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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 t h e s i s submitted i n p a r t i a l f u l f i l l m e n t of the requirements f o r the degree of Doctor of Philosophy in The f a c u l t y o f graduate studies (Department of Zoology) We accept t h i s t h e s i s as conforming t o the required standard  The University of B r i t i s h March 1986 ©  Columbia  Jean-Pierre L. Savard, 1986  7  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t  the L i b r a r y s h a l l make  it  and study.  f r e e l y a v a i l a b l e f o r reference  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  Itis  understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l n o t be allowed without my  permission.  Department o f  crc^-fyryy.  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  ( X ^ f l ,  ;  Columbia  mC  written  ii Abstract In t h i s s t u d y ,  I f i r s t d e s c r i b e and c h a r a c t e r i z e the 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 behaviour of Barrow's Goldeneye  (Bucephala  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 Bufflehead  (B.  albeola).  Second,  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 . Finally,  I  compare d u c k l i n g m o r t a l i t y  in  Barrow's  Goldeneye  and  Bufflehead. Barrow's Goldeneye, similar against  Common G o l d e n e y e  t e r r i t o r i a l behaviour: rivals.  breeding  they  and B u f f l e h e a d p a i r s have  defend a f i x e d ,  exclusive  area  P a i r s are 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 during  season,  and  i n t e r s p e c i f i c aggression  is  strongest  the  toward  c o n g e n e r s and 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 and 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 behaviour amalgamation  i s s i m i l a r t o t h a t of t h e d r a k e s i n t h e s p r i n g .  i s frequent  i n Barrow's Goldeneye  Brood  and i s an a c c i d e n t a l  outcome of t e r r i t o r i a l e n c o u n t e r s between b r o o d s .  Barrow's  Goldeneye  p a i r s a l s o d e f e n d 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 e s o n t h e  wintering  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 strong i n Barrow's Goldeneye.  Barrow's Goldeneye m a i n t a i n  monogamous  l o n g - t e r m p a i r bonds but 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 . Provision  of  nest  boxes  d e n s i t i e s o f B a r r o w ' s Goldeneye. boxes by B a r r o w ' s Goldeneye outcome of  resulted  in  an  increase  in  breeding  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  included:  p r e v i o u s use of  the previous breeding attempt,  the nest  nest box,  age o f t h e n e s t b o x a n d i t s  iii location.  P r o p o r t i o n s of n e s t boxes t h a t hatched, were preyed upon and  were d e s e r t e d , averaged r e s p e c t i v e l y 46+4% (S.E.), 31+3% years). 5% and  and 23+3%  (n=4  Minimum estimates of i n t r a s p e c i f i c nest parasitism ranged between 20%.  The  daily  m o r t a l i t y r a t e of Barrow's Goldeneye and  ducklings v a r i e d with rates were  years,  highest i n the  duckling age and  first  week  hatching date.  f o l l o w i n g hatching.  Bufflehead Mortality In years of  h i g h m o r t a l i t y , broods t h a t hatched e a r l y tended to s u r v i v e b e t t e r than l a t e h a t c h i n g broods.  Barrow's Goldeneye d u c k l i n g s 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  i n these species seems to be the  p r o v i s i o n of an e x c l u s i v e f e e d i n g area f o r the female or the young. argue  t h a t the  e v o l u t i o n of  interspecific  aggression  i n the  I  genus  Bucephala has been favoured by a h i g h l e v e l of i n t r a s p e c i f i c a g g r e s s i o n within the genus and s i g n i f i c a n t e x c l u s i o n of c o m p e t i t o r s .  f e e d i n g advantages o b t a i n e d from  the  The genus Bucephala p r o v i d e s one of the b e s t  examples of interference competition i n a g u i l d of related competitors.  iv T a b l e of  Contents  Page i i  Abstract List  Tables  vii  Figures  xi  Acknowledgements  xiv  List  of of  Chapter  I:  General introduction .  1) Management  1  framework  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 b) Behaviour and e c o l o g y of B a r r o w ' s Goldeneye c) Common Goldeneye and B u f f l e h e a d 4) Focus o f t h e study  Chapter  II:  . . .  12  . . . . .  13 14 14  G e n e r a l methods  17  sites  18  a) R i s k e C r e e k  18  b) C o l u m b i a V a l l e y  20  c) Vancouver  20  DStudy  2)General  methods  a) C a p t u r e b) A g e  and  21 marking  determination  c) S u r v e y s  21 21 22  v  Page  d)Statistical analysis Chapter III:  22  T e r r i t o r i a l Behaviour  23  Introduction  24  Methods  24  Results  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 a) T e r r i t o r i a l b e h a v i o u r - Breeding - Wintering  26 of p a i r s  26  areas  26  areas  40  b) T e r r i t o r i a l b e h a v i o u r of f e m a l e s w i t h b r o o d s 2) I n t e r s p e c i f i c a g g r e s s i o n  . .  40 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  64  with  broods  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 3) R e l a t i o n s h i p s between p a i r brood t e r r i t o r y  69  territory,  and 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  75  to  territory  e) R e m o v a l e x p e r i m e n t s Discussion  76 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) Brood 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  95  Summary  territory  97  vi Chapter IV:  Page  Use of n e s t boxes a n d n e s t i n g s u c c e s s  99  Introduction  100  Methods  102  Results  102  1) N e s t box u s e by a l l w i l d l i f e  102  2) N e s t box u s e by B a r r o w ' s G o l d e n e y e  105  a) N e s t i n g  success  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  119  egg l a y i n g  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  Discussion  126  Summary  129  Chapter 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  Introduction  131  Methods  131  Results  133  1) H a t c h i n g c h r o n o l o g y  133  2) M o r t a l i t y of 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 by b r o o d s i z e  137  c) D i r e c t m e t h o d  . . . .  149  Discussion  156  Summary  160  vii Chapter V I .  General d i s c u s s i o n  Page 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 l i m i t breeding d e n s i t i e s i n the genus Bucephala?  168  4) Management implications and research needs  169  Literature cited  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  viii L I S T OF TABLES Page Table Table  Table  Table  Table Table  Table  Table Table  1 2  3  4  5 6  7  8 9  T a b l e 10  T a b l e 11 T a b l e 12 T a b l e 13 T a b l e 14  T e r r i t o r i a l defense 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 presence of t h e i r mates  30  Comparison of a g g r e s s i v e i n t e r a c t i o n s of three territorial Barrow's Goldeneye drakes on 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  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  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 intruders  38  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  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 between t e r r i t o r i a l Barrow's Goldeneye drakes and c o n s p e c i f i c s i n winter  41  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 a r r o w ' s Goldeneye w i t h young and intruders  42  Brood amalgamation Bufflehead  45  i n Barrow's  Goldeneye  and  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  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 and 1984  51  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 w i t h i n t h e genus B u c e p h a l a  52  observed  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 a l l intruders that resulted i n fights  with  I n t e r a c t i o n s between t e r r i t o r i a l Goldeneye d r a k e s and d a b b l i n g ducks  Barrow's  I n t e r a c t i o n s between t e r r i t o r i a l Goldeneye d r a k e s and d i v i n g ducks  Barrow's  56 58 59  ix Page Table 15 Table 16  Table 17  Table 18 Table 19  Table 20  Table 21 Table 22 Table 23  L e v e l of a g g r e s s i o n i n i n t e r a c t i o n s b e t w e e n Barrow's Goldeneye drakes and other waterfowl ..  63  Number o f i n t e r s p e c i f i c a g g r e s s i o n s by Barrow's Goldeneye drakes i n r e l a t i o n t o the presence or absence o f t h e i r mates  65  Number of i n t e r a c t i o n s observed between female Barrow's Goldeneye and Bufflehead with broods, and other b i r d s  66  I n t r a - g e n e r i c a g g r e s s i o n i n broods o f Barrow's Goldeneye and broods of B u f f l e h e a d  67  I n t e n s i t y of the i n t e r a c t i o n s observed between females w i t h broods and i n t r a - and i n t e r s p e c i f i c intruders  68  Number o f c a s e s o f 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 f e m a l e s i n w i n t e r  70  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 the nest s i t e  73  R e s u l t s of the removal experiment 1984  on l a k e 68 i n 77  R e s u l t s of the removal experiment  on l a k e 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  R e l a t i o n s h i p between p r e v i o u s use of a nest box and subsequent use by Barrow's Goldeneye Nest box use i n r e l a t i o n to abundance of Barrow's Goldeneye on pond i n the previous year  Table 28 Table 29  Comparison o f n e s t i n g success between  108 110  cavity  n e s t i n g ducks  112  Table 30  Egg production i n nest boxes i n r e l a t i o n to year .  118  Table 31  Egg production i n r e l a t i o n to age of the box . . .  120  X  Page Table 32  Table 33  Table 34  Table 35 Table 36  Summary of counts c a r r i e d out by Ducks Unlimited i n C e n t r a l B r i t i s h Columbia and comparison w i t h counts on the study a r e a  125  Two-way anova on the e f f e c t of year and s p e c i e s (Barrow's G o l d e n e y e v s B u f f l e h e a d ) on mean hatching date  136  Four-way anova on the e f f e c t of species (Barrow's Goldeneye v s B u f f l e h e a d ) , year, age and h a t c h i n g date on m o r t a l i t y r a t e of young  138  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 i n r e l a t i o n t o y e a r s  139  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 i n r e l a t i o n t o age  140  Table 37  M o r t a l i t y of Barrow's Goldeneye ducklings  Table 38  Mortality of Bufflehead ducklings  154  Table 39  D i s t r i b u t i o n of losses between laying and 3 week o l d young i n nests t h a t hatched B i r d species captured using mirror traps  155 197  C o m p a r i s o n o f t h e number o f a g g r e s s i v e interactions observed between polygynous males and monogamous neighbouring males  214  Comparison of weight and wing length between male and female Barrow's Goldeneye  218  Table 40 Table 41  Table 42  ....  153  xi LIST OF FIGURES Page Figure  1  Location of study areas  19  Figure  2  Frequency of types 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 between t e r r i t o r i a l male Barrow's Goldeneye and i n t r u d e r s d u r i n g the breeding season  27  Frequency of t h r e a t s and a t t a c k s by t e r r i t o r i a l male Barrow's Goldeneye toward paired neighbouring males and b a t c h e l o r males  29  Percentage of t i m e spent by Barrow's Goldeneye males i n v a r i o u s a c t i v i t i e s i n r e l a t i o n t o the presence or absence of t h e i r mates  31  L o c a t i o n o f t e r r i t o r i e s of p a i r e d Barrow's Goldeneye drakes on l a k e 13 (1982) and l a k e 89 (1981)  35  A v e r a g e % o f t i m e s p e n t by m a l e and f e m a l e Barrow'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 their territory  36  Average % of time spent by f e m a l e and young Barrow'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 their territory  44  Average % of t i m e spent by female and young Bufflehead i n various a c t i v i t i e s w it hi n their territory  49  R e l a t i v e aggressiveness species toward intruders  54  Figure  Figure  Figure  Figure  Figure  Figure  Figure  3  4  5  6  7  8  9  F i g u r e 10 Figure 11  Figure 12  Figure 13 Figure 14  of the t h r e e Bucephala  Comparison of the p r o p o r t i o n s ' o f t h r e a t s and attacks i n i n t e r s p e c i f i c interactions  55  Aggressive responses of Barrow's Goldeneye drakes toward c o n s p e c i f i c s , congeners, diving ducks and d a b b l i n g ducks  57  F r e q u e n c i e s of a g g r e s s i v e i n t e r a c t i o n s and t o l e r a n c e s by t e r r i t o r i a l Barrow's Goldeneye drakes toward diving ducks and dabbling ducks . .  61  Distances between pair t e r r i t o r i e s and nest i n Barrow's Goldeneye  72  sites  Distances between brood t e r r i t o r i e s and nest s i t e s i n Barrow's Goldeneye  74  xii Page F i g u r e 15  F i g u r e 16  F i g u r e 17  F i g u r e 18 F i g u r e 19 F i g u r e 20 F i g u r e 21 F i g u r e 22  F i g u r e 23 F i g u r e 24  T e r r i t o r y boundaries of B a r r o w ' s Goldeneye 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 on l a k e 68 i n 1984  78  T e r r i t o r y b o u n d a r i e s of 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 p r i o r t o and f o l l o w i n g the removal e x p e r i m e n t o n l a k e 50 i n 1984  80  P r o p o r t i o n of n e s t boxes used by 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 box  107  P r o p o r t i o n of B a r r o w ' s Goldeneye nests 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  that . . .  Ill  I n f l u e n c e o f v i s i t s by o b s e r v e r s o n t h e f a t e s o f nests  114  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 date of initiation  115  clutch  P r o p o r t i o n s of n o n - h a t c h i n g n e s t s p r e y e d upon and deserted i n r e l a t i o n to c l u t c h i n i t i a t i o n date . .  116  I n f l u e n c e of the outcome of the previous 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  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 on the study area  122  Numbers  of  Barrow's  Goldeneye  and  Bufflehead  broods e s t i m a t e d on the study area  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  F i g u r e 26  Hatching d a t e s of B u f f l e h e a d broods  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 (weighted by b r o o d s i z e ) Barrow's Goldeneye d u c k l i n g s D a i l y m o r t a l i t y r a t e s (weighted by b r o o d s i z e ) Bufflehead ducklings  F i g u r e 28 F i g u r e 29  F i g u r e 30  broods  . . .  D a i l y m o r t a l i t y r a t e s (weighted by b r o o d s i z e ) Barrow's Goldeneye ducklings i n r e l a t i o n d u c k l i n g age  134 135  of 141 of 142 of to  D a i l y m o r t a l i t y r a t e s (weighted 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 .  144 145  xiii Page Figure 31  Daily mortality rates (weighted by brood size) of Barrow'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 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 t o hatching period  147  Figure 33  Figure 34  Figure 35  Figure 36  Daily mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings during the f i r s t week f o l l o w i n g hatching  148  D a i l y mortality rates (not weighted by brood size) of Barrow's Goldeneye d u c k l i n g s d u r i n g the f i r s t week f o l l o w i n g h a t c h i n g i n 1982  150  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  D a i l y mortality rates (not weighted by brood size) of Barrow's Goldeneye d u c k l i n g s d u r i n g the f i r s t week f o l l o w i n g h a t c h i n g i n 1984  152  xiv 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 research.  I thank  Gary  K a i s e r and 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 and encouragement d u r i n g t h e course of the study. assistants,  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  some o f whom worked 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  offered their services as volunteers. t h i s s t u d y a p l e a s a n t one:  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  Thanks t o Dave P o w e l l , John M c L a u g h l i n ,  T u r c o t t e , Andre B r e a u l t , J o n Gareau, L e s W i l l i s , Bogusha  Yves  Jedrzejewska,  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 Whitehead 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 , Sinclair,  Jamie Smith,  Tony  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 and encouragements.  I am g r a t e f u l t o M o i r a L e m o n ,  Pamela  Whitehead 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 dynamic  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 , Bob E m e r y .  I am g r a t e f u l t o E d H e n n a n ,  Ron B o y c h u c k ,  John E a d i e and R o r i Brown and  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 data on w a t e r f o w l s u r v e y s .  I would l i k e a l s o t o thank 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 the beginning of the study. T h i s s t u d y was s u p p o r t e d by 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 : Wildlife  Service,  Canadian N a t i o n a l  University  of B r i t i s h Columbia,  Sportsman's Fund,  Natural  Ducks  Canadian  Unlimited,  S c i e n c e s and E n g i n e e r i n g  Research C o u n c i l of Canada, B r i t i s h Columbia F i s h and W i l d l i f e B r a n c h , British Finally,  Columbia  Forest  Service,  and t h e Canadian  I would l i k e t o thank C a r o l e f o r h e r s u p p o r t ,  understanding throughout  the whole  study.  Forest  Service.  a s s i s t a n c e and  Chapter 1:  General introduction  1  Introduction T h i s t h e s i s arose from three separate but r e l a t e d i n t e r e s t s : i n t e r e s t i n the general n a t u r a l h i s t o r y of d i v i n g ducks, their  management,  a n d c) t h e t h e o r e t i c a l  c o m p e t i t i o n w i t h i n and between s p e c i e s . e s p e c i a l l y t h e Barrow's Goldeneye study s u b j e c t s :  problem  a) a n  b) a c o n c e r n f o r of  interference  Ducks o f t h e genus B u c e p h a l a ,  (Bucephala i s l a n d i c a ) . p r o v e d i d e a l a 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  Goldeneye,  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 appeared 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 1)  (see b e l o w ) .  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 two o t h e r b e t t e r Goldeneye  (B.  studied species:  clangula).  Bufflehead  The B a r r o w ' s  (B. a l b e o l a ) a n d Common  Goldeneye  has a  restricted  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 wintering i n B r i t i s h Columbia,  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 Goldeneye  i n view  of  several  threats  to the western North  American  population: 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 Columbia and A l a s k a has g r e a t l y spills  which could adversely  affect  food supply, Mussels (Mytilus) Vermeer  i n c r e a s e d the r i s k s of major o i l  1975).  2  w i n t e r i n g b i r d s and t h e i r  major  (Carthy and A r t h u r 1968, Vermeer and  2.  In the l a s t decade, l o g g i n g a c t i v i t i e s have 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 where the h i g h e s t b r e e d i n g d e n s i t i e s of Goldeneye a r e f o u n d , increasing  3.  r e d u c i n g t h e a v a i l a b i l i t y of n e s t i n g s i t e s a t an  rate.  Hunting p r e s s u r e i s recruitment  2)  Barrow's  high i n  some a r e a s ,  negatively  affecting  local  (Savard 1 9 8 2 a ) .  T h e o r e t i c a l framework a)  Competition  Crombie  (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  more  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 . (1957) f u r t h e r  stated that  if  the resources are not  Birch  in short  supply,  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 the process.  Miller  (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 dominant f o r m of c o m p e t i t i o n whenever 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 by d i r e c t e x p l o i t a t i o n  presumably 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 . common among i n v e r t e b r a t e s  interference  ( C r o m b i e 1947)  is  Exploitation competition i s and i s o f t e n found  between  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 and Davidson 1977), n e c t a r f e e d i n g b i r d s and i n s e c t s (Carpenter  1979,  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  1981,  Eadie  and  Keast  1982),  ungulates  and  grasshoppers  (Sinclair  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 . d e f e n s e has been r e p o r t e d i n a v a r i e t y 1957,  of animal groups:  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 ,  W e l l i n g t o n 1983),  arachnids  (Riechert  Baker 1983,  1981)  Territory  insects  (Moore  Fitzpatrick  crustaceans  (Dingle  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 ) , 3  1975).  and and  reptiles  (Rand 1967), f i s h e s  (Van Den Assem 1967,  Williams 1982), b i r d s (Howard 1920,  K a t z i r 1981a, Sammarco  Hinde 1956,  (Buechner 1961, Lockie 1966, Armitage 1974,  Brown 1964)  and  and mammals  Floody and Arnold 1975).  b) I n t r a s p e c i f i c competition Brown (1964) stated that i n t r a s p e c i f i c aggressiveness i s p r i m a r i l y a b e h a v i o u r a l response t o c o m p e t i t i o n f o r e c o l o g i c a l r e q u i s i t e s i n s h o r t supply  and  t h a t the predominant  aggressiveness  through  single  factor  natural selection  tending  should  be  to increase competition.  Competition, coupled with economic defendability of the l i m i t i n g resource, should l e a d t o t e r r i t o r i a l i t y . authors.  Noble  D e f i n i t i o n s of t e r r i t o r y vary among  (193 9) d e f i n e d a  territory  as  "any  defended  P i t e l k a (1959) s i m p l i f i e d the d e f i n i t i o n to "an exclusive area". encompassing d e f i n i t i o n was  g i v e n by Davies i n 197 8:  area".  The most  "Territoriality  o c c u r s whenever i n d i v i d u a l a n i m a l s or groups are spaced out more than would be expected from a random occupation of suitable habitats". (1980) and Wittenberger  (1981) give a detailed overview  d e f i n i t i o n s of t e r r i t o r i a l i t y . and O r i a n s (197 0) who  Morse  of the d i f f e r e n t  Here I s h a l l adopt the d e f i n i t i o n of Brown  d e f i n e d 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 r i v a l s .  This d e f i n i t i o n encompasses most of the  proposed d e f i n i t i o n s . In most p a s s e r i n e b i r d s , t e r r i t o r i e s are e s t a b l i s h e d b e f o r e p a i r i n g , and thus may p l a y a r o l e i n p a i r f o r m a t i o n (Hinde 1956, 1962).  Welty  In waterfowl, t e r r i t o r i e s are established after pair formation and  are not a factor i n pair formation. behaviour  McKinney (1965) reviewed the spacing  of several species of North American ducks and observed that i n  general, aggressive behaviour by males was associated with the presence of  4  a strong pair-bond.  He s u g g e s t e d t h a t  the r e s t r i c t i o n of  the  male'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 was a r e s u l t of the f e m a l e ' s a t t a c h m e n t 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 . spacing behaviour  T i t m a n and Seymour  territorial Northern  among t h e  Northern  Shoveler  (1981) compared t h e  of s i x North American s p e c i e s of d a b b l i n g ducks and  confirmed McKinney's observations. territoriality  to  T h e r e was a c l e a r g r a d i e n t of male  s p e c i e s they  studied ranging from the  P i n t a i l (Anas a c u t a )  (A. c l y p e a t a ) .  Northern  non-  to the s t r o n g l y t e r r i t o r i a l Shoveler  are attached to  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 season/ d e f e n d i t a c t i v e l y and f o r m s t r o n g and l o n g - l a s t i n g p a i r bonds showed t h a t  (Seymour 1974  a,b).  Titman  (1983)  M a l l a r d s defended t e r r i t o r i e s t h a t were e s s e n t i a l l y e x c l u s i v e  areas from a temporal point  of v i e w ,  although  they  often  overlapped  physically. B a l l e_t sX. maintains  (197 8) s h o w e d t h a t  t e r r i t o r i e s that  territoriality,  t h e A f r i c a n B l a c k Duck (A.  satisfy  the  classical  Similarly,  a t l e a s t t h r e e s p e c i e s of  (Tadorna) have 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  ducks,  definition  Riggert  1977,  W i l l i a m s 1979,  W e l l e r 1976),  1975), and B u f f l e h e a d  (Munro 1942,  I n the genus B u c e p h a l a .  Oldsquaw  P a t t e r s o n 1982).  In  Gauthier  the t e r r i t o r i a l b e h a v i o u r  1969, diving  (Tacjhyeres  (Clangula hyemalis)  Donaghey 1975,  b e e n w e l l d o c u m e n t e d (Munro 1 9 4 2 ,  shelducks  (Hori 1964a,  t e r r i t o r i a l i t y has been r e p o r t e d i n Steamer-Ducks  ( P e t t i n g i l l 1965,  spp.)  (Alison  1985).  of Bufflehead has  E r s k i n e 197 2 and Donaghey 197 5 ) .  drake 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 shore o f a pond f r o m w h i c h 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 mate. the  female  conspecifics.  of  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).  