (range = 0.5 - 19 min, n=33). Two Common Goldeneye p a i r s defended a t e r r i t o r y on a 4 ha pond. During 4 h of observations, the two males did 13 and 16 boundary displays l a s t i n g a total of 78 min and 81 min respectively. Sometimes a male would perform a boundary display alone, but this would usually spur similar displays from 37 Table 4. Number of i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d between t e r r i t o r i a l male Common Goldeneye and i n t r u d e r s (during 50 h of o b s e r v a t i o n ) . I ntruder Type of T h r e a t 1 i n t e r a c t i o n Attack T o t a l Male 121 51 172 P a i r 8 15 23 Female 9 19 28 Subadult 1 9 10 Group 1 4 5 T o t a l 140 98 238 Includes boundary d i s p l a y s . 38 Table 5. Number of i n t r a s p e c i f i c i n t e r a c t i o n s o b s e r v e d between t e r r i t o r i a l male B u f f l e h e a d and i n t r u d e r s (during 168 h of o b s e r v a t i o n s f o c u s s e d on n e i g h b o u r i n g Barrow's Goldeneye). Intruder Type of T h r e a t 1 i n t e r a c t i o n Attack T o t a l Male 12 74 86 P a i r 4 12 16 Female - 3 3 Subadult - 11 11 T o t a l 16 100 116 1 Includes boundary d i s p l a y s . 39 the neighbouring male. Displays between the two drakes occurred along a boundary l i n e which remained stable during the whole observation period. As i n Barrow's Goldeneye, dominance status changed with the l o c a t i o n of the encounter, each male being dominant in his territory. Wintering areas - Pairs of Barrow's Goldeneye defended t e r r i t o r i e s i n winter along protected rocky shorelines. Barrow's Goldeneye have long-lasting pair bonds and one pair was seen to re-unite on i t s wintering area (Appendix 2). The t e r r i t o r i a l behaviour of paired drakes i n winter i s es s e n t i a l l y i d e n t i c a l to that observed on the breeding areas (Table 6, Fig. 2). Boundary d i s p l a y s occur between neighbouring drakes. T e r r i t o r i a l drakes were more l i k e l y to be threatened whereas bachelor males were most often attacked (Table 6, X2=16.07, df=l, P=0.000). A l l conspecifics but the mate were excluded from the territory. Spacing behaviour of Common Goldeneye and Bufflehead has not yet been studied i n winter so i t i s not known i f they too are t e r r i t o r i a l . I have observed males of these species being aggressive toward other conspecifics but I did not d e f i n i t e l y e stablish i f t e r r i t o r i e s were defended. However, i t seems that pairs of Common Goldeneye i s o l a t e themselves from groups of unpaired birds. b) T e r r i t o r i a l behaviour of females with broods Following hatching, female Barrow's Goldeneye with young became highly aggressive and defended te r r i t o r i e s which averaged 0.91±0.08 ha i n size. They di d not t o l e r a t e any other adult goldeneye within 10 m of their young. A l l conspecifics were excluded from the territory. As with paired drakes, boundary displays were frequent between neighbouring broods (Table 7). Young of other broods were also attacked and excluded from the territory. Most interactions with adult birds occurred when the brood was 40 Table 6. I n t e r a c t i o n s between t e r r i t o r i a l Barrow's G o l deneye d r a k e s a n d c o n s p e c i f i c s i n w i n t e r ( n u m b e r o f i n t e r a c t i o n s o b s e r v e d d u r i n g 28 h of o b s e r v a t i o n ; 10 p a i r s o b s e r v e d ) . Boundary Threat Attack D i s p l a y s T o t a l T e r r i t o r i a l male 3 8 16 27 Bachelor male 17 49 - 66 Female 5 6 - 11 P a i r 26 24 - 50 Subadult 3 4 - 7 Group 2 5 - 7 T o t a l 56 96 16 168 41 Table 7. Number of i n t r a s p e c i f i c i n t e r a c t i o n s observed between f e m a l e Barrow's G o l d e n e y e w i t h young, and i n t r u d e r s ( d u r i n g 410 h of o b s e r v a t i o n ; more t h a n 50 b r o o d s observed). Type of i n t e r a c t i o n I ntruder Threat Attack Boundary D i s p l a y T o t a l Male 16 35 — 51 Female 65 431 - 4 96 Subadult - 4 - 4 Female with brood 64 43 141 248 Young 8 31 - 39 T o t a l 153 544 141 838 4 2 moving and a lone adult b i r d was i n i t s path. On small ponds, however, lone goldeneyes were attacked u n t i l they l e f t the pond. The aggressive behaviour of females was s i m i l a r to that of the t e r r i t o r i a l male: she adopted a threat posture, swam toward the intruder, and then dived or rushed toward i t . A l l lone females and males flew after such an attack, but v i o l e n t f i g h t s often erupted between females with broods. Young Barrow's Goldeneye spent twice as much time feeding as females did (Fig. 7). Females spent s i g n i f i c a n t l y more time i n aggression and i n alert posture than young. Goldeneye broods usually attempted to avoid each other. I attempted several times to drive a brood into the territory of another brood. This proved d i f f i c u l t because the female of the brood being driven would usually avoid entering another territory or would swim out of i t as soon as the disturbance ceased. On three occasions, however, fights broke out between the two females and the intruding brood was driven o f f the t e r r i t o r y . One i n t e r a c t i o n l a s t e d 30 min with the defending female constantly i n threat posture although the other female and her brood were hidden i n the reeds. Three fights occured before the intruding brood was driven o f f . When two or more broods used the same lake, exchange of young occasionally occurred between broods. This was most common on lakes with large numbers of broods. Over the five years of the study, the proportion of broods involved i n at l e a s t one exchange averaged 38±4% (Table 8). Brood mixing appeared t o be an i n d i r e c t r e s u l t of t e r r i t o r i a l aggressiveness. Females with broods are extremely aggressive and do not tolerate any other conspecifics i n their territory (Tables 7-9). I have observed the following outcomes of brood encounters: 1) Establishment of t e r r i t o r i a l boundaries: In at least five instances two broods shared the 43 F E E D I N G R E S T I N G A G G R E S S I O N A L E R T A C T I V I T Y O F F E M A L E A N D Y O U N G B A R R O W ' S G O L D E N E Y E Fig. 7 Average % of time (with 95% Confidence l i m i t s ) spent by female and young Barrow's Goldeneye in various a c t i v i t i e s within t h e i r t e r r i t o r y . (Duration of observations t o t a l l e d 27 5 h and 287 h for females and young respectively and were c o l l e c t e d during 166 observation periods distributed unequally between 32 broods.) 44 Table 8. Brood amalgamation in Barrow's Goldeneye and Bufflehead. Barrow's Goldeneye Bufflehead No. of broods No. of broods % No. of broods No. of broods No. of broods % No. of broods Year mixing mixing moving1 mixing mixing moving 1980 84 27 3 2 3 67 1 5 22 6 1981 84 23 27 5 7 3 1 8 2 5 9 1982 85 36 42 8 78 35 45 8 1983 95 3 9 41 14 7 3 3 8 52 11 1984 108 53 4 9 20 7 9 2 2 2 8 1 4 Total 456 178 39 50 370 128 35 48 1 Broods that changed lakes during brood rearing. Table 9. Number of i n t r a s p e c i f i c i n t e r a c t i o n s observed between female B u f f l e h e a d w i t h young, and i n t r u d e r s (during 110 h of o b s e r v a t i o n ; more than 20 broods observed). Type of i n t e r a c t i o n Intruder Threat A t t a c k Boundary D i s p l a y T o t a l Male 1 1 Female 1 19 - 20 Female wi t h brood 8 15 9 3 2 T o t a l 9 35 9 53 46 same lake but defended exclusive t e r r i t o r i e s from which they excluded other broods. Boundary displays were frequent, f i g h t s were observed occasionally. Exchanges of young between broods were frequent. 2) Expulsion of a brood from the lake: At l e a s t 13 cases of brood expulsion were recorded, three of which I witnessed (Appendix 3). In these three cases the brood was expelled following a violent fight between the females that lasted over 10 minutes. 3) Death of young: I witnessed two female Barrow's Goldeneye k i l l young Barrow's Goldeneye (see Appendix 3) and a female Barrow's Goldeneye k i l l 2 young Bufflehead. In each case, the v i c t o r i o u s female was the aggressor and the young of the defeated female the v i c t i m . 4) Complete or partial brood amalgamation: During a fight between two females, the young became alert and stayed together. Occasionally the young of the two broods mixed and one female gained young whereas the other lost some. In four cases where mixing involved young of different ages, the female with strange young was aggressive toward them at f i r s t , but eventually tolerated them. The strange young usually s u c c e s s f u l l y escaped the attacks of the female by mixing with the other young. In one case a defeated female l e f t the pond with 8 of her 9 young and at least 7 of the 17 young of the victorious female. Six young disappeared following this encounter. 5) Various combinations of the above: Outcomes of female encounters varied considerably due to various factors I w i l l discuss later. I observed several f i g h t s between females and several boundary displays at the edge of territories. Most often both females would stop and return to t h e i r own t e r r i t o r y . I describe the encounters that were witnessed i n d e t a i l i n Appendix 3. These cases indicate that females do not attempt to steal the young of other females but rather try to exclude 47 them from their territory. Considering the violence and duration of some of the fights, defeated females do not abandon their young but are forced to leave them. When the young are 5 or 6 weeks old some females leave the breeding ponds to f l y to molting lakes. Their remaining young may then amalgamate together and form large groups. This aggregation i s f a c i l i t a t e d by the decrease i n female aggressiveness as young grow older. Three times, I observed Barrow's Goldeneye broods containing young Bufflehead. Because both species are t e r r i t o r i a l , brood amalgamation can occur between them. The low frequency of these occurrences however may be due to the following: 1. Young Bufflehead are h a l f the size of young Barrow's Goldeneye of the same age and may be k i l l e d more rea d i l y . 2. Bufflehead females avoid Barrow's Goldeneye broods. 3. Because of their greater a g i l i t y female Bufflehead are very successful in decoying female goldeneye from their young. Whenever a female goldeneye would approach the brood, the female Bufflehead would rush her and lead her away from her brood, managing to stay out of reach of the female goldeneye. The aggressive behaviour of female Bufflehead with young was similar to that of Barrow's Goldeneye. Lone female Bufflehead were mostly attacked whereas boundary displays occurred between broods (Table 9). Time budgets of females and young were s i m i l a r to that of Barrow's Goldeneye, with young spending more time feeding than the female, whereas she spent more time i n aggression and a l e r t posture (Fig. 8). Barrow's Goldeneye and Bufflehead females played the same role as the male played earlier i n the season, they defended the territory and allowed their .CP4 young to feed undisturbed. The young spent on average as much time feeding as did the female i n the spring. 48 Fig. 8 Average % of time (with 95% Confidence l i m i t s ) spent by female and young Bufflehead in various a c t i v i t i e s within their territory. (Observations t o t a l l e d 145 h and 143 h for females and young r e s p e c t i v e l y and were c o l l e c t e d during 88 observation periods d i s t r i b u t e d between 11 broods.) 4 9 2) Interspecific Aggression a) Pairs on the breeding area Barrow's Goldeneye, Common Goldeneye and Bufflehead drakes showed aggressive behaviour toward other species of aquatic birds but especially toward each other (Table 10). Barrow's Goldeneye were observed to threaten and/or attack 19 other species. On ponds where the three species of Bucephala occurred, there was almost no overlap between t e r r i t o r i a l pairs because of i n t e r s p e c i f i c aggression. In the Columbia Valley, where the three species coexist, I recorded 580 i n t e r s p e c i f i c confrontations during 50 h of behavioural observations (Table 11). Intrageneric interactions were essentially similar to intraspecific ones. Males, p a i r s , females and subadults were excluded from the t e r r i t o r y . Interactions toward intruders other than males (pairs, females, subadults, groups) resulted i n more attacks than threats and the proportion of attacks did not d i f f e r among the species involved (X2=4.766, P=0.189, df=3). Interactions with males resulted usually i n more threats than attacks but the proportion varied according to the species involved (X2=53.43, P=0, df=3). Boundary displays were frequent between neighbouring Barrow's and Common Goldeneye males and averaged 6 min. i n length (range=l-38 min, n=21 displays). No boundary displays were observed between Bufflehead and goldeneyes. T e r r i t o r i a l Bufflehead drakes were always dominated by Barrow's and Common Goldeneye drakes, which often resulted i n poorly defined Bufflehead territories. Bufflehead drakes were expert at decoying attacking goldeneye drakes from their females and staying out of reach of the goldeneye. During a t y p i c a l attack, the Bufflehead drake would f l y o f f a few feet whenever the goldeneye dived toward him, and lead the goldeneye away from his mate. This behaviour allows some Bufflehead pairs 50 Table 10. Number of i n t r a - and 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 involving t e r r i t o r i a l drakes observed between 1981 and 1984. Aggressor (male) Intruder Barrow1s Common Goldeneye Goldeneye Bufflehead Horned Grebe (Podiceps auritus) Green-winged Teal 'Anas crecca) Mallard (A., platyrhynchos) Northern Pintail (A. acuta) Blue-winged Teal 1A. fliscors) Cinnamon Teal (A., cyanoptera) Northern Shoveler (A., cj Gadwall (A_. strepera) American Wigeon (&. Canvasback (Aythya valisj Redhead (Ay_. americana) Ring-necked Duck (Ay. collaris) Scaup (Ay. marila/affinis) Oldsquaw (Clangula hyemaljs) Surf Scoter (Melanitta perspicillata) White-winged Scoter (M. deglandi) Common Goldeneye (Bucephala clangula) Barrow's Goldeneye (B. islandica) Bufflehead (B. albeola) Ruddy Duck (Oxyura jamaicensis) American Coot (Fulica americana) 3 12 30 7 66 4 7 3 21 9 87 22 140 13 2 268 1377 466 27 13 1 4 238 97 106 2 2 2 2 1 11 1 1 8 28 116 Total interactions Total interspecific interactions Maximum observation length 1 (hours) 2577 1200 <150 449 211 <50 181 65 <50 1 Could not be estimated precisely. 51 Table 11. Number of interspecific interactions observed within the genus Bucephala (during 50 h of observation; T=threat, A=attack, F=fight). Aggressor 1 Common Goldeneye Barrow's Goldeneye Common Goldeneye Barrow's Goldeneye Intruding species Barrow's Common Bufflehead Bufflehead Total Type of interaction T A F T A F T A F T A F T A F Male 50 12 7 47 64 16 14 27 - 3 44 - 114 147 23 Pair 6 11 - 13 35 3 16 46 1 12 41 1 47 133 5 Female 3 8 - 8 59 - 1 1 - 1 4 - 13 72 -Subadult - - - - 8 - - - - - - - 8 -Group - - - 2 9 2 - - - 1 4 - 3 13 2 Total 59 31 7 70 175 21 31 74 1 17 93 1 177 373 30 Always a t e r r i t o r i a l drake. 52 to coexist among Barrow's Goldeneye, other Bufflehead occupy small ponds where there are no Barrow's Goldeneye. Outcomes of contests between Barrow's and Common goldeneye drakes were less predictable. Although the t e r r i t o r y owner was usually dominant within h i s t e r r i t o r y , some observations indicated that Barrow's Goldeneye had a slight advantage over Common Goldeneye. In interspecific encounters, Barrow's Goldeneye were more often aggressors than r e c i p i e n t s ; Common Goldeneye were equally observed as aggressors and as recipients, and Bufflehead were most often recipients (Fig.9). A detailed analysis of the proportion of threats and attacks i n 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 involving males suggest that Barrow's Goldeneye were more aggressive than Common Goldeneye and that Bufflehead were dominated by both species of goldeneyes (Fig. 10). Barrow's Goldeneye also i n i t i a t e d p r oportionally more f i g h t s than did Common Goldeneye (Table 12). I quantified interspecific aggressions of Barrow's Goldeneye i n 1982 on 20 ponds located near Riske Creek, B.C., where Bufflehead also occurred. T e r r i t o r i a l Barrow's Goldeneye drakes displayed aggressive behaviour toward a l l species of waterfowl present on the breeding ponds. However, the frequency and i n t e n s i t y of aggressive behaviour varied according to the species involved (Fig. 11). T e r r i t o r i a l drakes were more aggressive toward diving ducks than dabbling ducks. The number of aggressive acts per bird-hour ranged from 0.06 to 0.20 (x = 0.10+0.02, n=7) among dabbling duck species (Table 13) and from 0.17 to 1.00 (x" =0.41+0.13, n=6) among diving duck species (Table 14) a s i g n i f i c a n t difference (t=-11.0, P=0.000, df =11, log transformed data). The number of tolerated individuals per bird-hour was similar for dabbling and diving duck species and ranged from 0.07 to 0.13 (x = 0.10±0.01, n=7) among dabbling ducks and from 0.00 to 0.18 (x=0.08+0.03, n=6)) among diving 53 Fig. 9 Relative aggressiveness of the three Bucephala species towards intruders. (Proportion of time each species was the aggressor or the v i c t i m during interactions; n = number of i n t e r -actions; observations were made on at least 20 different pairs of each species.) 54 A G G R E 8 S O R / V I C T I M Fig. 10 Comparison of the proportions of threats and attacks i n i n t e r s p e c i f i c interactions (n = number of interactions; observations were made on at least 6 different pairs of each species). 5 5 Table 12. Number of i n t r a - and intergeneric encounters that resulted in fights. Common Goldeneye Barrow's Goldeneye No. of fights 17 48 No. of threats or attacks 318 455 G = 5.9, P<0.05 56 T O L E R A N C E / B I R D H O U R A G G R E S S I V E I N T E R A C T I O N / B I R D H O U R NO. O F T O L E R A N C E / N O . O F A G G R E 8 S I O N D A B B L I N G D U C K S DIVING D U C K S B U F F L E H E A D B A R R O W ' S GOLDENEYI T Y P E O F I N T R U D E R S Fig. 11 Aggressive responses of Barrow's Goldeneye drakes toward conspecifics, congeners, diving ducks and dabbling ducks. (The data has been scaled across intruder types. The total number of tolerance/bird hour = 0.17, of aggressive interaction/bird hour = 57.25, of the number of tolerance/number of aggression = 0.92.) 57 Table 13. Interactions between t e r r i t o r i a l Barrow's Goldeneye drakes and dabbling ducks (during 102 h of observation). No. of bird hours No. of tolerances No. of ag-gressions 1 No.tolerances/ No.aggression No.tolerances /bird hour No. aggressive interactions /bird hour Green^winged Teal 90 8 11 0.73 0.09 0.12 Mallard 219 21 21 1.00 0.10 0.10 Blue-winged Teal 299 22 59 0.37 0.07 0.20 Northern Shoveler 42 3 3 1.00 0.07 0.07 Gadwall 46 6 3 2.00 0.13 0.07 American Wigeon 186 22 12 1.83 0.12 0.06 Northern Pintail 23 3 2 1.50 0.13 0.09 Total 905 85 111 0.77 0.09 0.12 Threats and attacks combined. Table 14. Interactions between t e r r i t o r i a l Barrow's Goldeneye drakes and diving ducks (during 102 h of observation). No. aggressive No. of No. of No. of ag- No. tolerance/ No. tolerance interactions bird hours tolerances gressions 1 No. aggression /bird hour /bird hour Canvasback 12 (Aythya valisineria) 0 2 0.00 0.00 0.17 Redhead 139 (Aythya americana) 8 84 0.10 0.06 0.60 Ring-necked Duck 36 (Aythya collaris) 1 8 0.13 0.03 0.22 Scaup 244 (Aythya marila/affinis) 12 75 0.16 0.05 0.31 Surf Scoter 22 (Melanitta perspicillata) 4 4 1.00 0.18 0.18 Ruddy Duck 17 (Oxyura jamaicensis) 3 17 0.18 0.18 1.00 Total 470 28 200 0J4 0.06 0.43 Bufflehead 195 (Bucephala albeola) 3 214 0.01 0.02 1.10 Barrow's Goldeneye 318 (Bucephala islandica) 0 366 0.00 0.00 1.15 Threats and attacks combined. ducks (t=0.58, P=0.57, d f = l l ) . The r a t i o of the number of tol e r a t e d individuals over the total number of interactions averaged 1.20+0.22 for dabblers (n=7 species) and 0.26±0.15, for divers (n=6 species), a s i g n i f i c a n t difference (t=3.36, P=0.006, df=11), i n d i c a t i n g that diving ducks were tolerated less often and attacked more frequently than dabbling ducks. This was true for a l l types of intruders (Fig. 12). In a l l cases, the relative frequency of aggression was higher toward diving ducks than toward dabbling ducks. The number of aggressive inter actions/bird hour towards Blue-winged Teal was twice that toward other dabbling ducks. I looked at the proportion of tolerances and aggressions for species of dabbling ducks which had a s u f f i c i e n t sample size (Green-winged Teal, Mallard, Blue-winged Teal, American Wigeon) and combined data from the other species (Northern Shoveler, Gadwall, Northern P i n t a i l ) . The proportion of tolerances and aggressions differed among dabbling duck species (X2=17.98, P=0.002, df=4). However, once data from Blue-winged Teal were removed, there was no longer a significant difference among the remaining species (X2=3.19, P=0.364, df=3). Similar analyses with other diving ducks (i.e. not Bucephala) using Redhead, scaup, Ruddy Duck and a combination of the other species (Canvasback, Ring-necked Duck, Surf Scoter, White-winged Scoter) show that the proportion of tolerances to aggressions did not differ significantly among the species (X2=6.38, P=0.094, df=3). Similar conclusions are reached i f the species that were grouped together are excluded from the analysis. The l e v e l of aggression (proportion of threats to attacks) of Barrow's Goldeneye did not d i f f e r s i g n i f i c a n t l y toward species of dabbling ducks or toward species of diving ducks (Table 15). However, Barrow's Goldeneye were s i g n i f i c a n t l y more aggressive toward diving ducks, with 74% of the aggressive encounters 60 M A L E S P A I R S F E M A L E S G R O U P S T Y P E O F I N T R U D E R Fig. 12 Frequencies of aggressive i n t e r a c t i o n s and tolerances by t e r r i t o r i a l Barrow's Goldeneye drakes toward diving ducks and dabbling ducks. (Frequency of interactions and tolerances were significantly different between dabbling ducks and diving ducks for a l l types of intruders (X2 tests, P<0.05).) 61 being attacks, than toward dabbling ducks with only 39% of encounters being attacks (Table 15). I have shown e a r l i e r that Barrow's Goldeneye are interspecifically t e r r i t o r i a l against Bufflehead. Therefore I did not include Bufflehead i n the previous analysis. Bufflehead were almost never tolerated by Barrow's Goldeneye drakes and were threatened and attacked frequently. The i n t e n s i t y of aggressive i n t e r a c t i o n s toward Bufflehead was higher than toward other diving ducks; 88% of a l l interactions with Bufflehead (N=214) resulted i n attacks compared to only 75% (n=184) for other diving ducks (X2=11.03, P=0.001). The number of aggressions per b i r d hour between Barrow's Goldeneye and Bufflehead was higher than for other diving ducks and was s i m i l a r to the number of i n t r a s p e c i f i c encounters (Table 14). Similarly, the number of tolerances per bird hour was low and approached the level for intraspecific encounters (Table 14). The sex of the intruder did not seem to a f f e c t the aggressive behaviour of Barrow's Goldeneye drakes. T e r r i t o r i a l drakes were as aggressive toward females as toward males for both dabbling ducks (X2=2.16, P=0.142, df=l) and diving ducks (X2=1.22, P=0.269, df=l) (Fig. 12). Results are similar i f we consider an interaction with a pair as representing an i n t e r a c t i o n with a male and an i n t e r a c t i o n with a female. When a t e r r i t o r i a l drake attacked a p a i r , both members f l e d together. The interspecific aggressive behaviour of drakes was not related to the presence of their mate. During laying and incubation, males were at l e a s t as aggressive toward other species when t h e i r mate was absent as when she was ^resent i n the t e r r i t o r y (Table 16); (Sign Test, P=0.34, n=6) . 62 Table 15. Level of aggression i n i n t e r a c t i o n s between Barrow's Goldeneye drakes and other waterfowl. Type of interaction Species Threat Attack Green-winged Teal 8 3 Mallard 15 6 Blue-winged Teal 35 24 American Wigeon 5 7 (X2 Dabbling Ducks = 3.56 P=0.31) Redhead 22 61 Ring-necked Duck 2 10 Scaup 22 51 Surf Scoter 1 5 Ruddy Duck 3 14 (X2 Diving Ducks = 2.08 P=0.72) Total Dabbling Ducks 63 40 Total Diving Ducks 50 141 (X 2 Dabbling-Diving Ducks = 34.62 P=0.000) 63 b) Females with broods Following hatching, females with young became highly aggressive and established territories on their breeding ponds. By this time most males had l e f t the breeding area to molt. T e r r i t o r i a l females displayed a g g r e s s i v e behaviour toward a v a r i e t y of a q u a t i c b i r d s b e s i d e s conspecifics (Table 17). Female Barrow's Goldeneye and Bufflehead displayed similar interspecific aggression and were especially aggressive toward each other (Table 18). Few boundary displays were observed because of the dominance of Barrow's Goldeneye females with broods over Bufflehead females. However, Bufflehead females with broods dominated lone female goldeneye. They interacted more often with lone female goldeneye than with goldeneye broods and i n t e r a c t i o n s with lone females resulted i n proportionally more attacks (X2=5.47, P=0.02 df=l). Like t e r r i t o r i a l drakes, females were not equally aggressive toward a l l species (Table 19). Interactions of Barrow's Goldeneye females with Bufflehead resulted i n more attacks than those with dabbling and diving ducks (X2=35.3, P=0.000, df=2). They tended to be more aggressive toward diving ducks than dabbling ducks, but t h i s r e s u l t was not s i g n i f i c a n t (X2=2.80, P=0.082, df=l). The proportions of threats and attacks i n in t e r a c t i o n s of Bufflehead females with other b i r d s did not d i f f e r s i g n i f i c a n t l y (X2=5.09, P=0.090, df=2), but sample sizes are small. Bufflehead were always excluded from goldeneye territories whereas other diving ducks were occasionally tolerated. Dabbling ducks were only occasionally attacked. Most birds tended to avoid female goldeneye with broods, by swimming away from or around them. 64 Table 16. Number of interspecific aggressions (aggressive interactions/bird hours) by Barrow's Goldeneye drakes in relation to the presence or absence of their mates. Pair A Pair B Female present Female absent Female present Female absent Observation time (h) 20 25 15 35 Dabbling ducks Diving ducks Bufflehead 0.18 (95) 1 0.36 (14) 0.40 (15) 0.15 (302) 0.68 (37) 0.60 (25) 0.04 (90) 1.58 (19) 0.64 ( I D 0.08 (306) 3.22 (32) 0.63 (30) Total 0.23 (124) 0.23 (364) 0.34 (120) 0.40 (368) 1 Number of bird hours. 65 Table 17. Number of interactions observed between female Barrow's Goldeneye and Bufflehead with broods, and other birds. Aggressor Barrow's Victim Goldeneye Bufflehead (275 h ) 1 (130 h) Mallard Mallard brood Gadwall American wigeon American wigeon brood Green-winged Teal Green^winged Teal brood Blue-winged Teal Blue-winged Teal brood Northern Shoveler Redhead Ring-necked Duck Scaup Barrow's Goldeneye Barrow's Goldeneye brood Bufflehead Bufflehead brood Ruddy Duck Eared Grebe Horned Grebe Pied-billed Grebe American Coot Total interspecific interactions - 1 12 -4 -7 2 5 5 4 -- 2 4 4 1 -2 3 14 4 1 1 160 21 551 35 287 10 68 21 180 32 60 12 4 2 2 -1 -10 5 539 107 Number of hours of observation. 