Young 1 9 7 0 ,  sparsa)  defends  an a r e a  D e s c r i p t i o n of  of  water  Similarly, after from  which  she  it  t h e young h a t c h excludes  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 5  The  all is  l i m i t e d t o s h o r t q u a l i t a t i v e accounts (Munro 1918,  1939,  1954,  These indicate that  Myres 1957,  Bengtson 1971,  1972, Palmer 1976).  i t s behaviour i s s i m i l a r t o t h a t of the B u f f l e h e a d . behaviour o f Common Goldeneye i s p o o r l y understood. observed two c a p t i v e p a i r s defending  Harris et a l .  The t e r r i t o r i a l Bruggemann (1876)  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 d i s p l a y occurring a t the t e r r i t o r y  boundaries  s i m i l a r t o one used by B u f f l e h e a d d u r i n g t e r r i t o r i a l defense (Donaghey 197 5).  Cramp and Simmons  (1977) r e p o r t e d  Goldeneye defend t e r r i t o r i e s on t h e i r breeding describe the behaviour or c i t e any references.  that,  i n Europe,  Common  grounds, but they did not Nilsson (1969) describes  behaviour t h a t resembles t e r r i t o r i a l defense but e x p l a i n s i t s i m p l y as mate defense.  Carter  (1958) and Gibbs  (1961) mentioned t h a t 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 o n l y defend an area around t h e i r mate. 1939,  S i r e n 1952,  1979a, Dow 1982,  Several other studies on Common Goldeneye (Munro  P r i n c e 196 5, R a j a l a and Ormio 1971,  Fredga and Dow 1984)  Territoriality  do not mention 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  t o t h e breeding  Barrow's Goldeneye have been observed defending wintering  ground  observation).  (Ian  E r i k s s o n 1976,  Robertson personal  grounds.  t e r r i t o r i e s on t h e i r  communication;  personal  A l s o , S a y l e r and A f t o n (1981) suggested t h a t some Common  Goldeneye defended t e r r i t o r i e s on t h e i r wintering area. Comparison o f w i n t e r  and summer t e r r i t o r i a l i t y  Goldeneye and of any differences between the three  o f Barrow's  species of Bucephala  should t h e r e f o r e p r o v i d e i n s i g h t i n t o t h e e v o l u t i o n and f u n c t i o n s o f t e r r i t o r i a l behaviour i n t h i s group.  6  c)  Interspecific competition In the f i r s t t h i r d of t h e c e n t u r y ,  Volterra,  L o t k a and Gause  developed a s i m p l e mathematical model 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 t w o - s p e c i e s systems (reviews i n M i l l e r 1967, Pianka 1978).  This l e d to  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 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 cannot l i v e t o g e t h e r t h e same t i m e .  However,  deal only  equilibrium conditions,  with  197 8 ) .  Further,  natural  systems.  in  that  a t t h e same p l a c e a t  t h e model and t h e subsequent t h e o r y b u i l t on i t which are r a r e i n nature  (Pianka  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 Competitive  segment o f a b r o a d e r  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  c l a s s o f i n t e r s p e c i f i c phenomena  (Patten  1961),  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?80).  Some have even debated i f t h e p r i n c i p l e o f  competitive  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 purpose (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 hard t o observe i n nature  (Miller  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). are  those  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  involving  interspecific territoriality.  Interspecific  t e r r i t o r i a l i t y i s common among b i r d s (Simmons 1 9 5 1 , O r i a n s a n d W i l l s o n 1964,  Murray  1971)  E b e r s o l e 1977,  and h a s a l s o been r e p o r t e d  in fishes  (Low  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  1971,  (Johnson  a n d H u b b e l l 1974) C r u s t a c e a ( D i n g l e £ t a 2 . 1 9 7 3 ) , a n d mammals ( W o l f f e_t fll.  1983). 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  species e x h i b i t s p e r s i s t e n t aggressive behaviour  t o an i n t r u d i n g b i r d of  another s p e c i e s , showing i t some, i f n o t a l l , of t h e r e a c t i o n s u s u a l l y forthcoming  i n i n t r a s p e c i f i c encounters.  He a l s o h y p o t h e s i z e d  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 s e r v e d t o reduce or e l i m i n a t e competition 7  between c l o s e l y a l l i e d s p e c i e s w i t h a s i m i l a r ecology.  T h i s view  was  l a t e r shared by Lanyon (1956), O r i a n s and W i l l s o n (1964), Grant (1966), and  Miller  (1967).  Cody (196 9)  appearance or v o i c e b e c a u s e aggressiveness,  s t a t e d t h a t s p e c i e s may  similarities  increase  converge i n  interspecific  which leads to the i n d i v i d u a l s of two species maintaining  mutually exclusive t e r r i t o r i e s i n a common habitat. exclusion of competitors  This r e s u l t s i n the  for food from the individuals' t e r r i t o r i e s ,  and  i s therefore adaptive. Murray (1971) disagreed with the previous adaptive interpretations of interspecific territoriality territoriality,  territoriality  and  r e s u l t e d most o f t e n that i t was  proposed from  that  misdirected  interspecific intraspecific  not an adaptive c h a r a c t e r i s t i c , and  should even be selected against.  therefore  Murray (1976) l a t e r 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 his  convergence hypothesis d i d not l i n k any case of convergence with  case 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 ;  of any  hence the hypotheses do not explain  any real s i t u a t i o n , much l e s s a substantial body of fact. Several recent territoriality Thresher  studies i n f i s h e s suggest  that  interspecific  i s not a r e s u l t of m i s i d e n t i f i c a t i o n (Low 1971,  1974,  K a t z i r 1981b).  Ebersole  c o r r e l a t i o n between the frequency  (1977) found  a  Myrberg and significant  t h a t 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 Similarly,  Moore  overlap.  (1978) f o u n d a r e l a t i o n s h i p b e t w e e n d e g r e e of  i n t e r s p e c i f i c aggression by  territorial  Mockingbirds (Mimus polyglottos)  and the percentage of dietary overlap with b i r d s competing for f r u i t s on Mockingbird  territories.  8  Davies  (1978)  territoriality  rejected  Murray's  view  i s not adaptive and occurs through  that  interspecific  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 f i s h e s , and the very d i s t i n c t i v e songs t h a t e l i c i t 1977).  interspecific  He concluded  territoriality  a g g r e s s i o n i n some b i r d s (Catchpole  t h a t t h e evidence  i s beautifully  resource requirements.  suggests  that  interspecific  adapted t o the amount of o v e r l a p i n  Wittenberger  (1981) remarked t h a t , a c c o r d i n g t o  the m i s i d e n t i f i c a t i o n h y p o t h e s i s , i n t e r s p e c i f i c  territoriality  should  evolve among s i m i l a r species regardless of whether they compete with one another.  Instead, i t has evolved among competing species regardless of  whether they are s i m i l a r to one another. Murray's (1971) intention was t o caution against the a t t r i b u t i o n of adaptive advantages to any behaviour  without examining alternatives.  He  presented the m i s i d e n t i f i c a t i o n hypothesis as an a l t e r n a t i v e hypothesis t o the adaptationist view and showed with success that i t could explain many cases o f i n t e r s p e c i f i c a g g r e s s i o n . territoriality  In a recent review of i n t e r s p e c i f i c  (Murray 1981), he c l a r i f i e 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 behaviour  h i s v i e w s and s t a t e d t h a t  may originate either as an adaptation  to t h e presence o f c o m p e t i t o r s , or as a f o 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  i n t r a s p e c i f i c aggression.  that normally  stimulate  He maintained, however, t h a t i t can o n l y be  adaptive i n the dominant species, and that i t r e s u l t s i n segregation, not coexistence. behaviour  The o r i g i n and s i g n i f i c a n c e o f i n t e r s p e c i f i c  is still  the focus  o f debate  territorial  (Morse 1980, Murray 1981,  Wittenberger 1981). Interspecific waterfowl,  although  territoriality many  cases  9  h a s n o t y e t been d e s c r i b e d i n  of i n t e r s p e c i f i c  competition  by  e x p l o i t a t i o n (Erskine I960, Myres 1957, Donaghey 197 5, E r i k s s o n 1979a, Nudds 1980,  and Eadie and Keast  1982) and i n t e r s p e c i f i c  aggression  (McKinney e t a l . 1978, Weller 1976, Nuechterlein and Storer 1985a, Livezey a n d Humphrey 1985a) have i n t e r s p e c i f i c aggression  been  documented.  i s s t i l l unclear  Storer 1985b, Livezey and Humphrey 1985b).  The s i g n i f i c a n c e o f  (Murray 1985, Nuechterlein and The breeding d i s t r i b u t i o n s of  Barrow's Goldeneye, Common Goldeneye and B u f f l e h e a d o v e r l a p i n B r i t i s h Columbia (Bellrose 1978,  Palmer 1976).  Erskine (1959, 1960) and McLaren  (1963, 196 9) have r e p o r t e d c o m p e t i t i o n between Bufflehead f o r nesting c a v i t i e s .  Barrow's Goldeneye and  Other d e s c r i p t i v e accounts indicate that  competition may not be r e s t r i c t e d t o nest s i t e s (Munro 1939, Myres 1957, Robertson  and S t e l f o x 1969, Palmer  1976).  Myres  (1957)  observed  aggressive i n t e r a c t i o n s between Barrow's Goldeneye and Common Goldeneye. Myres (1957) and Donaghey (1975) reported aggression of Bufflehead toward Common Goldeneye.  Barrow's  Goldeneye and B u f f l e h e a d  also  exhibit  aggression toward other waterfowl species (Myres 1957, 1959a, Andrew 1960, Sugden 1960, Robertson and S t e l f o x 196 9, Bengtson 1972, E r s k i n e 1972, Donaghey 1975). may  be s t r o n g .  This indicates that competition on the breeding A study  of i n t e r s p e c i f i c  competition  grounds  i n t h e 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 t h e c o n t r o v e r s i a l  phenomenon of i n t e r s p e c i f i c competition  (Connor and Simberloff 1979, 1984,  G i l p i n and Diamond 1984).  d)  Functions of T e r r i t o r i a l i t y Many p u b l i c a t i o n s have f o c u s e d on the f u n c t i o n s of t e r r i t o r i a l i t y  s i n c e Howard's  (1920) book emphasized  10  t h e concept  (Alexander 1921,  Jourdain 1921,  Lack and Lack 1933,  Carpenter 1958,  Brown 1964,  Nice 1941,  Davies 1978).  diversity  of  territorial  behaviour  functions  of  territoriality,  Hinde 1956,  Tinbergen  1957,  These reviews have stressed the  i n b i r d s and  suggested  i n c l u d i n g : p r o t e c t i o n of  a t t r a c t i n g or protecting mates, protecting food,  nest  several sites,  spacing out of p a i r s to  reduce predation, disease and e x p l o i t a t i o n competition, and prevention of overpopulation. Whether t e r r i t o r i a l behaviour l i m i t s p o p u l a t i o n d e n s i t y has been widely  debated  (Lack and  Patterson 1980). behaviour 1968,  A few  Lack 1933,  Brown 1969,  Klomp 1972,  recent studies i n d i c a t e strongly that t e r r i t o r i a l  can and does l i m i t l o c a l population density (Watson and  Krebs 1971,  Fjeldsa 1973 b, Verner  (in Patterson 1980), Watson and Moss 1980, V i l l a g e 1983).  1980,  1977,  Hilden 1979,  Klomp 1980,  Charles  1972  Dhondt e i a l . 1982,  There a r e i n d i c a t i o n s t h a t t e r r i t o r i a l i t y may  s i m i l a r r o l e i n some waterfowl species:  Jenkins  have a  Bufflehead successfully exclude  other p a i r s from small ponds (Donaghey 1975, Gauthier 1985), A f r i c a n Black Ducks are strongly t e r r i t o r i a l and must hold a t e r r i t o r y to breed (Ball e± aJL. 1978)  and  territorial  behaviour  during  the breeding  season  may  r e g u l a t e Mountain Duck (Tadorna tadornoides) and Shelduck p o p u l a t i o n s (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  e f f e c t on the population during three periods of the year: 1.  During s p r i n g ; when p a i r e d drakes defend t e r r i t o r i e s e a r l y i n the breeding  season, p a i r s may  be excluded from breeding, or a t l e a s t  excluded from the better feeding areas. 2.  During summer; when females with young defend t e r r i t o r i e s , broods can be excluded from productive or safe ponds, and young can be k i l l e d aggressive  females. 11  by  3.  During winter; when paired drakes defend t e r r i t o r i e s on the wintering ground,  some p a i r s may  female may bonds may  f a i l to obtain a productive t e r r i t o r y and  not be as f i t when the s p r i n g m i g r a t i o n a r r i v e s .  the Pair  break because the male cannot defend a t e r r i t o r y .  Whether t e r r i t o r i a l behaviour not i s not known as few  l i m i t s Barrow's Goldeneye density or  studies have been done on the species.  An answer  to t h i s question would greatly enhance our a b i l i t y to manage the species. 3) Species framework a) D i s t r i b u t i o n 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 d i s c o n t i n u o u s , w i t h small  populations  associated with  the  North  Atlantic  two  Ocean and  a  comparatively large population associated with the P a c i f i c Ocean (Bellrose 197 8).  The  estimated  two  Atlantic  populations  a t 2,000 i n d i v i d u a l s  are  (Gardarsson  isolated, 1978,  one  i n Iceland  1979a,b) and one  Quebec estimated at 2,500 i n d i v i d u a l s (Reed and Bourget 1977).  in  More than  90% of the world population of Barrow's Goldeneye breed west of the Rocky Mountains and w i n t e r on the P a c i f i c Ocean from A l a s k a t o C a l i f o r n i a . Current population estimates are crude.  B e l l r o s e (197 8) r e p o r t e d 45,000  birds i n Alaska, and 70,000 to 100,000 b i r d s i n B r i t i s h Columbia whereas Munro and G o o d c h i l d (1981) r e p o r t e d 186,000 b i r d s f o r B r i t i s h Columbia. Estimates for Washington, Oregon and C a l i f o r n i a indicate l e s s than 8,000 birds (Anonymous 1979, A few  B e l l r o s e 1978,  H a r r i s £t a l . 1954).  other s t u d i e s have d e s c r i b e d the d i s t r i b u t i o n of Barrow's  Goldeneye i n B r i t i s h Columbia (Swarth 1926,  Munro 1939), i n  Yellowstone  National Park (Skinner 1937), i n Alaska (Gabrielson and L i n c o l n 1959, 1963)  and i n the eastern United States (Griscom 1945, Although  King  Hasbrouck 1944).  the population estimates are questionable, B r i t i s h Columbia 12  appears to be the center of abundance of the species.  Barrow's Goldeneye  i s the o n l y s p e c i e s of w a t e r f o w l i n Canada t h a t has most of the w o r l d 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 s p e c i e s p a r t i c u l a r l y s u s c e p t i b l e t o environmental  threats.  b) Behaviour and ecology of Barrow's Goldeneye The e l a b o r a t e c o u r t s h i p behaviour thoroughly described (Sawyer 1928,  of Barrow's Goldeneye has been  Myres 1957,  1959a, 1959b, N i c k e l l  1966,  Palmer 1976, Cramp and Simmons 1977, P o u r t o i s 197 8). Some authors have described the aggressive behaviour of the drake (Myres 1957, but  the  causes and  investigated.  consequences  of  such  aggression  B r i e f r e p o r t s (Andrew 196 0, Sugden 1960,  Palmer 1976),  have not  been  Robertson and  S t e l f o x 196 9) suggest t h a t f e m a l e s become h i g h l y a g g r e s s i v e a f t e r the young have hatched. Only a few Goldeneye. Columbia.  studies have documented the breeding biology of Barrow's  Palmer (1976) r e p o r t e d the work of Mary Jackson i n B r i t i s h Her work complemented the e a r l i e r observations of Munro (1918,  1939), Brooks (1920) and Bent (1923), and p r o v i d e d b a s i c i n f o r m a t i o n on c l u t c h s i z e and breeding success f o r the s p e c i e s . I c e l a n d i c p o p u l a t i o n by Bengtson (1971, 1972) a v a i l a b l e i n f o r m a t i o n on the breeding  Work on the s m a l l  p r o v i d e s the o n l y o t h e r  ecology of Barrow's Goldeneye.  Barrow's Goldeneye n e s t p r i m a r i l y i n t r e e 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 I c e l a n d they nest i n  c a v i t i e s on the ground among b a s a l t rocks, (Bengtson 197 0).  Similarly,  they use h o l e s i n b a s a l t c l i f f s i n e a s t e r n Washington ( H a r r i s 1954) . 13  al.  Barrow's Goldeneye feed on invertebrates during the breeding season, e s p e c i a l l y 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, M i t c h e l l 1952, Vermeer 1982, Koehl e t a l . 1984). This short review l i s t s most of the published l i t e r a t u r e on Barrow's Goldeneye a t the time my study was i n i t i a t e d .  c) Common Goldeneye and Bufflehead By  1980, s e v e r a l  detailed  congeners o f Barrow's Goldeneye.  s t u d i e s had been p u b l i s h e d on t h e Works by Munro (1942), E r s k i n e (1972)  and Donaghey (1975) provided a thorough overview and t e r r i t o r i a l behaviour of Bufflehead. studied i n Europe and North America  of the breeding biology  Common Goldeneye had been widely  (Munro 1939, Siren 1952, Carter 1958,  Gibbs 1961, t r i n c e 1965, 1968, R a j a l a and Ormio 1971, E r i k s s o n 197 9b). During the course of t h i s study, new studies have furthered our knowledge of the genus Bucephala. territoriality  Gauthier (1985) presented a d e t a i l e d analysis of  i n the Bufflehead, and Dow (1982) summarized a long-term  study o f the b r e e d i n g b i o l o g y o f Common Goldeneye.  She a l s o p u b l i s h e d  s e v e r a l papers on the f a c t o r s i n f l u e n c i n g t h e i r reproductive success i n nest boxes (Dow and Fredga 1983, 1984,  1985,  Fredga and Dow 1983, 1984).  4) Focus o f the study The main questions I asked were: 1.  I s the t e r r i t o r i a l behaviour of Barrow's Goldeneye s i m i l a r t o that of Bufflehead?  2.  A r e CoiMi.on Goldeneye t e r r i t o r i a l  i n North America  and, i f so, i s  t h e i r behaviour s i m i l a r t o that of Barrow's Goldeneye and Bufflehead?  14  3.  Are the three 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 evaluate t h i s ,  t e r r i t o r i a l i t y i n B a r r o w ' s Goldeneye?  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  To  reproductive  s u c c e s s o f B a r r o w ' s Goldeneye 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 of 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 by n e s t s i t e availability?  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 affect 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 Goldeneye?  9.  Will  an i n c r e a s e i n B a r r o w ' s Goldeneye  density negatively  influence  Bufflehead density? 10.  Can t e r r i t o r i a l b e h a v i o u r  i n Barrow's Goldeneye  limit  breeding  density? Questions Chapter IV, Each  1 to 5 are addressed i n Chapter  q u e s t i o n s 8-9 i n Chapter V, of  III,  q u e s t i o n s 6-7  and q u e s t i o n 10 i n Chapter  these questions has both  ever  b e e n done o n  b r e e d i n g e c o l o g y of B a r r o w ' s Goldeneye i n N o r t h A m e r i c a . however,  s i g n i f i c a n c e and f u n c t i o n s of I  i n s t a l l e d nest  boxes  to  the  The e m p h a s i s o f  was on 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 of  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  VI.  t h e o r e t i c a l and 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  the study,  in  intra-  of B a r r o w ' s Goldeneye and on  the  t e r r i t o r i a l i t y w i t h i n the genus B u c e p h a l a . increase breeding  d e n s i t i e s of  Goldeneye and t h u s f a c i l i t a t e t h e s t u d y of t e r r i t o r i a l i t y .  Barrow's  Monitoring  of  n e s t boxes p r o v i d e d d a t a on 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 Goldeneye and t h e i r  use of n e s t boxes.  15  I monitored s u r v i v a l  of  Barrow's Goldeneye  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 any e f f e c t  t e r r i t o r i a l i t y on r e p r o d u c t i v e s u c c e s s .  I devoted s p e c i a l a t t e n t i o n  of to  t h e i n t e r a c t i o n s between B a r r o w ' s Goldeneye and B u f f l e h e a d . I  have  Chapter I I , Chapter I I I ,  organized  the  remainder  of  the  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 s i s as  follows:  t h e g e n e r a l methods u s e d .  I d e s c r i b e , a n a l y s e , and 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  Barrow's Goldeneye  and i t s c o n g e n e r s .  In Chapter  IV,  I identify  q u a n t i f y some of 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 by B a r r o w ' s and t h e i r n e s t i n g s u c c e s s .  In Chapter V,  In In of and  Goldeneye  I a n a l y s e and compare 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 Chapter V I  I review  the  major 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 Appendix 1 , territorial  I d e s c r i b e t h e e f f i c i e n c y of m i r r o r t r a p s t o  waterfowl.  I n Appendix 2 ,  capture  I present evidence suggesting the  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 Goldeneye.  In Appendix 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 brood amalgamation i n Barrow's Goldeneye, f o u r c a s e s of p o l y g y n y  i n Barrow's  P o r t i o n s of Chapter I I I (Savard  1982b,c,  separately  (Savard  1984). 1985a,b,  Appendices  16  I  document  Goldeneye.  and C h a p t e r  1986).  and i n Appendix 4 ,  IV have a l r e a d y been p u b l i s h e d 1,  2 and  4 have  been  published  Chapter I I : General methods  17  1) STUDY SITES a) Riske Creek (summer) T h i s i s t h e main study area. Creek  I t c o v e r s about 100 km^ near  i n c e n t r a l B r i t i s h Columbia.  Plateau,  1000 m above s e a l e v e l  the C a r i b o o - A s p e n - L o d g e p o l e of K r a j i n a  (1969, 1973).  by Agropyron menziesii,  It  (Fig. 1).  Riske  i s l o c a t e d on the C h i l c o t i n The study a r e a i s i n c l u d e d i n  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  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  spicatum and stands o f Populus t r e m u l o i d e s , and Pinus c o n t o r t a  Pseudotsuga  ( C a n n i n g s a n d S c u d d e r 197 8 ) .  The most  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 o f t h e a r e a i s t h e rainshadow e f f e c t o f the Coast  Mountains  w i t h June having  ( B e i l 1974).  P r e c i p i t a t i o n averages  the highest monthly  precipitation.  35 cm a n n u a l l y , Average  annual  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 January and 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 temperatures a r e large  (Cannings a n d Scudder Lakes  (n=117).  within  1978).  t h e study  Conductivity  area  range  i n size  from  0.1 t o 5 4 . 0 h a  measurements vary g r e a t l y between these 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 25°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  f i s h e s (Scudder 1969). important, 1985).  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  a n d may a f f e c t  Cannings  s t r e a m s and a r e d e v o i d o f  the aquatic fauna  (1973), Topping  and Scudder  ( S c u d d e r 196 9 ,  Lancaster  (1977) a n d S p e n c e  (1979)  present d e t a i l e d a n a l y s i s of the 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 the study a r e a .  I n t h i s study 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  aggression of Barrow's Goldeneye, and studied t h e i r breeding b i o l o g y i n detail.  18  Fig. 1  L o c a t i o n of s t u d y a r e a s .  b) Columbia V a l l e y (summer) T h i s study s i t e was l o c a t e d i n t h e upper s e c t i o n of the Columbia v a l l e y near Invermere, B r i t i s h Columbia, Canada (Fig. 1).  The v a l l e y i s  p a r t of the Rocky Mountain Trench and i s b o r d e r e d on the west by the S e l k i r k Range and on the e a s t by v a r i o u s ranges of the Rocky Mountains. The v a l l e y can be divided i n t o two habitats:  (1) the flood p l a i n 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 t o 900 micromhos/cm;  (2) the  benches, 300 m above the f l o o d p l a i n , c o n t a i n s m a l l , i s o l a t e d l a k e s and ponds t h a t v a r y g r e a t l y i n c o n d u c t i v i t y . A sample of 12 upland ponds averaged 147 9+371 micromhos/cm i n c o n d u c t i v i t y and ranged from 220 t o 4,200 micromhos/cm.  The ponds on the benches are t h e r e f o r e s i m i l a r t o  those found near Riske Creek. This s i t e was chosen to look a t the t e r r i t o r i a l behaviour of Common Goldeneye and a t the spacing behaviour of the three species of Bucephala i n a zone of aympatry. c) Vancouver  (winter)  This study s i t e was located along the shores of Burrard Inlet i n and near Vancouver, B r i t i s h Columbia  (Fig. 1).  The shoreline consisted of a  mixture of sandy beaches and rocky shores. Goldeneye fed along the rocky shores, where they m a i n l y took mussels (Vermeer 1982).  At t h i s s i t e , I  s t u d i e d the w i n t e r i n g 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 1)  were c a p t u r e d on t h e b r e e d i n g a r e a s i n two  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 of  ways:  incubation.  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 (see A p p e n d i x  1 f o r d e t a i l s of the t r a p and i t s e f f i c i e n c y ) .  captured b i r d s were weighed, v a r i o u s colours (red, w h i t e , (circle,  oval,  square,  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 yellow,  cross,  Y)  green, gray,  b l u e , b l a c k ) and shapes  (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 to  facilitate  All  i d e n t i f i c a t i o n of  individuals.  Birds  paint,  rapidly  became  accustomed t o the 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 of 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 o f G o l l o p and M a r s h a l l (1954).  criteria  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 based on plumage g r o w t h .  The correspondence of t h o s e age c l a s s e s  w i t h t h e age of t h e d u c k l i n g s i n d a y s was d e r i v e d f r o m S c h n e i d e r and  Erskine  (197 2)  for  Bufflehead.  E r s k i n e ' s (197 2) d a t a d i f f e r e d , Scaup  (Aythya a f f i n i s )  (Taber 1971).  Schneider's  (196 5)  I u s e d t h e age c l a s s e s g i v e n f o r  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 age  Such d a t a a r e n o t a v a i l a b l e f o r  and  Lesser classes  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  had s i m i l a r g r o w t h p a t t e r n s . Goldeneye;  Because  (1965)  Scaup  Barrow's  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  Common Goldeneye  of  (Gibbs 1961).  Goldeneye 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 whereas those w i t h predominantly  dark  bills  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  21  were c l a s s i f i e d a s s u b a d u l t s . incubation,  when t h e b i l l s o f  This adult  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 t o 1984, four p a i r counts were done w i t h i n a 2week 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.  I t took from 2 t o 2 1/2 days t o complete a survey of t h e 117  ponds on the Riske Creek study area.  After broods had hatched, the ponds  were surveyed from 3 t o 4 times to determine the number of broods on the study area.  Because h a t c h i n g i s spread over s e v e r a l weeks, o n l y an  estimate can be obtained f o r numbers of broods.  d) S t a t i s t i c a l analysis Means a r e p r e s e n t e d throughout t h e t e x t + S.E. u n l e s s o t h e r w i s e specified.  Chi-square t e s t s were done on the observed f r e q u e n c i e s .  Student's T-test was used t o detect s i g n i f i c a n t differences between means. Data were l o g t r a n s f o r m e d when the v a r i a n c e of the two samples unequal.  was  Mulciple comparisons were performed using the Student Newman-  Keuls test (Zar 1974).  Because some aspects were studied i n only one year  whereas o t h e r s were s t u d i e d d u r i n g s e v e r a l y e a r s , t o t a l s v a r y between tables.  22  Chapter I I I :  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 Barrow's Goldeneye,  and t o c o n s i d e r i t s f u n c t i o n s .  chapter i s divided i n t o three parts. quantify  I  I d e s c r i b e and  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 the b r e e d i n g  and w i n t e r i n g a r e a s , part,  In the f i r s t p a r t ,  The  and o f  females during brood r e a r i n g .  d e s c r i b e and q u a n t i f y  I n t h e second  i n t e r s p e c i f i c aggression.  a n a l y s e v a r i o u s a s p e c t s of t h e t e r r i t o r y i t s e l f .  Finally,  I  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 of Common Goldeneye 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 of t e r r i t o r i a l i t y i n t h e genus.  METHODS I n 1982 I e s t i m a t e d t h e t i m e b u d g e t s of 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 hours. several  hours of o b s e r v a t i o n .  At  2 minute i n t e r v a l s ,  Observation periods l a s t e d from 1 to 4 I o b s e r v e d e a c h member o f  seconds and r e c o r d e d t h e i r  following categories: preening,  dominant  activity.  for  used  the  I  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 ) ,  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  displays).  a pair  (non-aggressive  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 an e s t i m a t e of  budget of each b i r d under o b s e r v a t i o n .  the  P r e l i m i n a r y s a m p l i n g had shown  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  several minutes duration.  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 . s a m p l i n g e f f o r t was d i s t r i b u t e d as f o l l o w s : between 0900 h and 1200 h , All  time  For Total  56 h b e f o r e 0 900 h , 4 9 h  36 h a f t e r 1800 h .  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 and brood c o u n t s  (see G e n e r a l  Methods)  were r e c o r d e d .  Intensive  behavioural  observations  were 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 of i n t e r a c t i o n s between territorial pairs.  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 of 24  pairs  (264 h)  and  o f f e m a l e s w i t h b r o o d s (410  h).  During these observations,  I observed  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 and r e c o r d e d a commentary 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  on a l l identity  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  classified  the  reactions  of  territorial  birds  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 and grouped them i n t o t h r e e threat,  a t t a c k and f i g h t .  A threat c o n s i s t e d of  to  intruders  categories:  the b i r d elongating  its  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 body, 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 or t u r n i n g sideways.  A t t a c k s were of t h r e e t y p e s :  1)  toward the v i c t i m ,  2) r u s h o v e r  3) a e r i a l  Fights  the water,  and  sometimes o c c u r r e d between neighbouring males.  underwater  dive  pursuit.  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 was u s u a l l y p r e c e d e d by a t h r e a t and an attack.  For each i n t e r a c t i o n , however,  I only recorded the highest l e v e l  reached. I n 1982,  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 Goldeneye.  I r e c o r d e d t h e number of 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 Barrow's Goldeneye  drake  without  a t t a c k e d , and d e f i n e d t h i s a s a case of t o l e r a n c e . r e c o r d s w e r e independent o b s e r v a t i o n s , t o l e r a t e d only once, goldeneye drake.  If  even i f  it  being threatened  or  To e n s u r e t h a t  the  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  stayed for  s e v e r a l minutes near  the  two or t h r e e b i r d s were t o l e r a t e d s i m u l t a n e o u s l y ,  they were recorded as a group.  Groups c o n t a i n i n g s e v e r a l s p e c i e s were  r e c o r d e d a s 1 t o l e r a n c e per s p e c i e s .  The f r e q u e n c y of 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 because 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 Goldeneye and 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 of b i r d s p r e s e n t on t h e pond,  itie number of b i r d - h o u r s was used when e x a m i n i n g t h e number  25  of i n t e r a c t i o n s recorded for each species. groups:  I divided waterfowl into three  1) dabbling ducks, which included M a l l a r d (Anas p l a t y r h y n c h o s ) ,  Gadwall (A. strepera), American Wigeon (A. americanus), Northern P i n t a i l (A., acuta), Green-winged T e a l (A. c r e c c a ) , Blue-winged T e a l Northern Shoveler  (A_. cjypeata) ?  (Aythya americana),  discors),  2) diving ducks, which included Redhead  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 d i s t i n g u i s h e d i n the f i e l d , marila i s a migrant i n the area whereas a f f i n i s breed i n the study area);  S u r f Scoter  jamaicensis):  ( M e l a n i t t a p e r s p i c i l l a t a ) and Ruddy Duck  (Oxyura  3) Congeners, B u f f l e h e a d (Bucephala a l b e o l a ) and Common  Goldeneye (B. C l a n g u l a ) .  A l l these s p e c i e s except the Surf Scoter and  Greater Scaup breed i n the study area.  RESULTS 1) I n t r a s p e c i f i c Aggression a) T e r r i t o r i a l behaviour of p a i r s B r e e d i n g a r e a s - 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 territorial  male t y p i c a l l y r e a c t e d t o  intruders by adopting a threat posture, f l a t t e n i n g and s l i g h t l y submerging h i s body, and e l o n g a t i n g h i s neck on the water (see Myres 1959b, Palmer 1976). him  I f the intruder persisted, the t e r r i t o r i a l male then swam toward  i n the threat  posture  and a t t a c k e d  him e i t h e r by d i v i n g and  resurfacing underneath or by rushing a t the intruder flapping h i s wings on the water.  Usually the intruder took f l i g h t but i n some cases f i g h t s and  even a e r i a l p u r s u i t ensued.  C o n f r o n t a t i o n s between males r e s u l t e d i n  proportionally fewer attacks  (42%)  (63%),  females  than confrontations with either p a i r s  (83%) or subadults  26  (76%) ( F i g . 2).  This  i s because  TYPE  OF  MALE " =997  INTERACTION  PAIR n= 2 24  CONSPECIFIC  Fig.  2  FEMALE  SUB-ADULT  n= i i 2  n = 24  INTRUDER  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 between t e r r i t o r i a l male B a r r o w ' s Goldeneye and i n t r u d e r s d u r i n g the 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 t o be more r i t u a l i z e d and l e s s v i o l e n t , r e s u l t i n g i n proportionally more threats than a t t a c k s (Fig. 3). Strange p a i r s i n t r u d i n g i n t o a t e r r i t o r y e l i c i t e d r e a c t i o n from t e r r i t o r i a l drakes. chased o f f the t e r r i t o r y .  the s t r o n g e s t  They were immediately a t t a c k e d and  T h i s i s not r e f l e c t e d  i n Fig. 2  because  i n t e r a c t i o n s with neighbouring p a i r s and strange p a i r s were not recorded separately. Although l e s s intense, interactions between neighbours l a s t e d longer. Drakes often made lengthy displays a t the boundaries of t h e i r  territories.  They f a c e d each other 3 t o 10 m a p a r t i n t h r e a t p o s t u r e , d i v i n g r e s u r f a c e a t the same l o c a t i o n .  to  Males a l s o swam p a r a l l e l t o 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 l a s t e d f o r 20 minutes. These d i s p l a y s o c c u r r e d a l m o s t e x c l u s i v e l y between n e i g h b o u r i n g t e r r i t o r i a l  drakes  (Fig. 2). T e r r i t o r i a l drakes were dominant t o a l l intruders on t h e i r t e r r i t o r y . On over 20 o c c a s i o n s I saw males chase a t r e s p a s s i n g n e i g h b o u r i n g male back  into h i s territory  t o be  chased  i n t u r n 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 a t t a c k e d f e m a l e s t h a t t r e s p a s s e d i n t o t h e i r territory.  There was no obvious e f f e c t of the presence of the female on  the  t e r r i t o r i a l aggressiveness of the male.  not  a f f e c t e d 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.  Time budgets of males were  4). The p r o p o r t i o n of time spent i n t e r r i t o r i a l defense  11% when the female was present and 13% when she was absent.  28  was  PAIRED  M A L E  UB ACH€L-OR  n B87  n  I N T R U D E R  Pig. 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 bachelor males. (x2=23.28, df=l, P<0.001; n=number of interactions)  29  B  48  Table 1.  T e r r i t o r i a l defense (number of i n t e r a c t i o n s ) by paired drakes i n r e l a t i o n t o the presence of their mates . 1  Females present (35 h ) Attack  Boundary Display  Male  14  34  18  Pair  -  3  Female  14  No. of interactions/hour  (60 h)  2  Threat  Threat  Attack  Boundary Display  66  13  18  19  50  -  3  1  3  4  8  -  -  -  1  11  -  12  37  18  69  15  32  23  70  Intruder  Total  Females absent  Total  1.97  Two neighbouring paired males were observed with and without t h e i r mates. Number of hours of observation.  Total  1.18  RE8TINQ  M A L E  PREENING  A C T I V I T Y  AGQRE88ION  DISPLAYING  :  Percentage of time spent by Barrow's Goldeneye males i n various activities in relation to the presence or absence of t h e i r 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 others the  (Tables 2 - 3 ) .  l o c a t i o n of  territories.  The number and t y p e s o f  the  territory  Pair B  t h e r e f o r e was t h e v i c t i m of pairs. B  or  was  the  central  pair  upon  neighbouring (Fig.  5a)  and  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  other  P a i r s A and D (Table 3) had 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 C,  (Fig.  i n t e r a c t i o n s depended  and t h e d i s t r i b u t i o n of  ( T a b l e 2)  than  because  5b).  goldeneye  their  Also  drakes  t h a n d r a k e A.  t e r r i t o r i e s bordered B and  fewer  territories  interactions with  was  m o d i f i e d d a i l y by t h e a r r i v a l or d e p a r t u r e of o t h e r p a i r s w h e r e a s  the  of  space o c c u p i e d by p a i r s A ,  other  E and F  territories  The  C had  Bufflehead  than  B and C r e m a i n e d c o n s t a n t  throughout  the  observation  period. 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 and s p e n t t h e i r t i m e f e e d i n g and r e s t i n g w i t h i n t h e i r mate's t e r r i t o r y .  Females  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 males  (Fig.  6). Both m a l e s and f e m a l e s spent s i m i l a r amounts of  p r e e n i n g and d i s p l a y i n g .  T h i s d i v i s i o n of  time  time suggests t h a t i n  the  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 , and 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 of t h e m a l e ' s t i m e , may n o t be 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 frequent spent  activity  feeding  of  by  m a l e s was r e s t i n g .  males and f e m a l e s  the female.  In f a c t ,  the  most  The average p r o p o r t i o n o f  time  respectively  d i d not  differ  s i g n i f i c a n t l y between t h e t h r e e sampled p e r i o d s (0500-0900 h ; 0900-1200 1700-2100 h)  (P=0.9 f o r m a l e s and P=0.7 f o r f e m a l e s ) .  h;  E a r l y i n t h e season  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 sometimes i n c i t e d t h e i r m a l e s t o attack intruders,  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  females.  32  Table  2.  Comparison of aggressive interactions of three 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 on contiguous 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 w e r e 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  Victim  Pair  A  Pair  Pair  A  —  19  Pair  B  22  Pair  C  Total  Pair  B had  the  B  1  Pair  C  Total  7  26  —  51  73  2  32  —  34  24  51  58  central  territory  33  (see F i g . 5 ) .  133  Table  3.  Number o f a g g r e s s i v e interactions i n which each territory 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 l a k e 89 ( 1 9 8 1 ) . Territory  holder  Barrow's Goldeneye  Bufflehead  A  B  C  D  E  F  Total  39  23  21  27  13  7  130  Bufflehead  6  2  4  13  8  8  41  Other  2  3  8  0  0  6  19  Total  47  28  33  40  21  21  190  Aggressor  or  victim  Barrow's Goldeneye  see  Fig. 5 for territory  locations.  34  L A K E 13  LAKE 8 8  100 meters  A BC D E F -  Fig. 5  BARROW'S GOLDENEYE TERRITORIES B U F F L E H E A D TERRITORIES  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  60 -  FEEDING  RESTING  PREENING  AGGRESSION  DISPLAYING  M A L E AND F E M A L E ACTIVITY  Fig. 6  A v e r a g e % o f t i m e ( ± S . E . ) s p e n t by male and 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 within their territory. (Nine p a i r s were o b s e r v e d and o b s e r v a t i o n t i m e p e r p a i r ranged between 7 h and 28 h a v e r a g i n g 1 6 . 3 h . )  36  The sex r a t i o of Barrow's Goldeneyes was biased toward males.  Males  outnumbered f e m a l e s by a f a c t o r o f 1.43+0.03 (n=8 counts over 4 y e a r s , each e s t i m a t e based on more than 500 b i r d s ) . skewed i f only unpaired b i r d s are considered:  The r a t i o i s even more  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 B u f f l e h e a d a l s o m a i n t a i n e d territories was  (Tables 4-5).  The t e r r i t o r i a l behaviour  s i m i l a r t o t h a t of the Barrow's Goldeneye:  between males r e s u l t e d i n a t t a c k s (30%)  intraspecific  of Common Goldeneye  fewer c o n f r o n t a t i o n s  (X =31.21, df=3, P<0.001) than 2  c o n f r o n t a t i o n s w i t h p a i r s (65%), f e m a l e s (68%) and yearlings (90%). The l a s t t h r e e c l a s s e s of i n d i v i d u a l s d i d 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 o f being a t t a c k e d (X2=2.23, df=2, p=0.33).  Bufflehead also  behaved s i m i l a r l y , excluding a l l c o n s p e c i f i c s b u t t h e i r mate.  However,  contrary t o Barrow's Goldeneye, attacks were as prominent towards males (in 86% of confrontations) as towards p a i r s (75%)  (X =1.25, df=l, P=0.26). 2  T h i s i s because few contiguous B u f f l e h e a d t e r r i t o r i e s were  observed.  T h e r e f o r e , most of the i n t e r a c t i o n s i n v o l v i n g males were w i t h b a c h e l o r males, whereas i n Barrow's Goldeneye, most i n t e r a c t i o n s w i t h  males  involved neighbouring t e r r i t o r i a l drakes and r a r e l y r e s u l t e d i n a t t a c k s (Fig. 3). Female Common Goldeneye and B u f f l e h e a d , l i k e f e m a l e Barrow's Goldeneye, r a r e l y took part i n t e r r i t o r i a l  defense.  Boundary displays were frequent between neighbouring p a i r s of Common Goldeneye.  They averaged 6 min (range = 0.5 - 19 min,  n=33).  Goldeneye p a i r s defended a t e r r i t o r y on a 4 ha pond.  Two Common  During  4 h of  o b s e r v a t i o n s , t h e two males d i d 13 and 16 boundary d i s p l a y s l a s t i n g a t o t a l of 78 min and 81 min respectively.  Sometimes a male would perform a  boundary display alone, but t h i s would usually spur s i m i l a r displays from  37  Table  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 and i n t r u d e r s (during 50 h o f observation). Type o f i n t e r a c t i o n  Intruder  Threat  1  Attack  Total  Male  121  51  172  Pair  8  15  23  Female  9  19  28  Subadult  1  9  10  Group  1  4  5  Total  140  98  238  I n c l u d e s boundary  displays.  38  Table  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 b e t w e e n 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 and i n t r u d e r s ( d u r i n g 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). Type o f i n t e r a c t i o n  Intruder  Threat  1  Attack  Total  Male  12  74  86  Pair  4  12  16  Female  -  3  3  Subadult  -  11  11  16  100  116  Total  1  Includes  boundary  displays.  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 s t a t u s changed w i t h the l o c a t i o n of the encounter, each male being dominant i n h i s t e r r i t o r y . 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 s h o r e l i n e s . Barrow's Goldeneye have l o n g l a s t i n g p a i r bonds and one p a i r was seen t o re-unite on i t s wintering area (Appendix  2).  essentially F i g . 2).  The t e r r i t o r i a l behaviour of p a i r e d drakes i n w i n t e r i s identical  Boundary  t o t h a t observed on the b r e e d i n g a r e a s (Table 6,  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 t o be t h r e a t e n e d whereas b a c h e l o r males were most o f t e n a t t a c k e d (Table 6, X =16.07, d f = l , P=0.000). 2  All  conspecifics but the mate were excluded from the t e r r i t o r y . Spacing behaviour of Common Goldeneye and Bufflehead has not yet been s t u d i e d i n w i n t e r 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 s p e c i e s being a g g r e s s i v e toward  c o n s p e c i f i c s but I d i d n o t d e f i n i t e l y defended.  other  e s t a b l i s h i f t e r r i t o r i e s were  However, i t seems t h a t p a i r s o f Common Goldeneye  isolate  themselves from groups of unpaired birds.  b)  T e r r i t o r i a l behaviour of females with broods F o l l o w i n g h a t c h i n g , female Barrow's Goldeneye w i t h young became  highly aggressive and defended size.  t e r r i t o r i e s which averaged  0.91±0.08 ha i n  They d i d not t o l e r a t e any other a d u l t goldeneye w i t h i n 10 m of  t h e i r young.  A l l conspecifics were excluded from the t e r r i t o r y .  As with  paired drakes, boundary d i s p l a y s 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 Goldeneye drakes and conspecifics in winter (number of 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 o f o b s e r v a t i o n ; 10 pairs observed).  Threat  Attack  Boundary Displays  Total  3  8  16  27  17  49  -  66  5  6  -  11  26  24  -  50  Subadult  3  4  -  7  Group  2  5  -  7  Total  56  96  16  168  Territorial Bachelor Female Pair  male  male  41  Table  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 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 o f o b s e r v a t i o n ; m o r e t h a n 50 b r o o d s observed). Type o f i n t e r a c t i o n  Intruder  Threat  Attack  Male  16  35  Female  65  Subadult Female w i t h Young Total  brood  Boundary D i s p l a y  Total  —  51  431  -  4 96  -  4  -  4  64  43  8  31  153  544  42  141  141  248 39 838  moving and a l o n e a d u l t b i r d was i n i t s path.  On s m a l l ponds, however,  l o n e goldeneyes were a t t a c k e d u n t i l they l e f t the pond.  The a g g r e s s i v e  behaviour of f e m a l e s was s i m i l a r t o t h a t of the t e r r i t o r i a l male: she adopted a t h r e a t p o s t u r e , swam toward the i n t r u d e r , and then d i v e d o r 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 o f t e n e r u p t e d between f e m a l e s w i t h broods. Barrow's Goldeneye (Fig. 7).  Young  spent t w i c e as much time f e e d i n g a s f e m a l e s d i d  Females spent s i g n i f i c a n t l y more t i m e i n a g g r e s s i o n and i n  a l e r t posture than young. Goldeneye broods usually attempted t o avoid each other.  I attempted  several times t o drive a brood i n t o the t e r r i t o r y of another brood.  This  proved d i f f i c u l t because t h e f e m a l e of t h e brood being d r i v e n would usually avoid entering another t e r r i t o r y or would swim out of i t as soon as the disturbance ceased.  On three occasions, however, f i g h t s broke out  between the two f e m a l e s and t h e i n t r u d i n g brood was d r i v e n o f f t h e territory.  One i n t e r a c t i o n l a s t e d 30 min w i t h t h e defending f e m a l e  constantly i n threat posture although the other female and her brood were hidden i n the reeds.  Three f i g h t s occured before the intruding brood was  driven o f f . When two or more broods used t h e same l a k e , occasionally occurred between broods. large numbers of broods.  exchange of young  This was most common on lakes with  Over the f i v e years of the study, the proportion  of broods i n v o l v e d i n a t l e a s t one exchange averaged 38±4% Brood  mixing  aggressiveness.  appeared  t o be an i n d i r e c t  result  of  (Table 8).  territorial  Females with broods are extremely aggressive and do not  tolerate any other conspecifics i n t h e i r t e r r i t o r y observed the following outcomes of brood encounters: t e r r i t o r i a l boundaries:  (Tables 7-9).  I have  1) Establishment of  In a t l e a s t f i v e instances two broods shared the 43  FEEDING  RESTING  ACTIVITY  Fig. 7  AGGRESSION  OF FEMALE AND YOUNG B A R R O W ' S  ALERT GOLDENEYE  Average % of time (with 95% Confidence l i m i t s ) 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 . (Duration of o b s e r v a t i o n s t o t a l l e d 27 5 h and 287 h f o r f e m a l e s 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 d u r i n g 166 o b s e r v a t i o n p e r i o d s distributed unequally between 32 broods.)  44  Table 8.  Brood amalgamation i n Barrow's Goldeneye and Bufflehead. Barrow's Goldeneye  No. of broods Year  No. of broods % mixing mixing  Bufflehead No. of broods moving  No. of broods  1  No. of broods % mixing mixing  No. of broods moving  1980  84  27  32  3  67  15  22  6  1981  84  23  27  5  73  18  25  9  1982  85  36  42  8  78  35  45  8  1983  95  39  41  14  73  38  52  11  1984  108  53  49  20  79  22  28  14  Total  456  178  39  50  35  48  1  Broods that changed lakes during brood rearing.  370  128  Table  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 y o u n g , and i n t r u d e r s ( d u r i n g 110 h o f o b s e r v a t i o n ; more t h a n 20 b r o o d s o b s e r v e d ) . Type o f  Intruder  Threat  Attack  Male  interaction Boundary D i s p l a y  1  Total 1  Female  1  19  -  20  Female w i t h b r o o d  8  15  9  32  Total  9  35  9  53  46  same l a k e but defended e x c l u s i v e t e r r i t o r i e s from which they excluded other broods. occasionally.  Boundary d i s p l a y s were f r e q u e n t , f i g h t s were observed Exchanges of young between broods were frequent.  2) E x p u l s i o n of a brood from the l a k e :  At l e a s t 13 cases of brood  e x p u l s i o n were recorded, t h r e e of which I w i t n e s s e d (Appendix 3).  