66 Table 18. Intra-generic aggression in broods of Barrow's Goldeneye and broods of Bufflehead (during 176 h of observation). Aggressor/ Victim Female Barrow's Goldeneye/ Bufflehead Female Bufflehead/ Barrow's Goldeneye ° Type of Boundary Boundary intruder Threat attack display Total Threat attack display Total Male 1 10 - 11 - 1 - 1 Female 12 42 1 55 7 25 - 33 Female with brood 17 162 1 180 6 4 — 10 Total 30 214 2 246 13 31 - 44 67 Table 19. Intensity of the interactions observed between females with broods and int r a - and interspecific intruders. Female aggressor Victim Barrow's Goldeneye % attack Bufflehead % attack Threat Attack Threat Attack Dabbling ducks 18 22 55 5 11 69 Diving ducks 74 161 69 4 34 89 Barrow's Goldeneye 82 465 85 7 27 79 Barrow's Goldeneye broods 206 42 17 6 4 40 Bufflehead 13 54 81 1 20 95 Bufflehead broods 18 162 90 19 19 50 68 The dominance of Barrow's Goldeneye females over Bufflehead females i s r e f l e c t e d i n t h e i r time budgets. Female B u f f l e h e a d spent proportionally less time i n t e r r i t o r i a l defense and more in alert posture than female Barrow's Goldeneye (Figs. 7-8). Most of the alertness of Bufflehead was due to the presence of female goldeneye nearby. c) Pairs on the wintering areas Barrow's Goldeneye occasionally reunite with t h e i r mates on the wintering areas and some pairs defend territories throughout the winter (Appendix 2). As on breeding areas, they display aggressive behaviour toward other species (Table 20). Although I d i d not quantify i t , t e r r i t o r i a l behaviour in winter appears similar to that observed i n the summer. Barrow's Goldeneye seemed most aggressive toward congeners and more aggressive toward diving ducks than dabbling ducks. The Surf Scoter i s the most common species in the winter habitat of Barrow's Goldeneye. They usually swim away when threatened or attacked by Barrow's Goldeneye. However, f l o c k s of scoters sometimes su c c e s s f u l l y invaded goldeneye t e r r i t o r i e s . Surf Scoters never displayed aggressive behaviour toward goldeneyes and always fl e d when attacked. Aggressiveness varied among goldeneye pa i r s : some tolerated intruding birds more than others. Only paired t e r r i t o r i a l drakes were interspecifically aggressive. Adults and subadults i n f l o c k s did not display any obvious aggressive behaviour when feeding. One marked pair had a territory along a small breakwater which was only accessible to them at high tide. At low tide the breakwater was surrounded by mud f l a t s and could not be used by the pair. This p a i r was both i n t r a - and i n t e r s p e c i f i c a l l y aggressive on th e i r t e r r i t o r y , but during low tides they sometimes joined with other goldeneyes and were not 69 Table 20. Number of cases of i n t r a - and i n t e r s p e c i f i c a g g r e s s i o n by t e r r i t o r i a l Barrow's Goldeneye males and females i n winter (during 28 h of o b s e r v a t i o n ) . Aggressor V i c t i m Male Female M a l l a r d 2 1 Scaup 4 -Common Goldeneye 8 -B u f f l e h e a d 6 -Surf Scoter 49 2 Hooded Merganser 1 1 Red-breasted Merganser 1 -Glaucous-winged G u l l 8 2 T o t a l 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 79 6 Barrow's Goldeneye 168 15 70 aggressive, indicating f l e x i b i l i t y in their aggressive behaviour. Females o c c a s i o n a l l y engaged i n i n t r a - and 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 . Occasionally they behaved as i f they were i n c i t i n g the male to attack intruders. 3) Relationships between pair territory, brood te r r i t o r y and nest site a) Pair territory and nest site In my study area, Barrow's Goldeneye nested i n tree c a v i t i e s or i n nest boxes. Therefore, nest sites were almost always outside the breeding pair's territory (a few trees stood i n shallow water). Distance between the pair territory and the nest site averaged 0.35 km and ranged from 0 to 2.9 km (Fig. 13). About h a l f of the nest s i t e s were adjacent to the t e r r i t o r y (Table 21). However, these s i t e s ranged between 0 and 125 m from the water edge. b) Nest site and brood territory Brood t e r r i t o r i e s averaged 0.33 km from the nest s i t e and ranged between 0 and 2.3 km (Fig. 14). However, 48% of the t e r r i t o r i e s were located on a lake within 100 m of the nest site. Broods tended to settle on the lake closest to their nest site i f the lake was suitable for brood rearing. T e r r i t o r i a l encounters sometimes forced broods to move to lakes farther away from their nest sites (see Appendix 3). c) Pair territory and brood territory Pair t e r r i t o r i e s averaged 0.70 + 0.07 ha (n=57) and ranged between 0.5 and 1.85 ha whereas brood terri t o r i e s ranged between 0.27 and 2.79 ha and averaged 1.08 + 0.12 ha (n=27). If only water l e s s than 3 m deep i s considered, p a i r t e r r i t o r i e s averaged 0.44 + 0.05 ha and brood t e r r i t o r i e s averaged 0.91 ± 0.08 ha. The l a t t e r estimate i s more 71 ~~1 D I S T A N C E F R O M N E S T S I T E (M ) Fig. 13 ~ Distances between pai r t e r r i t o r i e s and nest sites i n Barrow1s Goldeneye (n = 6 9). i i 72 I i Table 21. P r o p o r t i o n of t e r r i t o r i e s t h a t were a d j a c e n t t o t h e nest s i t e . T e r r i t o r y adjacent T e r r i t o r y not adjacent to the nest s i t e to the nest s i t e 1983 11 8 1984 20 19 73 C O U J E o E a U J i -Q O O tr m 11. O 24 -20 -16 12 8 -4 -8 16 3 2 6 4 128 2 5 6 5 1 2 1024 2048 4096 D I S T A N C E F R O M N E S T S I T E (M ) Fig. 14 Distances between brood t e r r i t o r i e s and nest sites in Barrow's Goldeneye (n = 130). 74 r e a l i s t i c , because most of the lakes i n the study area are l e s s than 3m deep, and paired goldeneyes rarely feed i n such deep areas, preferring to feed i n shallower waters near the shoreline. Brood terri t o r i e s were usually not the same as pair territories, and often were established on d i f f e r e n t lakes. When the pair t e r r i t o r y and the nest site were on different lakes, brood te r r i t o r i e s were established on the lake of the nest s i t e s more often (21 times) than on the lake of the pair territory (2 times). d) Fi d e l i t y to territory Pair ter r i t o r i e s tended to be located on the same lake i n successive years: 23 pairs established their pair territory on the same pond 2 years in a row, 10 pairs 3 years i n a row, and 1 pair four years in a row. Only 12 of the returning pairs (21%) changed lakes between years. Pairs also tended to use the same t e r r i t o r y each year. From a sample of 15 marked pa i r s , 7 used the same t e r r i t o r y on 2 consecutive years, 3 on 3 consecutive years and only 5 changed t e r r i t o r i e s the following year. Females usually brought th e i r broods to the same lake on consecutive years. From a sample of 28 broods, 21 used the same lake and only 7 changed. Of these 7, one moved to a nest s i t e on a d i f f e r e n t lake, 2 lakes became unsuitable for goldeneye and 4 broods were excluded from the lake they had used the year before because of t e r r i t o r i a l behaviour of already established broods. There i s some evidence that pairs also return to the same wintering territory each year (Appendix 2). e) Removal experiments To gain insight into the proximal factors determining territory sizes and boundaries I did two removals. I argued that i f t e r r i t o r y size was 75 determined solely by food abundance and i f the boundaries were established without reference to neighbouring pairs, then the removal of the central p a i r from three adjacent t e r r i t o r i e s would not r e s u l t i n t e r r i t o r y expansion. Conversely, i f territory size and boundaries are determined by i n t r a s p e c i f i c i n t e r a c t i o n s among neighbouring p a i r s , then af t e r the removal, the terr i t o r i e s of the two remaining pairs should expand into the vacant area and a new boundary should be established through intraspecific interactions. My results supported the second prediction: following the removal of the central p a i r , the other two p a i r s began to i n t e r a c t (Table 22) and, by the following day, t e r r i t o r i e s had expanded into the vacant area and a new boundary line was established (Fig. 15). However, i n spite of t h e i r expanded t e r r i t o r i e s the p a i r s concentrated t h e i r a c t i v i t y i n t h e i r old t e r r i t o r y . Results were s i m i l a r for the second removal: after the removal of the central pair, t e r r i t o r y boundaries s h i f t e d and the remaining two Barrow's Goldeneye pair and a Bufflehead pair interacted more frequently than prior to the removal (Table 23, Fig. 16). The Bufflehead pa i r attempted to f i l l the void created by the removal and partly succeeded. DISCUSSION a) Intraspecific aggression Intraspecific aggression i s behavioural competition for resources i n short supply (Brown 196 4). This aggression often r e s u l t s i n the establishment of t e r r i t o r i e s that are defended against conspecific competitors (Lanyon 1956, Welty 1962, Pianka 1978). Barrow's Goldeneye, Common Goldeneye and Bufflehead drakes actively maintain t e r r i t o r i e s on their breeding ponds. 76 Table 22. Results of the removal experiment on lake 68 i n 1984. No. of days Total no. Number of aggressive inter-of observation of hours actions between pairs A - B E H : A - C Before removal 3 6 11 6 0 After removal 1 7 12 - - 18 1 Pair B was removed; see Fig. 15 for location of the t e r r i t o r i e s . 77 BEFORE REMOVAL AFTER REMOVAL ABCDE - Barrow's Qoldeneye territories 1 - Bufflehead territory 100 meters Fig. 15 Territory boundaries of Barrow's Goldeneye prior to and fol l o w i n g the removal of pai r B on Lake 68 i n 1984. Y 78 Table 23. Results of the removal experiment on lake 50 in 1984. Number of aggressive inter-actions between pairs No. of days Total no. of observations of hours A-B B-C A-C A - l A-2 C-l C-2 Before removal 3 5 7 4 0 12 1 0 0 After removal 1 4 6 - - 14 4 18 0 9 1 Pair B was removed; see Fig. 16 for the location of the t e r r i t o r i e s . 79 BEFORE REMOVAL AFTER REMOVAL ABC - Barrow's Qoldeneye territories 1,2 - Bufflehead territories i 1 100 meters Fig. 16 Territory boundaries of Barrow's Goldeneye and Bufflehead prior to and following the removal of pair B on Lake 50 in 1984. 80 T e r r i t o r i e s defended by goldeneyes and Bufflehead s a t i s f y the e s s e n t i a l c h a r a c t e r i s t i c s of a t e r r i t o r y as l i s t e d by Brown and Orians (1970) . 1. A fixed area i s defended: although the territory boundaries fluctuate throughout the season, the territory i t s e l f remains i n the same section of the pond. Neighbouring pairs often establish boundary lines which remain stable for several days. However, brood territories are not the same as pair territories. 2. Te r r i t o r i a l displays evoke escape and avoidance i n rivals: goldeneyes and Bufflehead have a wide array of aggressive postures re l a t e d to t e r r i t o r i a l display, and which evoke avoidance i n r i v a l s (Erskine 1972, Palmer 1976). 3. The territory i s an exclusive area: conspecifics are excluded from an area. Several functions of t e r r i t o r i a l behaviour i n birds have been suggested: 1) Mate a t t r a c t i o n (McLaren 1972, Welsh 1975, Wittenberger 1981, Steen e£ aJL. 1985); 2) Mate protection and reproductive isolation (McKinney 1965, Morse 1980); 3) Defense of nest site (Wittenberger 1981); 4) Spacing out of nests (Lack 1954, 1966, McKinney 1965, Fjeldsa 1973 b); 5) Defense of food resources (Gibson 1971, G i l l and Wolf 1975, Gass £l. 1976, Moore 1978). I shall b r i e f l y consider each of these functions for Barrow's Goldeneye t e r r i t o r i a l i t y . 1. Mate attraction The t e r r i t o r y could help the owner i n a t t r a c t i n g mates. This i s un l i k e l y i n Barrow's Goldeneye as p a i r s are formed p r i o r to the establishment of the t e r r i t o r y : a) most p a i r s formed on the wintering areas; b) others formed on the center of the breeding ponds away from the 81 t e r r i t o r i e s ; c) t e r r i t o r i e s are always s e t t l e d by pairs. Females apparently select the territory i n waterfowl (Hochbaum 1944, Young 1970, Donaghey 197 5, Patterson 1982). Mate attraction clearly cannot explain brood t e r r i t o r i a l i t y . In winter, since only paired birds are t e r r i t o r i a l , the function i s obviously not to attract a mate. 2. Mate protection against sexual harassment Terr i t o r i a l defense by the male isolates the pair from conspecifics and thus reduces the r i s k s of interference during copulation. Such interference has been observed i n several species of birds (Armstrong 196 5). T e r r i t o r i a l defense would a l s o lower the r i s k of s t o l e n copulations and thus assure male paternity. However, I found that copulation does not always occur within the t e r r i t o r y , and I observed three copulations near groups of unpaired birds without interference from the latter. Forced copulation i s frequent within the genus Anas (McKinney et a i . 1983), but has never been reported i n the genus Bucephala (McKinney e± aJL. 1983, McKinney 1985, Gauthier 1985). In 5 years of intensive studies of goldeneye I have never witnessed an attempted forced copulation. Goldeneye drakes take several minutes before mounting a prone female (Nilsson 1969, Afton and Say ler 1982, Savard unpub. data), a delay that would make forced copulation d i f f i c u l t . Pair bonds i n Barrow's Goldeneye are strong (see Appendix 2). Marked p a i r s have been observed foraging i n large groups of goldeneyes in winter with l i t t l e harassment of females from unpaired males. Males then, lose their mates and which have been unsuccessful in re-pairing, return to their previous breeding area (see Appendix 2). I observed two of these males defend i r r e g u l a r l y , for a few days, the t e r r i t o r y they occupied the year before. This defense behaviour i n the 82 absence of the female again indicates that protection of the female against sexual harassment and/or protection of paternity i s not the main factor maintaining male t e r r i t o r i a l behaviour. If such mate protection was important, one would expect unpaired adult males to be attacked more v i o l e n t l y than intruding pairs. Casual observations indicate that strange pairs (neighbouring pairs excluded) e l i c i t stronger aggressive responses from territory owners than unpaired drakes. Quantitative studies are needed to confirm these observations. Paired females are quite aggressive and are rarely sexually harassed by males. I have seen paired females landing i n groups of unpaired goldeneye, af t e r returning from t h e i r nest s i t e s . Unpaired males swam toward these female but, confronted with aggressive responses or lack of response, they usually did not persist i n their displays. Gauthier (1985) found that Bufflehead females whose mates had been removed were not sexually harassed but rather aggressively attacked by neighbouring males. Some were even chased off th e i r t e r r i t o r y . If mate protection i s an important aspect of the t e r r i t o r i a l behaviour of Barrow's Goldeneye i t i s not sexually motivated, i.e. i t i s protection from aggressive males and not from courting males. Exclusion of strange females from the territory (see Fig. 2) supports the assertion that t e r r i t o r i a l behaviour of drakes i s not solely sexually motivated. 3. Protection of nest site T e r r i t o r i a l i t y may protect access to the nest site. Gauthier (1985) argued that t h i s function i s important i n Bufflehead, a species whose nesting cavities are often adjacent to the territory. He suggested that t e r r i t o r i a l aggressiveness of males impairs access to the nest by other females and therefore reduces nest parasitism. Pienkowski and Evans 83 (1982a) also indicated that^in isolated sites, nests of Shelducks tend to be adjacent to t e r r i t o r i e s and that i n these cases t e r r i t o r i a l i t y may reduce nesting interference and clutch parasitism. However, neither Gauthier (1985) nor Pienkowski and Evans (1982a) present conclusive data supporting t h i s hypothesis. Goldeneye nests can be up to 2 km from the pair t e r r i t o r y and even nests adjacent to the t e r r i t o r y are usually several metres inland. This considerably reduces the a b i l i t y of the male to exclude other females from the nest area. Further, males were not seen to protect the nest s i t e as such: they only t r i e d to exclude p a i r s and females from the water. Neighbouring boxes located adjacent to goldeneye t e r r i t o r i e s were often used successfully by several females. Direct observations indicate that females, although harassed by the t e r r i t o r i a l males when they flew over or landed i n the territory, successfully entered the boxes. E r s k i n e (197 2) r e p o r t s female B u f f l e h e a d n e s t i n g simultaneously in the same tree. The absence of direct protection of the nest s i t e by males indicates that t h i s i s probably not an important function of t e r r i t o r i a l i t y in Barrow's Goldeneye. 4. Spacing mechanism McKinney (1965) concluded that the main function of t e r r i t o r i a l i t y i n dabbling ducks was the spacing out of nests to reduce predation. T e r r i t o r i a l behaviour of male goldeneye spaces out p a i r s on lakes but, because the nest s i t e i s usually outside the t e r r i t o r y , t h i s does not necessarily translate into nest spacing. However, i t does force pairs to exploit food resources more evenly and may l i m i t density on certain ponds. 5. Defense of food resources Egg production and incubation impose great energy demands on females 84 (King 1973, R i c k l e f s 197 4, Krapu 197 9). In the spring, females spend twice as much time feeding as do males, an i n d i c a t i o n of a higher food requirement for females. Defense of a t e r r i t o r y and exclusion of conspecifics by the male provide the female with the following feeding advantages: 1) By remaining i n the same area, the female f a m i l i a r i z e s h e r s e l f with the resources of the t e r r i t o r y and with i t s s p a t i a l and temporal distribution. This may enhance her foraging efficiency (Hixon e± a l 1983, Gass and Sutherland 1985). 2) Exclusion of conspecif ic s from the area reduces feeding interference. Because goldeneye feed on f r e e swimming invertebrates which they capture by sight, the presence of other birds feeding nearby may reduce prey availability by either muddying the water and/or by causing the prey to seek refuge i n dense vegetation. 3) Food depletion may be reduced by exclusion of competitors. These factors each contribute to a greater feeding efficiency by the female and may allow her to be more selective i n her choice of prey. Gauthier (1985) showed that Bufflehead females who had lost their mates spent more time in a l e r t posture, fed for a shorter period of time and were the v i c t i m of more aggressive attacks than paired females. Pienkowski and Evans (1982a) found that p a i r s of Shelducks fed more e f f i c i e n t l y inside than outside their territory. Defense of winter t e r r i t o r i e s could s i m i l a r l y enhance feeding opportunities of the pair. However, the situation appears complex as some pairs apparently do not defend territories on the wintering areas. S i m i l a r l y , the female provides the same advantages for her young. Females, by excluding conspecifics from the brood t e r r i t o r y , provide better feeding opportunities for t h e i r young. Young ducklings are l e s s e f f i c i e n t foragers than adults and e x p l o i t a more l i m i t e d array of food ( H i l l and E l l i s 1984). Eriksson (1976, 197 8) showed that young Common Goldeneye fed s e l e c t i v e l y and preferred free-swimming prey. If young 85 Barrow's Goldeneye feed i n a similar way, females would enhance feeding opportunities for their young by maintaining exclusive territories. The importance of food abundance for duckling growth and s u r v i v a l has been shown i n several species of ducks: Pienkowski and Evans (1982a) showed that ducklings grew faster i n areas with low density of ducks, and Hunter et a l . (1984) showed that growth of Mallard and Black Duck (Anas rubripes) was negatively affected by a reduction i n food density. Street (1977) found a c o r r e l a t i o n between food abundance and duckling s u r v i v a l . Pienkowski and Evans (1982a) argued that by being t e r r i t o r i a l Shelducks reduced the r i s k of a duckling seeking protection from an intruding or nearby adult not ready to defend i t . S i m i l a r advantages would apply to young goldeneyes. I wish to stress, that space, not food as such, i s the resource defended by males. The male does not choose the size of the t e r r i t o r y based on food abundance but rather seems to defend an area as big as he can. On small lakes with single pairs, the whole lake becomes the t e r r i t o r y . T e r r i t o r y boundaries are only established when neighbouring pairs are present. Boundaries are the r e s u l t of confrontations between t e r r i t o r i a l p airs. Males expanded t h e i r t e r r i t o r i e s when I removed a neighbouring pair. Several other removal studies on other t e r r i t o r i a l species have shown s i m i l a r expansion of t e r r i t o r i e s by neighbours (Armitage 1974, Vines 1979, Hilden 1979, Hannon 1983, Norman and Jones 1984, Gauthier 1985). Also, several studies have shown that t e r r i t o r y size i s not correlated closely with food abundance but more closely with competitor density and/or male aggressiveness (Van Den Assem 1967, Krebs 1971, Watson and Moss 1971, Knapton and Krebs 1974, Hilden 1979, Myers £t a l . 1979a,b, Franzblau and Collins 1980, Wasserman 1983). 86 I suggest that an important function of t e r r i t o r i a l i t y i n Barrow's Goldeneye i s to provide an exclusive and undisturbed feeding area for the female (pair and winter territories) and for the young (brood territory). McKinney (1973), Seymour (1974a,b) and Titman and Seymour (1981) a l l reached a similar conclusion i n their studies of t e r r i t o r i a l behaviour of dabbling ducks. Patterson (1982) summarized several studies on Shelduck and reached the same conclusion. Donaghey (1975) and Gauthier (1985) in th e i r thorough investigations of t e r r i t o r i a l i t y i n Bufflehead also concluded that this was an important function. B) Brood amalgamation Brood amalgamation has been reported i n several species of waterfowl: Eiders (Somateria spp., Gorman and Milne 1972, Munro and Bedard 1977a); mergansers (Mergus spp., Bergman 1956, Erskine 1972); Scoters (Melanitta spp., Koskimies 1955); oldsquaw (Bent 1923, A l i s o n 197 5); shelducks (Tadorna spp., Williams 1974, Riggert 1977, Patterson e_£ a l . 1982); scaup (Aythya spp., Munro 1941, Hines 1977); Canada Goose (Branta canadensis. Warhurst e_t a l . 1983). The causes and functions of brood amalgamation s t i l l remain obscure for several species. In eiders, Gorman and Milne (1972) argued that brood amalgamation resulted from the parents leaving their young to go to better feeding areas. However, detailed studies of eiders in Canada did not support this hypothesis but indicated that brood amalgamation was caused by crowding and predation (Munro and Bedard 1977a,b, Bedard and Munro 1977). S i m i l a r l y Williams (1974) showed that brood amalgamation i n Shelduck resulted from aggressive t e r r i t o r i a l encounters and that parents attempted to keep their young rather than to drive them away as suggested by Hori (1964a,b, 1969). My observations on Barrow's Goldeneye support Williams' (1974) and Bedard and Munro's (1977) 87 Several factors may affect the outcome of brood encounters: Female aggressiveness: Boundaries are more l i k e l y to be established i f females are of similar strength. Age of young: If the young of the two broods are of similar age they can mix more e a s i l y . Also, older young can more e f f e c t i v e l y withstand attacks by the victorious female. Strength of female-duckling and duckling-duckling bonds: Imprinting i n cavity nesting ducks i s mainly auditory u n t i l nest exodus (Hess 1973). Visual imprinting at hatching i s weak and the female-duckling bond i s not f u l l y developed. Newly hatched young are more l i k e l y to amalgamate than older broods. Size of brood: Ducklings imprint on t h e i r s i b l i n g s as w e l l as on their parents (Hess 1973). In large broods the female-duckling bonds may be weaker than i n s m a l l broods, again f a v o u r i n g brood amalgamation. Location of the encounter: On small ponds, only one brood w i l l remain and others w i l l be excluded or amalgamation may occur. On larger lakes, several territories can be maintained and exclusion i s less l i k e l y . Chance: For amalgamation to occur, young must mix. Whether they do or not depends on the topography of the area and the l o c a t i o n and behaviour of the young at the time of the encounter. Behaviour of young: The behaviour of the young after mixing may a f f e c t t h e i r acceptance by the female. Graves and Whiten (1980) showed that adoption of strange chicks by Herring G u l l s (Larus  argentatus) depended on the behaviour of the chick. 88 It appears that, in Barrow's Goldeneye, brood amalgamation i s not a strategy used by females and/or young but simply an accidental outcome of t e r r i t o r i a l aggression. A s i m i l a r phenomenon e x i s t s i n coral reef f i s h e s (Thresher 1985) and also appears accidental. The absence of behaviour by the female or by the young that would favour brood amalgamation supports the non-adaptive origin of the phenomenon. Several authors have used the term creching to describe brood amalgamation i n waterfowl (Gorman and Milne 1972, Williams 1974, Munro and Bedard 1977a,b). Creching, however, implies adaptive behaviour (Davis 1982, Evans 1984) and thus the term i s not appropriate here. Also several studies have shown that brood amalgamation increased mortality and did not reduce i t (Williams 1974, Makepeace and Patterson 1980, Pienkowski and Evans 1982a). C) Interspecific aggression Simmons (1951) defined interspecific t e r r i t o r i a l i t y as an individual e x h i b i t i n g persistent aggressive behaviour to an intruding b i r d of a second species, and d i r e c t i n g toward i t some of the displays used i n i n t r a s p e c i f i c encounters. Walters (197 9) narrowed t h i s d e f i n i t i o n by including the concept of exclusive use of an area and proposed the term partial exclusion when there was not exclusive use. According to Simmons' definition, a l l three species of Bucephala are interspecifically t e r r i t o r i a l : Common Goldeneye and Barrow's Goldeneye exclude each other from t h e i r respective t e r r i t o r i e s and also exclude Bufflehead. Bufflehead exclude n o n - t e r r i t o r i a l goldeneye from t h e i r t e r r i t o r i e s but are dominated by t e r r i t o r i a l goldeneye drakes. Other sympatric diving ducks are regularly excluded from Bucephala te r r i t o r i e s 89 but not as consistently as congeners and thus f i t Walters' (1979) partial exclusion concept. Among ducks, interspecific t e r r i t o r i a l i t y has been reported only i n the genera Tachyeres and Bucephala (Weller 1976, t h i s study). I t i s f a i r l y common, however in other groups of birds (Orians and Willson 1964, Murray 1971, 1981). In most cases, the larger species i s the dominant one. When both competing species are of s i m i l a r s i z e , dominance by one species i s not obvious (Lanyon 1956, Gochfeld 1979). This also applies to Barrow's Goldeneye and Common Goldeneye; neither species clearly dominates the other, although Barrow's Goldeneye act more aggressively. Myres (1957) reported aggressive interactions between Barrow's Goldeneye drakes and Common Goldeneye, Bufflehead, Surf Scoter, Lesser Scaup, Ruddy Duck and American Coot (Fulica americana) but observed no interactions with dabbling ducks in spite of their abundance in his study area (only a few km away from mine). S i m i l a r l y , Bufflehead drakes have been reported to attack Lesser Scaup (Myres 1957, Erskine 1972, Donaghey 197 5), Common goldeneye (Myres 1957, Donaghey 197 5), Barrow's Goldeneye (Myres 1957) and Redhead (Erskine 1972). However, none of these authors reported interactions with dabbling ducks. These observations support my finding that Barrow's Goldeneye and Bufflehead are more aggressive toward diving ducks than dabbling ducks. What i s the significance of interspecific aggression i n Barrow's Goldeneye? Several functions of that behaviour have been suggested: 1) exclusion of predators (Walters 1979, Stephens 1984); 2) Exclusion of competitors for food (Orians and Willson 1964, Murray 1971, 1981, Moore 197 8, Walters 197 9, Katzir 1981a, Snow and Snow 1984, Nuechterlein and Storer 1985a); 3) sexual advertisement: i n t e r s p e c i f i c aggression may serve to reinforce pair bonds and show the female "how aggressive a male 90 i s " (Livezey and Humphrey 1985a, Nuechterlein and Storer 1985a); 4) interspecific aggression i s misdirected i n t r a s p e c i f i c aggression and has no advantages (Murray 1971, 1981). I consider each of these suggestions below. 1. Predator exclusion. This does not apply to Barrow's Goldeneye as none of the species excluded prey on goldeneye eggs or young. 2. Exclusion of competitors for food. A l k a l i n e ponds are simple habitats that frequently lack emergent plants. Nearly a l l of these ponds are devoid of f i s h e s and sustain high densities of aquatic arthropods. The d i v e r s i t y of arthropods i s often reduced by the high s a l i n i t y of these ponds (Cannings and Scudder 1978, Lancaster 1985). Therefore, there i s l i t t l e opportunity for waterfowl species to exploit different resources i n alkaline ponds. In the spring, female dabbling and diving ducks feed almost exclusively on invertebrates, and may compete with Barrow's Goldeneye (Bartonek and Hickey 1969, Bartonek and Murdy 1970, Swanson £t £l» 1979). Competition i s l i k e l y to be greater with diving ducks because of greater habitat and feeding method overlap: dabbling ducks feed mostly in shallow waters, whereas diving ducks and goldeneyes feed i n deeper waters by diving. Diets of Barrow's Goldeneye and Bufflehead are s i m i l a r (Munro 1939, 1942, Erskine 1972), and both species e s t a b l i s h t e r r i t o r i e s along pond shorelines and therefore use the same microhabitats. Aggression by Barrow's Goldeneye i s therefore correlated with the degree of food overlap and/or degree of po t e n t i a l foraging interference, being highest toward conspecifics and Bufflehead and higher toward diving ducks than dabbling 91 ducks. Quantitative data, however, are needed to support this hypothesis. By excluding other waterfowl from t h e i r t e r r i t o r i e s goldeneyes prevent interference i n feeding, and t h i s may r e s u l t i n greater avai l a b i l i t y of food for the t e r r i t o r i a l pair. In the spring, increased access to food should favour the production of early clutches and larger eggs, thus enhancing the survival of ducklings. Earlier broods have f i r s t choice of brood te r r i t o r i e s and usually dominate later broods because the female i s i n better condition and her young are older, and because of f a m i l i a r i t y and attachment to the t e r r i t o r y (Hinde 1956, P e t r i e 1984). Ducklings from larger eggs are larger and better able to withstand inclement weather (Krapu 1979, Ankney 1980). By defending a t e r r i t o r y , the female may enhance the survival of her young by reducing competition for food. In winter the male may create better feeding opportunities for both himself and the female by excluding other species from stretches of rocky shoreline where mussels grow. Surf Scoters, which also feed extensively on mussels, are often expelled. Flocks of scoters, however, often invaded goldeneye te r r i t o r i e s successfully, in a way similar to that described i n reef f i s h e s (Robertson gt si. 1976, Foster 1985). The simultaneous large number of trespassers rendered t e r r i t o r i a l defense ineffi c i e n t . Palmer (1976) reported that t e r r i t o r i a l Barrow's Goldeneye i n Iceland drove away any feeding or loafing Harlequin Ducks (Histrionicus histrionicus). Gardarsson (197 8) showed that the d i e t s of Barrow's Goldeneye and Harlequin Ducks i n Iceland are s i m i l a r , and that changes i n food supply a f f e c t the s u r v i v a l of the young of both species. Aggressiveness of grebes toward goldeneye and bufflehead on the breeding ponds also suggests that food may be a limiting resource. I observed Horned and Red-necked Grebes (Podiceps auritus, P. grisigena) attack Bufflehead and Barrow's Goldeneye on several occasions. 92 Donaghey (1975) reported several attacks on Bufflehead by these two species of grebes. Kirby (1976) described violent interactions between Pied-billed Grebes (Podilymbus podiceps) and young Common Goldeneye. If enhancement of feeding opportunities i s an important function of intraspecific t e r r i t o r i a l i t y , then closely related species exploiting the same resources should be excluded also, otherwise the advantage gained by excluding conspecifics w i l l be lost to competing species. Interspecific feeding t e r r i t o r i e s are well documented in hummingbirds (Cody 1968, Kodric-Brown and Brown 1978) and i n fi s h (Low 1971/ Myrberg and Thresher 1974, Ebersole 1977). Loyn £t a l . (1983) showed that i n t e r s p e c i f i c aggression by B e l l Miners (Manorina melanophrys) resulted i n significant increases i n food abundance within the territory. And Dow (1977) showed that i t resulted i n the sole occupancy of space and thus better foraging opportunities for Noisy Miners (M. melanocephala). 3. Sexual advertisement Barrow's Goldeneye are among the most strongly sexually dimorphic ducks (Livezey and Humphrey 1984; Appendix 5). During pair formation and early during territory establishment, females sometimes aggressively chase away other goldeneyes while their mates show l i t t l e aggressiveness. The males, however, seem to respond to t h e i r mate's behaviour and quickly become aggressive. Similar incitement behaviour by the female has been reported i n Shelducks (Pienkowski and Evans 1982a), and i n Steamer-Ducks (Nuechterlein and Storer 1985a). The latter authors postulated that male Steamer-Ducks attack birds of other species to display their belligerency and f i g h t i n g a b i l i t i e s to their females. In view of lack of evidence, t h i s should be considered as speculation. Furthermore, i n Barrow's Goldeneye, male aggressiveness i s not re l a t e d to the presence of the 93 female. Display of aggressiveness to impress the female can not, therefore, be the sole function of i n t e r s p e c i f i c aggression. Murray (1985) questioned t h i s i n t e r p r e t a t i o n . Also, sexual s e l e c t i o n does not explain the aggressiveness of females with broods toward other species, nor does i t explain the aggressiveness of the female i n winter. 4. Misdirected aggression It has been argued that i n t e r s p e c i f i c aggression i s sometimes a result of high intraspecific aggression (Murray, 1971, 1981, Nuechterlein and Storer 1985a), and i s maintained only because i t has l i t t l e cost associated with i t . Interactions of Barrow's Goldeneye with dabbling ducks f i t the pattern of misdirected aggression. Dabbling ducks are tolerated more often than attacked and, within a few minutes, a male goldeneye may t o l e r a t e a dabbling duck that he had previously attacked. The high level of aggression directed toward Blue-winged Teal could be due to the white crescent on the side of the head that male Blue-winged Teal share with male Barrow's Goldeneye. However, because female t e a l s are also attacked, plumage c o l o r a t i o n i s not the sole factor e l i c i t i n g aggression. Unfortunately, too few interactions were observed with lone Blue-winged Teal females (most of them were paired) to determine i f they were attacked less or more than males. When several species intrude into a goldeneye's territory, conspecifics are attacked f i r s t , then congeners and then diving ducks, suggesting that goldeneye discriminate among intruding species. At times, however, aggression i s more indiscriminate: Mary Jackson (in Bellrose 1978) reports a female goldeneye k i l l i n g her own young after the young had been colour-dyed. I have also seen an attack on a brood by the t e r r i t o r i a l male of that brood. Pienkowski and Evans (1982a) report that shelduck pairs sometimes mistakenly attack their own 94 young. Rasa (1969) found that pomacentrid fishes use size and behaviour as a clue for attack of an intruder. Katzir (1981b) showed that damselfishes recognised conspecifics by the i r colouration pattern. Further research i s needed to determine the factors e l i c i t i n g t e r r i t o r i a l aggression and conspecific recognition i n Barrow's Goldeneye. To my knowledge, a l l i n t e r s p e c i f i c a l l y aggressive species are also highly i n t r a s p e c i f i c a l l y aggressive, suggesting that i n t e r s p e c i f i c aggression evolved as a by-product of i n t r a s p e c i f i c aggression. In Barrow's Goldeneye, the co s t of i n t e r s p e c i f i c aggression appears negligible compared with that of intraspecif i c aggression. I have rarely observed a dabbling or diving duck respond aggressively to a threat or attack by a Barrow's Goldeneye; they either ignore the goldeneye or flee. Only t e r r i t o r i a l Common Goldeneye and Bufflehead sometimes respond aggressively, and Bufflehead are much smaller and e a s i l y dominated by Barrow's Goldeneye whereas the ranges of Common and Barrow's goldeneye do not overlap extensively. There i s therefore l i t t l e danger of inj u r y i n int e r s p e c i f i c confrontations. The extreme sexual dimorphism i n size i n the genus Bucephala (Livezey and Humphrey 1984, Appendix 5) i n d i c a t e s p o s s i b l e s e l e c t i o n f o r aggressiveness or some other size-related attribute i n males of the genus. I suggest that a high level of intraspecif i c aggression, coupled with some feeding advantages, has favoured the evolution and maintenance of interspecific aggression i n the genus Bucephala. D) The territory T e r r i t o r i e s of Barrow's Goldeneye do not f i t any of the proposed functional classifications of avian territories (Hinde 1956, Perrins and Birkhead 1983). Goldeneye carry out a l l their breeding a c t i v i t i e s within 95 the territory but nest outside i t . Nests located i n cavities in flooded trees can sometimes be within the t e r r i t o r y but t h i s i s the exception. Therefore, Barrow's Goldeneye have an all-purpose type A territory (Nice 1941) ( t e r r i t o r y which provides a l l requirements) with the s i g n i f i c a n t exception of the nest s i t e . Goldeneyes seem to require both a nesting cavity and a feeding t e r r i t o r y to breed successfully. I t appears that they prefer terr i t o r i e s i n close proximity to the nesting site (50% of the nest sites were adjacent to the pair territory). However, philopatry to both nest s i t e (see Chapter 3) and p a i r t e r r i t o r y may mask t h i s preference. Philopatry to pair territory i s well known in t e r r i t o r i a l species of birds (Hilden 1979, Redmond and Jenni 1982, Calder £t a i . 1983, Oring and Lank 1984). The advantages of returning to the same territory are: 1) a prior sense of ownership which would increase defensive motivation (Hinde 1956, Figler and Einhorn 1983). This i s supported by the behaviour of two marked Barrow's Goldeneye males which had l o s t t h e i r mates during the winter and had f a i l e d to re-pair. Upon t h e i r return on the lake where they defended t e r r i t o r i e s the previous year, they defended the same territory for almost two days although they were not paired. They clearly responded to the stimulus of t h e i r old t e r r i t o r y ; 2) f a m i l i a r i t y with t e r r i t o r i a l neighbours c o u l d reduce the i n t e n s i t y of aggressive i n t e r a c t i o n s required; 3) knowledge of food resources on the t e r r i t o r y should enhance foraging e f f i c i e n c y ( Hixon e_t a i - 1983, Gass and Sutherland 1985). A knowledge of territory quality combined with previous tenure creates an asymmetry between the value of a territory to the owner and an intruder; i.e. the t e r r i t o r y owner has more to lose than the intruder. Petrie (1984) and Ewald (1985) have shown that such asymmetries 96 influence dominance. Pair territories and brood te r r i t o r i e s rarely coincide and this can be a t t r i b u t e d i n part to the s c a r c i t y of nest s i t e s . Also, there i s probably l i t t l e s e l e c t i o n for brood t e r r i t o r i e s to coincide with p a i r territories because: A) boundaries of pair territories are established by males and collapse when they leave; B) brood t e r r i t o r i e s average twice the size of pair t e r r i t o r i e s ; C) brood density i s only a t h i r d of pair density; D) boundaries of brood t e r r i t o r i e s are established by females; and E) feeding requirements of young are probably different from those of females i n spring. Brood te r r i t o r i e s are usually established on the lake closest to the nest site. This strategy minimizes overland travel which exposes the young to increased r i s k s of predation and depletes t h e i r energy reserves. Movement between lakes i s due to aggressive expulsion by other females with broods, or to the poor quality of the nearest lake for raising broods. T e r r i t o r i a l i t y i s well developed i n Barrow's Goldeneye and within the genus Bucephala. Its main function seems to be to provide the female (pair and winter t e r r i t o r i e s ) and the brood (brood t e r r i t o r y ) an undisturbed feeding site. Further experimental work i s , however, needed to quantify better the influence of greater food a v a i l a b i l i t y on various aspects of the breeding and wintering ecology of Barrow's Goldeneye and i t s relatives. Summary 1) P a i r s of Barrow's Goldeneye, Common Goldeneye and Bufflehead are t e r r i t o r i a l during the breeding season and during the wintering season: They defend a fixed, exclusive area against r i v a l s . 2) Barrow's Goldeneye and Bufflehead females defend t e r r i t o r i e s a f t e r 97 their young have hatched, and their behaviour i s similar to that of the drakes i n the spring. 3) A l l three species of Bucephala have similar t e r r i t o r i a l behaviour on the breeding area. 4) Pairs of a l l three species are i n t e r s p e c i f i c a l l y t e r r i t o r i a l and interspecific aggression i s strongest toward congeners and stronger toward d i v i n g ducks than d a b b l i n g ducks. The i n t e n s i t y of i n t e r s p e c i f i c aggression i s thus correlated with the degree of resource use overlap between Barrow's Goldeneye and other species. 5) Barrow's Goldeneye and Bufflehead females are i n t e r s p e c i f i c a l l y t e r r i t o r i a l during the brood rearing-season. 6) Brood amalgamation i s an accidental outcome of t e r r i t o r i a l encounters between females. 7) Philopatry to terr i t o r i e s i s strong i n Barrow's Goldeneye. 8) Long-term pair bonds exist i n Barrow's Goldeneye. 9) The main function of t e r r i t o r i a l i t y seems to be the provision of an exclusive feeding area for the female or the young. 10) I argue that the evolution and maintenance of i n t e r s p e c i f i c aggression i n the genus Bucephala has been favoured by a high level of intraspecific aggression within the genus, and significant feeding advantages obtained from the exclusion of competitors. 98 Chapter IV: Use of nest boxes and nesting success 99 Introduction Barrow's Goldeneye are secondary hole nesters that use ex i s t i n g c a v i t i e s instead of excavating t h e i r own (McLaren 1963). In B r i t i s h Columbia, they may use o l d n e s t s of the Common Crow (Corvus  brachyrhynchos) (Edwards 1953, Sugden 1963), and even burrows of Yellow-b e l l i e d Marmot (Marmota fl a v i v e n t r i u s ) (Munro 1935), but they most commonly use tree cavities excavated by Pileated Woodpecker (Dryocopus  p i l e a t u s ) , (Munro 1939, Bellrose 1978) and Common F l i c k e r fColaptes  auratus) holes that have been enlarged by weathering (M.F. Jackson i n Bellrose 197 8). In the parkland habitat of B r i t i s h Columbia, tree cavities provide most nesting s i t e s for Barrow's Goldeneye, but logging a c t i v i t i e s have reduced the number of nest s i t e s near several breeding ponds. Barrow's Goldeneye may nest several kilometers from water (Munro 1939) and nest cavities can be over 20m above ground, making the finding and checking of natural cavities d i f f i c u l t . There has thus been no major study of i t s breeding biology. Barrow's Goldeneye are known to use nest boxes (Griffee 1958, McLaren 1963) but no quantitative studies have been done on their breeding success in nest boxes, and the impact of nest boxes on the population has not been documented. Nest boxes have been extensively used to manage and f a c i l i t a t e the study of other c a v i t y -nesting waterfowl (Grice and Rogers 196 5, Norman and Riggert 1977, Eriksson 1979 b). They have e f f i c i e n t l y increased breeding densities of Wood Duck (Aix sponsa) (Schreiner and Hendrickson 1951, McLaughlin and Grice 1952), B l a c k - b e l l i e d Whistling Duck (Dendrocygna autumnalis) (McCamant and Bolen 1979) and Common Goldeneye (Siren 1951, 1952, Johnson 1967). The provision of nest boxes has been the key i n the successful establishment of new populations of Wood Duck and Common Goldeneye (Doty 100 and Kruse 1972, Eriksson 1982, Dennis and Dow 1984). The breeding biology of Common Goldeneye i n nest boxes has been studied in detail (Siren 1951, Gibbs 1961, Johnson 1967, Eriksson 1979b, 1982, Bragin 1981, Dow 1982). However, most studies on Common Goldeneye were done where breeding densities were low compared to densities of Barrow's Goldeneye. During the breeding season, Barrow's Goldeneye are usually associated with productive waters (Skinner 1937, Harris e± s i . 1954, Bengtson 1971, Palmer 1976), whereas Common Goldeneye are often associated with flood plains and oligotrophic lakes of lower productivity (Siren 1952, Carter 1958, Gibbs 1961, Prince 1965, Palmer 1976, Danell and Sjoberg 1977, Eriksson 197 9b). Therefore, i n most studies of Common Goldeneye, d e n s i t i e s may not have been high enough for t e r r i t o r i a l behaviour to have any effect on nest box use or breeding success. This i s indicated by the fact that few of these studies mentioned t e r r i t o r i a l i t y in Common Goldeneye and most even suggested that they were probably not t e r r i t o r i a l . Therefore i t remains to be shown i f use of nest boxes by Barrow's Goldeneye i s similar to that of Common Goldeneye. My aims in this chapter are: 1. to determine the factors influencing the use of nest boxes by Barrow's Goldeneye; 2. to quantify t h e i r reproductive success in nest boxes; 3. to assess the impact of nest boxes on the size of the breeding population; and 4. to compare the results with those obtained i n two other studies using nest boxes: a) of a non-t e r r i t o r i a l species, the Wood Duck, and b) of a t e r r i t o r i a l species breeding at lower densities, the Common Goldeneye. 101 Methods Between 1981 and 1984, I erected 278 large (hole diameter >8 cm) and 71 small (hole diameter <8 cm) nest boxes. Nest boxes were based on the design of Lumsden e_t a l . (1980), and were b u i l t from rough plywood or rough cedar (Table 24). Boxes had side openings and were nailed on aspen, pine or f i r trees with the entrance between 4 and 5 m above ground. A layer of spruce shavings (2-3 cm deep) was added as nest material. Trees close to the water's edge were selected whenever possible, but because several lakes were surrounded by open grassland, boxes ranged from 0 to 400 m from the water's edge. Nest boxes were checked twice in 1981, but 3 to 10 times i n 1982-84. In 1984, a sample of 29 boxes was v i s i t e d every day to detect p a r a s i t i c laying. At the end of the breeding season, abandoned eggs were removed from the boxes, but old down and nest material were l e f t intact. Successful nests are those i n which at l e a s t one egg hatched. Any boxes i n which Barrow's Goldeneye eggs were l a i d were considered used by Barrow's Goldeneye. A preyed upon box i s one i n which at l e a s t one egg disappeared or was destroyed. Results 1) Use of nest boxes by a l l w i l d l i f e Three species accounted for 96% of the 537 breeding attempts recorded in large nest boxes during the four years of the study. Barrow's Goldeneye accounted for 70% of attempts, and American Kestrel (Falco spar ver ius) and European S t a r l i n g (Sturnus vulgaris) f o r 13% each (Table 25). The percentage of boxes that remained empty each year ranged from 19 to 33% (Table 25). In the boxes with entrances too small for Barrow's Goldeneye, European Starling, American Kestrel and Bufflehead accounted respectively 102 Table 24. Dimensions of nest boxes and dates of erection. Erection date Number of boxes Interior f l o o r area (cm2) Depth 1 (cm) Hole s i z e 2 (height x width . or diameter) (cm) Type of wood March 1981 140 660 35 11x13 plywood August 1981 30 660 35 11x13 plywood October 1982 42 660 35 11x13 plywood Ap r i l 1983 18 210 28 7 cedar April 1983 17 320 28 7 cedar A p r i l 1983 24 360 28 7 cedar Apr i l 1984 66 460 25 10 cedar A p r i l 1984 12 300 28 7 cedar 1 Measured from the base of the entrance hole to the bottom of the box. Hole size > 8 cm = large nest boxes; hole size < 8 cm = small nest boxes. 103 Table 25. Number of large nest boxes used by breeding w i l d l i f e . Year Use by Breeding species 1981 1982 1983 1984 Total Barrow's Goldeneye 37 90 117 132 376 American Kestrel 24 14 10 20 68 European Starling 27 5 22 14 68 Red Squirrel 6 2 5 3 16 Tree Swallow - 2 2 - 4 Northern Flicker 1 - 1 - 2 Bufflehead - - 1 1 2 Mountain Bluebird - - 1 - 1 Nest boxes not used by breeding species 41 44 37 82 204 Total number of boxes available 136 157 196 252 741 104 for 62%, 19% and 6% of the 108 breeding attempts (Table 26). Two nest boxes were used by two species i n the same season. In one case, an American Kestrel successfully raised a brood in a box after young red s q u i r r e l s had been raised there. In the second case, a Barrow's Goldeneye used a box from which a brood of European Starlings had fledged. Two species occasionally competed for the same box; this resulted usually in the nest being deserted by one or both species. During the four years of the study, American Kestrels took over 4 European Starling nests, and three mixed clutches of Hooded Merganser and Barrow's Goldeneye were recorded. Half of the 39 c o n f l i c t s observed (51%) however, occurred between Barrow's Goldeneye and European S t a r l i n g . Several empty nest boxes were used for roosting at night by American Ke s t r e l , Northern Flicker, European Starling, and during the day by flying squirrels. 2) Nest box use by Barrow's Goldeneye Barrow's Goldeneye used 37 nest boxes i n 1981 and 132 i n 1984, an increase of 350% over three years (Table 25). Barrow's Goldeneye preferred o l d boxes to newly i n s t a l l e d ones (Fig. 17). Nest boxes that were used by Barrow's Goldeneye were more l i k e l y to be used by goldeneye the following year than those that had not been used (Table 27). Also, boxes i n which Barrow's Goldeneye successfully hatched a brood were re-used proportionally more often by goldeneyes than boxes i n which the reproductive effort f a i l e d (Table 27). In 1981, nest boxes were placed on ponds that had received different levels of use by Barrow's Goldeneye i n 1980 to determine i f the presence of goldeneye on the lake would increase nest box u t i l i z a t i o n . Ponds l i t t l e used by Barrow's Goldeneye i n 1980 were not used more i n 1981, i n spi t e of the presence of nest boxes. Goldeneyes used only 1 of 18 boxes 105 Table 26. Number of s m a l l nest boxes used by breeding w i l d l i f e . Year Use by Breeding s p e c i e s 1983 1984 T o t a l American K e s t r e l 10 10 20 European S t a r l i n g 40 27 67 B u f f l e h e a d 1 6 6 Mountain B l u e b i r d 1 - 1 Tree Swallow 1 5 6 Red S q u i r r e l 2 5 7 F l y i n g S q u i r r e l 1 - 1 Nest boxes not used by breeding s p e c i e s 3 17 20 T o t a l number of boxes a v a i l a b l e 59 70 129 106 B O X E S USED BY OTHER 8 P E C I E 8 B O X E S USED BY BARROW'8 G O L D E N E Y E UNUSED B O X E S 11 I . I I NEW 1 YEAR OLD 2 YEARS OLD 3 YEARS OLD n«226 n«i97 n»i52 n«125 AQE OF NEST BOXES F i g . 17 Proportion of nest boxes used by Barrow's Goldeneye and other w i l d l i f e in relation to age of the nest box (n=number of nest boxes). 107 Table 27. Relationship between previous use of a nest box and subsequent use by Barrow's Goldeneye. Subsequent status Previous status Not used by Used by % used Barrow's Goldeneye Barrow's Goldeneye Not used by Barrow's Goldeneye 98 136 58 Used by Barrow's Goldeneye 54 X2=17.2, 171 P<0.001 76 Used and hatched 9 81 90 Used and fa i l e d 45 X2=l5.3f 90 P<0.001 67 108 on those lakes. Nest boxes located on ponds with high d e n s i t i e s of goldeneye (>5 subadults) had more use than those on ponds with low de n s i t i e s (<2 subadults) (Table 28, X2=3.907, df=2, p=0.048). a) Nesting success The proportions of Barrow's Goldeneye nests that hatched, were preyed upon, and were deserted, did not d i f f e r s i g n i f i c a n t l y during the four years of the study (Fig. 18, X2=10.07, df=3, p=0.12). These proportions averaged respectively 46±4%, 31±3% and 23+3% and are within the range of values found i n other cavity-nesting waterfowl (Table 29). Predation was an important cause of nest f a i l u r e s . The most destructive predator was the Black Bear (Ursus americanus). Bears destroyed 33 nest boxes during the study: 0 i n 1980, 5 i n 1981, 4 i n 1983, and 24 in 1984. Predation attempts were spread throughout the study area and probably involved several bears. Black Bears usually attacked nest boxes with incubating females i n them, leaving nearby boxes intact. This suggests that they were attracted to the boxes by noise or scent. In one case, however, a bear destroyed the four boxes erected at a single pond. Female goldeneye usually escaped a l i v e from boxes preyed upon by bears. Some predators removed eggs from boxes one at a time. Although I never observed predation, I suspect red squirrel (Tamiasciurus hudsonicus) to be the c u l p r i t . I once observed a s q u i r r e l attempting to enter a box from which single eggs had been taken but the s q u i r r e l f l e d when i t r e a l i s e d that the female goldeneye was i n the box. This partial predation caused several nest desertions. Marten (Martes americana) may also have been responsible for some egg loss. The remains of one female goldeneye were found in a box, suggesting predation. Besides the 33 nest boxes destroyed by Black Bears, 5 were lost when their support tree f e l l down naturally, 3 109 Table 28. Nest box use in relation to abundance of Barrow's Goldeneye on pond in the previous year. Barrow's Goldeneye abundance No.of Total no. Total no. Total no. No.nest No. nest Population Ponds yearlings pairs broods boxes boxes used % used Ponds with >5 subadults i n 1980 17 361 147 33 59 24 41 Ponds with <2 subadults i n 1980 2 2 5 3 8 1 9 52 1 2 23 Ponds with no goldeneye in 1980 6 0 0 0 1 8 1 6 n o HATCHED PREYED UPON DESERTED 1981 1982 1983 1984 n = 3 3 n = 8 9 n»115 n=131 YEAR Fig. 18 Proportion of Barrow's Goldeneye nests that hatched, were preyed upon and were deserted (n=number of nest boxes). I l l Table 29. Comparison of nesting success between cavity nesting ducks. Nest fate (%) Hatched Preyed upon Deserted Barrow's Goldeneye This study Common Goldeneye Johnson (1967) Eriksson (1979b) Br agin (1981) Wood Duck Nay lor (1960) Bellrose e£ a l . (1964) Morse and Wight (1969) Strange e£ a l . (1971) Jones and Leopold (1967) Grice and Rogers (1965) McLaughlin and Grice (1952) Black-bellied Whistling Duck Bolen (1967) McCamant and Bolen (1979) 112 46±4 31±3 23±3 62 20 18 27 38 35 42 28 28 75±5 10±3 9±2 37±6 52±5 10±2 74 7 19 29 17 55 29 69±5 64 61 31£L6 were f e l l e d by beavers (Castor canadensis), 1 by loggers and 1 was destroyed by vandals. The outcome of a nesting attempt was independent of the age of the box. Similar proportions of nests were successful i n new boxes and i n older boxes (X2=11.5, df=3, P>0.05). The majority of the desertions recorded were not due to observer interference, as most desertions occurred i n nests i n which the female was absent during the checks (Fig. 19). For the nest boxes where clutch i n i t i a t i o n dates could be determined, I divided i n i t i a t i o n dates each year i n four equal parts: early, mid-early, mid-late and late. Because the proportion of successful nests did not differ significantly between years (Fig. 18) I combined a l l the nests i n each category for a l l years. The proportion of nests that hatched did not differ significantly between early and mid-early clutches nor between mid-late and late clutches but was greater i n a l l early versus l a t e clutches (Fig. 20, X 2 Tests, df=l, P<0.05). Among the nests that f a i l e d , the proportion of deserted nests was s i m i l a r i n a l l clutch i n i t i a t i o n periods (Fig. 21, X2=1.70, df=3, P=0.64). Among the nest boxes that were used by Barrow's Goldeneye two years in a row, those which had been successful the previous year were more l i k e l y to be successful the following year (Fig. 22, X2=5.78, df=l, P<0.016). b) Productivity From 1981 to 1984, the number of eggs l a i d i n nest boxes increased 6-fold (Table 30). The average clutch size was significantly lower i n the f i r s t two years of the study and this was true whether deserted and preyed upon clutches were included or not (Table 30). The proportion of eggs that hatched was s i m i l a r i n 1982, 1983, and 1984 (X2=5.15, df=2, P<0.07) but was higher in 1981 (X2=39.8, df=l, P<.001), however these s t a t i s t i c a l 113 HATCHED PREYED UPON DESERTED Fig. 19 Influence of v i s i t s by observers on the fates of nests. 