In  these three cases the brood was expelled following a v i o l e n t f i g h t between the  females that l a s t e d over 10 minutes. 3)  Death of young:  young Barrow's Goldeneye kill  I witnessed two female Barrow's Goldeneye  kill  (see Appendix 3) and a female Barrow's Goldeneye  2 young B u f f l e h e a d . In each case, the v i c t o r i o u s female was  the  aggressor and the young of the d e f e a t e d female the v i c t i m . 4)  Complete  or p a r t i a l brood amalgamation:  During a f i g h t between  two females, the young became a l e r t and stayed together. Occasionally the young of the two broods mixed and one female g a i n e d young whereas the other l o s t some.  In four cases where mixing involved young of d i f f e r e n t  ages, the female with strange young was aggressive toward them a t f i r s t , but  e v e n t u a l l y t o l e r a t e d them.  The s t r a n g e young u s u a l l y 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 l e a s t 7 of  the 17 young of the v i c t o r i o u s female.  Six young disappeared f o l l o w i n g  t h i s encounter. 5)  Various combinations of the above:  Outcomes of female encounters  varied considerably due to various factors I w i l l discuss l a t e r . I observed s e v e r a l  f i g h t s between f e m a l e s and s e v e r a l  displays a t the edge of t e r r i t o r i e s . and r e t u r n t o t h e i r own t e r r i t o r y . w i t n e s s e d i n d e t a i l i n Appendix not  boundary  Most often both females would stop I d e s c r i b e the encounters t h a t were  3. These cases i n d i c a t e t h a t f e m a l e s do  attempt to steal the young of other females but rather t r y to exclude  47  them from t h e i r t e r r i t o r y .  Considering the violence and duration of some  of the f i g h t s , defeated females do not abandon their young but are forced to leave them. When the young are 5 or 6 weeks o l d some females leave the breeding ponds to f l y to molting lakes.  Their remaining young may then amalgamate  together and form l a r g e groups.  T h i s a g g r e g a t i o n 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 t i m e s , 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  occur between them.  The low frequency of these occurrences however may be  due t o the f o l l o w i n g : Barrow's Goldeneye  can  1. Young B u f f l e h e a d a r e h a l f the s i z e of young  of the same age and may  be k i l l e d more r e a d i l y .  2. Bufflehead females avoid Barrow's Goldeneye broods. 3. Because of t h e i r greater a g i l i t y female Bufflehead are very successful i n decoying female goldeneye from t h e i r 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 t o t h a t o f Barrow's Goldeneye.  similar  Lone female B u f f l e h e a d were m o s t l y  a t t a c k e d whereas boundary d i s p l a y s o c c u r r e d between broods (Table 9). Time budgets of f e m a l e s and young were s i m i l a r t o t h a t of Barrow's Goldeneye, with young spending more time feeding than the female, whereas she spent more time i n a g g r e s s i o n and a l e r t p o s t u r e (Fig. 8). Barrow's Goldeneye and Bufflehead females played the same r o l e as the male played e a r l i e r i n the season,  they defended the t e r r i t o r y and allowed t h e i r  young t o f e e d u n d i s t u r b e d .  .CP4  The young spent on average as much t i m e  feeding as d i d the female i n the spring.  48  Fig. 8  Average % of t i m e (with 95% Confidence l i m i t s ) spent by female and young Bufflehead i n various 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 . (Observations t o t a l l e d 145 h and 143 h f o r f e m a l e s 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 d u r i n g 88 o b s e r v a t i o n p e r i o d s d i s t r i b u t e d between 11 broods.)  49  2)  I n t e r s p e c i f i c Aggression a) P a i r s on the breeding area Barrow's Goldeneye, Common Goldeneye and B u f f l e h e a d  drakes  showed a g g r e s s i v e behaviour toward other s p e c i e s of a q u a t i c b i r d s b u t e s p e c i a l l y toward each other (Table 10).  Barrow's Goldeneye were observed  to t h r e a t e n and/or a t t a c k 19 other s p e c i e s . s p e c i e s of Bucephala o c c u r r e d ,  On ponds where the t h r e e  t h e r e was almost no o v e r l a p between  t e r r i t o r i a l p a i r s because of i n t e r s p e c i f i c a g g r e s s i o n .  In the Columbia  V a l l e y , where the t h r e e s p e c i e s c o e x i s t , I r e c o r d e d 580 i n t e r s p e c i f i c confrontations during  50 h of b e h a v i o u r a l  observations  (Table 11).  Intrageneric i n t e r a c t i o n s were e s s e n t i a l l y s i m i l a r t o i n t r a s p e c i f i c ones. Males, p a i r s , f e m a l e s and s u b a d u l t s were excluded from the t e r r i t o r y . Interactions toward intruders other than males (pairs, females,  subadults,  groups) r e s u l t e d i n more a t t a c k s than t h r e a t s and the p r o p o r t i o n o f a t t a c k s d i d n o t d i f f e r among t h e s p e c i e s i n v o l v e d (X =4.766, P=0.189, 2  df=3).  I n t e r a c t i o n s w i t h males r e s u l t e d u s u a l l y i n more t h r e a t s than  a t t a c k s but t h e p r o p o r t i o n v a r i e d a c c o r d i n g t o t h e s p e c i e s i n v o l v e d (X =53.43, P=0, df=3). 2  Boundary d i s p l a y s were f r e q u e n t between neighbouring Barrow's and Common Goldeneye males and averaged 6 min. i n length (range=l-38 min, n=21 displays). goldeneyes.  No boundary d i s p l a y s were observed between B u f f l e h e a d and T e r r i t o r i a l B u f f l e h e a d drakes were always dominated by  Barrow's and Common Goldeneye drakes, which o f t e n r e s u l t e d i n p o o r l y defined Bufflehead t e r r i t o r i e s .  Bufflehead drakes were expert a t decoying  attacking goldeneye drakes from t h e i r females and staying out of reach of the goldeneye. off  During a t y p i c a l a t t a c k , the B u f f l e h e a d drake would f l y  a few f e e t whenever t h e goldeneye d i v e d toward him, and l e a d t h e  goldeneye away from h i s mate.  This behaviour allows some Bufflehead p a i r s  50  Table 10. Number o f 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 t e r r i t o r i a l drakes observed between 1981 and 1984. Aggressor Barrow s Goldeneye 1  Intruder Horned Grebe (Podiceps auritus) Green-winged Teal 'Anas crecca) Mallard (A., platyrhynchos) Northern P i n t a i l (A. acuta) Blue-winged Teal 1A. fliscors) Cinnamon Teal (A., cyanoptera) Northern Shoveler (A., c j Gadwall (A_. strepera) American Wigeon (&. Canvasback (Aythya v a l i s j Redhead (Ay_. americana) Ring-necked Duck (Ay. c o l l a r i s ) Scaup (Ay. m a r i l a / a f f i n i s ) Oldsquaw (Clangula hyemaljs) Surf Scoter (Melanitta p e r s p i c i l l a t a ) 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  involving  (male)  Common Goldeneye  Bufflehead  1 4  2 2  2 2 1  11 1 1  13 2 268 1377 466 27 13  238 97 106  8 28 116  Total interactions Total i n t e r s p e c i f i c interactions  2577  449  181  1200  211  65  Maximum observation l e n g t h (hours)  <150  <50  <50  1  1  Could not be estimated p r e c i s e l y .  51  Table 11. Number of i n t e r s p e c i f i c 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  Barrow's  Common  Bufflehead  Bufflehead  Intruding species Type of interaction  Total  T  A  F  T  A  F  T  A  F  T  A  F  T  A  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  21  31  74  1  17  93  1  177  373  30  175  Always a t e r r i t o r i a l drake.  52  F  to coexist among Barrow's Goldeneye, other Bufflehead occupy small ponds where t h e r e are no Barrow's Goldeneye.  Outcomes of c o n t e s t s between  Barrow's and Common goldeneye drakes were l e s s predictable. Although the territory  owner  was u s u a l l y dominant w i t h i n  h i s territory,  some  observations indicated that Barrow's Goldeneye had a s l i g h t advantage over Common Goldeneye.  In i n t e r s p e c i f i c encounters,  Barrow's Goldeneye were  more o f t e n a g g r e s s o r s than r e c i p i e n t s ; Common Goldeneye were e q u a l l y observed as aggressors and as r e c i p i e n t s , and Bufflehead were most often r e c i p i e n t s (Fig.9).  A d e t a i l e d a n a l y s i s 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 i n v o l v i n g males suggest  that  Barrow's Goldeneye were more a g g r e s s i v e than Common Goldeneye and t h a t B u f f l e h e a d were dominated by both  s p e c i e s of goldeneyes  ( F i g . 10).  Barrow's Goldeneye a l s o i n i t i a t e d p r o p o r t i o n a l l y more f i g h t s than d i d Common Goldeneye (Table 12). I q u a n t i f i e d i n t e r s p e c i f i c aggressions of Barrow's Goldeneye i n 1982 on  20 ponds l o c a t e d near Riske  occurred. behaviour  Creek,  B.C., where B u f f l e h e a d  also  T e r r i t o r i a l Barrow's Goldeneye drakes d i s p l a y e d a g g r e s s i v e toward a l l species of waterfowl present on the breeding ponds.  However, t h e frequency  and i n t e n s i t y of a g g r e s s i v e behaviour  according t o the species involved (Fig. 11). aggressive  varied  T e r r i t o r i a l drakes were more  toward d i v i n g ducks than d a b b l i n g ducks.  The number of  a g g r e s s i v e a c t s per bird-hour ranged from 0.06 t o 0.20 (x = 0.10+0.02, n=7)  among d a b b l i n g duck s p e c i e s (Table 13) and from 0.17 t o 1.00 (x"  =0.41+0.13, n=6) among d i v i n g duck s p e c i e s difference  (t=-11.0, P=0.000, df =11,  (Table 14) a s i g n i f i c a n t  log transformed  data).  The number of  tolerated i n d i v i d u a l s per bird-hour was s i m i l a r f o r dabbling and d i v i n g duck s p e c i e s and ranged from  0.07 t o 0.13 (x = 0.10±0.01, n=7) among  d a b b l i n g ducks and from 0.00 t o 0.18 (x=0.08+0.03, n=6)) among d i v i n g 53  Fig. 9  Relative aggressiveness of the three Bucephala species towards intruders. (Proportion of time each s p e c i e s was t h e aggressor or the v i c t i m d u r i n g i n t e r a c t i o n s ; n = number o f i n t e r actions; observations were made on a t l e a s t 20 d i f f e r e n t p a i r s of each species.)  54  A G G R E 8 S O R  F i g . 10  /  V I C T I M  Comparison o f t h e p r o p o r t i o n s of t h r e a t s 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 a t l e a s t 6 d i f f e r e n t p a i r s of each species).  55  Table 12. Number of i n t r a - and i n t e r g e n e r i c encounters t h a t resulted i n f i g h t s . Common Goldeneye  Barrow's Goldeneye  No. of f i g h t s  17  48  No. of threats or attacks  318  455  G =  5.9, P<0.05  56  TOLERANCE/BIRD  AGGRESSIVE  NO. O F  HOUR  INTERACTION/BIRD  TOLERANCE/NO.  DABBLING DUCKS  OF  AGGRE8SION  DIVING D U C K S T Y P E  F i g . 11  HOUR  O F  BUFFLEHEAD  B A R R O W ' S GOLDENEYI  I N T R U D E R S  A g g r e s s i v e responses o f Barrow's Goldeneye drakes toward c o n s p e c i f i c s , congeners, d i v i n g ducks and d a b b l i n g ducks. (The d a t a has been scaled across intruder types. The t o t a l number of t o l e r a n c e / b i r d hour = 0.17, of 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 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 b i r d hours Green^winged Teal  No. of tolerances  No. of aggressions 1  No.tolerances/ No.aggression  No.tolerances / b i r d hour  No. aggressive interactions / b i r d hour  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  186  22  12  1.83  0.12  0.06  23  3  2  1.50  0.13  0.09  905  85  0.77  0.09  0.12  American Wigeon Northern P i n t a i l Total  Threats and attacks combined.  111  Table 14.  Interactions between t e r r i t o r i a l Barrow's Goldeneye drakes and d i v i n g ducks (during 102 h of observation). No. of b i r d hours  Canvasback (Aythya v a l i s i n e r i a )  No. of tolerances  No. of aggressions 1  No. tolerance/ No. aggression  No. tolerance / b i r d hour  No. aggressive interactions / b i r d hour  12  0  2  0.00  0.00  0.17  139  8  84  0.10  0.06  0.60  36  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 p e r s p i c i l l a t a )  4  4  1.00  0.18  0.18  Ruddy Duck (Oxyura jamaicensis)  17  3  17  0.18  0.18  1.00  Total  470  28  200  0.06  0.43  Bufflehead (Bucephala albeola)  195  3  214  0.01  0.02  1.10  Barrow's Goldeneye 318 (Bucephala islandica)  0  366  0.00  0.00  1.15  Redhead (Aythya americana) Ring-necked Duck (Aythya c o l l a r i s )  Threats and attacks combined.  0J4  ducks (t=0.58, P=0.57, d f = l l ) .  The r a t i o of the number of t o l e r a t e d  i n d i v i d u a l s over the t o t a l number of i n t e r a c t i o n s averaged 1.20+0.22 f o r dabblers  (n=7 s p e c i e s )  and 0.26±0.15,  for divers  (n=6 s p e c i e s ) , a  s i g n i f i c a n t d i f f e r e n c e (t=3.36, P=0.006, df=11), i n d i c a t i n g t h a t d i v i n g ducks were tolerated l e s s often and attacked more frequently than dabbling ducks.  This was true f o r a l l types of intruders (Fig. 12).  In a l l cases,  the r e l a t i v e frequency of aggression was higher toward diving ducks than toward dabbling ducks. The number of aggressive inter actions/bird hour towards Blue-winged T e a l was t w i c e  t h a t toward other  d a b b l i n g ducks.  I looked  a t the  p r o p o r t i o n of t o l e r a n c e s and a g g r e s s i o n s f o r s p e c i e s of d a b b l i n g ducks which had a s u f f i c i e n t sample s i z e (Green-winged T e a l , M a l l a r d , B l u e winged T e a l , American Wigeon) and combined data from t h e other s p e c i e s (Northern  Shoveler,  Gadwall,  Northern  Pintail).  The p r o p o r t i o n o f  tolerances and aggressions d i f f e r e d among dabbling duck species (X2=17.98, P=0.002, df=4). However, once data from Blue-winged T e a l were removed, there was no longer a s i g n i f i c a n t difference among the remaining (X =3.19, P=0.364, df=3). 2  species  S i m i l a r a n a l y s e s w i t h other d i v i n g ducks (i.e.  not Bucephala) using Redhead, scaup, Ruddy Duck and a combination  of the  other s p e c i e s (Canvasback, Ring-necked Duck, S u r f S c o t e r , White-winged Scoter) show t h a t the p r o p o r t i o n of t o l e r a n c e s t o a g g r e s s i o n s d i d not d i f f e r s i g n i f i c a n t l y among the species (X =6.38, P=0.094, df=3). 2  Similar  c o n c l u s i o n s a r e reached i f t h e s p e c i e s t h a t were grouped t o g e t h e r a r e excluded  from the a n a l y s i s .  The l e v e l o f a g g r e s s i o n  t h r e a t s t o a t t a c k s ) o f Barrow's Goldeneye d i d not d i f f e r  (proportion of significantly  toward s p e c i e s of d a b b l i n g ducks or toward s p e c i e s of d i v i n g ducks (Table 1 5 ) .  However,  Barrow's G o l d e n e y e w e r e s i g n i f i c a n t l y  a g g r e s s i v e toward d i v i n g ducks, w i t h 74% of the a g g r e s s i v e  60  more  encounters  MALES  PAIRS TYPE  F i g . 12  FEMALES  GROUPS  OF INTRUDER  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 t o l e r a n c e s 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 s i g n i f i c a n t l y d i f f e r e n t between dabbling ducks and diving ducks f o r a l l types of intruders (X t e s t s , P<0.05).) 2  61  being a t t a c k s , than toward d a b b l i n g ducks w i t h o n l y 39% of  encounters  being attacks (Table 15). I have shown e a r l i e r t h a t Barrow's Goldeneye 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 against Bufflehead.  Therefore I d i d not include Bufflehead i n  the previous analysis.  Bufflehead were almost never tolerated by Barrow's  Goldeneye drakes and  were t h r e a t e n e d  and  attacked  frequently.  The  i n t e n s i t y of a g g r e s s i v e 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) r e s u l t e d i n a t t a c k s compared t o o n l y 75% (n=184) f o r other d i v i n g ducks (X =11.03, P=0.001). 2  The number of a g g r e s s i o n s per b i r d hour between  Barrow's Goldeneye and Bufflehead was and was  higher than for other diving ducks  s i m i l a r t o the number of i n t r a s p e c i f i c encounters  S i m i l a r l y , the number of tolerances per b i r d hour was the l e v e l f o r i n t r a s p e c i f i c encounters The  sex  behaviour  of  the  i n t r u d e r d i d not  (X =2.16,  seem t o a f f e c t  (Fig. 12).  Territorial  toward f e m a l e s as toward males f o r both P=0.142, df=l)  2  low and approached  (Table 14).  of Barrow's Goldeneye drakes.  aggressive  and  diving  (Table 14).  ducks  (X =1.22, 2  the  aggressive  drakes were  as  dabbling  ducks  P=0.269,  df=l)  Results are s i m i l a r i f we consider an i n t e r a c t i o n with a pair  as r e p r e s e n t i n g an i n t e r a c t i o n w i t h a male and an i n t e r a c t i o n w i t h a female.  When a t e r r i t o r i a l drake a t t a c k e d a p a i r , both members f l e d  together. The  i n t e r s p e c i f i c aggressive behaviour  the presence of t h e i r mate.  of drakes was  not related to  During l a y i n g and incubation, males were at  l e a s t as a g g r e s s i v e toward other s p e c i e s when t h e i r mate was absent when she was  ^ r e s e n t i n the t e r r i t o r y (Table 16);  n=6) .  62  as  (Sign T e s t , P=0.34,  Table 15.  L e v e l of a g g r e s s i o n i n i n t e r a c t i o n s between Barrow's Goldeneye drakes and other waterfowl. Type of i n t e r a c t i o n  Species  Threat  Green-winged Teal  Attack  8  3  Mallard  15  6  Blue-winged Teal  35  24  5  7  American Wigeon  (X2 Dabbling Ducks = 3.56 P=0.31) Redhead  22  61  2  10  22  51  Surf Scoter  1  5  Ruddy Duck  3  14  Ring-necked Duck Scaup  (X2 Diving Ducks = 2.08 P=0.72) Total Dabbling Ducks  63  40  Total Diving Ducks  50  141  (X Dabbling-Diving Ducks = 34.62 P=0.000) 2  63  b) Females with broods Following hatching, females with young became highly aggressive established t e r r i t o r i e s on t h e i r breeding ponds. had  left  the b r e e d i n g  aggressive  behaviour  conspecifics  area t o molt.  (Table 17).  By t h i s time most males  Territorial  toward a v a r i e t y  and  females d i s p l a y e d  of a q u a t i c b i r d s  Female Barrow's Goldeneye and  besides  Bufflehead  displayed s i m i l a r i n t e r s p e c i f i c aggression and were e s p e c i a l l y aggressive toward each other (Table 18).  Few  boundary d i s p l a y s 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 i n t e r a c t e d more o f t e n w i t h l o n e female goldeneye than  w i t h goldeneye broods and i n t e r a c t i o n s w i t h lone f e m a l e s r e s u l t e d i n proportionally more attacks (X =5.47, P=0.02 df=l). 2  Like t e r r i t o r i a l drakes, all  species  (Table 19).  females were not equally aggressive toward  Interactions of Barrow's Goldeneye females with  Bufflehead resulted i n more attacks than those with dabbling and d i v i n g ducks (X =35.3, P=0.000, df=2). 2  They tended to be more aggressive toward  d i v i n g ducks than d a b b l i n g ducks, but t h i s r e s u l t was (X =2.80, P=0.082, d f = l ) . 2  i n t e r a c t i o n s of significantly  The  not  significant  p r o p o r t i o n s of t h r e a t s and  attacks i n  B u f f l e h e a d f e m a l e s w i t h other b i r d s d i d not (X =5.09, P=0.090, df=2), but 2  sample  s i z e s are  differ small.  Bufflehead were always excluded from goldeneye t e r r i t o r i e s whereas other d i v i n g ducks were o c c a s i o n a l l y t o l e r a t e d . occasionally attacked.  Dabbling  ducks were o n l y  Most b i r d s tended to avoid female goldeneye with  broods, by swimming away from or around them.  64  Table  16. Number of i n t e r s p e c i f i c aggressions (aggressive interactions/bird hours) 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.  Pair B  Pair A Female present  Female absent  Female present  Female absent  20  25  15  35  0.18 (95)  0.15 (302)  0.04 (90)  0.08 (306)  Diving ducks  0.36 (14)  0.68 (37)  1.58 (19)  3.22 (32)  Bufflehead  0.40 (15)  0.60 (25)  0.64 (ID  0.63 (30)  Total  0.23 (124)  0.23 (364)  0.34 (120)  0.40 (368)  Observation time (h) Dabbling ducks  1  1  Number of b i r d hours.  65  Table 17. Number of interactions observed between female Barrow's Goldeneye and Bufflehead with broods, and other birds. Aggressor  Victim  Barrow's Goldeneye (275 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 P i e d - b i l l e d Grebe American Coot  4 1 2 14 1 160 551 287 68 180 60 4 2 1 10  Total i n t e r s p e c i f i c interactions  539  12 4 7 5 4  -  Number of hours of observation.  66  1  Bufflehead (130 h) 1  2 5  2 4  -  3 4 1 21 35 10 21 32 12 2  5  107  Table 18.  Aggressor/ Victim Type of intruder  Intra-generic aggression i n broods of Barrow's Goldeneye and broods of Bufflehead (during 176 h of observation). Female Bufflehead/ Barrow's Goldeneye °  Female Barrow's Goldeneye/ Bufflehead  Threat  attack  Boundary display Total  Threat  attack  Boundary display Total  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  Male  67  Table 19.  Intensity of the interactions observed between females with broods and i n t r a - and i n t e r s p e c i f i c intruders. Female aggressor Bufflehead  Barrow's Goldeneye Victim  %  %  Attack  attack  5  11  69  69  4  34  89  465  85  7  27  79  206  42  17  6  4  40  Bufflehead  13  54  81  1  20  95  Bufflehead broods  18  162  90  19  19  50  Threat  Attack  attack  Dabbling ducks  18  22  55  Diving ducks  74  161  Barrow's Goldeneye  82  Barrow's Goldeneye broods  68  Threat  The dominance of Barrow's Goldeneye females over Bufflehead females is  reflected  in their  time  budgets.  Female  B u f f l e h e a d spent  proportionally l e s s time i n t e r r i t o r i a l defense and more i n a l e r t posture than f e m a l e Barrow's Goldeneye  (Figs. 7-8).  Most of the a l e r t n e s s of  Bufflehead was due to the presence of female goldeneye nearby. c) Pairs on the wintering areas Barrow's Goldeneye o c c a s i o n a l l y r e u n i t e w i t h t h e i r mates on the wintering areas and some p a i r s defend t e r r i t o r i e s throughout the winter (Appendix 2). toward  As on b r e e d i n g a r e a s , they d i s p l a y a g g r e s s i v e behaviour  other s p e c i e s  (Table 20).  Although  I d i d not q u a n t i f y i t ,  t e r r i t o r i a l behaviour i n winter appears s i m i l a r 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 i n the winter habitat of Barrow's Goldeneye. Barrow's Goldeneye.  They usually swim away when threatened or attacked by However, f l o c k s of s c o t e r s sometimes s u c c e s s f u l l y  invaded goldeneye t e r r i t o r i e s .  S u r f Scoters never displayed aggressive  behaviour toward goldeneyes and always f l e d when attacked. Aggressiveness v a r i e d among goldeneye p a i r s : some t o l e r a t e d i n t r u d i n g b i r d s more than others.  Only paired t e r r i t o r i a l drakes were i n t e r s p e c i f i c a l l y aggressive.  A d u l t s and s u b a d u l t s i n f l o c k s d i d not d i s p l a y any obvious a g g r e s s i v e behaviour when feeding. One marked p a i r had a t e r r i t o r y along a small breakwater which o n l y a c c e s s i b l e t o them a t h i g h t i d e .  was  A t low t i d e the breakwater  was  surrounded by mud f l a t s and c o u l d not be used by the p a i r . T h i s 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 a g g r e s s i v e on t h e i r t e r r i t o r y , but during low t i d e s they sometimes joined with other goldeneyes and were not  69  Table  20.  Number o f c a s e s o f i n t r a - and i n t e r s p e c i f i c by t e r r i t o r i a l Barrow's G o l d e n e y e m a l e s and w i n t e r ( d u r i n g 28 h o f o b s e r v a t i o n ) .  aggression females i n  Aggressor Victim Male  Female 1  Mallard  2  Scaup  4  Common G o l d e n e y e  8  Bufflehead  6  -  49  2  Hooded M e r g a n s e r  1  1  Red-breasted  1  -  8  2  79  6  168  15  Surf  Scoter  Merganser  Glaucous-winged  Total  Gull  interspecific  interactions  Barrow's Goldeneye  70  aggressive, indicating occasionally  f l e x i b i l i t y i n t h e i r aggressive behaviour.  engaged  in intra-  and  interspecific  Females  interactions.  O c c a s i o n a l l y they behaved as i f they were i n c i t i n g the male t o a t t a c k intruders. 3) Relationships between p a i r t e r r i t o r y , brood t e r r i t o r y and nest s i t e a) Pair t e r r i t o r y and nest s i t e In my study a r e a , Barrow's Goldeneye n e s t e d i n t r e e c a v i t i e s or i n nest boxes.  Therefore, nest s i t e s were almost always outside the breeding  pair's t e r r i t o r y  (a few trees stood i n shallow water).  Distance between  the pair t e r r i t o r y and the nest s i t e averaged 0.35 km and ranged from 0 to 2.9 km  (Fig. 13).  About h a l f of the n e s t s i t e s were a d j a c e n t t o 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 s i t e and brood t e r r i t o r y Brood t e r r i t o r i e s averaged 0.33 km between 0 and 2.3 km  (Fig. 14).  from the n e s t s i t e and ranged  However, 48% of the t e r r i t o r i e s were  located on a lake w i t h i n 100 m of the nest s i t e .  Broods tended t o s e t t l e  on the lake closest to their nest s i t e i f the lake was suitable f o r brood rearing.  T e r r i t o r i a l encounters sometimes forced broods t o move to lakes  farther away from their nest s i t e s  (see Appendix 3).  