114 72 . O < 64 . 56 -4 B -09 Ul 4 0 . u. O 32 -111 O 24 4 t r UJ a. 16 . 8 _ ft EARLY n - 8 2 1 } • I r • » as • • ^  v.- m t-x m MID-EARLY n - 8 2 MID-LATE n«80 CLUTCH INITIATION PERIOD Fig. 20 Hatching success in relation to date of clutch i n i t i a t i o n (n=number of nests). 1 1 5 EARLY MID-EARLY MID-LATE LATE n n 2 8 n»39 n=52 n«54 CLUTCH INITIATION PERIOD Fig. 21 Proportions of non-hatching nests preyed upon in relation to clutch i n i t i a t i o n date (n=number of nests). 116 BREEDING SUCCESS IN YEAR 2 HATCHED IN YEAR 1 FAILED IN YEAR 1 n . 8 1 n i 0 1 B R E E D I N G S U C C E S S I N Y E A R 1 Fig. 22 Influence of the outcome of the previous reproductive attempt i n a nest box on the outcome of future nesting attempts i n the same nest box (n=number of nests). 117 Table 30. Egg production in nest boxes in relation to year. No. of No.of eggs la i d % of eggs that were Average clutch size ± standard error Year boxes1 Hatched Predated Deserted A l l nests Successful nests only (no. of nests) 1981 33 217 65 10 26 6.58±0.56 A 2 7.79+0.71 A 2 (19) 1982 89 646 42 22 36 7.26+0.43 A 9.15+0.66 A (34) 1983 115 1127 42 13 45 9.80±0.43 B 12.81±0.63 B (42) 1984 131 1265 46 18 36 9.67+0.40 B l l . l l i 0 . 5 3 B (62) Only nest boxes whose fate was known. Averages with similar letters do not differ significantly (Newman-Keuls Multiple range test, P<0.05) (Zar 197 4). results should be considered cautiously because of the occasional lack of independence between the eggs of a given clutch (entire clutches are sometimes l o s t at the same time). Clutch sizes i n new and one-year-old nest boxes did not dif f e r significantly, but were significantly lower than clutches l a i d i n 2- and 3-year-old boxes (Table 31). A similar result i s obtained i f only successful nests are compared (Table 31). The proportion of eggs that hatched varied with the age of the box, being lowest i n 1-year old boxes and highest i n 3-year old boxes. Nest boxes that had not been used by Barrow's Goldeneye i n the p r e v i o u s year contained significantly smaller clutches (x=9J+0.51, n=50) than those that had been used by Barrow's Goldeneye, whether the nesting attempt was successful (X =13.04+0.06, n=46) or not (x"=12.17±0.69, n=35) (Newman-Keuls multiple range test, P<0.05, Zar 1974). c) Parasitic egglaying In 1984, 29 nest boxes were checked daily to assess laying patterns and to look for nest parasitism. More than 1 egg was l a i d within a 25 hour period i n 37 instances d i s t r i b u t e d i n 21 boxes. In 18 of those 37 cases, no egg was l a i d the following day, indicating that the appearance of two eggs may have been due to the checking schedule rather than to p a r a s i t i c laying. In the remaining 19 cases (in 13 boxes) two or more females were responsible for the additional eggs. Therefore, 13 of the 29 boxes (45%) checked were parasitized at least once, and 4 boxes (14%) were parasitized at least 3 times. In one case, 4 eggs were l a i d within a 25 h period, and i n 6 cases 3 eggs were l a i d w ithin 25 h. The average laying i n t e r v a l for a given box ranged between 16 and 72 hours. Such a spread indicates parasitic laying, the low values being due to multiple laying i n a box, whereas the large values are due to intermittent laying. Laying 119 Table 31. Egg production in relation to age of the box. Average clutch size + standard error % of eggs that were Hatched Predated Deserted n (No.of eggs) A l l nests 1 n Successful nests only n New boxes 48 14 38 355 6 . 57+0.39 A 2 54 7.71+0.59 A 2 24 1 year old boxes 34 21 45 895 7.59+0.38 A 118 9.08±0.62 A 39 2 year old boxes 47 12 41 1023 10.23+0.46 B 100 12.63+0.64 B 43 3 year old boxes 53 17 30 974 10.25+0.48 B 95 11.84±0.56 B 51 1 only nests whose fate was known. 2 Averages with similar letters do not differ significantly (Newman-Keuls Multiple range test, P<0.05) (Zar 1974) . patterns i n nest boxes ranged widely: i n one box 1 egg was added every second day, in others 1 egg was l a i d per day. In one box 8 eggs were l a i d , then a f t e r a gap of 7 days, 10 more eggs were added, a l l 18 eggs hatched successfully. In some other boxes, several days elapsed between eggs. Daily checks indicated that partial predation of a clutch did not necessarily cause desertion. However, a l l nests i n which yolk had spilled on the other eggs were deserted. If we assume that clutches containing more than 13 eggs are the product of parasitic laying, we can derive a conservative estimate of the frequency of parasitic laying for each year: 7% (n=41) in 1981, 7% (n=99) i n 1982, 20% (n=124) i n 1983 and 19% (n=145) i n 1984. This estimate i s conservative, as nest parasitism does not always r e s u l t i n larger clutches. Also, clutches deserted due to parasitism would not be included here unless they were deserted a f t e r they had more than 13 eggs. If we consider clutches containing more than 10 eggs as a product of parasitic laying, then our estimates of parasitic laying become: 10% in 1981, 20% i n 1982, 37% i n 1983 and 3 9% i n 1984. The 29 nests that were followed daily in 1984 suggest a higher frequency of parasitic laying (45%). Most of the parasitism occurred during egg laying; i n only two of 14 boxes did i t occur after the i n i t i a t i o n of incubation. d) Impact of nest boxes on population size In 1980, the year p r i o r to the e r e c t i o n of nest boxes, the populations of Barrow's Goldeneye and Bufflehead were estimated at 205+13 pa i r s and 109+11 p a i r s respectively (n=4 counts). By 1984 the Barrow's Goldeneye population had increased by 57% to 322±8 pairs whereas that of Bufflehead had increased by 42% to 155±15 pairs (Fig. 23). However, the number of Bufflehead pairs did not vary s i g n i f i c a n t l y during the f i v e 121 Fig. 23 Numbers of Barrow's Goldeneye and Bufflehead p a i r s e s t i m a t e d on the study area (95% Confidence l i m i t s are given). 122 years of the study (ANOVA, F=2.5, P=0.0 86) whereas number of Barrow's Goldeneye pairs did (ANOVA, F=34.7, P=0.000). Number of Barrow's Goldeneye p a i r s increased s i g n i f i c a n t l y i n the t h i r d year (1983) following the erection of nest boxes and again i n 1984 (Newman-Keuls test, P<0.05). From 1980 to 1982 there was no s i g n i f i c a n t difference i n numbers of goldeneye pairs. Brood counts r e f l e c t t h i s increase (Fig. 24). The number of broods of Barrow's Goldeneye was similar i n 1980 and 1981 and started to increase in 1982. By 1984 there were 24 more broods on the study area, an increase of 29%. Bufflehead broods increased from 1980 to 1982, then decreased i n 1983 and remained at the same level i n 1984. From 1980 to 1984 there was only a 6% increase i n the number of Bufflehead broods on the study area. Whether t h i s increase i s due to the presence of the nest boxes or j u s t r e f l e c t s a natural general increase i n the population can only be resolved by the use of control areas. Although I established no controls, surveys by Ducks Unlimited i n B.C. can be used to determine i f there were general increases i n Barrow's Goldeneye density in the area. The results vary greatly between areas. However none of the controls display results s i m i l a r to that of the study area (Table 32). Both goldeneye and Bufflehead increased in Chilco (area B) which was due to the flooding of several new ponds i n 1982. This suggests that the increase i n the breeding numbers of Barrow's Goldeneye observed i n the study area resulted from the nest oox program. DISCUSSION Barrow's Goldeneye d e n s i t y i n c r e a s e d by about 50% after the installation of nest boxes. The increase began in 1983, three years after the erection of the f i r s t boxes. This coincides with the year the young 123 65 -60 -55 -1980 1981 1882 1983 1984 YEAR Fig. 24 Numbers of Barrow's Goldeneye and Bufflehead broods estimated on the study area. 124 Table 32. Summary of counts carried out by Ducks Unlimited i n Central British Columbia and comparison with counts on the study area. Area Year No. of Barrow's Goldeneye pairs No. of Bufflehead pairs Barrow's pairs -Bufflehead pairs Al 1980 67 47 +20 1981 69 58 +11 1983 69 46 +23 B 1980 28 23 +15 1981 39 43 -4 19832 60 69 -9 C 1980 26 5 +21 1981 26 9 +15 1982 29 37 -8 1983 27 8 +19 D 1980 33 21 +12 1982 40 67 -27 1983 43 32 +11 E 1982 78 87 -9 1983 70 115 -45 1984 49 55 -6 F 1980 205 109 +96 1981 201 125 +76 1982 199 140 +59 1983 265 123 +142 1984 322 155 +167 Areas: A) Bald Mountain, 148 Mile House; B) Chilco; C) R o s e h i l l and Merrit; D) 70 Mile House; E) Chilcotin; F) Study area. The large increase i n the number of pa i r s i n 1983 was due to the creation of several new ponds suitable for diving ducks. This i s r e f l e c t e d i n a similar increase in goldeneye and Bufflehead numbers. 125 produced i n 1981 should have entered the breeding population. This coincidence, coupled with the information gathered from the control areas which showed no similar increase i n goldeneye numbers, strongly suggests that the the greater a v a i l a b i l i t y of nest s i t e s was the cause of t h i s increase. Gauthier (1985) and Peterson and Gauthier (1985) found a scarcity of large natural c a v i t i e s i n the aspen parkland of B.C.: there was an adequate supply of c a v i t i e s for Bufflehead but only 12% of the c a v i t i e s (n=135) had an entrance opening large enough for Barrow's Goldeneye. They found that Bufflehead avoided large nest boxes and made a limited use of small boxes which suggests that small natural cavities are abundant in the area. Preference of small entrance cavities by Bufflehead would reduce the chances of confrontation with female Barrow's Goldeneye which have been reported to k i l l nesting Bufflehead (Erskine 195 9, 196 0, 197 2, McLaren 196 9). There was no i n d i c a t i o n that t e r r i t o r i a l behaviour had a negative impact on nest box use. Aggression of paired drakes on the territory did not deter females from using nest boxes adjacent to i t . Nest boxes a few meters apart were used by d i f f e r e n t females. Because t e r r i t o r i a l aggression i s centered on the territory i t s e l f and not on the nest site, any impact of t e r r i t o r i a l behaviour on nest box use w i l l be i n d i r e c t , through an o v e r a l l l i m i t i n g e f f e c t on the population. T e r r i t o r i a l behaviour may l i m i t breeding d e n s i t i e s of Bufflehead (Gauthier 1985). Because Barrow's Goldeneye can use nest s i t e s 2 Km away from t h e i r breeding territory, the impact of t e r r i t o r i a l behaviour of pairs w i l l be l i m i t e d i n areas where water bodies are abundant. In my study, because the population was apparently limited by nest site availability, i t may take a few more years before any influence of t e r r i t o r i a l behaviour on 126 nest box use i s detected. Several factors affected the use of nest boxes by Barrow's Goldeneye: previous use, outcome of previous breeding attempt, age of box, and nest box lo c a t i o n . Nest boxes that had been used i n preceding years were l i k e l y to be re-used the following years and successful nests more so. S i m i l a r patterns of u t i l i z a t i o n have been found i n Common Goldeneye (Eriksson 1979 b, Dow and Fredga 1983, 1985). Barrow's Goldeneye preferred old boxes to newly-installed ones. This i s because most subadult females and unsuccessful females select t h e i r nest site the year prior to breeding (Eadie and Gauthier 1985). New boxes are not, therefore, a v a i l a b l e at the time of nest s i t e s e l e c t i o n . Nest boxes located on lakes frequented by goldeneye were more l i k e l y to be used. This again i s related to prospecting by females. Subadult females are more l i k e l y to prospect for nesting cavities on the lakes where they feed, and only i f unsuccessful there would they be expected to expand their searching radius. Early clutches were more l i k e l y to hatch than l a t e ones. This may reflect earlier breeding by older and experienced birds (Bellrose e i aJL 1964, Klomp 1970, Krapu and Doty 197 9, Afton 1984). In the f i r s t two years of the study, the average clutch size of Barrow's Goldeneye in nest boxes was lower than i n the l a s t 2 years. S i m i l a r l y , new and 1 year o l d nest boxes contained a lower average clutch size than older boxes. This may be due to young birds being more l i k e l y to use new cavities than older birds. S i m i l a r l y , new and 1-year-old boxes are more l i k e l y to contain a higher proportion of f i r s t time breeders than older boxes. In some waterfowl species, young and inexperienced breeders are known to produce smaller clutches than older birds (Heusman 1975, B a i l l i e and Milne 1982, 127 Rockwell fit a l . 1983, Afton 1984, Dow and Fredga 1984). Therefore, birds breeding i n nest boxes during the f i r s t few years of a nest box program do not represent a random sample of the population. This should be considered when studying the breeding ecology of a cavity-nesting species. Eriksson (1982) showed that clutch size i n newly established populations of Common Goldeneye was significantly smaller than i n a well-established population. He a t t r i b u t e d t h i s to the greater proportion of f i r s t - t i m e breeders i n newly established populations. Intraspecif i c nest parasitism, although common i n some species of waterfowl, i s s t i l l poorly understood (Clawson fit a l * 1979, McCamant and Bolen 197 9, Eriksson and Andersson 1982, Pienkowski and Evans 1982b). This phenomenon i s most common when nest sites are conspicuous, and there i s evidence that this behaviour increases nest desertion rates, adversely affecting reproductive success (Jones and Leopold 1967, Morse and Wight 1969, Zipko 197 9, Eriksson and Andersson 1982). The high l e v e l of desertion observed i n this study may be the result of disturbance by other females at the nest s i t e . Grenquist (196 3) and Jones and Leopold (1967) found i n the Wood Duck and Common Goldeneye that desertion rates increased i n years when a large number of newly matured birds attempted to breed, and attributed this to increased nesting interference. The proportion of successful Barrow's Goldeneye nests averaged 46%. This i s similar to proportions reported for other cavity-nesting waterfowl (Bellrose fit a l . 1964, Bolen 1967, Bragin 1981). Predation accounted for approximately 30% of the losses, thus production could be significantly increased by the use of predator-proof nest boxes. Nest success improved from 44% to 77% a f t e r i n s t a l l a t i o n of predator guards on B l a c k - b e l l i e d Whistling Duck boxes (Bolen 1967). My results indicate that nest boxes increased the density of Barrow's 128 Goldeneye i n the area. The a v a i l a b i l i t y of nesting c a v i t i e s may l i m i t Barrow's Goldeneye, whereas Bufflehead do not seem to be limited by nest site availability. Gauthier (1985) found that Bufflehead density did not increase with the provision of additional nest sites and suggested that t e r r i t o r i a l behaviour was l i m i t i n g the population. Common Goldeneye d e n s i t i e s have been increased by the i n s t a l l a t i o n of nest boxes (Siren 1951, 1952, Johnson 1967). SUMMARY 1) Barrow's Goldeneye ut i l i z e d nest boxes readily. 2) Breeding density of pairs was limited by availability of nest sites. 3) Factors affecting nest box use by Barrow's Goldeneye were similar to those found to influence Common Goldeneye: previous use, outcome of previous breeding attempts, age of nest box and location of nest box. 4) Proportions of nest boxes that hatched, were preyed upon, and were deserted averaged respectively 46±4% (S.E.), 31±3% and 23+3% (n=4 years). 5) The average clutch size was lower in the f i r s t two years of the study than i n the l a s t two, and lower i n new and 1-year-old boxes than older boxes. 6) Minimum estimates of intraspecif i c nest parasitism range between 5% i n 1981 and 20% i n 1983 whereas l e s s conservative estimates range between 10 and 45%. 129 Chapter V: Mortality of Barrow's Goldeneye and Bufflehead broods 130 Introduction I showed i n Chapter III that females with broods are highly aggressive and that t h i s aggression r e s u l t s occasionally i n duckling deaths. Brood amalgamation, which i s frequent i n Barrow's Goldeneye (Table 8) i s also due to t e r r i t o r i a l aggressiveness. Three studies have indicated that duckling s u r v i v a l i n Shelduck was low i n areas of high brood d e n s i t i e s where brood amalgamation was frequent (Williams 1974, Makepeace and Patterson 1980, Pienkowski and Evans 1982a). Several factors increase duckling mortality: predation (Munro and Bedard 1977b, Pienkowski and Evans 1982a), adverse weather (Koskimies 1955, Bengtson 1972), high breeding densities (Makepeace and Patterson 1980) and low food abundance (Bengtson 1972, Pehrsson 197 3, Street 1977). Bengtson (1972) found that not only did Barrow's Goldeneye ducklings suffer higher mortality at higher densities, but high densities of goldeneye increased the mortality of scaup ducklings. In this chapter, I compare the mortality rates of Barrow's Goldeneye and Bufflehead broods. I asked the following questions: 1) Does the mortality rate of ducklings f l u c t u a t e between years? 2) How does mortality rate change with duckling age? 3) Is duckling mortality similar i n Barrow's Goldeneye and Bufflehead? 4) Do e a r l y and l a t e hatching broods have s i m i l a r mortality rates? 5) Do increasing densities of goldeneye affect mortality rates of Bufflehead ducklings? METHODS Barrow's Goldeneye and Bufflehead broods stayed i n open water and rarely sought cover. This, with the lack of emergent vegetation on most ponds, greatly f a c i l i t a t e d brood checks. In 1980 and 1981, I v i s i t e d broods distributed among 100 ponds at intervals of 14 days. In 1982, 1983 131 and 1984, I increased the frequency of v i s i t s to 3 days. During each v i s i t , I recorded the location of the brood, the age of the young and the number of young i t contained. Most broods could be i d e n t i f i e d by a combination of age, number of young and location. Also many Barrow's Goldeneye females were marked with nasal disks (26% in 1982, 47% in 1983, 56% i n 1984). Reduction i n brood size between consecutive v i s i t s was assumed to i n d i c a t e d u c k l i n g m o r t a l i t y . On some ponds, broods amalgamated, increasing the number of young in one brood while decreasing i t i n another. In most cases, I could i d e n t i f y such occurrences and assigned the young to their respective broods. Broods which could not be followed individually were excluded from the analysis. I estimated brood mortality i n several ways. 1) I recorded the number of young present when a brood was f i r s t sighted and again when i t was l a s t sighted. The i n t e r v a l between these two records varied among broods. However, most broods were f i r s t sighted within a week from hatching and most were followed un t i l 4 weeks old. This technique allowed the determination of brood mortality on lakes where broods could not be followed individually because of frequent mixing. The method provided a minimum estimate of duckling mortality. 2) I calculated a mortality rate for each brood using the Mayfield method (Mayfield 1961, 1975). The method accounts for bias related to the age of the ducklings at f i r s t sighting by introducing into the calculations the period of time the ducklings were under observation. Mayfield (1961) developed the technique to estimate nest s u r v i v a l , but Ringelman and Longcore (198?) and Gauthier (1985) have used i t to estimate duckling s u r v i v a l rates. For each period, an exposure index was calculated: exposure=number of ducklings * length of period). I f 2 ducklings were 132 a l i v e f o r 2 d a y s t h e n t h e y r e p r e s e n t 4 d u c k l i n g - d a y s . M o r t a l i t y w a s e x p r e s s e d a s : l o s s e s / e x p o s u r e where l o s s e s a r e t h e number o f d u c k l i n g s t h a t d i e d d u r i n g t h e p e r i o d . A p r o b l e m a r i s e s w h e n t h e e x a c t t i m e o f d u c k l i n g l o s s i s n o t k n o w n . T h e n , a s s u m p t i o n s h a v e t o b e made. I c o n s i d e r e d t h r e e d i f f e r e n t a s s u m p t i o n s and l o o k e d a t how t h e y a f f e c t e d t h e r e s u l t s . A) I a s s u m e d t h a t t h e m o r t a l i t y r a t e w a s c o n s t a n t ( J o h n s o n 197 9 ) . B) I a s s u m e d t h a t l o s s e s w e r e d i s t r i b u t e d e q u a l l y d u r i n g t h e p e r i o d . C) I a s s u m e d t h a t a l l l o s s e s o c c u r r e d m i d - w a y t h r o u g h o u t t h e p e r i o d ( M a y f i e l d 1 9 6 1 ) . A l l t h r e e a s s u m p t i o n s y i e l d e d s i m i l a r d a i l y m o r t a l i t y e s t i m a t e s f o r b o t h B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d ( s e e F i g s . 2 7 - 2 8 ) . I t h e r e f o r e used o n l y a s s u m p t i o n A i n subsequent a n a l y s i s . F r o m t h e M a y f i e l d m e t h o d , t w o e s t i m a t e s o f d a i l y m o r t a l i t y c a n b e d e r i v e d : a w e i g h t e d e s t i m a t e , where e x p o s u r e s and l o s s e s a r e summed f o r a l l b r o o d s a n d t h e n t h e d a i l y m o r t a l i t y r a t e i s c a l c u l a t e d , a n d a n u n w e i g h t e d e s t i m a t e where m o r t a l i t y r a t e s a r e c a l c u l a t e d f o r each b r o o d i n d i v i d u a l l y and t h e n a v e r a g e d . I u s e d t h e j a c k k n i f e t e c h n i q u e (Cochran 1977) t o e s t i m a t e t h e v a r i a b i l i t y o f t h e w e i g h t e d d a i l y m o r t a l i t y r a t e s . RESULTS 1) H a t c h i n g c h r o n o l o g y The t i m i n g o f s p r i n g thaw a f f e c t e d t h e b r e e d i n g p h e n o l o g y o f B a r r o w ' s G o l d e n e y e . D u r i n g t h e f i v e y e a r s o f t h e s t u d y h a t c h i n g p e a k s v a r i e d b y two weeks ( F i g s . 2 5 - 2 6 ) . A t w o - w a y ANOVA i n d i c a t e d t h a t t h e mean h a t c h i n g d a t e v a r i e d s i g n i f i c a n t l y between y e a r s , t h a t B u f f l e h e a d h a t c h e d s l i g h t l y b u t s i g n i f i c a n t l y l a t e r (P<0.001) t h a n B a r r o w ' s Goldeneye a n d , t h a t t h e r e w e r e no i n t e r a c t i o n s b e t w e e n y e a r s a n d s p e c i e s i n d i c a t i n g t h a t b o t h s p e c i e s responded s i m i l a r l y each y e a r t o e n v i r o n m e n t a l f a c t o r s (Table 3 3 ) . I n a l l y e a r s , o v e r 7 0% o f t h e b r o o d s h a t c h e d w i t h i n a t h r e e week p e r i o d . 1 3 3 4 0 1980 n . 8 4 2 0 f I J U N E J U L Y H A T C H I N G D A T E Fig. 25 Hatching dates of Barrow's Goldeneye broods (n=number of broods). 134 1981 n = 7 3 UJ O g 4 0 ^ fit 2 0 - I . 1 rtifrrt,tmt-,rf1, 1983 no 7 3 t i t 4 0 -I 2 0 -I 1984 n = 7 9 8 15 22 J U N E 2 9 6 13 J U L Y H A T C H I N G D A T E 20 Fig. 26 Hatching dates of Bufflehead broods (n=number of broods). 135 Table 33. Two-way ANOVA on the effect of year and species (Barrow's Goldeneye vs Bufflehead) on mean hatching date. Analysis of variance Sum of Mean Signif. Source of variation squares DF square F of F Year 6.567 4 1.642 33.093 0.000 Species 0.733 1 0.733 14.784 0.000 2-way interactions 0.095 4 0.024 0.480 0.750 Explained 7.529 9 0.837 16.862 0.000 Residual 40.484 816 0.050 Total 48.013 823 0.058 136 The e a r l i e s t b r o o d h a t c h e d i n t h e f i r s t week o f J u n e a n d t h e l a t e s t h a t c h e d i n t h e second week o f J u l y . 2) M o r t a l i t y o f b r o o d s a) M a y f i e l d method - Unweighted by b r o o d s i z e ( a n a l y s e d o n a b r o o d b a s i s ) S p e c i e s , y e a r , a n d d u c k l i n g a g e , b u t n o t h a t c h i n g d a t e , h a d a s i g n i f i c a n t e f f e c t o n d a i l y m o r t a l i t y r a t e (Table 3 4 ) . The i n t e r a c t i o n between y e a r and age was a l s o s i g n i f i c a n t , i n d i c a t i n g t h a t t h e p a t t e r n o f m o r t a l i t y w i t h age d i f f e r e d between y e a r s . The absence o f any i n t e r a c t i o n b e t w e e n s p e c i e s a n d y e a r a n d s p e c i e s a n d p e r i o d i n d i c a t e s t h a t B a r r o w ' s G o l d e n e y e a n d B u f f l e h e a d r e s p o n d i n a s i m i l a r f a s h i o n t o f a c t o r s t h a t i n f l u e n c e m o r t a l i t y between y e a r s and p e r i o d s . C o m p a r i s o n o f means u s i n g t h e Newman-Keuls t e s t i n d i c a t e d t h a t t h e d a i l y m o r t a l i t y r a t e o f B a r r o w ' s G o l d e n e y e w a s s i g n i f i c a n t l y h i g h e r i n 1983 t h a n i n a n y o t h e r y e a r ( T a b l e 3 5 ) . D a i l y m o r t a l i t y r a t e o f B a r r o w ' s Goldeneye was h i g h e s t i n t h e f i r s t week a f t e r h a t c h i n g and h i g h e r i n t h e second and t h i r d weeks t h a n i n t h e f o u r t h week a n d d a i l y m o r t a l i t y r a t e o f B u f f l e h e a d was s i g n i f i c a n t l y h i g h e r i n t h e f i r s t week t h a n i n subsequent weeks (Table 36). Because o f empty c e l l s , b r o o d s aged 5 and 6 weeks w e r e e x c l u d e d f r o m t h i s a n a l y s i s . b) M a y f i e l d method - W e i g h t e d by b r o o d s i z e ( a n a l y s e d on a d u c k l i n g b a s i s ) B e c a u s e e s t i m a t e s a r e w e i g h t e d b y b r o o d s i z e a n d t h e v a r i a n c e i s e s t i m a t e d w i t h t h e j a c k k n i f e t e c h n i q u e , n o r m a l s t a t i s t i c a l t e s t s cannot be p e r f o r m e d . However, I p r e s e n t t h e d a i l y m o r t a l i t y e s t i m a t e s w i t h t h e i r 95% c o n f i d e n c e l i m i t s . B e c a u s e o f s m a l l e r v a r i a b i l i t y , r e s u l t s r e v e a l m o r e d i f f e r e n c e b e t w e e n y e a r s t h a n t h e p r e v i o u s a n a l y s i s ( F i g s . 2 7 - 2 8 ) . D a i l y m o r t a l i t y r a t e s o f B a r r o w ' s Goldeneye d u c k l i n g s were s i g n i f i c a n t l y h i g h e r (no o v e r l a p o f c o n f i d e n c e l i m i t s ) t h a n t h o s e o f B u f f l e h e a d d u c k l i n g s i n a l l y e a r s b u t 1984 when t h e y were l o w e r . M o r t a l i t y r a t e s o f 1 3 7 Table 34. Four-way analysis of variance on the e f f e c t of species (Barrow's Goldeneye vs Bufflehead), year, age and hatching date on mortality rate of young. Analysis of variance Sum of Mean Signif. Source of variation squares DF square F of F Species 0.041 1 0.041 11.645 0.001 Year 0.169 4 0.042 11.890 0.000 Age 0.588 5 0.118 33.003 0.000 Hatching date 0.012 2 0.006 1.618 0.199 Species/year 0.031 4 0.008 2.201 0.067 Species/age 0.027 5 0.005 1.537 0.175 Species/hatching date 0.004 2 0.002 0.603 0.547 Year / age 0.249 20 0.012 3.496 0.000 Year / hatching date 0.026 8 0.003 0.897 0.518 Age / hatching date 0.016 10 0.002 0.444 0.925 Residual 8.877 2492 0.004 Total 10.142 2553 0.004 138 Table 35. D a i l y m o r t a l i t y r a t e of Barrow's Goldeneye and Bufflehead ducklings i n r e l a t i o n to year. (Analysis derived from a three-way ANOVA (year, age and hatching date) n=12 ce l l s ; analysis not weighted by brood size.) Species Year Barrow's Goldeneye Bufflehead 1980 0.030 A 1 0.017 A B 1981 0.019 A 0.005 A 1982 0.016 A 0.008 A B 1983 0.052 B 0.024 B 1984 0.026 A 0.025 B Means with identical letters do not differ significantly P>0.05, Newman-Keuls Test (comparison within species only). 139 Table 36. D a i l y m o r t a l i t y r a t e of Barrow's Goldeneye and Bufflehead broods in relation to age. (Results derived from three-way ANOVA (year, age and hatching date) n=15 ce l l s ; analysis not wieghted by brood size.) Age (in days) Barrow's Goldeneye Bufflehead 1-7 0.053 A 1 0.032 A 8-14 0.028 B 0.014 B 15-21 0.020 B C 0.009 B 22-28 0.012 C 0.007 B Means with i d e n t i c a l l e t t e r s do not d i f f e r s i g n i f i c a n t l y P>0.05, Newman-Keuls Test (comparison within species only). 140 A S S U M P T I O N S U S E D • M O R T A L I T Y R A T E C O N S T A N T A L 0 8 S E S C O N S T A N T • L O S S E S A T M I D P O I N T T I t T T + • • • I 1 1 I I I I 1 I I I I I I 1 8 8 0 1*81 1*82 1 9 8 3 1 8 8 4 Fig. 27. Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings. (Based on Mayfield's method and under three d i f f e r e n t assumptions for duckling loss; 95% confidence l i m i t s of the estimates are given.) 1 » * • + * 141 A S 8 U M P T I O N 8 U S E D • M O R T A L I T Y R A T E C O N 8 T A N T A L O S S E S C O N S T A N T B L O S S E S A T M I D P O I N T T I T T T t * + • * i * • i * T 1 1 1 1 1 1 1 1 1 1 1 1 1 r 1 9 B 0 1BB1 1 * 8 2 1 » 8 3 1 8 8 4 Fig. 28 Daily mortality rates (weighted by brood size) of Bufflehead ducklings. (Based on Mayfield's method and under three d i f f e r e n t assumptions for duckling loss; 95% confidence l i m i t s of the estimates are given.) 142 both species fluctuated i n a s i m i l a r fashion, being highest i n 1983 and higher i n 1980 than i n 1981, 1982 and 1984. For 1981, 1982 and 1984 however, the pattern of mortality differed between the species. Mortality rate of Barrow's Goldeneye was s i m i l a r i n those three years whereas the mortality rate of Bufflehead increased from 1981 to 1984. S i m i l a r l y , weighted mortality estimates reveal more s i g n i f i c a n t differences i n mortality rates as a function of age (Figs. 29-30). In a l l years but 1980 the mortality rate of Barrow's Goldeneye ducklings was higher i n the f i r s t week a f t e r hatching. In most years, mortality rates had decreased considerably by the t h i r d week and remained f a i r l y constant u n t i l fledging. The pattern of mortality in relation to duckling age differed between years. It was similar i n 1981, 1982 and 1984 but differed in 1980 and 1983 when mortality was highest. Mortality rates of Bufflehead ducklings (Fig. 30) followed a s i m i l a r pattern to that of Barrow's Goldeneye ducklings: mortality rates were usually higher i n the f i r s t week following hatching and the pattern of mortality i n r e l a t i o n to duckling age varied between years. Although d a i l y mortality rate did not vary s i g n i f i c a n t l y with hatching period, there i s an indication that hatching date may influence mortality i n years of high mortality (Figs. 31-32). In 1983 weighted estimates of mortality rates d i f f e r e d s i g n i f i c a n t l y , being highest for late broods, and in 1980, broods that hatched mid-way through the season suffered lower mortality. During the f i v e years of the study, early broods tended to suffer lower mortality than late broods. For marked broods, the number of young at hatching was known. I therefore could look i n more detail at mortality during the f i r s t week of l i f e . Mortality pattern d i f f e r e d between years (Fig. 33). Daily mortality rate was higher in the f i r s t two days and tended to decrease in 143 \ 1-8 8 - 1 6 1 6 - 2 2 2 2 - 2 8 2 0 - 8 6 8 6 - 4 3 A O E IM 0 A Y 8 Fig. 29 Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings in relation to duckling age. (Mayfield's method: mortality rate assumed constant between observation periods; 95% confidence l i m i t s given.) 144 1-8 8-15 15-22 22-29 29-36 36-43 AGE IN DAYS Fig. 30 Daily mortality rates (weighted by brood size) of Bufflehead ducklings in relation to duckling age. (Mayfield's method: mo r t a l i t y rate assumed constant between observation periods; 95% confidence l i m i t s given.) 145 Fig. 31 Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings i n relation to hatching p e r i o d . (Mayfield's method: m o r t a l i t y r a t e assumed constant between observation periods; 95% confidence l i m i t s given.) 146 1980 1881 1982 YEAR 1883 ~T~ 1884 Fig. 32 Daily mortality rates (weighted by brood size) of Bufflehead ducklings in relation to hatching period. (Mayfield's method: mo r t a l i t y rate assumed constant between observation periods, 95% confidence l i m i t s given.) 147 104 1982 • 196 3 -A 1984 8 -3 ~~r~ 4 ~r~ 6 —f— 0 AGE IN DAY8 Fig. 33 Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching (Based on marked broods only; Mayfield 1 s method: mortality rate assumed constant between observation periods; 95% confidence l i m i t s given.) 148 the following days. Calculations of mortality on a per brood basis show a s i m i l a r pattern for 1982 and 1984 but do not show a decrease i n 1983 (Figs. 34,35,36). c) Direct method This method consisted of estimating the maximum number of young present on a lake after a l l broods had hatched and then again several weeks l a t e r . The difference i n the number of young counted provides a conservative estimate of mortality. Results are e s s e n t i a l l y s i m i l a r to those obtained with the Mayfield method. The percentage of young Barrow's Goldeneye l o s t ranged from 21% i n 1981 to 46% i n 1983 (Table 37). Years with the highest mortality were 1980 (35%) and 1983 (46%). Similar losses of young occurred in 1981, 1982 and 1984. The percentage of young lost by Bufflehead ranged from 12% i n 1981 to 36% i n 1983 (Table 38). In a l l years, except 1984, Barrow's Goldeneye lost proportionally more young than Bufflehead. Analysis of marked broods allowed the estimate of losses from laying until three weeks after hatching. Only broods that were observed during the whole period were considered. Over three years, 53% of the eggs l a i d (n=1384) produced 3-week-old young, 26% of the losses occurred before hatching, 52% in the f i r s t week of l i f e , 14% in the second week and 8% in the third week (Table 39). Patterns of losses varied between years, but in most years the greater proportion of losses occurred i n the f i r s t week following hatching. In 1984 losses were higher prior to hatching. 149 3 4 A G E IN 0 A Y 8 Fig. 34 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1982 (standard errors given). 150 144 1 3 6 -1 2 8 -1 2 0 -112 -24 -T 1 1 1 1 r 2 3 4 5 6 7 A G E I N D A Y S Fig. 35 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1983 (standard error given). • u 151 128 120 112 104 -8 6 -8 8 8 0 -72 -< 64 oc >• * 56 4 8 -j 4 0 -< O 3 2 -24 16 8 -1 3 A 9 E I N D A Y S Fig. 36 Daily mortality rates (not weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week following hatching i n 1984 (standard error given). 152 Table 37. Mortality of Barrow's Goldeneye ducklings. 1980 1981 1982 1983 1984 Number of broods 84 84 87 95 110 Maximum count of young early 584 612 621 779 922 Maximum count of young late (=5 weeks later) 380 481 489 420 731 Young lost 204 131 132 359 191 % lost 35 21 21 46 21 No. young/brood1 6.95 7.29 7.14 8.20 8.38 No. young lost/brood 2.43 1.56 1.52 3.78 1.74 Number of young present when brood f i r s t observed. 153 Table 38. Mortality of Bufflehead ducklings. 1980 1981 1982 1983 1984 Number of broods 68 75 78 73 74 Maximum count of young early 433 514 541 475 520 Maximum count of young late (=5 weeks later) 296 450 477 304 387 Young lost 137 64 64 171 133 % lost 32 12 12 36 26 No. young/brood-'- 6.37 6.85 6.94 6.51 7.03 No. young lost/brood 2.01 0.85 0.82 2.34 1.80 Number of young present when brood f i r s t observed. 154 Table 39. Distribution of losses between laying and 3-week old young from nests that hatched. Total % of losses losses from •  No. of No. of incubation Before Between Between Between Total % Year broods eggs l a i d to 21 days hatching days 0-7 days 7-14 days 14-21 of loss 1982 22 234 83 17 64 6 13 35% 1983 41 519 326 17 53 21 10 63% 1984 57 631 241 40 46 9 5 38% Total 120 1384 650 26 52 1 4 8 47% DISCUSSION I compared the influence of three d i f f e r e n t assumptions on the Mayfield estimate of d a i l y mortality rate (Figs. 27-28). F i r s t I used Mayfield's own assumption i.e. that mortality occurs mid-way in the period between observations (Mayfield 1961). Second I assumed that the mortality rate was constant between observations (Johnson 1979, Klett and Johnson 1982), and third I assumed that losses were equally distributed between observations. A l l three assumptions gave similar estimates (Fig. 27-28). Johnson (197 9) pointed out that Mayfield's assumption leads to bias i f nests, or i n t h i s case broods, are v i s i t e d infrequently. In t h i s study the bias should be negligible because intervals between v i s i t s were short and the number of broods or young sampled was high. Hatching chronology varied between years due to the timing of spring thaw. In 1980 , 81 and 82 some of the breeding ponds were s t i l l frozen in l a t e A p r i l , whereas i n 1983 and 1984, a l l ponds were free of ice by the t h i r d week of A p r i l . The greater proportion of broods hatching l a t e i n 1984 as opposed to 1983 could be attributed to a period of cold weather i n early May that followed a warm period and may have delayed laying for some females. Hammond and Johnson (1984) showed that spring weather determined the onset of laying in several species of waterfowl. Brood mortality was significantly higher in the f i r s t week following hatching for both Barrow's Goldeneye and Bufflehead which i s a t y p i c a l pattern i n waterfowl (McGilvrey 1969, B a l l e_t a l . 1975, Pienkowski and Evans 1982a, Ringelman and Longcore 1982, Patterson 1982, H i l l and E l l i s 1984, Mendenhall and Milne 1985). This was expected, as the young are especially vulnerable at hatching to predators, weather and intraspecific aggression because of their size and inexperience. Bengtson (1972) found that cold spells with precipitation caused a high mortality among newly-156 hatched ducklings. Koskimies and Lahti (1964), Hilden (1964), Makepeace and Patterson (1980) found that mortality of young ducklings increased i n bad weather. Kear (1965) showed that duckling yolk reserves last only for a few days. Thus, they would be e s p e c i a l l y affected by adverse weather conditions at hatching as this would impair their feeding efficiency and deplete t h e i r small reserves. Sjoberg and Danell (1982) found that aquatic insect av a i l a b i l i t y was reduced i n adverse weather, and H i l l and E l l i s (1984) showed that young ducklings at hatching are i n e f f i c i e n t divers and depend to some extent on small prey near the surface. Early hatching broods had a better survival than late hatching broods in years of high mortality (Figs. 31-32). Bengtson (1972) also found a decrease in survival for late hatchers i n Barrow's Goldeneye of Iceland. Among the fa c t o r s that may produce t h i s e f f e c t are 1) reduced food densities later i n the season (Pehrsson 1973); 2) Greater v u l n e r a b i l i t y of late-hatching broods to t e r r i t o r i a l aggressiveness because ea r l y -hatching females would already have established territories and developed a sense of ownership which would enhance their t e r r i t o r i a l aggressiveness (Petrie 1984); 3) females with late-hatching broods are more l i k e l y to be inexperienced breeders, and thus less efficient in protecting their young against predators or conspecifics. Several authors have shown that f i r s t -time breeders tend to breed l a t e r than experienced breeders (Grice and Rogers 1965, Krapu and Doty 1979, Lemieux 1959); 4) Early hatching broods have several advantages that may enhance t h e i r s u r v i v a l : a) reduced competition for food, b) f i r s t choice of t e r r i t o r y , c) they become attached to t h e i r t e r r i t o r y and benefit from the residence e f f e c t i n i n t r a - s p e c i f i c encounters (Petrie 1984, F i g l e r and Einhorn 1983), d) females have time to regain some of the weight lost during incubation 157 which would give them an advantage over newly hatched broods. Bufflehead young had lower mortality rates than Barrow's Goldeneye young i n a l l years but 1984, the l a s t year of the study. In 1984, the number of broods of Barrow's Goldeneye was the largest i n the four years of the study (Fig. 24). The increase i n mortality rate of Bufflehead ducklings r e l a t i v e to Barrow's Goldeneye ducklings may be due to interference or exploitation competition by Barrow's Goldeneye. I showed in Chapter III that Barrow's Goldeneye females with broods were aggressive toward Bufflehead females. I have witnessed female goldeneyes k i l l young Bufflehead. In 1984.three marked broods of Bufflehead were displaced from lakes by goldeneye broods and lost ducklings. Although female Bufflehead are often successful in decoying female goldeneye away from their young, their chance of finding a territory on a pond without Barrow's Goldeneye i s reduced as the density of Barrow's Goldeneye broods increases. Also, avoidance movements of goldeneye broods by Bufflehead increase the chance of intraspecific confrontations which can result in losses of ducklings. Williams (1974), Makepeace and Patterson (1980), and Pienkowski and Evans (1982a) have shown that the d a i l y mortality rate of shelduck ducklings increased significantly with density of broods. Shelducks, l i k e goldeneye and Bufflehead, are highly t e r r i t o r i a l (Patterson 1982). Why was mortality of Barrow's Goldeneye ducklings higher than that of Bufflehead ducklings i n 1980, 81, 82 and 83? Both species have s i m i l a r habitat preferences and s i m i l a r behaviour. Fluctuations i n m o r t a l i t y rates of both species were s i m i l a r from 1980 to 1983: mortality rates were highest i n 1983 and higher i n 1980 than i n 1981 and 1982. This indicates that both species responded s i m i l a r l y to factors that caused t h i s y e a r l y f l u c t u a t i o n i n s u r v i v a l rates. Weather may have caused the high mortality in 1983}as heavy rain and cold temperatures occurred during 158 peak hatching time. Among factors that may have contributed to the higher mortality of Barrow's Goldeneye ducklings are: 1) Greater s u s c e p t i b i l i t y of Barrow's Goldeneye ducklings to natural mortality factors than Bufflehead ducklings: Goldeneye ducklings are twice the size of Bufflehead ducklings, and thus have greater daily energy requirements (Kendeigh 1969, 1970, King 1973). Larger birds require a greater t o t a l intake of food than smaller birds and therefore may suffer more i n periods of food shortages. In some situ a t i o n s , however, t h i s e f f e c t w i l l be s l i g h t l y dampened by the ph y s i o l o g i c a l advantage of larger animals for t o l e r a t i n g cold (Kendeigh 196 9) and the higher metabolic rate of smaller animals (Kendeigh 197 0). 2) I n t r a s p e c i f i c aggression by females may have a greater impact on goldeneye mortality than on Bufflehead mortality: Barrow's Goldeneye females are larger and more aggressive than Bufflehead females. 3) Aggressive neglect (Ripley 1961) may increase duckling mortality i n Barrow's Goldeneye: Barrow's Goldeneye females spend large amounts of time i n aggressive interactions with conspecifics and other species. During that time t h e i r young are more susceptible to predation or attacks by other goldeneyes. 4) Barrow's Goldeneye usually nest farther from brood rearing ponds than Bufflehead. The overland journey may directly result in mortality, or may weaken the ducklings and increase their mortality once they reach the ponds. Further studies are needed to determine precisely the causes of this difference in mortality rate between these two species. The apparent negative impact of increasing goldeneye density on the survival of 159 Bufflehead ducklings (Fig. 27-28) deserves further attention. Any management directed toward increasing densities of Barrow's Goldeneye should be monitored c a r e f u l l y for impact on sympatric species of waterfowl. SUMMARY 1) M o r t a l i t y rates of Barrow's Goldeneye and Bufflehead ducklings differed from year to year and were higher among younger ducklings. 2) Patterns of duckling losses in relation to age varied between years. 3) In years when mortality was high, early broods tended to survive better than late broods. 4) Barrow's Goldeneye ducklings had a higher mortality rate than Bufflehead ducklings i n the f i r s t three years of the study but mortality rates of Bufflehead were higher in the 4th year. 160 Chapter VI: General Discussion 161 In t h i s t h e s i s , I set out to d e s c r i b e and c h a r a c t e r i z e the t e r r i t o r i a l behaviour of Barrow's Goldeneye and to evaluate i t s significance and function. I discuss and integrate some of the findings below. 1) T e r r i t o r i a l i t y I have shown that t e r r i t o r i a l behaviour i s w e l l developed i n Barrow's Goldeneye and i t s congeners. I found no major differences between the i n t r a s p e c i f i c t e r r i t o r i a l behaviour of Barrow's Goldeneye, Common Goldeneye and Bufflehead drakes during the breeding season. T e r r i t o r i a l behaviour of females with broods was s i m i l a r for Barrow's Goldeneye and Bufflehead, but was not studied i n the Common Goldeneye. However, descriptive accounts in literature indicate that t e r r i t o r i a l i t y in Common Goldeneye i s probably similar to the other species (Carter 1958, Siren 1952, Gibbs 1961). I have shown that some Barrow's Goldeneye are t e r r i t o r i a l i n winter, but I could not establish i f Common Goldeneye and Bufflehead were t e r r i t o r i a l at that time and further studies are needed. Barrow's Goldeneye feed mostly on mussels i n winter (Vermeer 1982, Koehl et a l . 1984), an easily defendable resource, whereas Common Goldeneye and Bufflehead feed mainly on free-swimming invertebrates (Wiemeyer 1967, Erskine 197 2, Palmer 1976, Vermeer 1982). According to Brown's (1964) model of t e r r i t o r i a l i t y , we would expect Barrow's Goldeneye to be t e r r i t o r i a l in winter but not Common Goldeneye and Bufflehead. However, observations by Nilsson (196 9) indicate that Common Goldeneye are aggressive i n winter and protect their mates. The behaviour described i s s i m i l a r to that observed i n t e r r i t o r i a l encounters. Nilsson further mentioned that sometimes small areas were defended by males. 162 T e r r i t o r i a l behaviour may have evolved as an extension of mate defense to include defense of an area for the exclusive use of the female. Defense of such areas should enhance protection of the female because once boundaries are e s t a b l i s h e d , a given p a i r would p r o f i t from the aggressiveness of neighbouring p a i r s i n terms of excluding unpaired intruders from the area. They could also develop a knowledge of the resources of the area which may increase their a b i l i t y to defend the area relative to an intruder (Petrie 1984, Figler and Einhorn 1983). Also, as I have indicated in Chapter III, exclusion of conspecifics and congeners from an area can enhance the foraging opportunities of the t e r r i t o r y holder. We should not expect to f i n d s i g n i f i c a n t c o r r e l a t i o n s between t e r r i t o r y size and food resources (Gauthier 1985), because t e r r i t o r y boundaries are set d i r e c t l y by pair density and not food density. Therefore, a non-significant correlation between territory size and food abundance (Gauthier 1985) does not necessarily indicate that food i s not an important aspect of t e r r i t o r i a l i t y . I contend that the main benefit of t e r r i t o r i a l i t y i n the genus Bucephala i s to provide an exclusive feeding area for the female i n the spring and winter and for the young i n summer. The importance of t h i s function has been stressed i n other studies of t e r r i t o r i a l waterfowl (McKinney 1973, Seymour 1974a, Titman and Seymour 1981, Donaghey 197 5, Patterson 1982, Gauthier 1985). Interspecific aggression in Barrow's Goldeneye i s correlated with the degree of food competition, Barrow's Goldeneye being most aggressive toward congeners and more aggressive toward diving ducks than dabbling ducks. Interspecific aggression has been reported in two other species of t e r r i t o r i a l waterfowl: the African Black Duck (McKinney e i a l . 1978) and 163 steamer-ducks (Nuechterlein and Storer 1985a, Livezey and Humphrey 1985a). The significance of t h i s aggression i n steamer-ducks i s s t i l l unclear (Murray 1985). Murray (1981), i n a comprehensive review of i n t e r s p e c i f i c t e r r i t o r i a l i t y i n a v a r i e t y of animals, r e j e c t e d the view t h a t interspecific t e r r i t o r i a l i t y i s an adaptation that allows competitors for food to occupy a common habitat (Simmons 1951, Orians and Willson 1964, Cody 1974, Davies 1978) and argued that i t leads to segregation and not coexistence. The restricted area of sympatry of Barrow's Goldeneye and Common Goldeneye and the apparent avoidance of productive ponds by Common Goldeneye may be an example of such segregation. More detailed studies of Barrow's Goldeneye and Common Goldeneye in areas of sympatry should help to determine i f Murray's a s s e r t i o n i s r i g h t . However, Murray's i n t e r p r e t a t i o n i s l i k e l y to be rig h t i n cases where one of the species dominates the other, eg. Barrow's Goldeneye versus Bufflehead. Most examples of i n t e r s p e c i f i c t e r r i t o r i a l i t y involve a dominant and a subordinate species (Orians and Willson 1964, Murray 1981). Murray (1981) states that interspecific territorialism can be adaptive to the dominant species i f i t r e s t r i c t s the a c t i v i t i e s of p o t e n t i a l l y competitive intruders. I have shown that Barrow's Goldeneye aggression excludes other species from the territory and therefore may improve feeding conditions. Dhondt (1977) and Minot (1981) showed that Great T i t s (Parus major) and Blue T i t s (Parus caeruleus) compete for foods during the breeding season and that the smaller Blue T i t i s the superior competitor, i.e. reaches a higher density than Great T i t s . Neither species i s i n t e r s p e c i f i c a l l y t e r r i t o r i a l but Great Tits are intr a s p e c i f i c i a l l y t e r r i t o r i a l . Possibly, 164 Bufflehead would have a s i m i l a r advantage over Barrow's Goldeneye i n exploitation competition. Interspecific aggression by Barrow's Goldeneye possibly reduces exploitation competition and thus i s advantageous to the goldeneye. I suggest that the high level of intraspecific aggression in Barrow's Goldeneye has f a c i l i t a t e d the evolution of interspecific territorialism, and that the feeding advantages gained maintain;. i t . Whether i n t e r s p e c i f i c aggression originated f i r s t as misdirected i n t r a s p e c i f i c aggression and was l a t e r maintained because i t conferred some adaptive advantages (reduction of food competition) or whether i t originated as a response to competition i s unknown. Losey (1981, 1982) showed experimentally that damselfish, with experience and e c o l o g i c a l cues, can perceive a new species as a competitor. A s i m i l a r learning process i s possible i n Barrow's Goldeneye. Detailed studies on the factors e l i c i t i n g interspecific aggression may help resolve the question, i.e. whether i t originated because of competition or accidentally. Experiments with the Icelandic population which i s allopatric with the Bufflehead may permit us to answer i t . 2) Competition between Barrow's Goldeneye and Bufflehead Birch (1957) indicated that competition occurs when two species u t i l i z e common resources i n short supply; or i f the resources are not in short supply, competition occurs when the animal seeking that resource harms another i n the process. Pianka (197 8) stated as a condition necessary for the coexistence of two populations that each population must i n h i b i t i t s own growth more than that of the other species. Several f a c t o r s i n t h i s study show that competition i s strong between Barrow's Goldeneye and Bufflehead and that the Barrow's Goldeneye i s the dominant 165 species: 1) Breeding density of Barrow's Goldeneye i s almost twice as high as that of Bufflehead when the reverse should be expected considering body s i z e and a v a i l a b i l i t y of n e s t i n g c a v i t i e s (Gauthier 1985). 2) Barrow's Goldeneye dominate Bufflehead i n t e r r i t o r i a l encounters and exclude them from t h e i r t e r r i t o r i e s . 3) Bufflehead exclude non-t e r r i t o r i a l goldeneyes from their territory. 4) Bufflehead avoid nesting c a v i t i e s with large entrances possibly because of Barrow's Goldeneye. 5) Mortality rate of Bufflehead young increased following an increase i n Barrow's Goldeneye density. These species compete for nesting c a v i t i e s , food resources, and territories. How do Bufflehead manage to coexist with Barrow's Goldeneye? This study has identified adaptations that may permit Bufflehead to coexist, and attain high densities in the presence of Barrow's Goldeneye. 1. Difference i n size. Several authors have argued that differences in beak and body sizes between species f a c i l i t a t e coexistence by permitting e x p l o i t a t i o n of d i f f e r e n t food resources (Orians and Willson 1964, Cody 1974). This i s unlikely for these two species on the breeding grounds as their diets are similar (Munro 1939, 1942, Erskine 1972, Palmer 1976). It may, however, be more important i n winter when both species occupy different habitats and have d i f f e r e n t d i e t s (Vermeer 1982). This greater segregation i n winter suggests that resources may be less abundant then. Schoener (1982) has argued that reduced overlap during lean times i s a general, but not inva r i a b l e , feature of competitive interactions. Smith e_£ a l . (1978) showed that i n times of reduced food abundance, diet similarity in groups of species with similar feeding methods decreases. The smaller size of the Bufflehead allows i t to use smaller nest c a v i t i e s than Barrow's 166 Goldeneye with these possible advantages: 1) Bufflehead are less l i k e l y than Barrow's Goldeneye to be l i m i t e d by nest s i t e a v a i l a b i l i t y . Nest parasitism i s l e s s frequent i n Bufflehead (Erskine 197 2, Donaghey 197 5, Gauthier 1985) than i n Barrow's Goldeneye (this study). In wood ducks nest parasitism has been shown to be greater when nest site a v a i l a b i l i t y i s reduced and/or nest conspicuousness increased. Parasitism has also been shown to i n c r e a s e nest d e s e r t i o n rate, adversely a f f e c t i n g reproductive success (Jones and Leopold 1967, Morse and Wight 1969, Zipko 1979, Eriksson and Andersson 1982). 2) Bufflehead are more l i k e l y to find nesting cavities closer to their breeding ponds than Barrow's Goldeneye. This should greatly reduce overland travel for Bufflehead, reducing risks of predation or loss. 3) Smaller cavity entrances exclude more predators than larger entrances would, again reducing r i s k s of predation. A l l of this should translate into higher survival for Bufflehead, and may explain in part the lower brood mortality of Bufflehead versus Barrow's Goldeneye in this study. Other possible advantages of a smaller size are: 1) Lower food requirements for growth which may allow Bufflehead to occupy small shallow lakes avoided by goldeneyes, and to survive better i n times of food shortage. 2) Superior a g i l i t y compared to the goldeneye. This explains the a b i l i t y of Bufflehead to decoy aggressive Barrow's Goldeneye from their mate or brood, staying just out of reach. Barrow's Goldeneye cannot decoy other goldeneye effectively and must fight or retreat. Armstrong (1952) describes s i m i l a r r e l a t i o n s h i p s between the Ringed Plover (Charadius hiaticula) and the L i t t l e Ringed Plover (C. dubius), the latter decoying aggressive Ringed Plover away from his mate in similar fashion to the B u f f l e h e a d . 3) B e t t e r manoeuverability i n submerged aquatic vegetation which would enable them to e x p l o i t densely vegetated ponds 167 better than Barrow's Goldeneye. Bufflehead breed successfully i n sympatry with both Barrow's Goldeneye and Common Goldeneye (Palmer 1976) whereas the zone of sympatry between Barrow's Goldeneye and Common Goldeneye i s very small. My data suggest that Barrow's Goldeneye may dominate Common Goldeneye but further studies are needed to confirm that. 2. High level of intraspecific aggression i n Barrow's Goldeneye. Ripley (1961) described a phenomenon he called aggressive neglect in which a dominant, aggressive species, exposes i t s nest or young to increased mortality because of the time i t spends i n aggressive interactions. Several qualitative observations suggest that this may occur i n Barrow's Goldeneye. Male and female Bufflehead sometimes decoy attacking goldeneye f o r 5 or even 10 minutes during which time the goldeneye does not protect i t s mate or brood. 