c) Pair t e r r i t o r y and brood t e r r i t o r y P a i r 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 t e r r i t o r i e s ranged between 0.27 and 2.79 ha and averaged 1.08 + 0.12 ha (n=27). considered, p a i r territories  territories  averaged  I f o n l y water l e s s than 3 m deep i s  averaged  0.91 ± 0.08 ha.  71  0.44  The  +  0.05  latter  ha  and  brood  e s t i m a t e i s more  ~~1  D I S T A N C E F R O M N E S T SITE (M)  F i g . 13 ~ D i s t a n c e s between p a i r t e r r i t o r i e s and n e s t s i t e s i n Barrow s Goldeneye (n = 6 9). 1  i i  72 I i  Table  21.  Proportion nest site.  of  territories  T e r r i t o r y adjacent to the nest s i t e  that  were  adjacent  the  T e r r i t o r y not a d j a c e n t to the nest s i t e  1983  11  8  1984  20  19  73  to  24 CO U J  E o E  a  20 -  16  U J  iQ O O tr  m 11.  O  12  8 4  -  8  16  32  64  128  256  512  1024 2048  D I S T A N C E F R O M N E S T SITE (M)  F i g . 14  D i s t a n c e s between brood t e r r i t o r i e s and n e s t s i t e s i n Barrow's Goldeneye (n = 130).  74  4096  r e a l i s t i c , because most of t h e l a k e s i n t h e study area are l e s s than 3m deep, and paired goldeneyes r a r e l y feed i n such deep areas, preferring t o feed i n shallower  waters near the shoreline.  Brood t e r r i t o r i e s were usually not the same as pair t e r r i t o r i e s , and o f t e n were e s t a b l i s h e d on d i f f e r e n t l a k e s .  When t h e p a i r t e r r i t o r y and  the nest s i t e were on d i f f e r e n t lakes, brood t e r r i t o r i e s were established on t h e l a k e of the nest s i t e s more o f t e n (21 times) than on t h e l a k e of the pair t e r r i t o r y (2 times). d) F i d e l i t y t o t e r r i t o r y Pair t e r r i t o r i e s tended t o be located on the same lake i n successive years:  23 p a i r s established their pair t e r r i t o r y on the same pond 2 years  i n a row, 10 p a i r s 3 years i n a row, and 1 p a i r four years i n a row. Only 12 of the returning p a i r s (21%) changed lakes between years. tended t o use the same t e r r i t o r y each year. pairs,  7 used  consecutive  the same t e r r i t o r y  y e a r s and o n l y  From a sample of 15 marked  on 2 c o n s e c u t i v e  years,  changed.  3 on 3  5 changed t e r r i t o r i e s t h e f o l l o w i n g y e a r .  Females u s u a l l y brought t h e i r broods t o the same l a k e on years.  Pairs also  consecutive  From a sample of 28 broods, 21 used t h e same l a k e and o n l y 7 Of these 7, one moved t o a nest s i t e on a d i f f e r e n t l a k e , 2  lakes became unsuitable for goldeneye and 4 broods were excluded from the l a k e they had used the year before because of t e r r i t o r i a l behaviour o f already established broods.  There i s some evidence that p a i r s also return  to the same wintering t e r r i t o r y each year (Appendix 2).  e) Removal experiments To gain i n s i g h t i n t o the proximal factors determining t e r r i t o r y s i z e s and b o u n d a r i e s I d i d two removals.  75  I argued t h a t i f t e r r i t o r y s i z e was  determined s o l e l y by food abundance and i f the boundaries were established without reference to neighbouring pairs, then the removal of the central pair  from  t h r e e 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 t e r r i t o r y size and boundaries are determined  intraspecific  i n t e r a c t i o n s among neighbouring p a i r s ,  then a f t e r  by the  removal, the t e r r i t o r i e s of the two remaining p a i r s should expand into the vacant area and a new boundary should be established through i n t r a s p e c i f i c interactions.  My r e s u l t s supported the second prediction:  removal of the c e n t r a l  pair,  the other two  following  p a i r s began t o  the  interact  (Table 22) and, by the f o l l o w i n g day, t e r r i t o r i e s had expanded i n t o the vacant area and a new  boundary l i n e was  established  (Fig. 15).  However,  i n s p i t e of t h e i r expanded t e r r i t o r i e s the p a i r s c o n c e n t r a t e d  their  a c t i v i t y i n t h e i r o l d t e r r i t o r y . R e s u l t s were s i m i l a r f o r the  second  removal:  a f t e r the removal of the c e n t r a l p a i r , t e r r i t o r y boundaries  s h i f t e d and the remaining two Barrow's Goldeneye p a i r and a B u f f l e h e a d pair interacted F i g . 16).  more f r e q u e n t l y  than p r i o r t o the removal (Table 23,  The B u f f l e h e a d p a i r attempted t o f i l l the v o i d c r e a t e d by the  removal and p a r t l y  succeeded.  DISCUSSION a) I n t r a s p e c i f i c aggression I n t r a s p e c i f i c aggression i s behavioural competition f o r resources i n short  supply  establishment competitors  (Brown 196 4).  This aggression  of t e r r i t o r i e s t h a t  (Lanyon 1956,  Welty 1962,  often  a r e defended Pianka 1978).  results  against  in  the  conspecific  Barrow's Goldeneye,  Common Goldeneye and Bufflehead drakes a c t i v e l y 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 of observation  Total no. of hours  Number of aggressive i n t e r actions between p a i r s A-B  EH:  A-C  Before removal  3  6  11  6  0  After removal  7  12  -  -  18  1  1  Pair B was removed; see F i g . 15 f o r l o c a t i o n of the t e r r i t o r i e s .  77  BEFORE  AFTER  ABCDE 1  100  F i g . 15  REMOVAL  REMOVAL  - Barrow's Q o l d e n e y e t e r r i t o r i e s - Bufflehead  territory  meters  T e r r i t o r y boundaries of Barrow's Goldeneye p r i o r to and f o l l o w i n g t h e removal o f p a i r B on Lake 68 i n 1984. Y  78  Table 23.  Results of the removal experiment on lake 50 i n 1984. Number of aggressive interactions between p a i r s No. of days of observations  Total no. of hours  A-B  Before removal  3  5  7  After removal  4  6  -  1  1  Pair B was removed;  B-C 4 -  A-C 0  A - l A-2 12  14  4  C-l 1  18  see F i g . 16 for the l o c a t i o n of the t e r r i t o r i e s .  79  C-2  0  0  0  9  BEFORE  AFTER  ABC  REMOVAL  REMOVAL  - Barrow's Q o l d e n e y e  1,2 - B u f f l e h e a d  territories  1  i  100  F i g . 16  territories  meters  T e r r i t o r y boundaries of Barrow's Goldeneye and Bufflehead p r i o r t o and following the removal of p a i r B on Lake 50 i n 1984.  80  Territories  defended by goldeneyes and B u f f l e h e a d  satisfy  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 O r i a n s (1970) . 1.  A f i x e d area i s defended: although the t e r r i t o r y boundaries f l u c t u a t e  throughout the season, the t e r r i t o r y i t s e l f remains i n the same section of the pond.  Neighbouring p a i r s often establish boundary l i n e s which remain  stable f o r several days. pair 2.  However, brood t e r r i t o r i e s are not the same as  territories. T e r r i t o r i a l displays evoke escape and avoidance i n r i v a l s : goldeneyes  and B u f f l e h e a d have a wide a r r a y of a g g r e s s i v e p o s t u r e s r e l a t e d t o t e r r i t o r i a l d i s p l a y , and which evoke avoidance i n r i v a l s (Erskine 1972, Palmer 1976). 3.  The t e r r i t o r y i s an exclusive area:  conspecifics are excluded from an  area. Several suggested:  f u n c t i o n s of t e r r i t o r i a l  behaviour i n b i r d s have  been  1) Mate a t t r a c t i o n (McLaren 1972, Welsh 1975, W i t t e n b e r g e r  1981, Steen e£ aJL. 1985); (McKinney 1965, Morse 1980);  2) Mate protection and reproductive i s o l a t i o n 3) Defense of nest s i t e (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 1976, Moore 1978). Barrow's Goldeneye  £l.  I s h a l l b r i e f l y consider each of these functions f o r territoriality.  1. Mate a t t r a c t i o n The t e r r i t o r y c o u l d h e l p t h e owner i n a t t r a c t i n g mates. unlikely  i n Barrow's  Goldeneye  e s t a b l i s h m e n t of the t e r r i t o r y : areas;  as  pairs  a r e formed  prior  This i s t o the  a) most p a i r s formed on t h e w i n t e r i n g  b) others formed on the center of the breeding ponds away from the  81  territories; apparently  c) t e r r i t o r i e s are  always s e t t l e d by  pairs.  s e l e c t the t e r r i t o r y i n waterfowl (Hochbaum 1944,  Donaghey 197 5, P a t t e r s o n brood t e r r i t o r i a l i t y .  1982).  In winter,  Females  Young  1970,  Mate a t t r a c t i o n c l e a r l y cannot explain since only paired b i r d s are t e r r i t o r i a l ,  the function i s obviously not to a t t r a c t a mate. 2. Mate protection against sexual harassment T e r r i t o r i a l defense by the male i s o l a t e s the p a i r from conspecifics and  thus reduces the r i s k s of i n t e r f e r e n c e d u r i n g  copulation.  Such  i n t e r f e r e n c e has been observed i n s e v e r a l s p e c i e s of b i r d s (Armstrong 196 5).  Territorial  copulations  and  defense would  also  lower  thus a s s u r e male p a t e r n i t y .  the  risk  of  stolen  However, I found  that  c o p u l a t i o n does not always occur w i t h i n the t e r r i t o r y , and I observed three copulations the l a t t e r .  near groups of unpaired birds without interference from  Forced copulation i s frequent w i t h i n the genus Anas (McKinney  et a i . 1983), but has never been reported i n the genus Bucephala (McKinney e± aJL. 1983, studies  McKinney 1985,  of  copulation.  goldeneye  I  G a u t h i e r 1985).  have  never  In 5 y e a r s of  witnessed  an  intensive  attempted  forced  Goldeneye drakes take several minutes before mounting a prone  female (Nilsson 1969,  Afton and Say l e r 1982,  Savard unpub. data), a delay  t h a t would make f o r c e d c o p u l a t i o n d i f f i c u l t . Goldeneye are s t r o n g (see Appendix 2).  P a i r bonds i n Barrow's  Marked p a i r s have been observed  foraging i n large groups of goldeneyes i n winter with l i t t l e harassment of females from unpaired males. Males  then,  lose t h e i r mates and which have been unsuccessful  p a i r i n g , return to t h e i r previous observed two  b r e e d i n g area  (see Appendix 2).  of these males defend i r r e g u l a r l y , f o r a few  t e r r i t o r y they o c c u p i e d the year before.  82  in re-  days,  I the  T h i s defense behaviour i n the  absence of t h e female a g a i n i n d i c a t e s t h a t p r o t e c t i o n of t h e 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. I f such mate p r o t e c t i o n was important, one would expect u n p a i r e d a d u l t males t o be a t t a c k e d more v i o l e n t l y than i n t r u d i n g p a i r s .  Casual  o b s e r v a t i o n s i n d i c a t e t h a t strange p a i r s (neighbouring p a i r s excluded) e l i c i t stronger aggressive responses from t e r r i t o r y owners than unpaired drakes.  Quantitative studies are needed to confirm these observations.  Paired females are quite aggressive and are r a r e l y sexually harassed by males.  I have seen p a i r e d f e m a l e s l a n d i n g i n groups of u n p a i r e d  goldeneye, a f t e r r e t u r n i n g 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 d i d not p e r s i s t i n t h e i r displays.  Gauthier (1985)  found t h a t B u f f l e h e a d f e m a l e s whose mates had been removed were not sexually harassed but rather aggressively attacked by neighbouring males. Some were even chased o f f t h e i r t e r r i t o r y .  I f mate p r o t e c t i o n 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 s e x u a l l y m o t i v a t e d , i.e. i t i s p r o t e c t i o n from a g g r e s s i v e males and not from courting males.  Exclusion of strange females from the t e r r i t o r y  (see F i g . 2) supports the assertion t h a t t e r r i t o r i a l behaviour of drakes i s not s o l e l y sexually motivated. 3.  Protection of nest s i t e T e r r i t o r i a l i t y may protect access t o the nest s i t e .  Gauthier (1985)  argued t h a t t h i s f u n c t i o n i s important i n B u f f l e h e a d , a s p e c i e s whose nesting c a v i t i e s are often adjacent t o the t e r r i t o r y .  He suggested that  t e r r i t o r i a l aggressiveness of males impairs access t o the nest by other f e m a l e s and t h e r e f o r e reduces n e s t p a r a s i t i s m . Pienkowski and Evans  83  (1982a) also indicated t h a t ^ i n i s o l a t e d s i t e s , nests of Shelducks tend to be a d j a c e n t t o t e r r i t o r i e s and t h a t i n these cases t e r r i t o r i a l i t y reduce n e s t i n g i n t e r f e r e n c e and c l u t c h p a r a s i t i s m . Gauthier  (1985) nor Pienkowski  supporting t h i s hypothesis. p a i r t e r r i t o r y and  and  may  However, n e i t h e r  Evans (1982a) present conclusive data  Goldeneye n e s t s can be up t o 2 km from the  even n e s t s a d j a c e n t t o the t e r r i t o r y are u s u a l l y  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  t o p r o t e c t the n e s t s i t e as such: they o n l y t r i e d t o 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 o f t e n used s u c c e s s f u l l y by s e v e r a l females. observations indicate that females,  although harassed by the  Direct  territorial  males when they flew over or landed i n the t e r r i t o r y , successfully entered the  boxes.  Erskine  (197 2)  reports  simultaneously i n the same tree.  female  Bufflehead  nesting  The absence of d i r e c t protection of the  nest s i t e by males i n d i c a t e s t h a t 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 i n 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 l a k e s but, because the n e s t s i t e i s u s u a l l y o u t s i d e the t e r r i t o r y , t h i s does not necessarily translate i n t o nest spacing. exploit food resources more evenly and may  5.  However, i t does force p a i r s to l i m i t density on c e r t a i n ponds.  Defense of food resources Egg production and incubation impose great energy demands on  84  females  (King 1973,  R i c k l e f s 197 4, Krapu 197 9).  In the s p r i n g , f e m a l e s spend  t w i c e as much t i m e f e e d i n g as do males, an i n d i c a t i o n of a h i g h e r requirement  f o r females.  Defense of a t e r r i t o r y  and  food  e x c l u s i o n of  c o n s p e c i f i c s by the male p r o v i d e the female w i t h the f o l l o w i n g f e e d i n g advantages:  1) By remaining  i n the same area, the f e m a l e f a m i l i a r i z e s  h e r s e l f w i t h the r e s o u r c e s of the t e r r i t o r y and w i t h i t s s p a t i a l temporal d i s t r i b u t i o n . a l 1983, area  This may  enhance her foraging e f f i c i e n c y (Hixon e±  Gass and Sutherland 1985). 2) Exclusion of conspecif i c s from  reduces f e e d i n g  and  interference.  Because goldeneye f e e d on  the free  swimming invertebrates which they capture by sight, the presence of other birds feeding nearby may  reduce prey a v a i l a b i l i t y by either muddying the  water and/or by c a u s i n g the prey t o seek refuge i n dense v e g e t a t i o n . 3) Food d e p l e t i o n may  be reduced by e x c l u s i o n of c o m p e t i t o r s .  These  f a c t o r s each contribute to a greater feeding e f f i c i e n c y by the female and may  allow her to be more s e l e c t i v e i n her choice of prey.  Gauthier  (1985)  showed that Bufflehead females who had l o s t t h e i r mates spent more time i n a l e r t p o s t u r e , f e d f o r a s h o r t e r p e r i o d of t i m e and were the v i c t i m of more aggressive attacks than paired females.  Pienkowski and Evans (1982a)  found t h a t p a i r s of Shelducks f e d more e f f i c i e n t l y i n s i d e than o u t s i d e their t e r r i t o r y .  Defense of winter  t e r r i t o r i e s c o u l d s i m i l a r l y enhance  feeding opportunities of the pair.  However, the s i t u a t i o n appears complex  as some p a i r s apparently do not defend t e r r i t o r i e s on the wintering areas. S i m i l a r l y , the female p r o v i d e s the same advantages f o r her young. Females, by e x c l u d i n g c o n s p e c i f i c s from the brood t e r r i t o r y ,  provide  b e t t e r f e e d i n g o p p o r t u n i t i e s f o r t h e i r young. Young d u c k l i n g s a r e l e s s e f f i c i e n t f o r a g e r s than a d u l t s and e x p l o i t a more l i m i t e d a r r a y of f o o d ( H i l l and E l l i s 1984).  E r i k s s o n (1976, 197 8) showed t h a t young Common  Goldeneye f e d s e l e c t i v e l y and p r e f e r r e d free-swimming prey.  85  I f young  Barrow's Goldeneye feed i n a s i m i l a r way,  females would enhance feeding  opportunities for t h e i r young by maintaining exclusive t e r r i t o r i e s .  The  importance of food abundance f o r d u c k l i n g growth and s u r v i v a l has been shown i n s e v e r a l s p e c i e s 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 n e g a t i v e l y a f f e c t e d by a r e d u c t i o n i n food d e n s i t y . found a  correlation  between food  abundance and  S t r e e t (1977)  duckling  survival.  Pienkowski and Evans (1982a) argued t h a t by being t e r r i t o r i a l Shelducks reduced the r i s k of a d u c k l i n g seeking p r o t e c t i o n from an i n t r u d i n g or nearby a d u l t not ready t o defend i t .  S i m i l a r advantages would a p p l y t o  young goldeneyes. I wish t o s t r e s s , t h a t space, not food as such, i s the defended by males. The male does not choose the s i z e of the  resource territory  based on food abundance but r a t h e r seems t o defend an area as b i g as he can.  On  small lakes with  territory.  T e r r i t o r y boundaries a r e only established when neighbouring  p a i r s are present. t e r r i t o r i a l pairs. neighbouring p a i r . s p e c i e s have  Boundaries are the r e s u l t of c o n f r o n t a t i o n s between Males expanded t h e i r t e r r i t o r i e s when I removed a S e v e r a l other removal s t u d i e s on other  shown s i m i l a r  (Armitage 1974, V i n e s 1979, 1984,  s i n g l e p a i r s , the whole l a k e becomes the  Gauthier 1985).  expansion of  territorial  t e r r i t o r i e s by  neighbours  H i l d e n 1979, Hannon 1983, Norman and Jones  A l s o , s e v e r a l s t u d i e s have shown t h a t t e r r i t o r y  size i s not correlated c l o s e l y with food abundance but more c l o s e l y competitor  density and/or male aggressiveness  (Van Den Assem 1967,  1971, Watson and Moss 1971, Knapton and Krebs 1974, a l . 1979a,b, Franzblau and C o l l i n s 1980,  86  Hilden 1979,  Wasserman 1983).  with Krebs  Myers £t  I suggest t h a t an i m p o r t a n t f u n c t i o n 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 f o r the female (pair and winter t e r r i t o r i e s ) and f o r the young McKinney  (brood t e r r i t o r y ) .  (1973), Seymour (1974a,b) and Titman and Seymour (1981) a l l  reached a s i m i l a r conclusion i n t h e i r studies of t e r r i t o r i a l behaviour of dabbling ducks.  Patterson (1982) summarized  and reached the same conclusion. their  several studies on Shelduck  Donaghey (1975) and Gauthier (1985) i n  thorough i n v e s t i g a t i o n s of t e r r i t o r i a l i t y  i n Bufflehead  also  concluded that t h i s 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,  mergansers (Mergus spp., Bergman 1956, spp., K o s k i m i e s 1955); oldsquaw  Munro and Bedard 1977a);  Erskine 1972); Scoters (Melanitta  (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 c a n a d e n s i s . Warhurst e_t a l . 1983).  The causes and f u n c t i o n s of brood amalgamation  s t i l l remain obscure f o r s e v e r a l s p e c i e s .  In e i d e r s , Gorman and M i l n e  (1972) argued t h a t brood amalgamation resulted from the parents leaving t h e i r young to go to better feeding areas.  However, d e t a i l e d studies of  eiders i n Canada d i d not support t h i s hypothesis but indicated that brood amalgamation was caused by crowding and p r e d a t i o n  (Munro and Bedard  1977a,b, Bedard and Munro 1977). S i m i l a r l y W i l l i a m s (1974) showed t h a t brood amalgamation i n Shelduck r e s u l t e d from a g g r e s s i v e  territorial  encounters and that parents attempted t o keep t h e i r young rather than t o 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 a f f e c t the outcome of brood encounters: Female aggressiveness:  Boundaries are more l i k e l y to be established  i f females are of s i m i l a r strength. Age of young: can mix  If the young of the two broods are of s i m i l a r age they  more e a s i l y .  Also,  older  young can  more  effectively  withstand attacks by the v i c t o r i o u s female. Strength of female-duckling and duckling-duckling bonds:  Imprinting  i n c a v i t y n e s t i n g ducks i s m a i n l y a u d i t o r y u n t i l n e s t exodus (Hess 1973).  Visual imprinting a t 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. S i z e of brood:  D u c k l i n g s i m p r i n t 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). may  be weaker  In large broods the female-duckling bonds  than i n s m a l l broods,  again favouring  brood  amalgamation. L o c a t i o n of the encounter:  On s m a l l ponds, o n l y one brood  will  remain and o t h e r s w i l l be e x c l u d e d or amalgamation may occur. larger lakes, several t e r r i t o r i e s  On  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 a t the time of the encounter. Behaviour of young:  The behaviour of the young a f t e r m i x i n g  a f f e c t t h e i r acceptance by the female.  may  Graves and Whiten  (1980)  showed t h a t a d o p t i o n of s t r a n g e c h i c k s by H e r r i n g G u l l s  (Larus  argentatus) depended on the behaviour of the chick.  88  I t appears that, i n 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 a g g r e s s i o n . A s i m i l a r phenomenon e x i s t s i n c o r a l r e e f fishes  (Thresher 1985)  behaviour  by  and a l s o appears a c c i d e n t a l .  the female  or by  the young  that  The absence  would  favour  of  brood  amalgamation supports the non-adaptive o r i g i n of the phenomenon. S e v e r a l a u t h o r s have used the term c r e c h i n g t o d e s c r i b e brood amalgamation i n waterfowl (Gorman and Milne 1972, Williams 1974, Munro and Bedard 1977a,b).  C r e c h i n g , however, i m p l i e s a d a p t i v e behaviour (Davis  1982, Evans 1984) and thus the term i s not appropriate here.  Also several  studies have shown that brood amalgamation increased m o r t a l i t y and d i d not reduce i t ( W i l l i a m s 1974, Makepeace and P a t t e r s o n 1980, Pienkowski and Evans 1982a). C) I n t e r s p e c i f i c aggression Simmons (1951) defined 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  as an i n d i v i d u a l  e x h i b i t i n g p e r s i s t e n t a g g r e s s i v e behaviour t o an i n t r u d i n g b i r d of a second s p e c i e s , and d i r e c t i n g toward i t some of the d i s p l a y s used i n i n t r a s p e c i f i c encounters.  W a l t e r s (197 9) narrowed t h i s d e f i n i t i o n by  i n c l u d i n g the concept of e x c l u s i v e use of an area and proposed the term p a r t i a l exclusion when there was not exclusive use. According t o Simmons' d e f i n i t i o n , a l l three species of Bucephala are interspecifically territorial:  Common Goldeneye and Barrow's Goldeneye  exclude each other from t h e i r r e s p e c t i v e t e r r i t o r i e s and a l s o exclude Bufflehead.  B u f f l e h e a d exclude n o n - t e r r i t o r i a l goldeneye from  their  t e r r i t o r i e s but a r e dominated by t e r r i t o r i a l goldeneye drakes.  Other  sympatric diving ducks are regularly excluded from Bucephala t e r r i t o r i e s  89  but not as c o n s i s t e n t l y as congeners and thus f i t Walters' (1979) p a r t i a l exclusion concept. Among ducks, 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 been reported only  i n the genera Tachyeres and Bucephala (Weller 1976, t h i s study).  It i s  f a i r l y common, however i n other groups of b i r d s (Orians and W i l l s o n Murray 1971, 1981). one.  1964,  In most cases, the l a r g e r s p e c i e s i s the dominant  When both competing s p e c i e s a r e 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 c l e a r l y dominates the other, although Barrow's Goldeneye act more aggressively. Myres (1957) r e p o r t e d a g g r e s s i v e i n t e r a c t i o n s between Barrow's Goldeneye drakes and Common Goldeneye, B u f f l e h e a d , S u r f S c o t e r , L e s s e r Scaup, Ruddy Duck and American Coot ( F u l i c a americana) but observed  no  i n t e r a c t i o n s with dabbling ducks i n s p i t e of their abundance i n h i s study area (only a few km away from mine).  S i m i l a r l y , B u f f l e h e a d 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  reported i n t e r a c t i o n s with dabbling ducks.  authors  These observations support  my  f i n d i n g that Barrow's Goldeneye and Bufflehead are more aggressive toward diving ducks than dabbling ducks. What i s the significance of i n t e r s p e c i f i c aggression i n Barrow's Goldeneye?  S e v e r a l f u n c t i o n s of t h a t behaviour  1) exclusion of predators  (Walters 1979,  have been  Stephens 1984);  suggested:  2) Exclusion of  c o m p e t i t o r s f o r food (Orians and W i l l s o n 1964, Murray 1971, 1981, Moore 197 8, W a l t e r s 197 9, K a t z i r 1981a, Snow and Snow 1984, N u e c h t e r l e i n and S t o r e r 1985a);  3) sexual advertisement:  i n t e r s p e c i f i c aggression  serve to reinforce pair bonds and show the female "how 90  may  aggressive a male  is"  (Livezey  and  Humphrey  1985a,  N u e c h t e r l e i n and  S t o r e r 1985a);  4) i n t e r s p e c i f i c aggression i s m i s d i r e c t e d i n t r a s p e c i f i c a g g r e s s i o n has  no  advantages  (Murray  1971,  1981).  