3) Does t e r r i t o r i a l behaviour l i m i t breeding d e n s i t i e s i n the genus Bucephala? This i s a d i f f i c u l t question to answer because of the diverse scales at which the question could be addressed (pond l e v e l , region l e v e l , population level). Watson and Moss (1970) l i s t three conditions necessary to show that social interactions l i m i t breeding populations: a) that a substantial part of the population does not breed; b) that such non-breeders are physiologically capable of breeding; c) that the breeding animals are not completely using up some resource, such as food, space, or nest s i t e s . There i s now evidence that some species can be and are l i m i t e d by t e r r i t o r i a l behaviour (Hilden 197 9, Patterson 1980, Klomp 1980). There i s no doubt that in the genus Bucephala t e r r i t o r i a l behaviour 168 of both drakes and females with broods can and does l i m i t d e n s i t i e s of pairs and broods on individual ponds. Whether this affects more than the distribution of pairs and broods remains to be shown. This w i l l depend i n part on the a v a i l a b i l i t y of suitable habitat nearby. I believe that t e r r i t o r i a l behaviour can l i m i t the population of breeding Bucephala species. However, I view t e r r i t o r i a l behaviour as an adaptation to exploit resources optimally at medium population levels. At low density l e v e l s i t has l i t t l e advantages and at very high density l e v e l s i t i s l i k e l y to break down because of high intruder pressure. However the high densities required for this breakdown to occur are probably never reached in natural conditions. T e r r i t o r i a l i t y i s more l i k e l y to l i m i t Bufflehead densities than Barrow's Goldeneye densities simply because Bufflehead must face both intra and interspecific competition for space. Also, breeding densities of Barrow's Goldeneye are often controlled by nest s i t e a v a i l a b i l i t y . Once t h i s l i m i t i n g factor i s removed, i t i s l i k e l y that t e r r i t o r i a l i t y during the breeding season may affect breeding densities. Bengtson (197 2) reported increased mortality of ducklings when Barrow's Goldeneye densities were high. Other studies indicate that t e r r i t o r i a l i t y may regulate t e r r i t o r i a l waterfowl species (Riggert 1977, McKinney e± al* 1978, Evans and Pienkowski 1982, Patterson 1982). 4) Management implications and research needs Most of the findings of this study have management applications as l i t t l e was known of the breeding and wintering ecology of Barrow's Goldeneye when this study was initiated. However, l i k e most studies, this study revealed further needs for research. 1) I have shown that Barrow's Goldeneye readily use nest boxes and that breeding d e n s i t i e s can be increased by t h e i r use. Two factors 169 accounted for most of the nesting failures: predation and desertion. Research i s needed on ways of deterring predation by black bears, on the causes of nest desertion, and on intraspecific nest parasitism. 2) The strong t e r r i t o r i a l behaviour of Barrow's Goldeneye should be considered i n any management oriented toward increasing t h e i r density. I have shown that pair density and especially brood density can be l i m i t e d on i n d i v i d u a l ponds by t e r r i t o r i a l behaviour. Also the study suggested that increase i n goldeneye density may have a negative impact on Bufflehead. More research i s needed to confirm and quantify this impact. 3) I suggested that one of the main functions of t e r r i t o r i a l i t y was the provision of an exclusive and undisturbed feeding area. I presented circumstantial evidence for this, but experimental studies are needed to confirm i t . Studies focused on the foraging behaviour and on the impact of food density on reproduction i n terms of laying rates, egg size , nesting chronology, young growth, young s u r v i v a l , would be enlightening. 4) Relationships between Barrow's Goldeneye and Common Goldeneye i n areas of sympatry need to be qu a n t i f i e d further. Are Barrow's Goldeneye really superior competitors? Are Common Goldeneye slowly invading the breeding range of Barrow's Goldeneye? 5) Survival of ducklings varied considerably between years. The cause of this variation needs to be quantified. My observations indicate that weather may be important. Also, at high densities, t e r r i t o r i a l behaviour may be important. The impact of high densities of Barrow's Goldeneye on the sur v i v a l of Bufflehead ducklings needs further quantification. The causes behind the higher survival of Bufflehead 170 ducklings compared to Barrow's Goldeneye ducklings s t i l l have to be identified. 6) Waterfowl have usually been ignored i n academic research as uninteresting from a theoretical point of view. Most studies have been management-oriented with l i t t l e concern for t h e o r e t i c a l concepts. I have shown here, not only that studies of waterfowl ecology can address central theoretical questions, i.e. competition, population regulation, t e r r i t o r i a l i t y , etc., but also, that the answer to these t h e o r e t i c a l questions have important management applications. My message i s that we should s t r i v e , whenever possible, to consider both theoretical and practical implications of a study. Both theory and management would benefit greatly from such an approach. 171 LITERATURE CITED Afton, A.D. and R.D. Sayler. 1982. So c i a l courtship and pair bonding of Common Goldeneye (Bucephala clangula) wintering in Minnesota. Can. Field-Nat. 96:295-300. Afton, A.D. 1984. Influence of age and time on reproductive performance of female Lesser Scaup. Auk 101:255-265. Alatalo, R.V., A. Carlson, A. Lundberg and S. Ulfstrand. 1981. The conflict between male polygyny and female monogamy: the case of the pied flycatcher (Ficedula hypoleuca). Amer. Nat. 117: 738-753. Alexander, H.G. 1921. T e r r i t o r y i n b i r d l i f e . B r i t . Birds 14:271-275. Alison, R.M. 1975. Breeding biology and behaviour of the Oldsquaw (Clangula hyemalis L.). Ornithol. Monogr. No. 18. Anderson, M.G., R.D. Sayler and A.D. Afton. 1980. A decoy trap for diving ducks. J. Wildl. Manage. 44:217-219. Andersson, G. 1981. Influence of f i s h on waterfowl and lakes. Anser 20:21-34 (In Swedish with English summary). Andrew, D.G. 1960. Aggressive behaviour of Barrow's Goldeneye with young. British Birds 53:572-573. Ankney, CD. 1980. Egg weight, survival, and growth of lesser snow goose goslings. J. Wildl. Manage 44:174-182. Anonymous. 197 9. Concept p l a n f o r waterfowl wintering habitat preservation. U.S. Fish and W i l d l i f e Service, Portland, Oregon. 146pp. Armitage, K.B. 1974. Male behaviour and t e r r i t o r i a l i t y i n the yellow-bellied marmot. J. Zool., London 172:233-265. Armstrong, E.A. 1952. The distraction displays of the L i t t l e Ringed Plover and t e r r i t o r i a l competition with the Ringed Plover. Brit. Birds 45:55-59. Armstrong, E.A. 1965. The ethology of bird display and bird behaviour, an introduction to the study of bird psychology. Dover, New York. B a i l l i e , S.R. and H. Milne. 1982. The influence of female age on breeding in the Eider (Somateria mollissima). Bird Study 29:55-66. Baker, R.R. 1983. Insect t e r r i t o r i a l i t y . Ann. Rev. Entom. 28:65-89. Ball , I.J., D.S. Gilmer, L.M. Cowardin and J.H. Riechmann. 1975. Survival of Wood Duck and Mallard broods in north-central Minnesota. J. Wildl. Manage. 39:776-780. 172 B a l l , J.G., P.G.H. F r o s t , W.R. S i e g f r i e d and F. McKinney. 1978. T e r r i t o r i e s and l o c a l movements of Af r i c a n Black Ducks. Wildfowl 29:61-69. Bartonek, J.C. and J.J. Hickey. 196 9. Food h a b i t s of Canvasbacks, Redheads and Lesser Scaups in Manitoba. Condor 71:280-290. Bartonek, J.C. and H.W. Murdy. 1970. Summer foods of Lesser Scaup i n Subarctic Taiga. Arctic 23:35-44. Bedard, J. and J. Munro. 1977. Brood and creche s t a b i l i t y i n the Common Eider of the St. Lawrence estuary. Behaviour 60:221-236. B e i l , CE. 1974. Forest associations of the southern Cariboo Zone, British Columbia. Syesis 7:201-233. Bellrose, F.C., K.L. Johnson and T.U. Meyers. 1964. Relative value of natural cavities and nesting houses for Wood Ducks. J. Wildl. Manage. 28:661-676. Bellrose, F.C. 1978. Ducks, geese and swans of North America. Stackpole Books, Harrisburg, Pa., 544pp. Bengtson, S.A. 1970. Location of nest-sites of ducks in Lake Myvatn area, north-east Iceland. Oikos 21:218-229. Bengtson, S.A. 1971. Habitat selection of duck broods in Lake Myvatn area North-east Iceland. Ornis Scand. 2:17-26. Bengtson, S.A. 197 2. Reproduction and fl u c t u a t i o n s i n the size of duck populations at Lake Myvatn, Iceland. Oikos 23:35-58. Bent, A.C. 1925. L i f e h i s t o r i e s of North American Wild Fowl. Order: Anseres (Part II). U.S. Natl. Mus. B u l l . 130. Washington, D.C. 396pp. Bergman, G. 1956. Om Kullsam manslagning hos skrakar, Mergus serrator och Mergus merganser. Fauna och Flora (1956): 97-110. Birch, L.C. 1957. The meaning of competition. Amer. Nat. 91:5-18. Blohm, R.J. 1978. Migrational homing of male Gadwalls to breeding grounds. Auk 95:763-766. Bolen, E.G. 1967. Nesting boxes for B l a c k - b e l l i e d Tree Ducks. J. W i l d l . Manage. 31:7 94 -7 97. Bolen, E.G. 1971. Pair-bond tenure i n the Bl a c k - b e l l i e d Tree Duck. J. Wildl. Manage. 35:385-388. Bragin, A.B. 1981. Breeding ecology of the goldeneye (Bucephala clangula) in a r t i f i c i a l nests. Ornithologia 16:22-32 (In Russian). Brooks, A. 19^3. Notes on the birds of the Cariboo d i s t r i c t , B.C. Auk 20:277-284. 173 Brooks, A. 1920. Notes on some American ducks. Auk 37:353-367. Brown, J.H. and D.W. Davidson. 1977. Competition between seed-eating rodents and ants in desert ecosystems. Science 196:880-882. Brown, J.H., A. Kodric-Brown, T.C. Whitman and H.W. Bone. 1981. Competition between hummingbirds and insects for the nectar of two species of shrubs. Southwestern Nat. 26:133-145. Brown, J.L. 1964. The evolution of d i v e r s i t y i n avian t e r r e s t r i a l communities. Wilson Bull. 76:160-169. Brown, J.L. 1969. T e r r i t o r i a l behaviour and population regulation i n birds. Wilson Bull. 81:293-329. Brown, J.L. and G.H. Orians 197 0. Spacing patterns i n mobile animals. Ann. Rev. Ecol. Syst. 1:239-263. Bruggemann. 1976. Zool. Garten (Berlin) 17:366-368. Cited by Palmer 1976. Buechner, H.K. 1961. Te r r i t o r i a l behaviour in Uganda Kob. Science 133:698-699. Butterfield, P.A. 197 0. The pair bond i n the Zebra Finch. In Social behaviour in birds and mammals. J.H. Crook ed., Academic Press, New York. Calder, W.A. I l l , N.M. Waser, S.M. Hiebert, D.W. Inouye and S. M i l l e r . 1983. S i t e - f i d e l i t y , longevity, and population dynamics of Broad-t a i l e d Hummingbirds: a ten-year study. Oecologia (Berlin) 56:359-364. Cannings, R.A. 1973. An ecological study of some of the Chironomidae inhabiting a series of saline lakes in central British Columbia, with special reference to Chironomus tentans Fabricius. M.Sc. Thesis, Dept. Zool., Univ. British Columbia. Cannings, R.A. and G.E. Scudder. 197 8. The l i t t o r a l chironomidae (Diptera) of saline lakes i n central B r i t i s h Columbia. Can. J. Zool. 56:1144-11F5. Carpenter, C.R. 1958. T e r r i t o r i a l i t y : a review of concepts and problems. In Behaviour and evolution. A. Roe and G.G. Simpson eds., Yale Univ. Press, New Haven. Carpenter, F.L. 197 9. Competition between hummingbirds and insects for nectar. Amer. Zool. 19:1105-1114. Carter, B.C. 1958. The American Goldeneye i n central New Brunswick. Can. Wildl. Serv. W i l d l . Manage. B u l l . Ser. 2, No. 9. Carthy, J.D. and D.R. Arthur (eds). 196 8. The b i o l o g i c a l e f f e c t s of o i l pollution on l i t t o r a l communities. Fid. Stud. Suppl. 2. 174 Catchpole, C.K. 1977. A g g r e s s i v e responses of male sedge warblers (Acrocephalus schoenobaenus) to playback of species song and sympatric song, before and after pairing. Anim. Behav. 25:489-496. Charles, J.K. 1972. T e r r i t o r i a l behaviour and the l i m i t a t i o n s of population size i n crows, Corvus corone and C. cornix. Unpubl. Ph.D. thesis, Univ. of Aberdeen, Scotland. (Cited in Patterson 1980.) Clawson, R.L., G.W. Hartman and L.H. Fredrickson. 1979. Dump nesting in a Missouri Wood Duck population. J. Wildl. Manage 43:347-355. Cochran, W.G. 1977. Sampling techniques. John Wiley and Sons, New York, Toronto, 428pp. Cody, M.L. 196 8. I n t e r s p e c i f i c t e r r i t o r i a l i t y among hummingbird species. Condor 70:270-271. Cody, M.L. 196 9. Convergent c h a r a c t e r i s t i c s i n sympatric species: a possible relation to interspecific competition and aggression. Condor 71:222-239. Cody, M.L. 1974. Competition and the structure of b i r d communities. Monographs in Population Biology 7:1-318. Connell, J.H. 1983. On the prevalence and r e l a t i v e importance of interspecific competition: evidence from f i e l d experiments. Amer. Nat. 122:661-696. Connor, E.F. and D. S i m b e r l o f f . 197 9. The assembly of s p e c i e s communities: chance or competition? Ecology 60:1132-1140. Connor, E.F. and D. Simberloff. 1984. Neutral models of species' co-occurrence patterns. In Ecological communities, conceptual issues and the evidence. D.R. Strong, D. Simberloff, L.G. Abele and A.B. T h i s t l e eds., Princeton University Press, Princeton, pp. 316-332. Cottam, C. 1939. Food habits of North American diving ducks. U.S. Dep. Agric. Tech. B u l l . 643. 143 pp. Coulson, J.C. and C.S. Thomas. 1983. Mate choice i n the Kittiwake g u l l . In Mate choice. P. Bateson ed., Cambridge Univ. Press, London, New York. pp.361-376. Cramp, S. and K.E.L. Simmons (eds.). 1977. The birds of the Western Palearctic Vol. 1. , Oxford Univ. Press. Crombie, A.C. 1947. Inter-specific competition. J. Anim. Ecol. 16:44-73. Danell, K. and K. Sjoberg. 1977. Seasonal emergence of chironomids i n r e l a t i o n to egglaying and hatching of ducks i n a restored lake (northern Sweden). Wildfowl 28:129-135. 175 D a v i e s , N.B. 1978. E c o l o g i c a l q u e s t i o n s about t e r r i t o r i a l b e h a v i o u r . In B e h a v i o u r a l e c o l o g y , a n e v o l u t i o n a r y a p p r o a c h . J . R . K r e b s a n d N . B . D a v i e s e d s . , S i n a u e r A s s o c i a t e s I n c . , S u n d e r l a n d , M a s s a c h u s e t t s . D a v i s , L .S. 1982. C r e c h i n g b e h a v i o u r o f A d e l i e P e n g u i n c h i c k s ( P y g o s c e l i s  a d e l i a e ) . N. Z. J . Z o o l . 9:279-286. Den B o e r , P . J . 1980. E x c l u s i o n o r c o e x i s t e n c e a n d t h e t a x o n o m i c o r e c o l o g i c a l r e l a t i o n s h i p between s p e c i e s . N e t h . J . Z o o l . 30:278-306. D e n n i s , R.H. a n d H. Dow 1984. The e s t a b l i s h m e n t o f a p o p u l a t i o n o f g o l d e n e y e ( B u c e p h a l a c l a n g u l a ) b r e e d i n g i n S c o t l a n d . B i r d S t u d y 31:217-222. D h o n d t , A . A . 1977. I n t e r s p e c i f i c c o m p e t i t i o n b e t w e e n G r e a t a n d B l u e t i t . N a t u r e 268:521-523. D h o n d t , A . A . , J.s. S c h i l l e m a n s a n d J . D e L a e t . 1982. B l u e t i t t e r r i t o r i e s i n p o p u l a t i o n s a t d i f f e r e n t d e n s i t y l e v e l s . A r d e a 70:185-188. Diamond, J . M . 197 8. N i c h e s h i f t s a n d t h e r e d i s c o v e r y 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 . Amer. S c i . 66:322-331. D i n g l e , H. a n d R.L . C a l d w e l l . 196 8. The a g g r e s s i v 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 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 (Crustacea: s t o m a t o p o d a ) . B e h a v i o u r 33:115-136. D i n g l e , H . , R . C . H i g h s m i t h , K . E . E v a n s a n d R . L . C a l d w e l l . 1973. I n t e r s p e c i f i c a g g r e s s i v e b e h a v i o u r i n t r o p i c a l r e e f s t o m a t o p o d s , and i t s p o s s i b l e e c o l o g i c a l s i g n i f i c a n c e . O e c o l o g i a 13:55-64. Donaghey, R.H. 1975. S p a c i n g b e h a v i o u r o f b r e e d i n g B u f f l e h e a d (Bucephala  a l b e o l a ) o n p o n d s i n t h e s o u t h e r n b o r e a l f o r e s t . M . S c . T h e s i s U n i v . A l b e r t a , Edmonton, A l b e r t a , Canada. D o t y , H.A. a n d A . D . K r u s e . 1972. T e c h n i q u e s f o r e s t a b l i s h i n g l o c a l b r e e d i n g p o p u l a t i o n s o f Wood Ducks. J . W i l d l . Manage 36:428-435. Dow, D.D. 1977. I n d i s c r i m i n a t e i n t e r s p e c i f i c a g g r e s s i o n l e a d i n g t o a l m o s t s o l e occupancy o f space by a s i n g l e s p e c i e s o f b i r d . Emu 77:115-121. Dow, H. 1982. B r e e d i n g e c o l o g y o f t h e g o l d e n e y e ( B u c e p h a l a c l a n g u l a ) . P h . D . T h e s i s , U n i v . N e w c a s t l e , U.K. Dow, H. a n d F. F r e d g a . 1983. B r e e d i n g a n d n a t a l d i s p e r s a l o f t h e g o l d e n e y e , B u c e p h a l a c l a n g u l a . J . A n i m . E c o l . 52:681-695. Dow, H. and S. F r e d g a . 1984. F a c t o r s a f f e c t i n g r e p r o d u c t i v e o u t p u t o f t h e g o l d e n e y e duck (Bucephala c l a n g u l a ) . J . A n i m . E c o l . 53:679-692. Dow, H. a n d S . F r e d g a . 1985. S e l e c t i o n o f n e s t s i t e s b y a h o l e - n e s t i n g d u c k , t h e g o l d e n e y e (Bucephala c l a n g u l a ) . I b i s 127:16-30. D z i n b a l , K . A . 1982. E c o l o g y o f H a r l e q u i n D u c k s i n P r i n c e W i l l i a m S o u n d , A l a s k a , d u r i n g summer. M.Sc. T h e s i s , Oregon S t a t e U n i v e r s i t y . 176 Eadie, J.McA. and A. Keast. 1982. Do goldeneye and perch compete for food? Oecologia 55:225-230. Eadie, J.McA. and G. Gauthier. 1985. Prospecting for nest s i t e s by cavity-nesting ducks of the genus Bucephala. Condor 87:528-534. Ebersole, J.P. 1977. The adapt i v e s i g n i f i c a n c e of i n t e r - s p e c i f i c t e r r i t o r i a l i t y in the reef f i s h Eupomacentrus leucostictus. Ecology 58:914-920. Edwards, R.Y. 1953. Barrow's Goldeneye using crow nests i n B r i t i s h Columbia. Wilson Bull. 65:197-198. Eriksson, M.O.G. 197 6. Food and f e e d i n g h a b i t s of downy goldeneye Bucephala clangula (L.) ducklings. Ornis Scand. 7:159-169. Eriksson, M.O.G. 1978. Lake s e l e c t i o n by goldeneye ducklings i n r e l a t i o n to the abundance of food. Wildfowl 29:81-85. Eriksson, M.O.G. 1979a. Competition between freshwater fi s h and goldeneye (Bucephala clangula) for common prey. Oecologia (Berl.) 41:99-107. Eriksson, M.O.G. 1979b. Aspects of the breeding biology of the goldeneye Bucephala clangula. Hoi. Ecol. 2:186-194. Eriksson, M.O.G. 1982. Differences between o l d and newly established Goldeneye (Bucephala clangula) populations. Ornis Fenn. 59:13-19. Eriksson, M.O.G. and M. Andersson. 1982. Nest parasitism and hatching success i n a population of goldeneye (Bucephala clangula). Bird Study 29:49-54. Erskine, A.J. 1959. A j o i n t clutch of Barrow's Goldeneye and Bufflehead eggs. Can. F i e l d Nat. 73:131. Erskine, A.J. 196 0. Further notes on i n t e r s p e c i f i c competition among hole-nesting ducks. Can. Field Nat. 74:161-162. Erskine, A.J. 1961. Nest s i t e tenacity and homing i n the bufflehead. Auk 78:389-396. Erskine, A.J. 1972. Buffleheads. Can. W i l d l . Serv., Monog. Ser. No. 4. Evans, P.R. ana M.W. Pienkowski. 1982. Behaviour of shelducks Tadorna  tadorna i n a winter flock: Does regulation occur? J. Anim. Ecol. 51:241-262. Evans, R.M. 1984. Some causal and functional c o r r e l a t e s of creching i n young white pelicans. Can. J. Zool. 62:814-819. Ewald, P.W. 1985. Influences of asymmetries in resource quality and age on aggression and dominance i n Black-chinned Hummingbirds. Anim. Behav. 33:705-719. 177 Figler, M.H. and D.M. Einhorn. 1983. The t e r r i t o r i a l p r i o r residence e f f e c t i n convict c i c h l i d s (Cjchlasc-ma niarofasciatum Gunther): Temporal aspects of establishment and retention, and proximate mechanisms. Behaviour 85:157-183. Fitzpatrick, S.M. and W.G. Wellington. 1983. Insect t e r r i t o r i a l i t y . Can. J. Zool. 61:471-486. Fjeldsa, J. 1973aAntagonistic and heterosexual behaviour of the horned grebe, Podiceps auritus. Sterna 12:161-217. Fjeldsa, J. 1973b. Territory and the regulation of population density and recruitment i n the horned grebe Podiceps auritus arcticus Boje, 1822. Videnskabelige Meddelelson f r a Dansk Naturhistorix Forening 136:117-189. Floody, O.R. and A.P. Arnold. 197 5. Uganda Kob (Adenota kob thomasi): t e r r i t o r i a l i t y and the spatial distributions of sexual and agonistic behaviours at a t e r r i t o r i a l ground. Ze i t s c h r i f t fur Tierpsychologie 37:192-212. Ford, N.L. 1983. V a r i a t i o n i n mate f i d e l i t y i n monogamous birds. I n Current ornithology, Vol. 1. R.F. Johnston ed., Plenum Press, New York, pp 329-356. Foster, S.A. 1985. Group foraging by a coral reef f i s h : a mechanism for gaining access to defended resources. Anim. Behav. 33:782-792. Franzblau, M.A. and J.P. C o l l i n s . 1980. Test of a hy p o t h e s i s of t e r r i t o r y regulation i n an insectivorous b i r d by experimentally increasing prey abundance. Oecologia 46:164-170. Fredga, S. and H. Dow. 1983. Annual v a r i a t i o n i n the reproductive performance of goldeneyes. Wildfowl 34:120-126. Fredga, S. and H. Dow. 1984. Factors a f f e c t i n g the size of a l o c a l population of goldeneye (Bucephala clangula L.) breeding i n Sweden. Viltrevy 13:225-255. Frith, H.J. and S.J.J.F. Davies. 1961. Ecology of the Magpie Goose (Anseranas semipalmata) latham (Anatidae). C.S.I.R.O. W i l d l i f e Research 6:91-141. Gabrielson, I.N. and F.C. Lincoln. 1959. Birds of Alaska. The Stackpole Co., Harrisburg, Pa. and W i l d l . Manage. Inst., Washington, D.C., 922p. Gardarsson, A. 197 8. D i s t r i b u t i o n and numbers of the Barrow's Goldeneye (Bucephala islandica) i n Iceland. Natturu Fraedin Gurinn 48:162-191. Gardarsson, A. 197 9a. Waterfowl populations of Lake Myvatn and recent changes in numbers and food habits. Oikos 32:250-270. Gardarsson, A. 1979b. Population trends i n diving ducks at Myvatn, Iceland, i n relation to food. Verh. Orn. Ges. Bayern 23:191-200. 178 Gass, C.L., G. Angehr and J. Centa 1976. Regulation of food supply by feeding t e r r i t o r i a l i t y i n the rufous hummingbird. Can. J. Zool. 54:2046-2054. Gass, CL. and G.D. Sutherland. 1985. S p e c i a l i z a t i o n by t e r r i t o r i a l hummingbirds on experimentally enriched patches of flowers: energetic p r o f i t a b i l i t y and learning. Can. J. Zool. 63:2125-2133. Gauthier, G. 1985. A functional analysis of t e r r i t o r i a l behaviour i n breeding Bufflehead. Ph.D. Thesis, Dept. Zool., Univ. of B r i t i s h Columbia, Vancouver, Canada, 165pp. Gibson, F. 1971. The breeding b i o l o g y of the American Avocet (Recurvirostra americana) in central Oregon. Condor 73:444-454. Gibbs, R.M. 1961. Breeding ecology of the Common Goldeneye, (Bucephala  clangula americana) i n Maine. M.Sc. Thesis, Univ. of Maine, Orono. G i l l , F.B. and Wolf, L.L. 197 5. Economics of feeding t e r r i t o r i a l i t y i n the golden-winged sunbird. Ecology 56:333-345. Gilpin, M.E. and J.M. Diamond. 1984. Are species co-occurrences on islands non-random, and are n u l l hupothesis useful i n community ecology. In Ecological communities: conceptual issues and the evidence. D.R. Strong, D. Simberloff, L.G. Abele and A.B. T h i s t l e ed., Princeton University Press, Princeton, pp. 297-315. Gochfeld, M. 1979. I n t e r s p e c i f i c t e r r i t o r i a l i t y i n Red-breasted Meadow larks and a method for estimating the mutuality of t h e i r participation. Behav. Ecol. Sociobiol. 5:159-170. Gollop, J.B. and W.H. Marshall. 1954. A guide for aging duck broods i n the f i e l d . Miss. Flyway Counc. Tech. Sect. 14pp. Gorman, W.L. and H. Milne. 197 2. Creche behaviour i n the Common Eider Somateria m_. mollissima L. Ornis Scand. 3:21-25. Grant, P.R. 1966. The coexistence of two wren species of the genus Thryothorus. Wilson Bull. 78:266-278. Graves, J.A. and A. Whiten. 1980. Adoption of strange chicks by Herring Gulls Larus argentatus L. Z. Tierpsychol. 54:267-278. Grenquist, P. 1963. Hatching losses of Common Goldeneye i n the Finnish Archipelago. Proc. XIII Int. Ornithol. Congr.:685-689. Grice, D. and J.P. Rogers. 196 5. The Wood Duck i n Massachusetts Mass. Div. Fisheries and Game. Proj. W-19-R. 96pp. Griffee, W.E. 1958. Notes on Oregon nesting of American Merganser and Barrow's Goldeneye. Murrelet 39:26. Griscom L., 1945. Barrow's Goldeneye i n Massachusetts. Auk 62:401-405. 179 Hammond, M.C. and D.H. Johnson. 1984. Effect of weather on breeding ducks i n North Dakota. U.S. Dept. Inter., Fish and W i l d l i f e Serv., Fish and W i l d l i f e Tech. Rept. No. 1. Harmon, S.J. 1983. Spacing and breeding density of Willow Ptarmigan i n response to an experimental a l t e r a t i o n of sex r a t i o . J. Anim. Ecol. 52:807-820. Harris, S.W., CL. Buechele and CF. Yocom. 1954. The status of Barrow's Goldeneye in Eastern Washington. Murrelet 35:33-38. Hasbrouck, M.E. 1944. The status of Barrow's Goldeneye i n the Eastern United States. Auk 61:544-554. Hepp, G.R. and J.D. Hair. 1984. Dominance i n w i n t e r i n g w a t e r f o w l (Anatini): effects on distribution of sexes. Condor 86:251-257. Hess, E.H. 1973. Imprinting, early experience and the developmental psychobiology of attachment. Behav. Science Series, Van Nostrand Reinhold Company, New York, Toronto. Heusmann, H.W. 1975. Several aspects of the nesting biology of y e a r l i n g Wood Ducks. J. Wildl. Manage. 39:503-507. Hilden, 0. 1964. Ecology of duck populations i n the i s l a n d group of Valassaaret, Gulf of Bothnia. Ann. Zool. Fenn. 1:153-279. Hilden, 0. 1979. T e r r i t o r i a l i t y and s i t e tenacity of Temminck's S t i n t (Calidris temminckii). Ornis Fenn. 56:56-74. H i l l , D.A. and N. E l l i s . 1984. Survival and age r e l a t e d changes i n the foraging behaviour and time budget of Tufted ducklings Aythya fuliqula. Ibis 126:544-550. Hinde, RJ*u 1956. The biological significance of the terr i t o r i e s of birds. Ibis 98:340-369. Hines, J.E. 1977. Nesting and brood ecology of Lesser Scaup at Waterhen Marsh, Saskatchewan. Can. Field Nat. 91:248-255. Hixon, M.A. 197 9. Competitive i n t e r a c t i o n s and spatiotemporal patterns among C a l i f o r n i a r e e f f i s h e s of the genus Embiotica. Ph.D. Dissertation, Univ. of Calif., Santa Barbara. Hixon, M.A., F.L. Carpenter and D.C Paton. 1983. T e r r i t o r y area, flower density, and time budgeting i n hummingbirds: an experimental and theoretical analysis. Amer. Nat. 122:366-391. Hochbaum, H.A. 1944. The Canvasback on a prairie marsh. Am. Wildl. Inst. Washington, D.C. 201pp. Hori, J. 196 4a. The breeding biology of the Shelduck (Tadorna tadorna). Ibis 106:333-360. 180 Hori, J. 1964b. Parental care i n the Shelduck. Wildfowl Trust. Ann. Rep. 15:100-103. Hori, J. 196 9. So c i a l and population studies i n the Shelduck. Wildfowl Trust Ann. Rep. 20:5-22. Howard, H.E. 1920. Territory in bird l i f e . Murray, London. Hunter, M.L. Jr., J.W. Witham and H. Dow. 1984. E f f e c t s of a ca r b a r y l -induced depression i n invertebrate abundance on the growth and behaviour of American black duck and mallard ducklings. Can. J. Zool. 62:452-456. Jackson, J.B.C. 1981. 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 species' d i s t r i b u t i o n s : the ghosts of theories and data past. Amer. Zool. 21:889-901. Jaeger, R.G., D. Kalvarsky and N. Shimizu. 1982. T e r r i t o r i a l behaviour of the Red-backed salamander: expulsion of intruders. Anim. Behav. 30:490-496. Johnson, C. 1964. The evolution of t e r r i t o r i a l i t y i n the Odonata. Evolution 18:89-92. Johnson, D.H. 197 9. Estimating nest success: the Mayfield method and an alternative. Auk 96:651-661. Johnson, L.K. and S.P. Hubbell. 1974. Aggression and competition among stingless bees: f i e l d studies. Ecology 55:120-127. Johnson, L.L. 1967. The common goldeneye duck and the rol e of nesting boxes i n i t s management i n North Central Minnesota. J. Minnesota Acad. S c i . 34:110-113. Jones, R.E., and A.S. Leopold. 1967. Nesting interference i n a dense population of wood ducks. J. Wildl. Manage. 31:221-228. Jourdain, F.C.R. 1921. Review of territory l i f e i n birds. Ibis 3:322-324. Katzir, G. 1981a. Aggression by the Damselfish (Dacyllus aruanus L.) towards conspecif ics and heterospecif ics. Anim. Behav. 