I consider  each  of  and  these  suggestions below.  1. Predator exclusion. T h i s does not apply t o Barrow's Goldeneye as none of the s p e c i e s excluded prey on goldeneye eggs or young. 2. Exclusion of competitors f o r food. A l k a l i n e ponds a r e s i m p l e h a b i t a t s t h a t f r e q u e n t l y l a c k emergent plants.  N e a r l y a l l of these ponds are devoid of f i s h e s and s u s t a i n h i g h  d e n s i t i e s of a q u a t i c arthropods.  The d i v e r s i t y of arthropods i s o f t e n  reduced by the high s a l i n i t y of these ponds (Cannings and Scudder Lancaster 1985).  1978,  Therefore, there i s l i t t l e opportunity for waterfowl  species to e x p l o i t d i f f e r e n t resources i n a l k a l i n e ponds. In  the  spring,  female  dabbling  e x c l u s i v e l y on i n v e r t e b r a t e s , and may (Bartonek  and Hickey 1969,  Competition  and  d i v i n g ducks  feed  almost  compete w i t h Barrow's Goldeneye  Bartonek and Murdy 1970,  Swanson £t £l» 1979).  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 i n shallow waters, whereas d i v i n g ducks and goldeneyes f e e d i n deeper waters by diving.  D i e t s of Barrow's Goldeneye and B u f f l e h e a d a r e s i m i l a r (Munro  1939, 1942, E r s k i n e 1972), and both s p e c i e s 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 c o r r e l a t e d with the degree of food overlap and/or degree of p o t e n t i a l f o r a g i n g i n t e r f e r e n c e , being h i g h e s t toward conspecifics and Bufflehead and higher toward diving ducks than dabbling  91  ducks.  Quantitative data, however, are needed to support t h i s hypothesis.  By e x c l u d i n g other w a t e r f o w l from t h e i r prevent  interference  i n feeding,  and  this  a v a i l a b i l i t y of food for the t e r r i t o r i a l pair. access to food should favour  territories may  result  goldeneyes in  greater  In the spring, increased  the production of e a r l y clutches and larger  eggs, thus enhancing the survival of ducklings.  E a r l i e r broods have f i r s t  choice of brood t e r r i t o r i e s and usually dominate l a t e r broods because the f e m a l e i s i n b e t t e r c o n d i t i o n and her young are o l d e r , and because of f a m i l i a r i t y and attachment t o the t e r r i t o r y (Hinde 1956, Ducklings  from l a r g e r eggs a r e l a r g e r and  better able to  i n c l e m e n t weather (Krapu 1979, Ankney 1980). the female may for food.  P e t r i e 1984).  By defending a t e r r i t o r y ,  enhance the survival of her young by reducing  In winter the male may  withstand  competition  create better feeding opportunities f o r  both himself and the female by excluding other species from stretches of rocky  s h o r e l i n e where mussels grow.  Surf S c o t e r s ,  extensively on mussels, are often expelled.  which a l s o f e e d  Flocks of scoters, however,  often invaded goldeneye t e r r i t o r i e s successfully, i n a way d e s c r i b e d i n r e e f f i s h e s (Robertson  gt  si.  1976,  s i m i l a r to that  F o s t e r 1985).  The  simultaneous l a r g e number of t r e s p a s s e r s rendered t e r r i t o r i a l defense inefficient. 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 l o a f i n g Harlequin Ducks (Histrionicus h i s t r i o n i c u s ) .  Gardarsson (197 8) showed t h a t the d i e t s of Barrow's Goldeneye and Ducks i n I c e l a n d are s i m i l a r , and  t h a t changes i n food supply  s u r v i v a l of the young of both s p e c i e s .  Aggressiveness  Harlequin affect  of grebes toward  goldeneye and bufflehead on the breeding ponds also suggests that food may l i m i t i n g resource.  the  be a  I observed Horned and Red-necked Grebes (Podiceps auritus,  P. g r i s i g e n a ) a t t a c k B u f f l e h e a d and Barrow's Goldeneye on s e v e r a l o c c a s i o n s .  92  Donaghey (1975) reported several attacks on Bufflehead by these two species of grebes.  Kirby (1976) described v i o l e n t interactions between P i e d - b i l l e d Grebes  (Podilymbus podiceps) and young Common Goldeneye. If enhancement of feeding opportunities i s an important function of intraspecific territoriality,  then c l o s e l y related species exploiting the  same resources should be excluded also, otherwise the advantage gained by excluding conspecifics w i l l be l o s t t o competing  species.  Interspecific  f e e d i n g t e r r i t o r i e s a r e w e l l documented i n hummingbirds Kodric-Brown 1974,  and Brown 1978)  E b e r s o l e 1977).  and i n f i s h  Loyn £ t a l .  (Low 1971/  (Cody  1968,  Myrberg and Thresher  (1983) showed t h a t  interspecific  aggression by B e l l Miners (Manorina melanophrys) resulted i n s i g n i f i c a n t increases i n food abundance w i t h i n the t e r r i t o r y . that i t resulted i n the sole occupancy  And Dow  (1977) showed  of space and thus better foraging  opportunities f o r Noisy Miners (M. melanocephala).  3. Sexual advertisement Barrow's Goldeneye are among the most s t r o n g l y s e x u a l l y d i m o r p h i c ducks (Livezey and Humphrey 1984; Appendix 5).  During pair formation and  early during t e r r i t o r y establishment, females sometimes aggressively chase away other goldeneyes while t h e i r mates show l i t t l e aggressiveness.  The  males, however, seem t o respond t o t h e i r mate's behaviour and q u i c k l y become aggressive.  S i m i l a r 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 l a t t e r authors postulated that male  Steamer-Ducks attack birds of other species to display t h e i r belligerency and f i g h t i n g a b i l i t i e s t o t h e i r f e m a l e s . this  should be  Goldeneye,  In view o f l a c k of evidence,  c o n s i d e r e d as s p e c u l a t i o n . Furthermore,  i n Barrow's  male a g g r e s s i v e n e s s i s not r e l a t e d t o the presence of the  93  female.  Display  of  aggressiveness  to  impress  the  f e m a l e can  t h e r e f o r e , be the s o l e f u n c t i o n of i n t e r s p e c i f i c a g g r e s s i o n . (1985) questioned t h i s i n t e r p r e t a t i o n . explain the aggressiveness  not,  Murray  A l s o , sexual s e l e c t i o n does not  of females with broods toward other species,  nor does i t explain the aggressiveness of the female i n winter. 4. Misdirected aggression I t has been argued t h a t 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 sometimes a r e s u l t of high i n t r a s p e c i f i c aggression  (Murray, 1971,  and S t o r e r 1985a), and  o n l y because i t has l i t t l e c o s t  associated with i t .  i s maintained  1981,  I n t e r a c t i o n s of Barrow's Goldeneye w i t h  ducks f i t the p a t t e r n of m i s d i r e c t e d a g g r e s s i o n .  dabbling  Dabbling ducks a r e  t o l e r a t e d more o f t e n than a t t a c k e d and, w i t h i n a few goldeneye may  Nuechterlein  minutes, a male  t o l e r a t e a d a b b l i n g duck t h a t he had p r e v i o u s l y a t t a c k e d .  The high l e v e l 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 w i t h male Barrow's Goldeneye. also attacked, aggression.  However, because female t e a l s a r e  plumage c o l o r a t i o n i s not the s o l e f a c t o r  Unfortunately, too few  i n t e r a c t i o n s were observed  eliciting with lone  Blue-winged Teal females (most of them were paired) to determine i f they were attacked l e s s or more than males.  When several species intrude i n t o  a goldeneye's t e r r i t o r y , conspecifics are attacked f i r s t , and then d i v i n g ducks, s u g g e s t i n g intruding species.  then congeners  t h a t goldeneye d i s c r i m i n a t e among  At times, however, aggression i s more indiscriminate:  Mary Jackson (in B e l l r o s e 1978)  reports a female goldeneye k i l l i n g her  young a f t e r the young had been colour-dyed. a brood by the t e r r i t o r i a l  I have also seen an attack on  male of t h a t brood.  Pienkowski and  (1982a) report that shelduck p a i r s sometimes mistakenly  94  own  Evans  attack t h e i r  own  young. as  Rasa (1969) found that pomacentrid f i s h e s use s i z e and behaviour  a clue f o r attack  damselfishes  of an i n t r u d e r .  recognised  Katzir  c o n s p e c i f i c s by t h e i r  (1981b) showed  that  colouration pattern.  Further research i s needed t o determine the f a c t o r s e l i c i t i n g  territorial  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 a g g r e s s i v e s p e c i e s a r e a l s o highly  intraspecifically  aggressive,  suggesting  that  interspecific  a g g r e s s i o n evolved as a by-product of i n t r a s p e c i f i c a g g r e s s i o n . Barrow's G o l d e n e y e ,  the cost  o f i n t e r s p e c i f i c aggression  n e g l i g i b l e compared with that of i n t r a s p e c i f i c aggression.  In  appears  I have r a r e l y  observed a d a b b l i n g or d i v i n g duck respond a g g r e s s i v e l y t o a t h r e a t or attack by a Barrow's Goldeneye; they either ignore the goldeneye or f l e e . Only t e r r i t o r i a l  Common Goldeneye and B u f f l e h e a d sometimes respond  a g g r e s s i v e l y , and B u f f l e h e a d a r e much s m a l l e r and e a s i l y dominated by Barrow's Goldeneye whereas the ranges of Common and Barrow's goldeneye do not o v e r l a p e x t e n s i v e l y . There i s t h e r e f o r e l i t t l e danger o f i n j u r y i n i n t 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, A p p e n d i x  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 s i z e - r e l a t e d a t t r i b u t e i n males of the genus. I suggest that a high l e v e l of i n t r a s p e c i f i c aggression, coupled with some feeding  advantages,  has f a v o u r e d  t h e e v o l u t i o n and maintenance of  i n t e r s p e c i f i c aggression i n the genus Bucephala. D) The t e r r i t o r y T e r r i t o r i e s of Barrow's Goldeneye do not f i t any of t h e proposed functional c l a s s i f i c a t i o n s of avian t e r r i t o r i e s Birkhead 1983).  (Hinde 1956, Perrins and  Goldeneye carry out a l l t h e i r breeding a c t i v i t i e s w i t h i n 95  the t e r r i t o r y but nest outside i t .  Nests located i n c a v i t i e s  i n flooded  t r e e s can sometimes be w i t h i n the t e r r i t o r y but t h i s i s the e x c e p t i o n . Therefore, 1941)  Barrow's Goldeneye have an all-purpose type A t e r r i t o r y  ( t e r r i t o r y which p r o v i d e s a l l requirements) w i t h the  e x c e p t i o n of the n e s t s i t e .  (Nice  significant  Goldeneyes seem to r e q u i r e both a n e s t i n g  c a v i t y and a f e e d i n g t e r r i t o r y to breed s u c c e s s f u l l y .  I t appears t h a t  they prefer t e r r i t o r i e s i n close proximity to the nesting s i t e (50% of the nest s i t e s were adjacent to the pair t e r r i t o r y ) . both  nest  site  (see  Chapter 3)  and  pair  However, philopatry to  territory  may  mask  this  preference. Philopatry to pair t e r r i t o r y i s w e l l known i n t e r r i t o r i a l species of b i r d s (Hilden 1979, Lank 1984).  Redmond and Jenni 1982,  Calder £t a i . 1983,  Oring and  The advantages of returning to the same t e r r i t o r y are:  1) a  prior sense of ownership which would increase defensive motivation (Hinde 1956,  F i g l e r 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 d u r i n g the w i n t e r and had f a i l e d t o r e - p a i r .  Upon t h e i r r e t u r n on the l a k e where  they defended t e r r i t o r i e s the p r e v i o u s y e a r ,  they defended the  t e r r i t o r y for almost two days although they were not paired. responded t o the s t i m u l u s of t h e i r o l d t e r r i t o r y ; territorial  neighbours could  reduce  the  They c l e a r l y  2) f a m i l i a r i t y  intensity  of  i n t e r a c t i o n s r e q u i r e d ; 3) knowledge of food r e s o u r c e s on the should  enhance  foraging  efficiency  ( Hixon e_t a i -  same  1983,  with  aggressive territory Gass  and  Sutherland 1985). A knowledge of t e r r i t o r y q u a l i t y combined with previous tenure creates an asymmetry between the value of a t e r r i t o r y to the owner and an i n t r u d e r ; i.e. the t e r r i t o r y intruder.  owner has more t o l o s e than  the  P e t r i e (1984) and Ewald (1985) have shown that such asymmetries  96  influence dominance. Pair t e r r i t o r i e s and brood t e r r i t o r i e s r a r e l y coincide and t h i s can be a t t r i b u t e d i n p a r t t o the s c a r c i t y of n e s t s i t e s .  Also, there i s  p r o b a b l y l i t t l e s e l e c t i o n f o r brood t e r r i t o r i e s t o c o i n c i d e w i t h p a i r t e r r i t o r i e s because:  A) boundaries of pair t e r r i t o r i e s are established by  males and collapse when they leave; the s i z e of p a i r t e r r i t o r i e s ; density; and  D) boundaries  C) brood d e n s i t y i s o n l y a t h i r d of p a i r  of brood t e r r i t o r i e s are established by  E) feeding requirements  females i n spring.  B) brood t e r r i t o r i e s average twice  females;  of young are probably d i f f e r e n t from those of  Brood t e r r i t o r i e s are usually established on the lake  closest to the nest s i t e .  This strategy minimizes overland t r a v e l which  exposes the young t o i n c r e a s e d r i s k s of p r e d a t i o n and d e p l e t e s 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 q u a l i t y of the nearest lake for r a i s i n g broods. T e r r i t o r i a l i t y i s w e l l developed i n Barrow's Goldeneye and w i t h i n the genus Bucephala. (pair  and  winter  I t s main f u n c t i o n seems to be t o p r o v i d e the f e m a l e territories)  and  the  brood  (brood  territory)  an  undisturbed feeding s i t e . Further experimental work i s , however, needed to q u a n t i f y b e t t e r the i n f l u e n c e of g r e a t e r food a v a i l a b i l i t y on v a r i o u s a s p e c t s of the breeding and w i n t e r i n g ecology of Barrow's Goldeneye and i t s relatives.  Summary 1)  P a i r s of Barrow's Goldeneye, Common Goldeneye and B u f f l e h e a d a r e t e r r i t o r i a l d u r i n g the b r e e d i n g season:  2)  season and d u r i n g the w i n t e r i n g  They defend a f i x e d , exclusive area against r i v a l s .  Barrow's Goldeneye and Bufflehead f e m a l e s defend t e r r i t o r i e s a f t e r 97  t h e i r young have hatched,  and t h e i r behaviour  i s s i m i l a r to that of  the drakes i n the spring. 3)  A l l three species of Bucephala have s i m i l a r t e r r i t o r i a l behaviour  on  the breeding area. 4)  P a i r s of a l l t h r e e s p e c i e s a r e 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 i n t e r s p e c i f i c aggression i s strongest toward congeners and toward  diving  interspecific  ducks than  d a b b l i n g ducks.  The  a g g r e s s i o n i s thus c o r r e l a t e d w i t h  and  stronger  intensity  of  the degree of  resource use overlap between Barrow's Goldeneye and other species. 5)  Barrow's Goldeneye and B u f f l e h e a d females  are  interspecifically  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 t e r r i t o r i e s i s strong i n Barrow's Goldeneye.  8)  Long-term pair bonds e x i s t 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 f o r the female or the young. 10)  I  argue  that  the  e v o l u t i o n and  maintenance  of  interspecific  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 w i t h i n the genus, and s i g n i f i c a n t feeding advantages obtained from the exclusion of competitors.  98  Chapter IV:  Use o f nest boxes and nesting success  99  Introduction Barrow's Goldeneye a r e secondary h o l e n e s t e r s t h a t use e x i s t i n g c a v i t i e s i n s t e a d o f e x c a v a t i n g t h e i r own (McLaren 1963). Columbia,  they  may  use o l d n e s t s  o f t h e Common  In B r i t i s h  Crow  (Corvus  brachyrhynchos) (Edwards 1953, Sugden 1963), and even burrows of Yellowbellied  Marmot  (Marmota f l a v i v e n t r i u s )  (Munro 1935), but they  most  commonly use tree c a v i t i e s excavated by P i l e a t e d Woodpecker (Dryocopus pileatus),  (Munro 1939, B e l l r o s e 1978) and Common F l i c k e r  fColaptes  auratus) h o l e s t h a t have been e n l a r g e d by w e a t h e r i n g (M.F. Jackson i n B e l l r o s e 197 8).  In t h e p a r k l a n d h a b i t a t of B r i t i s h  Columbia, t r e e  c a v i t i e s provide most nesting s i t e s f o r Barrow's Goldeneye, b u t l o g g i n g a c t i v i t i e s have reduced t h e number of n e s t s i t e s near s e v e r a l b r e e d i n g ponds. Barrow's Goldeneye may nest s e v e r a l k i l o m e t e r s from water (Munro 1939) and nest c a v i t i e s can be over 20m above ground, making the f i n d i n g and checking of natural c a v i t i e s d i f f i c u l t . study of i t s breeding biology. boxes (Griffee 1958,  There has thus been no major  Barrow's Goldeneye are known t o use nest  McLaren 1963) but no quantitative studies have been  done on their breeding success i n nest boxes, and the impact of nest boxes on  the population  has n o t been documented.  Nest boxes have  e x t e n s i v e l y used t o manage and f a c i l i t a t e the study o f other nesting  been  cavity-  w a t e r f o w l (Grice and Rogers 196 5, Norman and R i g g e r t 1977,  Eriksson 1979 b).  They have e f f i c i e n t l y increased breeding densities o f  Wood Duck (Aix sponsa) (Schreiner and Hendrickson 1951, McLaughlin and G r i c e 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 p r o v i s i o n of nest boxes has been the key i n the s u c c e s s f u l  establishment of new populations of Wood Duck and Common Goldeneye (Doty 100  and Kruse 1972, Eriksson 1982, Dennis and Dow 1984). The breeding b i o l o g y of Common Goldeneye i n n e s t boxes has been studied i n d e t a i l (Siren 1951, Gibbs 1961, Johnson 1967, Eriksson 1979b, 1982, Bragin 1981, Dow 1982).  However, most studies on Common Goldeneye  were done where b r e e d i n g d e n s i t i e s were low compared t o d e n s i t i e s o f Barrow's Goldeneye.  During t h e b r e e d i n g season, Barrow's Goldeneye a r e  u s u a l l y a s s o c i a t e d w i t h p r o d u c t i v e waters (Skinner 1937, H a r r i s e± s i . 1954, Bengtson 1971, Palmer 1976), whereas Common Goldeneye a r e o f t e n associated with f l o o d p l a i n s and o l i g o t r o p h i c lakes of lower productivity (Siren 1952, Carter 1958, Gibbs 1961, Prince 1965, Palmer 1976, Danell and Sjoberg 1977, E r i k s s o n 197 9b).  T h e r e f o r e , i n most s t u d i e s of Common  Goldeneye, d e n s i t i e s may not have been h i g h enough  for t e r r i t o r i a l  behaviour t o have any e f f e c t on nest box use or breeding success. indicated by the f a c t that few of these studies mentioned i n Common Goldeneye and most even suggested territorial.  This i s  territoriality  that they were probably not  T h e r e f o r e i t remains t o be shown i f use of nest boxes by  Barrow's Goldeneye i s s i m i l a r t o that of Common Goldeneye. My aims i n t h i s chapter are: the  use o f nest  1. t o determine the f a c t o r s influencing  boxes by Barrow's Goldeneye;  reproductive success i n nest boxes;  2. t o q u a n t i f y  their  3. t o assess the impact of nest boxes  on the size of the breeding population; and 4. to compare the r e s u l t s with those  obtained  territorial  i n two other s t u d i e s u s i n g n e s t boxes:  s p e c i e s , the Wood Duck,  and b) o f a t e r r i t o r i a l  breeding a t lower densities, the Common Goldeneye.  101  a) o f a nonspecies  Methods Between 1981 and 1984,  I erected 278 large (hole diameter >8 cm) and  71 small (hole diameter <8 cm) nest boxes. d e s i g n of Lumsden e_t a l . rough cedar (Table 24).  Nest boxes were based on the  (1980), and were b u i l t from rough plywood or  Boxes had side openings and were n a i l e d on aspen,  p i n e or f i r t r e e s w i t h the entrance between 4 and 5 m above ground. layer of spruce shavings (2-3 cm deep) was added as nest material.  A  Trees  c l o s e t o the water's edge were s e l e c t e d whenever p o s s i b l e , but because s e v e r a l l a k e s were surrounded by open g r a s s l a n d , boxes ranged from 0 t o 400 m from the water's edge. Nest boxes were checked twice i n 1981, but 3 to 10 times i n 1982-84. In 1984, a sample o f 29 boxes was v i s i t e d every day t o d e t e c t p a r a s i t i c laying.  A t the end o f the b r e e d i n g season, abandoned eggs were removed  from the boxes, but o l d down and nest material were l e f t i n t a c t . S u c c e s s f u l n e s t s a r e those i n which a t 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 a t 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 f o r 96% of the 537 breeding attempts recorded i n large nest boxes during the four years of the study. Barrow's Goldeneye accounted f o r 70% o f attempts, and  American Kestrel (Falco spar ver ius)  and European S t a r l i n g (Sturnus v u l g a r i s ) f o r 13% each (Table 25).  The  percentage of boxes t h a t remained empty each year ranged from 19 t o 33% (Table 25).  In the boxes with entrances too small f o r Barrow's Goldeneye,  European S t a r l i n g , American Kestrel and Bufflehead accounted respectively 102  Table 24. Dimensions of nest boxes and dates of erection.  Erection date  March 1981  Number of boxes  Interior f l o o r area (cm ) 2  Depth (cm)  1  Hole s i z e Type o f wood (height x w i d t h . or diameter) (cm) 2  140  660  35  11x13  plywood  August 1981  30  660  35  11x13  plywood  October 1982  42  660  35  11x13  plywood  A p r i l 1983  18  210  28  7  cedar  A p r i l 1983  17  320  28  7  cedar  A p r i l 1983  24  360  28  7  cedar  A p r 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 s i z e > 8 cm = large nest boxes; hole s i z e < 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 K e s t r e l  24  14  10  20  68  European S t a r l i n g  27  5  22  14  68  Red S q u i r r e l  6  2  5  3  16  Tree Swallow  -  2  2  -  4  Northern  1  -  1  -  2  Bufflehead  -  -  1  1  2  Mountain Bluebird  -  -  1  -  1  41  44  37  82  204  136  157  196  252  741  Flicker  Nest boxes not used by breeding species Total number of boxes a v a i l a b l e  104  f o r 62%, 19% and 6% of the 108 breeding attempts (Table 26). Two nest boxes were used by two s p e c i e s i n the same season.  In one  case, an American Kestrel successfully raised a brood i n a box after young red s q u i r r e l s had been r a i s e d t h e r e .  In the second case, a Barrow's  Goldeneye used a box from which a brood of European S t a r l i n g s had fledged. Two species occasionally competed f o r the same box; t h i s resulted usually i n the nest being deserted by one or both species.  During the four years  of the study, American Kestrels took over 4 European S t a r l i n g nests, and t h r e e mixed c l u t c h e s of Hooded Merganser and Barrow's Goldeneye were recorded.  H a l f of the 39 c o n f l i c t s observed (51%) however, o c c u r r e d  between Barrow's Goldeneye and European S t a r l i n g .  S e v e r a l empty n e s t  boxes were used f o r r o o s t i n g a t n i g h t by American K e s t r e l , Northern F l i c k e r , European S t a r l i n g , and during the day by f l y i n g 2)  squirrels.  Nest box use by Barrow's Goldeneye Barrow's Goldeneye used 37 n e s t boxes i n 1981 and 132 i n 1984, an  increase  o f 350%  over t h r e e y e a r s  (Table 25).  Barrow's  Goldeneye  p r e f e r r e d o l d boxes t o newly i n s t a l l e d ones (Fig. 17). Nest boxes t h a t were used by Barrow's Goldeneye were more l i k e l y to be used by goldeneye the f o l l o w i n g y e a r than those t h a t had not been used (Table 27).  Also,  boxes i n which Barrow's Goldeneye successfully hatched a brood were r e used p r o p o r t i o n a l l y more o f t e n by goldeneyes than boxes i n which the reproductive e f f o r t f a i l e d  (Table 27).  In 1981, nest boxes were placed on ponds that had received d i f f e r e n t l e v e l s of use by Barrow's Goldeneye i n 1980 to determine i f the presence of goldeneye on t h e l a k e would i n c r e a s e 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 s p i t e of the presence of n e s t boxes.  105  Goldeneyes used o n l y 1 of 18 boxes  Table  26.  Number  of s m a l l nest  b o x e s u s e d by b r e e d i n g  wildlife.  Year Use b y Breeding species  1983  1984  Total  American  Kestrel  10  10  20  European  Starling  40  27  67  Bufflehead  1  6  6  Mountain  1  -  1  Swallow  1  5  6  Squirrel  2  5  7  1  -  1  3  17  20  59  70  129  Tree Red  Flying  Bluebird  Squirrel  Nest boxes n o t used by b r e e d i n g s p e c i e s T o t a l number o f boxes a v a i l a b l e  106  BOXES USED BY OTHER  8PECIE8  B O X E S U S E D B Y BARROW'8  UNUSED  GOLDENEYE  BOXES  11  NEW n«226  1 YEAR OLD n«i97 AQE  F i g . 17  OF  I.II  2 YEARS OLD n»i52 NEST  3 YEARS OLD n«125  BOXES  P r o p o r t i o n o f n e s t boxes used by Barrow's Goldeneye and other w i l d l i f e i n r e l a t i o n t o age of the nest box (n=number of nest boxes).  