29:835-841. Katzir, G. 1981b. Visual aspects of species recognition i n the Damselfish Dascyllus aruanus L. (Pisces: Pomacentridae). Anim. Behav. 29:842-849. Kear, J. 1965. The internal food reserves of hatching mallard ducklings. J. Wildl. Manage. 29:523-528. Kear, J. 1970. The adaptive r a d i a t i o n of parental care i n waterfowl. I n Social behaviour in birds and mammals. J.H. Crook ed., Academic Press, New York. Kendeigh, S.C. 1969. Tolerance of cold and Bergmann's rule. Auk 86:13-25. 181 Kendeigh, S.C. 1970. Energy requirements for existence i n relation to size of bird. Condor 72:60-65. King, J.G. 1963. Duck banding i n a r c t i c Alaska. J. W i l d l . Manage. 27: 356-362. King, J.R. 1973. Energetics of reproduction in birds. In Breeding biology of b i r d s . D.S. Farner ed., N a t i o n a l Academy of S c i e n c e s , Washington,D.C, pp. 78-107. Kirby, R.E. 1976. Breeding chronology and i n t e r - s p e c i f i c r e l a t i o n s of Pied-billed Grebes i n northern Minnesota. Wilson B u l l . 88:493-495. Klett, A.T. and D.H. Johnson. 1982. V a r i a b i l i t y i n nest s u r v i v a l rates and implications to nesting studies. Auk 99:77-87. Klomp, H. 1970. The determination of c l u t c h - s i z e i n birds. A review. Ardea 58:1-124. Klomp, H. 1972. Regulation of the si z e of b i r d populations by means of t e r r i t o r i a l behaviour. Neth. J. Zool. 22:456-488. Klomp, H. 1980. Fluctuations and s t a b i l i t y in great t i t populations. Ardea 68:205-224. Knapton, R.W. and J.R. Krebs. 1974. Settlement patterns, t e r r i t o r y s i z e and breeding density i n the song sparrow (Melospiza melodia). Can. J. Zool. 52:1413-1420. Kodric-Brown, A. and J.H. Brown. 1978. Influence of economics, i n t e r -s p e c i f i c competition and sexual dimorphism i n t e r r i t o r i a l i t y of migrant rufous hummingbirds. Ecology 59:285-296. Koehl, P.S., T.C Rothe and D.U. Derksen. 1984. Winter food habits of Barrow's Goldeneye i n Southeast Alaska. In Marine birds: t h e i r f e e d i n g ecology and commercial f i s h e r i e s r e l a t i o n s h i p s . D.N. Nettleship, G.A. Sanger and P.F. Springer eds., Min. Supply and Services Canada, No. CW66-651. Can. Wildl. Serv. Special Publ., Ottawa. t>p. 1-5. Koskimies, J. 1955. Juvenile mortality and population balance i n the Velvet Scoter (Melanitta fusca) in maritime conditions. Acta XI Congr. Int. Orn. 1954. Basle, pp. 476-47 9. Koskimies, J. and L. L a h t i . 1964. Cold-hardiness of the newly hatched young i n r e l a t i o n to ecology and d i s t r i b u t i o n i n ten species of European ducks. Auk 81:281-307. Krajina, V.J. 196 9. Ecology of fo r e s t trees i n B r i t i s h Columbia. Ecol. West. N. America 2:1-46. Krajina, V.J. 1973. Biogeoclimatic zones of B r i t i s h Columbia. Map published by Bri t i s h Columbia Ecological Reserves Committee, Bri t i s h Columbia Dept. Lands, Forests and Water Resources. 182 Krapu, G.L. and H.A. Doty. 197 9. A g e - r e l a t e d a s p e c t s of M a l l a r d reproduction. Wildfowl 30:35-39. Krapu, G.L. 1979. Nutrition of female dabbling ducks during reproduction. In Waterfowl and Wetlands - an integrated review. T.A. Bookhout ed., Proc. 1977 Symp. The Wildl. Soc., Madison, Wis. pp. 59-70. Krebs, J.R. 1971. Territory and breeding density in the great t i t , Parus major L. Ecology 52:2-22. Kuchel, C.R. 1977. Some aspects of the behaviour and ecology of Harlequin ducks breeding i n G l a c i e r National Park, Montana. M.Sc. Thesis, University of Montana, Montana. Lack, D. and L. Lack. 1933. Territory reviewed. Brit. Birds 27:179-199. Lack, D. 1954. The natural regulation of animal numbers. Clarendon Press, Oxford. Lack, D. 1966. Population studies of birds. Clarendon Press, Oxford. Lancaster, J. 1985. Structure of arthropod communities in some saline lakes of central B r i t i s h Columbia. M.Sc. thesis, Dept. Zool., Univ. British Columbia, Vancouver, Canada. Lanyon, W.E. 1956. T e r r i t o r i a l i t y i n the meadowlarks, genus S t u r n e l l a . Ibis 98:485-489. Lemieux, L. 1959. The breeding biology of the Greater Snow Goose on By lot Island, Northwest Territories. Can. Field Nat. 73:117-128. Limpert, R.J. 1980. Homing succes of adult buffleheads to a Maryland wintering site. J. Wildl. Manage. 44:905-908. Livezey, B.C. and P.S. Humphrey. 1984. Sexual dimorphism i n continental steamer-ducks. Condor 86:368-377. Livezey, B.C. and P.S. Humphrey. 1985a. T e r r i t o r i a l i t y and i n t e r s p e c i f i c aggression in steamer-ducks. Condor 87:154-157. Livezey, B.C. and P.S. Humphrey. 1985b. I n t e r s p e c i f i c aggression i n steamer-ducks. Condor 87:567-568. Lockie, J.D. 1966. T e r r i t o r y i n small carnivores. Symp. Zool. Soc. Lond. 18:143-165. Lokemoen, J.T. and D.E. Sharp. 197 9. Assessment of n a s a l marker materials and designs used on dabbling ducks. W i l d l . Soc. B u l l . 13:53-56. Losey, G.S. J r . 1981. Experience leads to attack of novel species by an i n t e r s p e c i f i c t e r r i t o r i a l Damselfish, Eupomacentrus f a s c i o l a t u s . Anim. Behav. 29:1271-1272. 183 L o s e y , G.S. J r . 1982. E c o l o g i c a l c u e s and e x p e r i e n c e m o d i f y i n t e r s p e c i f i c a g g r e s s i o n by t h e d a m s e l f i s h S t e g a s t e s f a s c i o l a t u s . B e h a v i o u r 81:14-3 7 . Low, R . M . 1 9 7 1 . I n t e r s p e c i f i c t e r r i t o r i a l i t y i n a p o m a c e n t r i d r e e f f i s h P o m a c e n t r u s f l a v i c a u d a W h i t l e y . E c o l o g y 5 3 : 6 4 8 - 6 5 4 . L o y n , R . H . , R.G. R u n n a l l s , G.Y. F o r w a r d a n d J . T y e r s . 1 9 8 3 . T e r r i t o r i a l B e l l M i n e r s a n d o t h e r b i r d s a f f e c t i n g p o p u l a t i o n s o f i n s e c t p r e y . S c i e n c e 221:1411-1413. Lumsden, H . G . , R.E . P a g e , M. G a u t h i e r . 1 9 8 0 . C h o i c e o f n e s t b o x e s b y Common Goldeneye i n O n t a r i o . W i l s o n B u l l . 9 2 : 4 9 7 - 5 0 5 . Makepeace, M. a n d I . J . P a t t e r s o n . 1 9 8 0 . D u c k l i n g m o r t a l i t y i n t h e s h e l d u c k i n r e l a t i o n t o d e n s i t y , a g g r e s s i v e i n t e r a c t i o n and w e a t h e r . W i l d f o w l 3 1 : 5 7 - 7 2 . M a r t o f , B. 1953. T e r r i t o r i a l i t y i n t h e g r e e n f r o g , Rana c l a m i t a n s . E c o l o g y 3 4 : 1 6 5 - 1 7 4 . M a y f i e l d , H.F. 1 9 6 1 . N e s t i n g s u c c e s s c a l c u l a t e d f r o m e x p o s u r e . W i l s o n B u l l . 7 3 : 2 5 5 - 2 6 1 . M a y f i e l d , H. 197 5 . S u g g e s t i o n s f o r c a l c u l a t i n g n e s t s u c c e s s . W i l s o n B u l l . 8 7 : 4 5 6 - 4 6 6 . McCamant, R . E . a n d E.G. B o l e n . 197 9. A 1 2 - y e a r s t u d y o f n e s t b o x u t i l i z a t i o n b y B l a c k - b e l l i e d W h i s t l i n g D u c k s . J . W i l d l . M a n a g e . 4 3 : 9 3 6 - 9 4 3 . M c G i l v r e y , F . B . 196 9. S u r v i v a l i n Wood Duck b r o o d s . J . W i l d l . M a n a g e . 3 3 : 7 3 - 7 6 . M c K i n n e y , F. 196 5 . S p a c i n g a n d c h a s i n g i n b r e e d i n g d u c k s . W i l d f o w l T r u s t 1 6 t h A n n . R e p . , p p . 9 2 - 1 0 6 . M c K i n n e y , F. 197 3 . E c o e t h o l o g i c a l a s p e c t s o f r e p r o d u c t i o n . I n B r e e d i n g b i o l o g y o f b i r d s . D . S . F a r n e r e d . , N a t . A c a d . S c i . , W a s h i n g t o n , D.C. p p . 6 - 2 1 . M c K i n n e y , F. 1985. P r i m a r y and s e c o n d a r y male r e p r o d u c t i v e s t r a t e g i e s o f d a b b l i n g d u c k s . I n A v i a n m o n o g a m y . P . A . G o w a t y a n d D.W. M o c k e d s . , O r n i t h o l . M o n o g r . 3 8 ( i n p r e s s ) . M c K i n n e y , F . W . R . S i e g f r i e d , I . J . B a l l a n d P . G . H . F r o s t . 1 9 7 8 . B e h a v i o u r a l s p e c i a l i z a t i o n s f o r r i v e r l i f e i n t h e A f r i c a n B l a c k Duck (Anas s p a r s a E y t o n ) . Z. T i e r p s y c h o l . 4 8 : 3 4 9 - 4 0 0 . M c K i n n e y , F. a n d P. S t o l e n . 1 9 8 2 . E x t r a - p a i r - b o n d c o u r t s h i p a n d f o r c e d c o p u l a t i o n among c a p t i v e G r e e n - w i n g e d T e a l (Anas c r e c c a c a r o l i n e n s i s ) . A n i m . Behav. 30:461-474. 1 8 4 McKinney, F. and D.J. Bruggers. 1983. Status and breeding behaviour of the Bahama Pin t a i l and the New Zealand Blue Duck. Jn Symposium on breeding birds i n c a p t i v i t y . J. Delacour ed.f I.F.C.B., Hollywood, C a l i f o r n i a February 23-27. pp. 211-221. McKinney, F., S.R. Derrickson, and P. Mineau. 1983. Forced copulation i n waterfowl. Behav. 86:250-294. McLaren, I.A. 1972. Polygyny as the adaptive function of breeding territory in birds. Trans. Connect. Acad. Sciences. 44:189-210. McLaren, W.D. 1963. A preliminary study of nes t - s i t e competition i n a group of hole nesting birds. MjSc. thesis, Univ. of British Columbia, Vancouver. McLaren, W.D. 1969. Further data on interspecific competition at a joint bufflehead-goldeneye nest site. Can. Field-Nat. 83:59-60. McLaughlin, CL. and D. Grice. 1952. The effectiveness of large-scale erection of wood duck boxes as a management procedure. North Amer. Wildl. Conf. 17:242-259. Mendenhall, V.M. and H. Milne. 1985. Factors affecting duckling survival of Eiders Somateria mollissima i n northern Scotland. Ibis 127:148-158. Miller, R.S. 1967. Pattern and process i n competition. Adv. Ecol. Res. 4:1-74. Minot, E.O. 1981. E f f e c t s of i n t e r s p e c i f i c competition for food i n breeding Blue and Great T i t s . J . Anim. Ecol. 50:375-385. Mitchell, G.F. 1952. A study of the d i s t r i b u t i o n of some members of the Nyrocinae wintering on the coastal waters of southern B r i t i s h Columbia. Unpubl. M.A. thesis, Univ. of British Columbia, Vancouver, B.C., Canada. Moore, F.R. 197 8. I n t e r s p e c i f i c aggression: toward whom should a Mockingbird be aggressive? Behav. Ecol. Sociobiol. 3:173-176. Moore, N.W. 1957. T e r r i t o r y i n dragonflies and birds. Bird Study 4:125-130. Morse, D.H. 1980. Behavioural mechanisms i n ecology. Harvard Univ. Press Cambridge, Massachusetts, 383pp. Morse, T.E. and H.M. Wight. 196 9. Dump nesting and i t s e f f e c t on production i n wood ducks. J. Wildl. Manage. 33:284-293. Munro, J. and J. Bedard. 1977a. Creche formation i n the Common Eider. Auk 94:759-771. Munro, J. and J. Bedard. 1977b. G u l l predation and creching behaviour i n the Common Eider. J. Anim. Ecol. 46:799-810. 185 Munro, J.A. 1918. The Barrow's Goldeneye i n the Okanagan Valley, British Columbia. Condor 20:3-5. Munro, J.A. 1923. A preliminary report on the r e l a t i o n of various ducks and g u l l s to the propogation of sockeye salmon at Henderson Lake, Vancouver Island, B.C. Can. Field-Nat. 37:107-116. Munro, J.A. 1935. Barrow's Goldeneye nesting in Marmot's burrow. Condor 37:82-83. Munro, J.A. 193 9. Studies of waterfowl i n B r i t i s h Columbia, Barrow's Goldeneye, American Goldeneye. Trans. Royal Can. Inst. 48:259-318. Munro, J.A. 1941. Studies of waterfowl in British Columbia: Greater Scaup duck, Lesser Scaup duck. Can. J. Res. 19D:113-136. Munro, J.A. 1942. Studies of waterfowl i n B r i t i s h Columbia: Bufflehead. Can. J. Res. 20D:133-160. Munro, W.T. and S.R. Goodchild. 1981. Preliminary duck management plan for B r i t i s h Columbia. Province of B r i t i s h Columbia. Ministry of Environment. Murray, B.G. Jr. 1971. The ecological consequences of i n t e r s p e c i f i c t e r r i t o r i a l behaviour in birds. Ecol. 52:414-423. Murray, B.G. J r . 1976. A c r i t i q u e of i n t e r s p e c i f i c t e r r i t o r i a l i t y and character convergence. Condor 78:515-518. Murray, B.G. J r . 1981. The o r i g i n s of adaptive i n t e r s p e c i f i c territorialism. Biol. Rev. 56:1-22. Murray, B.G. Jr . 1985. I n t e r s p e c i f i c aggression i n steamer-ducks. Condor 87 : 567. Myers, J.P., P.G. Connors, and F.A. P i t e l k a . 197 9a. T e r r i t o r i a l i t y i n non-breeding shorebirds. I n Shorebirds i n marine environments. Studies i n avian biology. Vol. 2. F.A. P i t e l k a ed., Cooper Ornith. Society, Berkeley, California, pp. 231-246. Myers, J.P., P.G. Connors and F.A. P i t e l k a . 197 9b. T e r r i t o r y s i z e i n wintering Sanderlings: the e f f e c t s of prey abundance and intruder density. Auk 96:551-561. Myrberg, A.A. J r . and R.E. Thresher. 1974. I n t e r s p e c i f i c aggression and i t s relevance to the concept of t e r r i t o r i a l i t y i n reef fishes. Amer. Zool. 14:81-96. Myres, M.T. 1957. An introduction to the behaviour of the goldeneyes: Bucephala i s l a n d i c a and B. clangula (class ayes, f a m i l y anatidae). M.Sc. Thesis, Dept. Zool., Univ. of British Columbia. Myres, M.T. 1959a. The behaviour of the sea ducks. Ph.D. thesis, Univ. British Columbia, Vancouver, B.C 186 Myres, M.T. 1959b. D i s p l a y behaviour of B u f f l e h e a d , s c o t e r s and goldeneyes at copulation. Wilson Bull. 71:159-168. Naylor, A.E. 1960. The Wood Duck i n C a l i f o r n i a with special reference to the use of nest boxes. C a l i f . Fish and Game 46:237-269. Nice, M.M. 1941. The rol e of t e r r i t o r y i n b i r d l i f e . Amer. Midi. Nat. 26:441-487. Nickell, W.P. 1966. Behaviour of Barrow's Goldeneye i n Wyoming. Wilson Bull. 78:121-122. Nilsson, L. 196 9. The behaviour of Bucephala clangula i n winter. Var Fagelvarld 28:199-210.(In German). Noble, G.K. 1939. The role of dominance i n the social l i f e of birds. Auk 56:263-273. Norman, F.I. and T.L. Riggert. 1977. Nest boxes as nest s i t e s for Australian waterfowl. J. Wildl. Manage 41:643-649. Norman, M.D. and G.P. Jones. 1984. Determinants of t e r r i t o r y s i z e i n the pomacentrid reef fi s h . Oecologia 61:60-69. Nudds, T.D. 1980. Resource v a r i a b i l i t y , competition and the structure of waterfowl communities. Ph.D. Thesis, Univ. Western Ontario. Nuechterlein, G.L. and R.W. Storer 1985a. Aggressive behaviour and interspecific k i l l i n g by Flying Steamer-Ducks i n Argentina. Condor 87 : 87 -91. Nuechterlein, G.L. and R.W. Storer. 1985b. I n t e r s p e c i f i c aggression i n Steamer-DuJcs. Condor 87:567-568. Orians, G.H. and M.F. Willson. 1964. I n t e r - s p e c i f i c t e r r i t o r i e s of birds. Ecology 45:736-745. Oring, L.W. and D.B. Lank. 1984. Breeding area f i d e l i t y , natal philopatry and the social system of sandpipers. In Shorebird breeding behaviour and populations, J. Burger and B.L. O l l a eds., Behaviour of marine animals. Vol. 5. Current perspectives i n research, pp. 125-147. Otte, D. and A. Joern. 197 5. Insect t e r r i t o r i a l i t y and i t s evolution: population studies of desert grasshoppers and creosote bushes. J. Anim. Ecol. 44:29-54. Palmer, R.S. 1976. Handbook of North American birds Vol. 3. Waterfowl (Part 2). Yale Univ. Press, New Haven and London. Patten, B.C. 1961. Competitive exclusion. Science 134:1599-1601. Patterson, I.J. 1980. T e r r i t o r i a l behaviour and the l i m i t a t i o n of population density. Ardea 68:53-62. 187 Patterson, I.J. 1982. The Shelduck: a study i n behavioural ecology. Cambridge Univ. Press, New York. 276pp. Patterson, I.J., A. Gilboa and D.J. Tozer. 1982. Rearing other peoples' young; brood mixing i n the shelduck Tadorna tadorna. Anim. Behav. 30:199-202. Pehrsson, 0. 1973. Nutrition of small ducklings regulating breeding area and reproductive output i n the Long-tailed Duck (Clangula hyemalis). XI Int. Congr. Game B i o l . Stockholm, Sept. 3-7. National Swedish Environmental Protection Board, pp. 259-264. Perrins, CM. and T.R. Birkhead. 1983. Avian ecology. Oxford. Blackie and Son Ltd., Glasgow and London, 221pp. Peterson, B. and G. Gauthier. 1985. Nest s i t e use by cavity-nesting birds of the Cariboo Parkland, Br i t i s h Columbia. Wilson Bull. 97:319-331. Petrie, M. 1984. T e r r i t o r y s i z e i n the Moorhen (Gallinula chloropus) an outcome of RHP asymmetry between neighbors. Anim. Behav. 32:861-870. P e t t i n g i l l , O.S. Jr . 196 5. Kelp geese and f l i g h t l e s s steamer-ducks i n the Falklands Islands. Living Bird 10:65-77. Pianka, E.R. 1978. Evolutionary ecology. Harper and Row, New York. Pienkowski, M.W. and P.R. Evans. 1982a. Breeding behaviour, p r o d u c t i v i t y and survival of colonial and non-colonial Shelducks Tadorna tadorna. Ornis Scand. 13:101-116. Pienkowski, M.W. and P.R. Evans. 1982b. Clutch parasitism and nesting interference between shelducks at Aberlady Bay. Wildfowl 33:159-163. Pitelka, F.A. 1959. Numbers, breeding schedule, and t e r r i t o r i a l i t y i n Pectoral Sandpipers of Northern Alaska. Condor 61:233-262. Poston, H.J. 1974. Home range and breeding biology of the Shoveler. Can. Wil d l . Serv. Rept. Ser. 25. Pourtois, A. 1978. Contribution a l a description du oomportement et de l a b i o l o g i e du Garrot Arlequin et du Garrot d'Islande sur leur l i e u x de nidif ication. Aves 15:52-54. Prince, H.H. 196 5. The breeding ecology of Wood Duck (Aix sponsa L.) and Common Goldeneye (Bucephala clangula L.) i n ce n t r a l New Brunswick. M.Sc. Thesis, Univ. of New Brunswick, Fredericton. Prince, H.H. 1968. Nest sites used by Wood Ducks and Common Goldeneye i n New Brunswick. J. Wildl. Manage. 32:489-500. Rajala, P. and T. Ormio. 1971. On the nesting of the goldeneye (Bucephala  clangula L.) i n the Meltaus Game Research Area i n Northern Finland 1959-1966. Finn. Game Res. 31:3-9. 188 Rand, A.S. 1967. The adaptive s i g n i f i c a n c e of t e r r i t o r i a l i t y i n iguanid l i z a r d s . In Li z a r d ecology W.W. Milstead ed., Columbia: Univ. of Missouri Press, pp. 106-115. Rasa, O.A.E. 196 9. T e r r i t o r i a l i t y and the establishment of dominance by means of visual cues i n Pomacentrus jenkinsi (Pisces: Ppmacentrridae). Z. Tierpsychol. 26:825-845. Redmond, R.L. and D.A. Jenni. 1982. Natal philopatry and breeding area f i d e l i t y of Long-billed Curlews (Numenius americanus): Patterns and evolutionary consequences. Behav. Ecol. Sociobiol. 10:277-279. Reed, A. and A. Bourget. 1977. D i s t r i b u t i o n and abundance of waterfowl wintering i n southern Quebec. Can. Field-Nat. 91:1-7. Ricklefs, R.E. 1974. Energetics of reproduction i n birds. In Avian Energetics. R.A. Paynter j r . ed., Nutt. Ornith. Club, Cambridge, pp. 152-297. Riechert, S.E. 1981. The consequences of being t e r r i t o r i a l : Spiders, a case study. Amer. Nat. 117:871-892. Ringelman, J.K. and J.R. Longcore. 1982. Survival of juvenile Black Ducks during brood rearing. J. Wildl. Manage. 43:622-628. Ripley, S.D. 1961. Aggressive neglect as a factor i n i n t e r s p e c i f i c competition in birds. Auk 78:366-371. Riggert, T.L. 1977. The biology of the Mountain Duck on Rottnest Island, Western Australia, Wildl. Monogr., No. 52. Robertson, I. and H.S. Stelfox. 196 9. Some i n t e r s p e c i f i c intolerance between Barrow's Goldeneye and other duck species during brood rearing. Can. Field-Nat. 83:407-408. Robertson, D.R., H.P.A. Sweatman, E.A. Fletcher and M.G. Cle l l a n d . 1976. Schooling as a mechanism for circumventing the t e r r i t o r i a l i t y of competitors. Ecology 57:1208-1220. Rockwell, R.F., C.S. Findlay, and F. Cooke. 1983. Life history, studies of the Lesser Snow Goose (Anser caerulescens caerulescens). 1. The influence of age and time on fecundity. Oecologia 56:318-322. Rowley, I. 1983. Re-mating i n birds. In Mate choice. P. Bateson ed., Cambridge Univ. Press, London, New York, pp.331-360. Sammarco, P.W. and A.H. Williams. 1982. D a m s e l f i s h t e r r i t o r i a l i t y : Influence on Diadema distribution and implications for coral community structure. Mar. Ecol. Prog. Ser. 8:53-59. Savard, J.-P.L. 1982a. Preliminary assessment of hunting pressure near Riske Creek, B r i t i s h Columbia. Regional Report, Canadian W i l d l i f e Service, Pacific and Yukon Region. 25pp. 189 Savard, J.-P.L. 1982b. Barrow's Goldeneye nest-box u t i l i z a t i o n i n the Cariboo parkland, British Columbia: Year 1. Can. Wildl. Serv. Progress Notes, No. 131. Savard, J.-P.L. 1982c. Intra- and i n t e r - s p e c i f i c competition between Barrow's Goldeneye (Bucephala islandica) and Bufflehead (Bucephala albeola) . Can. J. Zool. 12:343 9-3446. Savard, J.-P.L. 1984. Terr i t o r i a l behaviour of Common Goldeneye, Barrow's Goldeneye and Bufflehead i n areas of sympatry. Ornis Scand. 15:211-216. Savard, J.-P.L. 1985a. Use of a mirrror trap to capture t e r r i t o r i a l waterfowl. J . Field Ornith. 56:177-178. Savard, J.-P.L. 1985b. Evidence of long-term p a i r bonds i n Barrow's Goldeneye (Bucephala islandica). Auk 102:389-391. Savard, J.-P.L. 1986. Polygyny in Barrow's Goldeneye. Condor 88: in press. Sawyer, E.J. 1928. The courtship of the Barrow's Goldeneye. Wilson Bull. 40:5-17. Sayler, R.D. and A.D. Afton. 1981. Ecological aspects of common goldeneye (Bucephala clangula) wintering on the upper Mississippi River. Ornis Scand. 12:99-108. Schneider, K.B. 196 5. Growth and plumage development of ducklings i n interior Alaska. M.Sc. Thesis, Univ. Alaska, Alaska. Schoener, T.W. 196 8. Sizes of feeding t e r r i t o r i e s among birds. Ecology 49:123-141. Schoener, T.W. 1982. The controversy over i n t e r s p e c i f i c competition. Amer. Scientist 70:586-595. Schoener, T.W. 1983. F i e l d experiments on i n t e r s p e c i f i c competition. Amer. Nat. 122:240-285. Schreiner, K.M. and G.O. Hendrickson. 1951. Wood duck production aided by nesting boxes, Lake Odessa, Iowa, i n 1950. Iowa Bird L i f e 21:6-10. Scott, D.K. 1980. Functional aspects of the pai r bond i n winter i n Bewick's swans (Cygnus columbianus bewickii). Behav. Ecol. Sociobiol. 7 : 323-327. Scudder, G.G.E. 196 9. The fauna of saline lakes on the Fraser Plateau i n Bri t i s h Columbia. Verh. Internat. Verein. Limnol. 17:430-439. Seymour, N.R. 1974a. T e r r i t o r i a l behaviour of w i l d shovelers at Delta, Manitoba. Wildlife Trust Ann. Rept. 25:49-55. Seymour, N.R. 1974b. Site attachment i n the northern shoveler. Auk 91:423-427. 190 Siegfried, W.R. 197 9. Social behaviour of the A f r i c a n Comb Duck. Li v i n g Bird. 17:85-104. Simmons, K.E.L. 1951. Inter-specific territorialism. Ibis 93:407-413. Sinclair, A.R.E. 1975. The resource l i m i t a t i o n of trophic l e v e l s i n tropical grassland ecosystems. J. Anim. Ecol. 44:497-520. Siren, M. 1951. Increasing the goldeneye population with nest boxes. Suomen Riist a 6:83-101. Siren, M. 1952. Studies on the breeding biology of the goldeneye (Bucephala clangula). R i i s t a t . Julk. 8:101-111. Sjoberg, K. and K. Danell. 1982. Feeding activity of ducks in relation to d i e l emergence of chironomids. Can. J. Zool. 60:1383-1416. Skinner, M.P. 1937. Barrow's Goldeneye i n the Yellowstone National Park. Wilson Bull. 49:3-10. Smith, J.N.M., P.R. Grant, B.R. Grant, I.J. Abbott and L.K. Abbott. 197 8. Seasonal v a r i a t i o n i n feeding habits of Darwin's ground finches. Ecology 59:1137-1150. Snow, B.K. and D.W. Snow. 1984. Long-term defence of f r u i t by M i s t l e Thrush (Turdus viscivorus). Ibis 126:39-49. Spence, J.R. 197 9. Microhabitat s e l e c t i o n and regional coexistence i n water-striders (Heteroptera; Gerridae). Ph.D. Thesis, Dept. Zool., Univ. British Columbia. Spurr, E. and H. Milne. 1976. Adaptive s i g n i f i c a n c e of autumn pai r formation i n the Common Eider (Somateria mollissima L.). Ornis Scand. 7:85-89. Steen, J.B., H.C. Pederson, K.E. Erikstad, K.B. Hansen, K. Hoydal and A. Stordal. 1985. The s i g n i f i c a n c e of cock t e r r i t o r i e s i n Willow Ptarmigan. Ornis Scand. 16:277-282. Stephens, M.L. 1984. I n t e r s p e c i f i c a g g r e s s i v e behaviour of the polyandrous Northern Jacana (Jacana spinosa). Auk 101: 508-518. Stolen, P. and F. McKinney. 1983. Bigamous behaviour of captive Cape Teal. Wildfowl 34:10-13. Strange, T.H., E.R. Cunningham and J.W. Goertz. 1971. Use of nest boxes by Wood Ducks in Mississippi. J. Wildl. Manage. 35:786-797. Street, M. 1977. The food of Mallard ducklings i n a wet gravel quarry, and i t s relation to duckling survival. Wildfowl 28:113-125. Sugden, L.G. 196 0. An observation of i n t e r s p e c i f i c s t r i f e between Barrow's Goldeneye and Lesser Scaup. Can. Field-Nat. 74:163. Sugden, L.G. 1963. Barrow's Goldeneye using crow nests. Condor 65:330. 191 Swanson, G.A., G.L. Krapu and J.R. Serie. 197 9. Foods of laying female dabbling ducks on the breeding grounds. Jja Waterfowl and Wetlands -an i n t e g r a t e d review. T.A. Bookhout ed., La Crosse P r i n t i n g , Wisconsin, pp. 47-57. Swarth, H.S. 1926. Report on a c o l l e c t i o n of birds and mammals from the A t l i n region, northern B r i t i s h Columbia. Univ. C a l i f . Publ. i n Zool. 30:51-155. Taber, R.D. 1971. C r i t e r i a of sex and age. In W i l d l i f e Management techniques, R.H. G i l e s J r . ed., The W i l d l . Soc, Washington, D.C. pp. 325-402. Thresher, R. 1985. Brood-directed parental aggression and early brood loss in the coral reef f i s h , Acanthochrornis polyacanthus (ppmacen.tr idae). Anim. Behav. 33:897-907. Tinbergen, N. 1957. The functions of territory. Bird Study 4:14-27. Titman, R.D. 1983. Spacing and three-bird fl i g h t s of Mallards breeding i n pothole habitat. Can. J. Zool. 61:839-847. Titman, R.D. and N.R. Seymour. 1981. A comparison of pursuit f l i g h t s by six North American ducks in the genus Anas. Wildfowl 32:11-18. Topping, M.S. and G.G.E. Scudder. 1977. Some physical and chemical features of saline lakes i n central British Columbia. Syesis 10:145-166. Van Den Assem, J. 1967. T e r r i t o r y i n the three-spined stickleback (Gasterosteus aculeatus L.). Behav. Suppl. 16. Vermeer, K. 1981. Food and populations of Surf Scoters i n B r i t i s h Columbia. Wildfowl 32:107-116. Vermeer, K. 1982. Food and d i s t r i b u t i o n of three Bucephala species i n British Columbia waters. Wildfowl 33:22-30. Vermeer, K. and R. Vermeer. 1975. Oi l threat to birds on the Canadian west coast. Can. F i e l d Nat. 89:278-298. Verner, J. 1977. On the adaptive s i g n i f i c a n c e of t e r r i t o r i a l i t y . Amer. Nat. 111:769-775. Village, A. 1983. The ro l e of ne s t - s i t e a v a i l a b i l i t y and t e r r i t o r i a l behaviour i n l i m i t i n g the breeding density of kestrels. J. Anim. Ecol. 52:635-645. Vines, G. 197 9. S p a t i a l d i s t r i b u t i o n s of t e r r i t o r i a l aggressiveness i n oyster catchers. Anim. Behav. 27:300-308. Walters, J. 197 9. I n t e r s p e c i f i c aggressive behaviour by long-toed lapwings (Vanellus crassirostris). Anim. Behav. 27:969-981. 192 Warhurst, R.A., T.A. Bookhout and K.E. Bednarik. 1983. Ef f e c t of gang brooding on s u r v i v a l of Canada Goose goslings. J. W i l d l . Manage. 47:1119-1124. Wasserman, F.E. 1983. T e r r i t o r i e s of Rufous-sided Townees contain more than minimal food resources. Wilson Bull. 95:664-666. Watson, A. and D. Jenkins. 196 8. Experiments on population control by t e r r i t o r i a l behaviour i n red grouse. J. Anim. Ecol. 37:595-614. Watson, A. and R. Moss. 1970. Dominance, spacing behaviour and aggression i n r e l a t i o n to population l i m i t a t i o n i n vertebrates. I n Animal populations i n r e l a t i o n to t h e i r food resources. A. Watson ed., Blackwell, Oxford, ppl67-218. Watson, A. and R. Moss. 1971. Spacing as affected by t e r r i t o r i a l behaviour, habitat and nutrition i n Red Grouse (Lagopus 1. scoticus). In Behaviour and environment. The use of space by animals and men. A.H. Esser ed., Plenum, New York, pp92-lll. Watson, A. and R. Moss. 1980. Advances i n our understanding of the population dynamics of red grouse from a recent f l u c t u a t i o n i n numbers. Ardea 68:103-111. Weller, M.W. 1976. Ecology and behaviour of steamer-ducks. Wildfowl 27:45-53. Welsh, D.A. 1975. Savannah sparrow breeding and t e r r i t o r i a l i t y on a Nova Scotia dune beach. Auk 92:235-251. Welty, j.C. 1982. The l i f e of birds. W.B. Saunders Company, Philadelphia. Wiemeyer, S.N. 1967. Bufflehead food habits, parasites, and biology i n Northern C a l i f o r n i a . M.Sc. T h e s i s , Humboldt S t a t e C o l l e g e , California, 99pp. Williams, M. 1979. The social structure, breeding and population dynamics of Paradise Shelduck i n the Gisborne-east coast d i s t r i c t . Notornis 26:213-272. Williams, M.J. 1974. Creching behaviour of the shelduck Tadorna tadorna (L.). Ornis Scand. 5:131-143. Wittenberger, J.F. 1981. Animal social behaviour. Duxbury Press, London, 722pp. Wittenberger, J.F. and R.L. T i l s o n . 1980. The evolution of monogamy: hypotheses and evidence. Ann. Rev. Ecol. Syst. 11:197-232. Wolff, J.O., M.H. Freeberg and R.D. Dueser. 1983. I n t e r s p e c i f i c t e r r i t o r i a l i t y i n two sympatric species of Peromyscus (Rodentia: Cricetidae). Behav. Ecol. Sociobiol. 