107  Table 27. R e l a t i o n s h i p between p r e v i o u s use of a nest box and subsequent use by Barrow's Goldeneye. Subsequent status Previous status  Not used by Barrow's Goldeneye  Used by Barrow's Goldeneye  % used  Not used by Barrow's Goldeneye  98  136  58  Used by Barrow's Goldeneye  54 171 X =17.2, P<0.001  76  81  90  90  67  2  Used and hatched Used and f a i l e d  9 45 X2=l5.3  108  f  P<0.001  on those l a k e s . goldeneye  Nest boxes l o c a t e d on ponds w i t h high d e n s i t i e s o f  (>5 subadults) had more use than those on ponds w i t h low  d e n s i t i e s (<2 subadults) (Table 28, X =3.907, df=2, p=0.048). 2  a)  Nesting success The proportions of Barrow's Goldeneye nests that hatched, were preyed  upon, and were d e s e r t e d , 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 d u r i n g the f o u r y e a r s o f the study ( F i g . 18, X =10.07, df=3, p=0.12). These p r o p o r t i o n s 2  averaged respectively 46±4%, 31±3% and 23+3% and are w i t h i n the range of values found i n other cavity-nesting waterfowl P r e d a t i o n was d e s t r u c t i v e predator  an important  (Table 29).  cause of n e s t f a i l u r e s .  was the B l a c k Bear  (Ursus americanus).  destroyed 33 nest boxes during the study: 0 i n 1980, 5 i n 1981, and 24 i n 1984.  The most Bears  4 i n 1983,  Predation attempts were spread throughout the study area  and probably i n v o l v e d s e v e r a l bears.  B l a c k Bears u s u a l l y a t t a c k e d n e s t  boxes with incubating females i n them, leaving nearby boxes intact. suggests that they were attracted t o the boxes by noise or scent.  This In one  case, however, a bear d e s t r o y e d the f o u r boxes e r e c t e d a t a s i n g l e pond. Female goldeneye u s u a l l y escaped a l i v e from boxes preyed upon by bears. Some p r e d a t o r s removed eggs from boxes one a t a time.  Although I never  observed predation, I suspect red s q u i r r e l (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 t o enter a box from  which s i n g l e eggs had been taken b u t 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 p a r t i a l predation caused  s e v e r a l nest d e s e r t i o n s . Marten (Martes americana) may a l s o have been responsible f o r some egg loss.  The remains of one female goldeneye were  found i n a box, suggesting predation.  Besides the 33 nest boxes destroyed  by Black Bears, 5 were l o s t when t h e i r support tree f e l l down naturally, 3  109  Table 28.  Nest box use i n r e l a t i o n t o abundance of Barrow's Goldeneye on pond i n the previous year. Barrow's Goldeneye abundance  Population  No.of Total no. Total no. Total no. Ponds yearlings pairs broods  No.nest No. nest boxes boxes used  % used  Ponds with >5 subadults i n 1980  17  361  147  33  59  24  41  subadults i n 1980  22  5  38  19  52  12  23  Ponds with no goldeneye i n 1980  6  0  0  0  18  1  6  Ponds with <2  no  HATCHED PREYED UPON DESERTED  1981  1982  n =33  n =89  1983 n»115  1984 n=131  YEAR  F i g . 18  P r o p o r t i o n of Barrow's Goldeneye n e s t s t h a t hatched, were preyed upon and were d e s e r t e d (n=number of nest boxes).  Ill  Table 29.  Comparison of nesting success between c a v i t y nesting ducks. Nest fate (%) Hatched  Preyed upon  Barrow's Goldeneye This study  46±4  31±3  Common Goldeneye Johnson (1967) Eriksson (1979b) Br agin (1981)  62 27 42  20 38 28  Wood Duck Nay l o r (1960) B e l l r o s e 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)  75±5 37±6 74 29 29 69±5 64  10±3 52±5 7 17  B l a c k - b e l l i e d Whistling Duck Bolen (1967) McCamant and Bolen (1979)  61 31£L6  112  Deserted  23±3  18 35 28  9±2 10±2 19 55  were f e l l e d  by beavers  (Castor c a n a d e n s i s ) , 1 by l o g g e r s and 1 was  destroyed by vandals. The outcome of a n e s t i n g attempt was independent of the age of the box. S i m i l a r p r o p o r t i o n s of n e s t s were s u c c e s s f u l i n new boxes and i n o l d e r boxes (X =11.5, df=3, P>0.05). 2  r e c o r d e d were not due t o observer  The m a j o r i t y of the d e s e r t i o n s  i n t e r f e r e n c e , as most d e s e r t i o n s  o c c u r r e d i n n e s t s i n which the female was absent (Fig. 19). determined,  d u r i n g t h e checks  For the n e s t boxes where c l u t c h i n i t i a t i o n dates c o u l d be I d i v i d e d i n i t i a t i o n d a t e s each year i n f o u r equal p a r t s :  early, mid-early, mid-late and l a t e .  Because the proportion of successful  nests d i d not d i f f e r s i g n i f i c a n t l y between years (Fig. 18) I combined a l l the n e s t s i n each c a t e g o r y f o r a l l y e a r s .  The p r o p o r t i o n of n e s t s t h a t  hatched d i d not d i f f e r s i g n i f i c a n t l y between early and mid-early clutches nor between mid-late and l a t e clutches but was greater i n a l l early versus l a t e c l u t c h e s ( F i g . 20, X failed,  2  T e s t s , d f = l , P<0.05).  the p r o p o r t i o n of d e s e r t e d n e s t s was  Among the n e s t s t h a t similar  i n i t i a t i o n periods (Fig. 21, X =1.70, df=3, P=0.64). 2  i n a l l clutch  Among the nest boxes  that were used by Barrow's Goldeneye two years i n a row, those which had been s u c c e s s f u l the p r e v i o u s year were more l i k e l y t o be s u c c e s s f u l the f o l l o w i n g year  (Fig. 22, X =5.78, df=l, P<0.016). 2  b) Productivity From 1981 to 1984, the number of eggs l a i d i n nest boxes increased 6fold  (Table 30).  The average clutch s i z e was s i g n i f i c a n t l y lower  i n the  f i r s t two years of the study and t h i s was true whether deserted and preyed upon c l u t c h e s were i n c l u d e d or not (Table 30). The p r o p o r t i o n of eggs t h a t hatched was s i m i l a r i n 1982, 1983, and 1984 (X =5.15, df=2, P<0.07) 2  but was higher i n 1981 (X =39.8, df=l, P<.001), however these 2  113  statistical  HATCHED  F i g . 19  PREYED UPON  DESERTED  I n f l u e n c e o f v i s i t s by o b s e r v e r s on t h e f a t e s of n e s t s .  114  72 . 64 .  O < 09  Ul  u. O  56 4B -  1 } •  4 0 .  r  32 -  •  •»•as ^  111  O tr  24  v.-  4  m  ft  UJ  a.  I  16 .  t-  8 _  x EARLY n-82  m  MID-EARLY n-82  MID-LATE  CLUTCH INITIATION  F i g . 20  n«80  PERIOD  Hatching success i n r e l a t i o n t o date of clutch i n i t i a t i o n (n=number of nests).  115  EARLY nn28  MID-EARLY n»39  MID-LATE n=52  C L U T C H INITIATION PERIOD  F i g . 21  P r o p o r t i o n s o f non-hatching nests preyed upon 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 date (n=number of n e s t s ) .  116  LATE n«54  BREEDING S U C C E S S IN YEAR 2  HATCHED IN YEAR 1  n. 81 BREEDING  F i g . 22  FAILED IN YEAR 1  ni 01 SUCCESS  IN Y E A R  1  I n f l u e n c e o f the outcome 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 attempt i n a nest box on t h e outcome of future nesting attempts i n the same nest box (n=number of nests).  117  Table 30.  Egg production i n nest boxes i n r e l a t i o n t o year. % of eggs that were No.of eggs laid Hatched Predated Deserted  Average c l u t c h s i z e ± standard error  Year  No. of boxes  1981  33  217  65  10  26  6.58±0.56 A  1982  89  646  42  22  36  7.26+0.43 A  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  ll.lli0.53 B  1  Successful nests only (no. of nests)  A l l nests  2  7.79+0.71 A 9.15+0.66 A  2  (19) (34)  (62)  Only nest boxes whose fate was known. Averages with s i m i l a r 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 (Newman-Keuls Multiple range test, P<0.05) (Zar 197 4).  r e s u l t s should be considered cautiously because of the occasional lack of independence between the eggs of a g i v e n c l u t c h sometimes l o s t a t the same t i m e ) .  (entire c l u t c h e s are  C l u t c h s i z e s i n new  and o n e - y e a r - o l d  nest boxes d i d not d i f f e r s i g n i f i c a n t l y , but were s i g n i f i c a n t l y lower than clutches l a i d i n 2- and 3-year-old boxes (Table 31).  A s i m i l a r result i s  obtained i f only successful nests are compared (Table 31).  The proportion  of eggs t h a t hatched v a r i e d w i t h the age of the box, b e i n g l o w e s t i n 1year o l d boxes and h i g h e s t i n 3-year o l d boxes. been u s e d by  Nest boxes t h a t had not  Barrow's Goldeneye i n the p r e v i o u s y e a r  contained  s i g n i f i c a n t l y smaller clutches (x=9J+0.51, n=50) than those that had been used by Barrow's Goldeneye, whether the nesting attempt was =13.04+0.06, n=46) or not  successful (X  (x"=12.17±0.69, n=35) (Newman-Keuls m u l t i p l e  range t e s t , P<0.05, Zar 1974).  c) P a r a s i t i c egglaying In 1984,  29 nest boxes were checked d a i l y to assess laying patterns  and t o look f o r n e s t p a r a s i t i s m .  More than 1 egg was  hour p e r i o d i n 37 i n s t a n c e s d i s t r i b u t e d i n 21 boxes. cases, no egg was of  two  eggs may  l a i d the following day,  l a i d w i t h i n a 25 In 18 of those 37  indicating that the appearance  have been due to the checking schedule r a t h e r than t o  p a r a s i t i c l a y i n g . In the remaining 19 cases ( i n 13 boxes) two or more females were responsible f o r the additional eggs.  Therefore, 13 of the 29  boxes (45%) checked were parasitized a t l e a s t once, and 4 boxes (14%) were p a r a s i t i z e d a t l e a s t 3 times.  In one case, 4 eggs were l a i d w i t h i n a 25 h  p e r i o d , and i n 6 cases 3 eggs were l a i d w i t h i n 25 h.  The average l a y i n g  i n t e r v a l f o r a g i v e n box ranged between 16 and 72 hours.  Such a spread  indicates p a r a s i t i c laying, the low values being due to m u l t i p l e laying i n a box, whereas the l a r g e v a l u e s a r e due t o i n t e r m i t t e n t l a y i n g .  119  Laying  Table 31. Egg production i n r e l a t i o n t o age of the box. Average c l u t c h s i z e + standard error % of eggs that were Hatched Predated Deserted  n (No.of eggs)  A l l nests  n  1  Successful nests only  n  New boxes  48  14  38  355  6 . 57+0.39 A  1 year o l d 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 o l d boxes  53  17  30  10.25+0.48 B  11.84±0.56 B  51  974  2  54  95  7.71+0.59 A  2  24  1  only nests whose fate was known.  2  Averages with s i m i l a r 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 (Newman-Keuls M u l t i p l e range t e s t , P<0.05) (Zar 1974) .  p a t t e r n s i n nest boxes ranged w i d e l y :  i n one box 1 egg was added every  second day, i n o t h e r s 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 o f 7 days, 10 more eggs were added, a l l 18 eggs hatched eggs.  successfully. In some other boxes, several days elapsed between Daily checks indicated that p a r t i a l predation of a clutch d i d not  necessarily cause desertion.  However, a l l nests i n which yolk had s p i l l e d  on the other eggs were deserted. I f we assume t h a t c l u t c h e s c o n t a i n i n g more than 13 eggs a r e the product of p a r a s i t i c laying, we can derive a conservative estimate of the frequency of p a r a s i t i c laying f o r each year:  7% (n=41) i n 1981, 7% (n=99)  i n 1982, 20% (n=124) i n 1983 and 19% (n=145) i n 1984. conservative, clutches.  as n e s t  This estimate i s  p a r a s i t i s m does not always r e s u l t  i n larger  Also, clutches deserted due to parasitism would not be included  here u n l e s s they were d e s e r t e d a f t e r they had more than 13 eggs. consider clutches containing more than 10 eggs as a product laying, then our estimates of p a r a s i t i c laying become: i n 1982, 37% i n 1983 and 3 9% i n 1984.  I f we  of p a r a s i t i c  10% i n 1981, 20%  The 29 n e s t s t h a t were f o l l o w e d  d a i l y i n 1984 suggest a higher frequency of p a r a s i t i c laying  (45%).  Most  of the parasitism occurred during egg laying; i n only two of 14 boxes d i d i t occur after the i n i t i a t i o n of incubation.  d) Impact of nest boxes on population s i z e In 1980,  the year  prior  t o t h e e r e c t i o n of n e s t boxes, the  populations of Barrow's Goldeneye and Bufflehead were estimated a t 205+13 p a i r s and 109+11 p a i r s r e s p e c t i v e l y (n=4 counts).  By 1984 the Barrow's  Goldeneye population had increased by 57% to 322±8 p a i r s whereas that of B u f f l e h e a d had i n c r e a s e d by 42% t o 155±15 p a i r s (Fig. 23). However, the number o f B u f f l e h e a d p a i r s d i d not v a r y s i g n i f i c a n t l y d u r i n g the f i v e  121  F i g . 23  Numbers o f Barrow'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 on t h e s t u d y a r e a (95% Confidence l i m i t s are given).  122  y e a r s 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 i n c r e a s e d s i g n i f i c a n t l y i n the t h i r d year e r e c t i o n of nest boxes and a g a i n i n 1984 From 1980  t o 1982  t h e r e was  (1983) f o l l o w i n g the  (Newman-Keuls t e s t , P<0.05).  no s i g n i f i c a n t d i f f e r e n c e i n numbers of  goldeneye p a i r s . Brood counts r e f l e c t t h i s i n c r e a s e (Fig. 24). of Barrow's Goldeneye was i n 1982. of 29%. 1983  The number of broods  s i m i l a r i n 1980 and 1981 and started to increase  By 1984 there were 24 more broods on the study area, an increase Bufflehead broods increased from 1980  and remained a t the same l e v e l i n 1984.  to 1982, From 1980  then decreased i n to 1984  there was  only a 6% increase i n the number of Bufflehead broods on the study area. Whether t h i s i n c r e a s e i s due to the presence of the n e s t boxes or j u s t r e f l e c t s a n a t u r a l g e n e r a l i n c r e a s e i n the p o p u l a t i o n can o n l y 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 i n the area. vary greatly between areas. similar  t o t h a t of  the  new  results  However none of the controls display r e s u l t s study  area  (Table 32).  Bufflehead increased i n Chilco (area B) which was several  The  ponds i n 1982.  T h i s suggests  Both goldeneye  and  due to the flooding of  t h a t the i n c r e a s e 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 i n s t a l l a t i o n of nest boxes.  density  i n c r e a s e d by about 50%  The increase began i n 1983,  the erection of the f i r s t boxes.  after  the  three years a f t e r  T h i s coincides with the year the young 123  65 60 55 -  1980  1981  1882  1983  1984  YEAR  F i g . 24  Numbers o f Barrow's Goldeneye and B u f f l e h e a d broods estimated on the study area.  124  Table 32.  Summary of counts c a r r i e d out by Ducks Unlimited i n Central B r i t i s h Columbia and comparison with counts on the study area. No. of Bufflehead pairs  No. of Barrow's Goldeneye p a i r s  Barrow's p a i r s Bufflehead p a i r s  Area  Year  Al  1980 1981 1983  67 69 69  47 58 46  +20 +11 +23  B  1980 1981 1983  28 39 60  23 43 69  +15 -4 -9  2  C  1980 1981 1982 1983  26 26 29 27  5 9 37 8  +21 +15 -8 +19  D  1980 1982 1983  33 40 43  21 67 32  +12 -27 +11  E  1982 1983 1984  78 70 49  87 115 55  -9 -45 -6  F  1980 1981 1982 1983 1984  205 201 199 265 322  109 125 140 123 155  +96 +76 +59 +142 +167  Areas: Merrit;  A) B a l d Mountain, 148 M i l e House; B) C h i l c o ; D) 70 Mile House; E) C h i l c o t i n ; F) Study area.  C) R o s e h i l l and  The l a r g e i n c r e a s e i n t h e number of p a i r s i n 1983 was due t o the c r e a t i o n of s e v e r a l new ponds s u i t a b l e f o r d i v i n g ducks. T h i s i s r e f l e c t e d i n a similar increase i n goldeneye and Bufflehead numbers.  125  produced i n 1981  should have e n t e r e d the breeding p o p u l a t i o n .  This  coincidence, coupled with the information gathered from the control areas which showed no s i m i l a r increase i n goldeneye numbers, strongly suggests t h a t the the g r e a t e r 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  large natural cavities  (1985) found a scarcity of  i n the aspen p a r k l a n d  of B.C.:  t h e r e was  an  adequate supply of c a v i t i e s f o r B u f f l e h e a d but o n l y 12% of the c a v i t i e s (n=135) had an entrance opening large enough f o r Barrow's Goldeneye.  They  found that Bufflehead avoided large nest boxes and made a l i m i t e d use of small boxes which suggests that small natural c a v i t i e s are abundant i n the area.  Preference of small entrance c a v i t i e s by Bufflehead would reduce  the chances of c o n f r o n t a t i o n w i t h f e m a l e Barrow's Goldeneye which have been r e p o r t e d t o 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 t h a t t e r r i t o r i a l behaviour had a n e g a t i v e impact on nest box use.  Aggression of paired drakes on the t e r r i t o r y d i d  not deter females from using nest boxes adjacent to i t . meters a p a r t were used by  different  females.  Nest boxes a few  Because  territorial  aggression i s centered on the t e r r i t o r y i t s e l f and not on the nest s i t e , any impact of t e r r i t o r i a l behaviour through an o v e r a l l behaviour  may  limiting effect  on nest box use w i l l be on  the p o p u l a t i o n .  l i m i t breeding d e n s i t i e s of B u f f l e h e a d  Because Barrow's Goldeneye can use  nest  s i t e s 2 Km  breeding t e r r i t o r y , the impact of t e r r i t o r i a l behaviour l i m i t e d i n areas where water b o d i e s a r e abundant. the population was  indirect,  Territorial  (Gauthier 1985). away from  their  of p a i r s w i l l  be  In my study, because  apparently 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 , i t may  take a few more y e a r s b e f o r e any i n f l u e n c e of t e r r i t o r i a l behaviour 126  on  nest box use i s detected. Several f a c t o r s affected the use of nest boxes by Barrow's Goldeneye: previous use, outcome of previous breeding attempt, age of box, box l o c a t i o n .  Nest boxes t h a t had been used i n  and nest  p r e c e d i n g y e a r s were  l i k e l y to be re-used the f o l l o w i n g y e a r s and s u c c e s s f u l n e s t s more so. S i m i l a r p a t t e r n s of u t i l i z a t i o n have been found (Eriksson 1979 b, Dow  and Fredga 1983,  i n Common Goldeneye  1985).  Barrow's Goldeneye preferred o l d boxes to newly-installed ones.  This  i s because most s u b a d u l t f e m a l e s and u n s u c c e s s f u l f e m a l e s s e l e c t t h e i r nest s i t e the year p r i o r to breeding  (Eadie and Gauthier 1985).  New  boxes  are not, t h e r e f o r e , a v a i l a b l e a t the time of n e s t s i t e s e l e c t i o n .  Nest  boxes l o c a t e d on l a k e s f r e q u e n t e d by goldeneye were more l i k e l y t o 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 c a v i t i e s on the lakes where they f e e d , and o n l y i f u n s u c c e s s f u l t h e r e would they be expected  t o expand  t h e i r searching radius. E a r l y c l u t c h e s were more l i k e l y t o hatch than l a t e ones. r e f l e c t e a r l i e r breeding by older and 1964,  Klomp 1970,  experienced  This  may  b i r d s (Bellrose e i aJL  Krapu and Doty 197 9, A f t o n 1984).  In the f i r s t  two  years of the study, the average clutch size of Barrow's Goldeneye i n nest boxes was lower than i n the l a s t 2 y e a r s .  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. may  be due to young b i r d s being more l i k e l y to use new  This  c a v i t i e s than older  b i r d s . S i m i l a r l y , new and 1-year-old boxes are more l i k e l y t o c o n t a i n a higher  p r o p o r t i o n of f i r s t  time b r e e d e r s  than o l d e r boxes.  In some  waterfowl species, young and inexperienced breeders are known to produce smaller clutches than older b i r d s (Heusman 1975,  127  B a i l l i e and Milne  1982,  Rockwell fit a l . 1983,  Afton 1984,  Dow  and Fredga 1984).  Therefore, b i r d s  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 s i z e i n newly established populations  of Common Goldeneye was population.  s i g n i f i c a n t l y smaller than i n a well-established  He a t t r i b u t e d t h i s t o the g r e a t e r p r o p o r t i o n of f i r s t - t i m e  breeders i n newly established populations. I n t r a s p e c i f i c n e s t p a r a s i t i s m , although common i n some s p e c i e s of waterfowl,  i s s t i l l poorly understood  (Clawson fit a l * 1979,  Bolen 197 9, E r i k s s o n and Andersson 1982, This  Pienkowski and Evans 1982b).  phenomenon i s most common when nest s i t e s are conspicuous, and there  i s evidence  that t h i s behaviour  a f f e c t i n g reproductive success 1969,  McCamant and  Zipko  197 9,  increases nest desertion rates, adversely (Jones and Leopold 1967,  E r i k s s o n and  Andersson 1982).  desertion observed i n t h i s study may f e m a l e s a t the nest s i t e .  Morse and Wight  The  high l e v e l  of  be the r e s u l t of disturbance by other  G r e n q u i s t (196 3) and Jones and Leopold (1967)  found i n the Wood Duck and Common Goldeneye that desertion rates increased i n y e a r s when a l a r g e number of newly matured b i r d s attempted t o breed, and a t t r i b u t e d t h i s to increased nesting interference. The p r o p o r t i o n of s u c c e s s f u l Barrow's Goldeneye nests averaged 46%. This i s s i m i l a r to proportions reported for other cavity-nesting waterfowl (Bellrose fit a l . 1964, approximately  30%  Bolen 1967,  Bragin 1981).  Predation accounted f o r  of the losses, thus production could be  increased by the use of predator-proof nest boxes.  significantly  Nest success improved  f r o m 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 r e s u l t s i n d i c a t e 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 o f n e s t i n g c a v i t i e s may l i m i t  Barrow's Goldeneye, whereas Bufflehead do not seem t o be l i m i t e d by nest site availability.  Gauthier  (1985) found that Bufflehead density d i d not  increase with the provision of a d d i t i o n a l nest s i t e s and suggested t e r r i t o r i a l behaviour  was l i m i t i n g the p o p u l a t i o n .  that  Common Goldeneye  d e n s i t i e s have been i n c r e a s e d by the i n s t a l l a t i o n of nest boxes ( S i r e n 1951,  1952, Johnson 1967).  SUMMARY 1)  Barrow's Goldeneye u t i l i z e d nest boxes r e a d i l y .  2)  Breeding density of p a i r s was l i m i t e d by a v a i l a b i l i t y of nest s i t e s .  3)  Factors a f f e c t i n g nest box use by Barrow's Goldeneye were s i m i l a r t o those found t o influence Common Goldeneye: previous breeding attempts,  4)  previous use, outcome of  age of nest box and l o c a t i o n of nest box.  P r o p o r t i o n s of n e s t boxes t h a t hatched, were preyed upon, and were d e s e r t e d averaged r e s p e c t i v e l y 46±4% (S.E.), 31±3% and 23+3% (n=4 years).  5)  The average clutch size was lower i n 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  o l d e r 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 c o n s e r v a t i v e e s t i m a t e s range between 10 and 45%.  129  Chapter V: Mortality o f Barrow's Goldeneye and Bufflehead broods  130  Introduction I  showed  i n Chapter I I I t h a t  females with  broods a r e  highly  a g g r e s s i v e and t h a t t h i s a g g r e s s i o n r e s u l t s o c c a s i o n a l l y i n d u c k l i n g deaths.  Brood amalgamation, which i s f r e q u e n t i n Barrow's Goldeneye  (Table 8) i s also due to t e r r i t o r i a l aggressiveness. i n d i c a t e d t h a t d u c k l i n g s u r v i v a l i n Shelduck was  Three studies have low  i n areas of h i g h  brood d e n s i t i e s where brood amalgamation was f r e q u e n t ( W i l l i a m s Makepeace and  P a t t e r s o n 1980,  Pienkowski and Evans 1982a).  1974,  Several  f a c t o r s increase duckling m o r t a l i t y : p r e d a t i o n (Munro and Bedard 1977b, Pienkowski and Evans 1982a), adverse weather (Koskimies 1955, Bengtson 1972), high breeding d e n s i t i e s (Makepeace and Patterson 1980) and low abundance (Bengtson 1972, Pehrsson 197 3, S t r e e t 1977). found  food  Bengtson (1972)  t h a t not o n l y d i d Barrow's Goldeneye d u c k l i n g s  suffer  higher  mortality at higher densities, but high d e n s i t i e s of goldeneye increased the m o r t a l i t y of scaup ducklings. In t h i s chapter, I compare the m o r t a l i t y rates of Barrow's and B u f f l e h e a d broods. mortality  I asked the f o l l o w i n g q u e s t i o n s :  r a t e of d u c k l i n g s f l u c t u a t e between y e a r s ?  Goldeneye  1) Does the 2) How  does  m o r t a l i t y rate change with duckling age?  3) Is duckling m o r t a l i t y s i m i l a r  i n Barrow's Goldeneye and B u f f l e h e a d ?  4) Do e a r l y and l a t e h a t c h i n g  broods have s i m i l a r m o r t a l i t y r a t e s ?  5) Do  i n c r e a s i n g d e n s i t i e s of  goldeneye a f f e c t m o r t a l i t y rates of Bufflehead ducklings?  METHODS Barrow's Goldeneye and B u f f l e h e a d broods stayed i n open water and r a r e l y sought cover.  This, with the lack of emergent vegetation on most  ponds, g r e a t l y f a c i l i t a t e d brood checks.  In 1980  and 1981,  broods d i s t r i b u t e d among 100 ponds a t i n t e r v a l s of 14 days.  131  I visited  In 1982,  1983  and 1984, visit,  I i n c r e a s e d the frequency  of v i s i t s to 3 days.  During each  I recorded the l o c a t i o n of the brood, the age of the young and  number of young i t contained.  Most broods c o u l d be  combination of age, number of young and l o c a t i o n .  i d e n t i f i e d by  assumed t o  Reduction  47% i n 1983,  i n brood s i z e between c o n s e c u t i v e v i s i t s  indicate duckling mortality.  