12:237-242. Young, CM. 1970. T e r r i t o r i a l i t y i n the Common Shelduck (Tadorna  tadorna). Ibis 112:230-33 5. 193 Zar, J.H. 1974. B i o s t a t i s t i c a l analysis. Prentice-Hall, Inc., Englewood C l i f f s , New Jersey. Zipko, S.J. 197 9. E f f e c t s of dump nests and habitat on reproductive ecology of wood ducks, Ajx sponsa (Linnaeus). Ph.D. Dissertation, Rutgers State Univ.,New Jersey, 169pp. 194 Appendix 1. Use of a mirror trap to capture t e r r i t o r i a l waterfowl 195 As part of a study on the breeding ecology of Barrow's Goldeneye (Bucephala islandica) i n central British Columbia, I wanted to capture and i n d i v i d u a l l y mark adult drakes to f a c i l i t a t e the study of t e r r i t o r i a l behavior. I could not obtain hand-reared birds to use as decoys and decided to try mirrors. Instead of a clover-leaf trap with open entrances as used by Donaghey (197 5), I used a spring-door decoy trap as described by Anderson et a l . (1980). I used folding wire dog cages (0.5 x lm) which I f i t t e d with a tripping mechanism similar to that described by Anderson et a l . (1980). A glass mirror (0.4 x 0.8m) was fixed with wires at the closed end of the trap. To reach the mirror, the bird had to swim over the treadle that closed the trap door. Each trap was positioned i n open water within a Barrow's Goldeneye territory in lm of water. Four aluminium poles held the cage f i x e d and at a height so that the treadle and the mirror base were under water. It took l e s s than 10 min to i n s t a l l a trap. Results reported here are from 519 trap hours (daylight only): 12 h/trap i n 1982 (2 traps), 35 h/trap i n 1983 (5 traps), and 80h/trap i n 1984 (4 traps). Each trap was checked at least twice a day, early morning and sunset. A l l trapping was done during egg laying and early incubation when t e r r i t o r i a l behavior was the strongest. We captured 41 Barrow's Goldeneye, 27 males and 16 females, with mirror traps (Table 40). In t e r r i t o r i e s where a goldeneye drake was captured, e f f o r t per trap averaged 10.7 h and ranged from 4 to 28 h (n=25). In those where a female was captured, trapping e f f o r t averaged 17.5 h and ranged between 7 and 33 h (n=16). Female Barrow's Goldeneye usually do not take part i n t e r r i t o r i a l defense but have been observed to attack other females. 196 Whenever a female goldeneye was captured, her mate swam around the trap and stayed close to i t . If two traps had been located side by side, i t i s l i k e l y that the male would have been captured also. When males were captured, their mate never came close to the trap. Traps set up i n Barrow's Goldeneye t e r r i t o r i e s also captured other species (Table 40). These species, with the exception of the American Wigeon (Anas americana), are w e l l known for t h e i r aggressive behavior during the breeding season (Fjeldsa 1973 a, Donaghey 197 5, Titman and Seymour 1981). Birds must see t h e i r r e f l e c t i o n i n the mirror before entering the trap. Improper orientation, wind, and sun often reduced the mirror's efficiency. In addition, individual birds may vary i n their reaction to mirrors. Although mirror traps cannot be used to mark large numbers of birds they may prove useful i n l o c a l i z e d studies, e s p e c i a l l y when accessibility or costs prohibit the use of captive decoys. 197 Table 40. B i r d s p e c i e s captured u s i n g m i r r o r t r a p s . Year Species 1982 1983 1984 Horned Grebe (Podiceps a u r i t u s ) Gadwall (Anas strepera) American Wigeon (Anas amer,icana) Blue-winged T e a l (Anas dj,scQfS) Northern Shoveler (Ajijag clypeata> Barrow's Goldeneye (Bucephala j s l a n d i c a ) B u f f l e h e a d (Bucephala 1/0 7/0 1/0 3 I / O 1 2/0 6/2 1/0 8/6 1/0 0/1 12/10 1/0 1 males/females 198 Appendix 2. Evidence of long-term pair bonds in Barrow's Goldeneye 199 Geese, swans and ducks that cooperate i n raising young maintain long-term pair bonds (Kear 1970, Bolen 1971, Weller 1976, Patterson 1982). In most H o l a r c t i c ducks the female r a i s e s the young alone, new p a i r s are formed every year on wintering and/or migration areas, and males follow their philopatric female to breeding areas (Hochbaum 1944, Rowley 1983, and others). Female Barrow's Goldeneye (Bucephala islandica) return to the same breeding area every year and often use the same nesting s i t e s (Palmer 1976). Males accompany the i r mates from wintering areas, defend t e r r i t o r i e s on the breeding ground and then leave for unknown molting areas when the female i s incubating. They are not seen again on the breeding ponds u n t i l the following spring. In t h i s paper, I present evidence indicating that some Barrow's Goldeneye pairs remain intact from year to year in spite of a long separation and that pair reunion occurs on the wintering areas. During a study of the breeding ecology of Barrow's Goldeneye i n c e n t r a l B r i t i s h Columbia, I captured and marked 15 adult drakes and 81 adult females with nasal disks. The return rate of females to the study area was 77% (n=36) i n 1982 and 7 5% (n=81) i n 1983, i n d i c a t i n g a high degree of s i t e f i d e l i t y . S i m i l a r rates of return for females have been found i n other cavity nesting ducks (Erskine 1961, Dow and Fredga 1983). The return rate of drakes was 71% (n=7) i n 1982 and 63% (n=15) i n 1983. Two of three p a i r s marked i n 1982 returned i n t a c t i n 1983 and the other did not return. The females of these two returning p a i r s had raised broods in 1982, and were therefore separated from their mates for at least four months. The existence of long-term pair bonds was confirmed i n 1984, when three of seven marked pairs returned intact. Of the remaining four pairs, one s p l i t and only one member returned i n the other three. 200 The two females that had l o s t t h e i r mates had re-paired when resighted but the four males had not. These four males returned to the same pond where they had been captured the previous year and one even defended a territory for two days. Usually, unpaired males do not defend territories. One Barrow's Goldeneye drake marked on his territory in 1982 defended the same t e r r i t o r y i n 1983 and 1984. S i m i l a r l y , three other paired males were resighted on the same t e r r i t o r y the following year. Although the females of these males were not marked, i t i s l i k e l y that they retained their previous mates because females apparently select the t e r r i t o r y i n most t e r r i t o r i a l waterfowl (Hochbaum 1944, Young 1970, Donaghey 1975). The preceding observations indicate that Barrow's Goldeneye pairs can remain i n t a c t from year to year i n spite of a long separation and that unpaired males home to their previous breeding area. Homing of unpaired drakes to breeding areas has been reported i n several dabbling ducks (Poston 1974, Blohm 197 8) and diving ducks (Bengtson 197 2, A l i s o n 197 5, Donaghey 1975). Breeding philopatry i n unpaired males would increase their chances of finding a mate, or of reuniting with a previous mate. It could also enhance their survival because of their familiarity with the resources of the area. I now consider where and how p a i r s re-unite. Within a week of the arrival of Barrow's Goldeneye on their wintering areas in southern coastal B r i t i s h Columbia, i n early November, some pa i r s are already defending territories. From a total of 34 territories defended along a 5km stretch of shoreline i n Burrard Inlet near Vancouver, B.C., in February and March 1983, 59% were established by mid-December and 85% by late December. This rapid formation of pairs soon after arrival on the wintering areas, when 201 there i s l i t t l e courtship, suggests that pairs reunite then. In 1983, 55% of the 400 males present i n Burrard Inlet on November 17 had arrived by November 1 compared to only 11% of the 200 females. This earlier arrival of the males supports the contention that most p a i r s reunite on the wintering ground rather than on f a l l staging areas. Spurr and Milne (1976) found s i m i l a r pair formation i n the Common Eider (Somateria  mollissima). This too involved l i t t l e courtship. Butterfield (1970) also observed that pairs of Zebra Finch (Poephila guttata) that reunited after separation displayed l i t t l e courtship. I was fortunate to document the reunion of one pair of Barrow's Goldeneye on the wintering area. A drake marked on his breeding territory in 1982 was resighted near Vancouver, B.C, defending a winter territory at the t i p of a small j e t t y . He was paired with an unmarked female and they remained i n th e i r t e r r i t o r y a l l winter. In A p r i l 1983 the male defended the same breeding t e r r i t o r y as i n 1982. He was paired, presumably with the female with whom he had wintered. We marked her that summer and she raised a brood while the male departed for the molting grounds. On October 29, 1983 we sighted the male i n a small group of goldeneye (37 males, 3 females, 10 immatures), 2 km east of h i s 1982 winter t e r r i t o r y . Daily checks indicated that he remained there u n t i l November 12. On November 8, we sighted h i s mate i n a large group of goldeneye (84 males, 39 females, 1 immature), 4 km from the location of the male. This coincided with the f i r s t big i n f l u x of adult females on the wintering areas. On the next day (November 9) the female had joined her mate and the pair was in a small goldeneye group (5 males, 2 females, 1 immature) 1.5 km from their 1982 winter territory. 202 On November 12 the pair had joined a large group of goldeneye (175 males, 79 females, 30 immatures) and were at the location where we f i r s t saw the female. They stayed for 11 days in this large group mainly feeding and resting. On November 22 they l e f t the group and attempted to establish a territory 2 km east of their old territory but were apparently unsuccessful because, on December 12, they were back on t h e i r old 1982 territory. They defended the territory a l l winter and were last sighted there on A p r i l 12, 1984 at 0715 h. The next day (April 13) they were seen on t h e i r breeding t e r r i t o r y at 1120 h. They had covered the 320 km distance in one night and had apparently migrated alone, as they were not seen in any groups prior to their departure from the wintering area. This observation indicates that f i d e l i t y to wintering areas i n Barrow's Goldeneye may be as strong as f i d e l i t y to breeding areas. Homing by members of a pair would f a c i l i t a t e pair reunion. Homing to wintering areas has also been documented in Bufflehead (Bucephala albeola) (Erskine 1961, Limpert 1980), Oldsquaw (Clangula hiemalis) (Alison 1975), and Common Eider (Spurr and Milne 1976), indicating that pair reunion may also occur i n these species. Pair bonds i n Barrow's Goldeneye are strong. Although forced copulation i s common among waterfowl, i t has never been reported i n the genus Bucephala (McKinney £t a l . 1983), and I have not witnessed any such attempts i n four years of intensive studies of Barrow's Goldeneye and Bufflehead. Goldeneye drakes take several minutes before mounting a prone female (Afton and Sayler 1982, Savard unpub. data). Such physiological and/or behavioural delay would make forced copulation d i f f i c u l t . Pairs copulate throughout winter as w e l l as during incubation. This may reinforce pair bonds as may t e r r i t o r i a l defense. 203 A few studies on seabirds have shown that pairs that re-unite are more successful than pairs that s p l i t (Coulson and Thomas 1983). Scott (1980) and Hepp and Hair (1984) found that pairing i n waterfowl enhanced the dominance status of both partners and improved t h e i r foraging opportunities. Rowley (1983) l i s t s several possible advantages of pair reunion over the formation of new pair bonds. The advantages of pair reunion i n Barrow's Goldeneye may include: 1) obtaining an experienced mate, whose a b i l i t i e s are known; 2) f a m i l i a r i t y of the male with the breeding and wintering terr i t o r i e s which gives him a stronger motivation to defend them because of a previous sense of ownership. This w i l l enhance the chances of the female to retain her previous territory; 3) a reduction of the time and energy spent in courtship. There i s also evidence in the literature that other migrating diving ducks may have long l a s t i n g pair bonds: Harlequin Ducks (Histrionicus  histrionicus) (Bengtson 1972, Kuchel 1977, Dzinbal 1982), Oldsquaw (Alison 1975), Common Eider (Spurr and Milne 1976). I suggest that s t a b i l i t y and renewal of pair bonds i s more common i n ducks than has been previously thought. It i s l i k e l y that this w i l l be confirmed as more adult males are individually marked in future studies. 204 Appendix 3 Witnessed brood encounters i n Barrow's Goldeneye 205 I present here records of four witnessed brood encounters that shed some light on the mechanisms and functions of brood amalgamation. 1st encounter: Lake 77, July 8, 1985. One of the females was marked with nasal disks (female M). 0630 h: When f i r s t seen, the marked female (M) was f i g h t i n g with an unmarked female (U). M had 3 young approximately 2 weeks old. U won the fight and M flew away. U swam away followed by M's young. In the next 10 min, M made three unsuccessful attempts to regain her young, but each time was chased away by U. M flew away. U swam toward her 5 young, also approximately 2 weeks old. 0640 h: U attacked the three young of M. The young had not mixed with U's young and were a few meters away. Following the attack, M's young swam away and hid near shore. 0645 h: M flew back toward her young but was immediately attacked by U who pursued her on the water and i n the air for five minutes. M again flew out of sight and U returned to her territory. U landed near M's young, then swam toward her own young. M's young followed U swimming behind her, but af t e r swimming a few meters U turned around and attacked the young who f l e d back near shore among flooded trees. U returned to her young. 0654 h: M made another unsuccessful attempt to regain her young and was chased o f f again by U. U returned from her a e r i a l pursuit at 0657 h and, after she landed i n her territory, M's young came out of the flooded trees and swam toward her. U attacked them and they retreated among the flooded trees. U returned to her young. 0659 h: M's young l e f t the flooded trees and again swam toward U and her young. U attacked them and they returned to the flooded trees. 0703 h: U swam toward the flooded trees and attacked M's young and 206 successfully chased them o f f her t e r r i t o r y . U stopped pursuing the young and adopted a threat posture. 0708 h: M flew i n and landed inside U's t e r r i t o r y c a l l i n g loudly. However, her young had l e f t U's territory and were swimming away. U was at the border of her territory threatening the young and had not noticed M. 0714 h: U returned to her young followed by M's young 20 m behind. 0715 h M saw her young and flew to the other side of U's t e r r i t o r y . She c a l l e d her young and they swam to her. M and her young swam toward emergent vegetation. 0724 h: Brood M came out of emergent vegetation and swam away from U's territory. U was feeding within her territory with her young. 0752 h: Brood M encountered another unmarked t e r r i t o r i a l brood (A). A attacked M and after a short but violent fight pursued her i n the air. M flew out of sight and A landed near M's young. She seemed confused. Her young were sleeping on a log 30 m away. A tried to at t r a c t M's young and swam behind them. She did not appear aggressive but the young, probably because of their previous encounter with female U, swam away and did not respond to her During the next hour, M's young remained alone on the water. They were visited three times by A who did not display any aggression toward them. 0854 h: The young of A (11 young 3 weeks old) l e f t t h e i r log and started feeding. A swam toward M's young followed by one of her young. When they came near M's young, the young who followed A displayed to her (head pumping) and started vocalizing. After this display by her young, A attacked the three young of M and chased them. A 207 attacked M's young twice but could not catch them. A stopped her attacks and resumed feeding. M's young swam away from brood A. M was not seen again. 0908 h: End of observations. 2nd encounter: Lake 13/ June 27, 1983. A l l three females were marked with nasal disks. 0750 h: Female C l e d her four newly hatched young to the water. As she reached the pond, she was immediately attacked by A who had ten nine-day-old young. A dominated C: she climbed on C's back, and b i t her neck and wings. C escaped on shore. A then attacked one of C's young, grabbed i t by the neck and shook i t under water. This prompted C to leave shore and attack A to protect her young. A dominated C and drove her away. Meanwhile, C's young escaped i n emergent vegetation and became separated from the other three young. A returned to her young and preened on shore. While A was res t i n g on shore, C regrouped her young and swam out of A's t e r r i t o r y . As C entered the t e r r i t o r y of the second brood (B), she was attacked by female B. Again C was dominated by B and swam away leaving her young behind. B then attacked the young of C. She grabbed one of the young by the neck and shook i t hard. C attempted twice to rescue her young but was chased off by B each time. B k i l l e d the young. The other young had sought refuge i n emergent vegetation. 0900 h: C was preening on shore with no young. 208 0930 h: C had regrouped her three young and was resting on shore. By the next day, C had led her young to a neighbouring lake 600 m away. Ten days later a l l her young had died. 3rd encounter: Lake 31 June 16, 1984. The two females were marked. 1328 h: Female A had established her t e r r i t o r y on the lake 14 days earlier, after her 10 young had hatched. Female B's 11 young were jumping out of the box. B led them toward the lake only 3 m away but was attacked on land by A who grabbed her right wing, climbed on her back biting her continuously. This lasted at least 5 min. A kept B from reaching the lake and B walked toward the fo r e s t with A s t i l l having hold of her wing. Female A released B 40 m from shore and B went o f f with her 11 young through the forest. A returned to her young on the lake but remained close to the area where the f i r s t encounter occurred. The v i o l e n t attack by A contrasted with the submission of B who did not fight back but rather tried to escape. The following day, B was located on a lake 700 m away with only 6 young. The next day she had lost a l l her young who may have mixed with another brood on the lake. A remained on her lake and successfully raised a l l her young. 4th encounter: Lake 106, June, 1981. Neither of the broods was marked. When I arrived at the lake, two female Barrow's Goldeneye were fighting. The defeated female escaped to shore. Then the victorious female attacked one of the young and k i l l e d i t . The other young escaped on shore. I searched the shoreline of the pond and found two other dead ducklings and two l i v i n g ones hiding i n the grass. There were no other birds on the pond besides the goldeneye. It i s clear from these examples that females do not attempt to steal other females' young. Females abandon t h e i r young only after v i o l e n t f i g h t s , and even make several attempts to regain them. These four observations suggest that brood amalgamation i s not a strategy used by the females and/or young but simply an accidental outcome of t e r r i t o r i a l aggression. 210 Appendix 4. Polygyny i n Barrow's Goldeneye 211 A male i s considered polygynous whenever he forms a prolonged pair bond with two or more females whose nesting cycles overlap i n time (Wittenberger 1981). Polygyny i s rare i n waterfowl (Wittenberger and T i l s o n 1980, Ford 1983) and commonly occurs i n only two species, the Magpie Goose (Anseranas semipalmata) and the A f r i c a n Comb Duck (Sarkidiornis melanotos) (Frith and Davies 1961, Siegfried 1979). Studies of captive bir d s have indicated that some southern hemisphere dabbling ducks may occasionally be polygynous (McKinney and Stolen 1982, Stolen and McKinney 1983, McKinney and Bruggers 1983). S i m i l a r studies of North American dabbling ducks have not documented polygyny (Stolen and McKinney 1983). Among North American diving ducks, polygyny has been reported only i n the Canvasback (Aythya v a l i s i n e r i a ) (Anderson, M. i n Ford 1983). Common Goldeneye (Bucephala clangula) and Barrow's Goldeneye (£. islandica) have been observed defending two females and t h i s suggested that polygyny may occur i n these species (Eriksson, M. pers. comm., Savard per. obser.). I describe here four cases of polygyny observed i n 1984 among 220 p a i r s of Barrow's Goldeneye during a study of t e r r i t o r i a l behaviour i n the interior of British Columbia, Canada. Case 1 Pair A (female marked with nasal disks) arrived on i t s breeding pond (Lake 13) on A p r i l 13 when 90% of the lake was s t i l l covered with ice. By April 15, two other pairs had established territories. Female B (marked) was f i r s t seen A p r i l 17 on the pond and did not seem paired. This was unusual as unpaired adult females are rarely seen on the breeding areas. On A p r i l 18, male A was defending a territory from which he excluded a l l goldeneyes but females A and B. Three monogamous males also defended t e r r i t o r i e s on the lake and there were several unpaired males on 212 neighbouring ponds. No aggression was observed between females A and B. Female A started laying on A p r i l 20 and female B on A p r i l 29; each l a i d 8 eggs i n the same nest boxes they had used the previous year. Female A started incubation on May 3 and Female B on May 17. The nest of female A was destroyed by a Black Bear (Ursus americanus) on May 4 whereas that of female B was deserted on May 27 because of egg predation by American Red S q u i r r e l (Tamiasciurus hudsonicus). We were able to i d e n t i f y the polygynous male after his capture on May 13. Both females remained with him in the territory until his departure on June 5. The two females then spent most of t h e i r time on lake 13 associating temporarily with other females but rarely together. They were last seen on July 5. Both females had been marked in earlier years so that their breeding history was partially known. Female A nested i n 1982 and 1983 in the same nest box she used i n 1984, and rai s e d a brood on Lake 13. In 1983 her breeding territory was on Lake 13 and her mate was monogamous. Female B nested i n 1983 i n the same box she used i n 1984 and also raised a brood on Lake 13. Because no polygynous males were seen i n the area i n 1983 i t i s assumed that she was paired with a monogamous male. I t i s also l i k e l y that her mate's territory was also on Lake 13. Case 2 In t h i s case, I witnessed the a c q u i s i t i o n of the second female: Pair C (female marked) was f i r s t seen on a lake beside their breeding pond at 0500 h on A p r i l 4. At 1600 h, they landed on t h e i r breeding pond and challenged an established pair. After a violent fight i n which both sexes p a r t i c i p a t e d , pair C took over the t e r r i t o r y . On A p r i l 5, 6 and 7, the male was observed defending the t e r r i t o r y . At 0645 h on A p r i l 8, a neighouring p a i r , pair D, copulated. At 06 55 h, male C attacked male D 213 and after a violent fight male D l e f t the pond, abandoning his mate. Male C did not show any aggression toward female D but female C did. At 0710 h, male C approached female D and both displayed to each other. Female C was ignored i n the following days as male C spent more time with female D. However male C s t i l l defended his original territory by chasing a l l goldeneyes that approached female C. Both females remained with male C and were observed copulating with him at least once. Female C initi a t e d her clutch on May 5 and hatched 14 young. It i s not known i f female D nested. Case 3 A male (G) with two females was observed on A p r i l 30, defending a territory on a small pond which also supported another t e r r i t o r i a l pair. On May 1 we captured and marked the polygynous male. He was last seen on May 26. Case 4 On May 2 a male with two females, one of which was marked (E) defended a t e r r i t o r y on a pond where 3 other p a i r s had also established territories. Female H had bred on that pond i n 1982 and 1983. On May 11 we captured and marked the other female (I). Female H l a i d 12 eggs i n the same box she had used i n 1982 and 1983, but her box was destroyed by a Black Bear. I could not determine i f Female I bred. I compared the aggressiveness of the polygynous males with that of neighbouring pairs to see i f polygynous males tended to be more aggressive than monogamous males (Table 41). The results are inconclusive. In only one case (pair G) was the polygynous male more aggressive. Polygynous Barrow's Goldeneye drakes formed simultaneous pair bonds with two females. Polygyny in Barrow's Goldeneye could be promoted by the 214 following factors: (1) Breeding ponds are very productive (Cannings and Scudder 197 8) so that the resources of the t e r r i t o r y may not be s i g n i f i c a n t l y altered by the presence of a second female; (2) Males do not provide parental assistance (Munro 193 9); (3) Polygyny increases reproductive success of males (Wittenberger 1981). However, several factors also act to l i m i t polygyny. They are (1) the existence of strong and stable pair bonds (Appendix 2); (2) aggressiveness of both paired males and females toward strange females (Chapter III); (3) pair formation occurring on the wintering ground and not related to territory q u a l i t y (Palmer 1976, Appendix 2); (4) sex r a t i o biased toward males (Bellrose 197 8, Savard unpubl. data); (5) A b i l i t y of females to f i n d a new mate more readily than males (Savard unpubl. data). The low degree of polygyny observed in the population studied (<2%, n=220 pairs) suggests that polygyny in Barrow's Goldeneye i s not a common breeding strategy but rather an unusual occurrence. Models based on habitat or male qualities to explain polygyny (Wittenberger 1981) do not apply here and have been questioned in other cases (Alatalo £t a l . 1981). I propose that strong philopatry and attachment to breeding t e r r i t o r i e s and nest s i t e s by females, l o s s of previous mate or the mate f a i l u r e to establish or regain the female territory, and familiarity between birds involved, lead i n some cases to polygyny i n Barrow's Goldeneye. These factors have not always been considered in previous studies of polygyny and may prove important i n explaining the occasional occurrence of polygyny in other species. 215 Appendix 5. Sexual dimorphism in Barrow's Goldeneye 216 Livezey and Humphrey (1984) compared sexual dimorphism (in weight) of several species of waterfowl and showed that species of the genus Bucephala were among the most dimorphic species. Weights of Barrow's Goldeneye are rare i n the l i t e r a t u r e (Bellrose 1978, Palmer 1976). I thus compare here weight of males and females captured during the study. In 1983 and 1984 males were respectively 1.4 times and 1.6 times heavier than females (Table 42). This ratio may slightly overestimate the difference in weight between males and females because most females were weighed l a t e into incubation. Vermeer (1981) reports an average weight i n winter for males of 1173 g (n=18) and of 823 g (n=13) for females for a weight r a t i o of 1.4. Males' wings averaged 23 mm longer than those of females i n both 1983 and 1984 (Table 42). 217 Table 42. Comparison of weight3 and wing length between male and female Barrow's Goldeneye. Weight1 (g) Male Wing length (mm) Male Year Male Female Female Male Female Female 1983 1002.8+26.32 717.6±5.1 1.4 237.3+2.0 214.7+0.5 1.1 n=9 n=69 n=7 n=68 1984 1121.9+23.9 703.8±4.2 1.6 238.8+1.3 215.0+0.5 1.1 n=13 n=59 n=12 n=57 1 Differences i n weight and wing length between males and females were s t a t i s t i c a l l y significant in both years (T-test P<0.05). 2 standard error. 3 Males were weighed between May 1 and June 1. Most females were weighed in the last week of the incubation period between May 20 and June 20. 218 

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