On  some p o n d s ,  amalgamated, increasing the number of young i n one brood while it  i n another.  In most cases,  was  broods  decreasing  I c o u l d i d e n t i f y such o c c u r r e n c e s  assigned the young to t h e i r respective broods.  a  A l s o many Barrow's  Goldeneye females were marked with nasal disks (26% i n 1982, 56% i n 1984).  the  and  Broods which could not be  followed i n d i v i d u a l l y were excluded from the analysis. I estimated  brood m o r t a l i t y i n s e v e r a l ways.  number of young present when a brood was was l a s t s i g h t e d . broods.  1) I recorded  the  f i r s t sighted and again when i t  The i n t e r v a l between these two r e c o r d s v a r i e d among  However, most broods were f i r s t s i g h t e d w i t h i n a week from  hatching and most were followed u n t i l 4 weeks old. the determination  This technique  allowed  of brood m o r t a l i t y on lakes where broods could not  followed i n d i v i d u a l l y because of frequent mixing.  The method provided  be a  minimum estimate of duckling mortality. 2)  I calculated a m o r t a l i t y rate for each brood using the Mayfield method  (Mayfield 1961,  1975).  The method accounts f o r bias related to the age of  the ducklings at f i r s t  sighting by introducing into the c a l c u l a t i o n s the  p e r i o d of time the d u c k l i n g s were under o b s e r v a t i o n . developed the technique  t o e s t i m a t e nest s u r v i v a l , but Ringelman and  Longcore (198?) and G a u t h i e r survival rates.  M a y f i e l d (1961)  (1985) have used i t t o e s t i m a t e  For each p e r i o d , an exposure index  exposure=number of d u c k l i n g s * l e n g t h of p e r i o d ) .  132  was  duckling  calculated:  I f 2 d u c k l i n g s were  a l i v e for  2 days then they represent 4 d u c k l i n g - d a y s .  expressed as:  losses/exposure  where l o s s e s a r e t h e number  that died during the period. duckling loss  i s not  Mortality of  was  ducklings  A p r o b l e m a r i s e s when t h e e x a c t t i m e  known.  Then,  a s s u m p t i o n s have  of  t o be 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 they a f f e c t e d t h e results. 197 9 ) .  A) B)  period. period  I assumed t h a t  I assumed t h a t  C)  (Johnson the  I assumed t h a t a l l l o s s e s o c c u r r e d mid-way throughout  the  ( M a y f i e l d 1961).  27-28).  r a t e was c o n s t a n t  l o s s e s were d i s t r i b u t e d e q u a l l y during  A l l three assumptions y i e l d e d s i m i l a r d a i l y  mortality estimates for Figs.  the m o r t a l i t y  both Barrow's Goldeneye  and B u f f l e h e a d  (see  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 be derived: all  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  broods and then the  daily mortality  unweighted e s t i m a t e where m o r t a l i t y 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 . 1977)  rate  i s c a l c u l a t e d , and  rates are c a l c u l a t e d f o r  an  each b r o o d  I used t h e j a c k k n i f e t e c h n i q u e  t o e s t i m a t e the v a r i a b i l i t y of the weighted d a i l y m o r t a l i t y  (Cochran rates.  RESULTS 1)  Hatching chronology 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 phenology o f B a r r o w ' s  Goldeneye.  D u r i n g the f i v e y e a r s of the study h a t c h i n g peaks v a r i e d by  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 , but  significantly later  t h a t Bufflehead hatched s l i g h t l y  (P<0.001) t h a n B a r r o w ' s Goldeneye  and,  that  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  there both  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 33). 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 . 133  40  1980  n.84  20  f  I  JUNE HATCHING F i g . 25  JULY DATE  Hatching d a t e s of Barrow's Goldeneye (n=number of broods).  134  broods  UJ O  g  fit  40 ^  1981  n = 73  1983  no 7 3  20-I  . 1  40  rtifrrt,tmt-,rf , 1  t i t  n = 79  1984  -I  2 0 -I  8  15  22  29  6  F i g . 26  20  JULY  JUNE HATCHING  13  DATE  Hatching d a t e s of B u f f l e h e a d broods (n=number of broods).  135  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. Analysis of variance Source of v a r i a t i o n  Sum of squares  DF  Mean square  F  Signif. 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  h a t c h e d i n t h e second week o f  latest  July.  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 on a b r o o d b a s i s ) Species,  year,  and d u c k l i n g age,  but  s i g n i f i c a n t e f f e c t on d a i l y m o r t a l i t y  rate  not  hatching  (Table 34).  date,  had  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 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 .  a  of  The absence o f any i n t e r a c t i o n  between s p e c i e s and y e a r and s p e c i e s and 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 Goldeneye and 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 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 . t h e Newman-Keuls Goldeneye  was  (Table 35).  Comparison o f means u s i n g  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 of s i g n i f i c a n t l y higher  that  i n 1983  than  in  any  Barrow's  other  year  D a i l y m o r t a l i t y r a t e of 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 and d a i l y m o r t a l i t y r a t e of 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). empty c e l l s ,  Because o f  broods 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 - Weighted by brood s i z e (analysed 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 by 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 performed.  However,  I present the d a i l y m o r t a l i t y estimates w i t h  95% c o n f i d e n c e l i m i t s .  their  Because of 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  more 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 .  27-28).  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 higher  (no  overlap  of  confidence  limits)  than  those  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 . 137  of  Bufflehead  M o r t a l i t y rates of  Table 34. Four-way a n a l y s i s of v a r i a n c e on the e f f e c t of s p e c i e s (Barrow's Goldeneye vs Bufflehead), year, age and hatching date on m o r t a l i t y rate of young. Analysis of variance Source of v a r i a t i o n  Sum of squares  DF  Mean square  F  Signif. 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  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  0.004  2  0.002  0.603  0.547  Hatching  date  Species/hatching  date  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  8.877  2492  0.004  10.142  2553  0.004  /  Residual Total  138  Table 35. D a i l y m o r t a l i t y r a t e o f Barrow's G o l d e n e y e and Bufflehead ducklings i n r e l a t i o n t o year. (Analysis derived from a three-way ANOVA (year, age and hatching date) n=12 c e l l s ; a n a l y s i s not weighted by brood size.)  Species Year  Barrow's Goldeneye  1980  0.030 A  1981  Bufflehead  0.017  A B  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  1  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 w i t h i n species o n l y ) .  139  Table 36. D a i l y m o r t a l i t y r a t e o f Barrow's G o l d e n e y e and Bufflehead broods i n r e l a t i o n t o age. (Results derived from three-way ANOVA (year, age and hatching date) n=15 c e l l s ; analysis not wieghted by brood size.)  Age  (in days)  Barrow's Goldeneye  Bufflehead  0.032 A  1-7  0.053 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  1  Means w i t h 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 o n l y ) .  140  ASSUMPTIONS •  MORTALITY  A  L08SES  •  LOSSES  T  USED RATE  CONSTANT  CONSTANT AT  MID  1»  POINT  *  I t T  I  1  1880  F i g . 27.  1  T  I  +  •  I  I  1*81  •  1  I  1*82  •  •  I  I  +  I  1983  I  1884  Daily mortality rates (weighted by brood size) of Barrow's Goldeneye d u c k l i n g s . (Based on Mayfield's method and under t h r e e d i f f e r e n t assumptions for duckling l o s s ; 95% c o n f i d e n c e l i m i t s of the estimates are given.)  141  *  I  I  AS8UMPTION8  USED  •  MORTALITY  RATE  A  LOSSES  CONSTANT  B  LOSSES  A T MID  CON8TANT  POINT  T T  I  1  19B0  Fig.  t  T  1  T  T  •  i  *  1  1  1  1BB1  28  *  i  *  1  1  1  1*82  1  1  1  *  +  1  1  1»83  D a i l y m o r t a l i t y rates (weighted by brood size) of B u f f l e h e a d d u c k l i n g s . (Based on Mayfield's method and under three d i f f e r e n t assumptions for duckling l o s s ; 95% confidence l i m i t s of the estimates are given.)  142  1884  •  r  both s p e c i e s f l u c t u a t e d i n a s i m i l a r f a s h i o n , being h i g h e s t i n 1983 and h i g h e r i n 1980 than i n 1981, 1982 and 1984.  For 1981, 1982 and 1984  however, the pattern of mortality d i f f e r e d between the species.  Mortality  r a t e o f Barrow's Goldeneye was s i m i l a r i n those t h r e e y e a r s whereas t h e m o r t a l i t y r a t e of B u f f l e h e a d  i n c r e a s e d from 1981 t o 1984. S i m i l a r l y ,  weighted m o r t a l i t y e s t i m a t e s r e v e a l more s i g n i f i c a n t d i f f e r e n c e s 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. considerably fledging.  mortality  r a t e s had decreased  by the t h i r d week and remained f a i r l y  constant  until  The pattern of mortality i n r e l a t i o n to duckling age d i f f e r e d  between years. and  In most y e a r s ,  I t was s i m i l a r i n 1981, 1982 and 1984 but d i f f e r e d i n 1980  1983 when m o r t a l i t y was h i g h e s t .  ducklings  ( F i g . 30) f o l l o w e d  Goldeneye d u c k l i n g s :  M o r t a l i t y rates of Bufflehead  a s i m i l a r pattern  to that  o f Barrow's  m o r t a l i t y r a t e s were u s u a l l y higher i n t h e f i r s t  week f o l l o w i n g h a t c h i n g  and the p a t t e r n o f m o r t a l i t y i n r e l a t i o n t o  duckling age varied between years. Although d a i l y m o r t a l i t y hatching  rate d i d not vary  significantly  period, there i s an i n d i c a t i o n that hatching  m o r t a l i t y i n y e a r s of high m o r t a l i t y ( F i g s . 31-32).  with  date may influence In 1983 weighted  e s t i m a t e s of m o r t a l i t y r a t e s d i f f e r e d s i g n i f i c a n t l y , b e i n g h i g h e s t f o r l a t e broods, and i n 1980, broods that hatched mid-way through the season s u f f e r e d lower m o r t a l i t y .  During t h e f i v e y e a r s of the study, e a r l y  broods tended to suffer lower mortality than l a t e broods. For marked broods, the number o f young a t h a t c h i n g  was known.  I  therefore could look i n more d e t a i l at mortality during the f i r s t week of life.  Mortality  pattern  d i f f e r e d between y e a r s  ( F i g . 33).  Daily  mortality rate was higher i n the f i r s t two days and tended t o decrease i n 143  \  1-8  8-16  16-22 AOE  F i g . 29  22-28 IM  20-86  86-43  0AY8  D a i l y mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings i n r e l a t i o n to d u c k l i n g age. (Mayfield's method: mortality r a t e assumed c o n s t a n t between o b s e r v a t i o n periods; 95% confidence l i m i t s given.)  144  1-8  8-15  15-22  22-29  29-36  AGE IN DAYS  F i g . 30  Daily mortality rates (weighted by brood size) of Bufflehead ducklings i n r e l a t i o n to duckling age. (Mayfield's method: m o r t a l i t y r a t e assumed c o n s t a n t between observation periods; 95% confidence l i m i t s given.)  145  36-43  F i g . 31  D a i l y mortality rates (weighted by brood size) of Barrow's Goldeneye ducklings i n r e l a t i o n to hatching period. (Mayfield's method: m o r t a l i t y r a t e assumed c o n s t a n t b e t w e e n o b s e r v a t i o n p e r i o d s ; 95% c o n f i d e n c e l i m i t s given.)  146  ~T~  1980  1982  1881  1883  1884  YEAR  F i g . 32  D a i l y mortality rates (weighted by brood size) of Bufflehead ducklings i n r e l a t i o n t o 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 o b s e r v a t i o n p e r i o d s , 95% confidence l i m i t s given.)  147  104  1982 • 196 3 -A 1984  8 -  ~~r~  —f—  0  3 AGE  F i g . 33  4  ~r~ 6  IN D A Y 8  D a i l y m o r t a l i t y rates (weighted by brood size) of Barrow's Goldeneye d u c k l i n g s d u r i n g t h e f i r s t week f o l l o w i n g hatching (Based on marked broods only; Mayfield s method: m o r t a l i t y rate assumed constant between o b s e r v a t i o n p e r i o d s ; 95% confidence l i m i t s given.) 1  148  the following days.  Calculations of m o r t a l i t y on a per brood basis show a  s i m i l a r p a t t e r n f o r 1982  and 1984  but do not show a decrease  in  1983  (Figs. 34,35,36). c)  D i r e c t method T h i s method c o n s i s t e d of e s t i m a t i n g the maximum number of young  p r e s e n t on a l a k e a f t e r a l l broods had hatched weeks l a t e r .  and then again s e v e r a l  The d i f f e r e n c e i n the number of young counted p r o v i d e s a  conservative estimate of mortality. R e s u l t s are e s s e n t i a l l y s i m i l a r t o those obtained with the Mayfield method. The percentage of young Barrow's Goldeneye l o s t ranged from 21% i n 1981 t o 46% i n 1983 with the highest m o r t a l i t y were 1980 of young occurred i n 1981,  1982 and 1984.  B u f f l e h e a d ranged from 12% years, except 1984,  (35%) and 1983  i n 1981  (Table 37).  (46%).  Years  S i m i l a r losses  The percentage of young l o s t by  to 36%  i n 1983  (Table 38).  In a l l  Barrow's Goldeneye l o s t proportionally more young than  Bufflehead. Analysis of marked broods allowed the estimate of losses from laying u n t i l three weeks after hatching.  Only broods that were observed  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 l o s s e s o c c u r r e d  during  before  hatching, 52% i n the f i r s t week of l i f e , 14% i n the second week and 8% i n the t h i r d week (Table 39).  Patterns of losses varied between years,  but  i n 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 AGE  F i g . 34  4 IN  0AY8  D a i l y m o r t a l i t y r a t e s (not weighted by brood s i z e ) o f Barrow's Goldeneye d u c k l i n g s d u r i n g the f i r s t week f o l l o w i n g h a t c h i n g i n 1982 (standard errors given).  150  144  136-  128-  120-  112 -  24 -  • u  T  1  1  1  1  r  2  3  4  5  6  7  AGE  F i g . 35  IN  DAYS  D a i l y m o r t a l i t y r a t e s (not weighted by brood s i z e ) o f Barrow's Goldeneye d u c k l i n g s d u r i n g the f i r s t week f o l l o w i n g h a t c h i n g i n 1983 (standard error given).  151  128  120  112  104 -  86  -  88  80  -  72 <  oc  64  >•  *  56 48 -  j < O  40 -  32 24 16  8 -  1 3 A 9 E  F i g . 36  IN  D A Y S  D a i l y m o r t a l i t y r a t e s (not weighted by brood s i z e ) of Barrow's Goldeneye d u c k l i n g s d u r i n g the f i r s t week f o l l o w i n g h a t c h i n g 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 e a r l y  584  612  621  779  922  Maximum count of young l a t e (=5 weeks l a t e r )  380  481  489  420  731  Young l o s t  204  131  132  359  191  35  21  21  46  21  6.95  7.29  7.14  8.20  8.38  2.43  1.56  1.52  3.78  1.74  % lost No. young/brood  1  No. young lost/brood  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 e a r l y  433  514  541  475  520  Maximum count of young l a t e (=5 weeks l a t e r )  296  450  477  304  387  Young l o s t  137  64  64  171  133  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  % lost  Number of young present when brood f i r s t observed.  154  Table 39.  D i s t r i b u t i o n of losses between laying and 3-week o l d young from nests that hatched. Total losses from No. of incubation Before eggs l a i d to 21 days hatching  % of losses • Between Between days 0-7 days 7-14  Year  No. of broods  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%  120  1384  650  26  52  14  8  47%  Total  Between days 14-21  Total % of l o s s  DISCUSSION I compared the i n f l u e n c e of t h r e e d i f f e r e n t assumptions on the M a y f i e l d e s t i m a t e of d a i l y m o r t a l i t y r a t e (Figs. 27-28).  F i r s t I used  Mayfield's own assumption i.e. that m o r t a l i t y occurs mid-way i n the period between observations (Mayfield 1961). Second I assumed that the m o r t a l i t y rate was constant between observations  (Johnson 1979, K l e t t and Johnson  1982), and t h i r d I assumed that losses were equally d i s t r i b u t e d between observations.  A l l three assumptions gave s i m i l a r estimates  (Fig. 27-28).  Johnson (197 9) p o i n t e d o u t t h a t M a y f i e l d ' s assumption l e a d s t o b i a s i f n e s t s , or i n t h i s case broods, a r e v i s i t e d i n f r e q u e n t l y . In t h i s study the bias should be n e g l i g i b l e because i n t e r v a l s between v i s i t s were short and the number of broods or young sampled was high. Hatching chronology v a r i e d between years due t o the timing of spring thaw.  In 1980 , 81 and 82 some of the breeding ponds were s t i l l frozen i n  l a t e A p r i l , whereas i n 1983 and 1984, a l l ponds were f r e e o f i c e by the t h i r d week o f A p r i l .  The g r e a t e r p r o p o r t i o n o f broods h a t c h i n g l a t e i n  1984 as opposed t o 1983 could be a t t r i b u t e d t o a period of c o l d weather i n early May that followed a warm period and may have delayed laying f o r some females.  Hammond and Johnson (1984) showed that spring weather determined  the onset of laying i n several species of waterfowl. Brood m o r t a l i t y was s i g n i f i c a n t l y higher i n the f i r s t week following h a t c h i n g f o r both Barrow's Goldeneye and B u f f l e h e a d which i s a t y p i c a l p a t t e r n i n w a t e r f o w l (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 M i l n e 1985).  T h i s was expected, a s t h e young are  e s p e c i a l l y vulnerable a t hatching t o predators, weather and i n t r a s p e c i f i c aggression because of t h e i r size and inexperience.  Bengtson (1972) found  that cold s p e l l s with p r e c i p i t a t i o n caused a high mortality among newly156  hatched  ducklings.  Koskimies and Lahti (1964), Hilden (1964), Makepeace  and Patterson (1980) found that m o r t a l i t y of young ducklings increased i n bad weather. a few days.  Kear (1965) showed that duckling yolk reserves l a s t only for Thus, they would be e s p e c i a l l y a f f e c t e d by adverse weather  conditions at hatching as t h i s would impair t h e i r feeding e f f i c i e n c y deplete t h e i r small reserves. aquatic insect a v a i l a b i l i t y was Ellis  Sjoberg and D a n e l l (1982) reduced  found  i n adverse weather, and H i l l  (1984) showed t h a t young d u c k l i n g s a t h a t c h i n g are  and that and  inefficient  divers and depend to some extent on small prey near the surface. Early hatching broods had a better s u r v i v a l than l a t e hatching broods i n y e a r s of high m o r t a l i t y (Figs. 31-32). decrease  Bengtson (1972) a l s o found a  i n s u r v i v a l f o r l a t e hatchers i n Barrow's Goldeneye of Iceland.  Among the f a c t o r s t h a t may  produce t h i s e f f e c t are  d e n s i t i e s l a t e r i n the season (Pehrsson 1973); of  l a t e - h a t c h i n g broods t o t e r r i t o r i a l  1) reduced  2) G r e a t e r  vulnerability  aggressiveness  because e a r l y -  hatching females would already have established t e r r i t o r i e s and a sense of ownership which would enhance t h e i r t e r r i t o r i a l (Petrie 1984);  food  developed  aggressiveness  3) females with late-hatching broods are more l i k e l y to be  inexperienced breeders, and thus l e s s e f f i c i e n t i n protecting t h e i r young against predators or conspecifics. Several authors have shown that f i r s t t i m e b r e e d e r s tend t o breed l a t e r than experienced b r e e d e r s (Grice and Rogers 1965,  Krapu and Doty 1979,  Lemieux 1959);  have s e v e r a l advantages t h a t may c o m p e t i t i o n f o r food,  4) Early hatching broods  enhance t h e i r s u r v i v a l :  b) f i r s t c h o i c e of t e r r i t o r y ,  a)  reduced  c) they become  a t t a c h e d t o t h e i r t e r r i t o r y and b e n e f i t from the r e s i d e n c e e f f e c t i n intra-specific  encounters  (Petrie  1984,  Figler  and  Einhorn  1983),  d) females have time to regain some of the weight l o s t during incubation  157  which would give them an advantage over newly hatched broods. B u f f l e h e a d young had lower m o r t a l i t y rates than Barrow's Goldeneye young i n a l l y e a r s 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 ( F i g . 24). The i n c r e a s e i n m o r t a l i t y r a t e of B u f f l e h e a d ducklings  relative  t o Barrow's Goldeneye  d u c k l i n g s may  interference or e x p l o i t a t i o n competition by Barrow's Goldeneye.  be  due  to  I showed  i n Chapter I I I that Barrow's Goldeneye females with broods were aggressive toward Bufflehead females. Bufflehead.  I have witnessed female goldeneyes k i l l young  In 1984.three marked broods of Bufflehead were displaced from  lakes by goldeneye broods and l o s t ducklings.  Although female Bufflehead  are often successful i n decoying female goldeneye away from t h e i r young, their chance of finding a t e r r i t o r y 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 i n t r a s p e c i f i c confrontations which can r e s u l t i n losses of ducklings. Williams (1974), Makepeace and Patterson (1980), and Pienkowski and  Evans  (1982a) have shown t h a t the d a i l y m o r t a l i t y r a t e of shelduck d u c k l i n g s increased s i g n i f i c a n t l y with density of broods. and Bufflehead, are highly t e r r i t o r i a l  Shelducks, l i k e goldeneye  (Patterson 1982).  Why was mortality of Barrow's Goldeneye ducklings higher than that of B u f f l e h e a d d u c k l i n g s i n 1980, 81, 82 and 83?  Both s p e c i e s have s i m i l a r  h a b i t a t p r e f e r e n c e s and s i m i l a r behaviour.  Fluctuations i n mortality  r a t e s of both s p e c i e s were s i m i l a r from 1980 t o 1983: were h i g h e s t i n 1983 and h i g h e r i n 1980  mortality rates  than i n 1981 and 1982.  This  i n d i c a t e s t h a t both s p e c i e s responded s i m i l a r l y t o f a c t o r s t h a t caused t h i s yearly fluctuation i n survival rates.  Weather may have caused the  high m o r t a l i t y i n 1983 as heavy rain and c o l d temperatures occurred during }  158  peak hatching time.  Among f a c t o r s that may  have contributed to the higher  m o r t a l i t y of Barrow's Goldeneye ducklings are: 1)  G r e a t e r s u s c e p t i b i l i t y of Barrow's Goldeneye d u c k l i n g s t o n a t u r a l m o r t a l i t y f a c t o r s than Bufflehead ducklings:  Goldeneye ducklings are  twice the size of Bufflehead ducklings, and thus have greater d a i l y energy requirements require a greater t h e r e f o r e may  (Kendeigh 1969, total  1970,  i n t a k e of food  King 1973). than  Larger b i r d s  s m a l l e r b i r d s and  s u f f e r more i n p e r i o d s of food shortages.  In some  s i t u 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 physiological  advantage of l a r g e r a n i m a l s  for tolerating  (Kendeigh 196 9) and the higher m e t a b o l i c r a t e of s m a l l e r  cold  animals  (Kendeigh 197 0). 2)  I n t r a s p e c i f i c a g g r e s s i o n by f e m a l e s may  have a g r e a t e r impact on  goldeneye m o r t a l i t y than on Bufflehead mortality: Barrow's Goldeneye females are larger and more aggressive than Bufflehead females. 3)  Aggressive neglect (Ripley 1961) Barrow's Goldeneye:  During  increase duckling m o r t a l i t y i n  Barrow's Goldeneye females spend large amounts  of t i m e i n a g g r e s s i v e species.  may  interactions with  c o n s p e c i f i c s and  other  t h a t t i m e t h e i r young a r e more s u s c e p t i b l e t o  predation or attacks by other goldeneyes. 4)  Barrow's Goldeneye usually nest farther from brood rearing ponds than Bufflehead. or may  The overland journey may  d i r e c t l y r e s u l t i n mortality,  weaken the ducklings and increase t h e i r m o r t a l i t y once they  reach the ponds. Further studies are needed to determine p r e c i s e l y the causes of t h i s difference i n m o r t a l i t y rate between these two species.  The apparent  n e g a t i v e impact of i n c r e a s i n g goldeneye density on the survival of  159  B u f f l e h e a d d u c k l i n g s ( F i g . 27-28) deserves f u r t h e r a t t e n t i o n . Any management directed toward increasing d e n s i t i e s of Barrow's Goldeneye should be monitored c a r e f u l l y f o r impact on sympatric  s p e c i e s of  waterfowl.  SUMMARY 1)  M o r t a l i t y r a t e s o f Barrow's Goldeneye and B u f f l e h e a d  ducklings  d i f f e r e d from year t o year and were higher among younger ducklings. 2)  Patterns of duckling l o s s e s i n r e l a t i o n t o age varied between years.  3)  In y e a r s when m o r t a l i t y was h i g h , e a r l y broods tended t o s u r v i v e better than l a t e broods.  4)  Barrow's Goldeneye d u c k l i n g s  had a higher  B u f f l e h e a d d u c k l i n g s i n the f i r s t  m o r t a l i t y rate  t h r e e y e a r s of the study but  mortality rates of Bufflehead were higher i n the 4th year.  160  than  Chapter VI:  General Discussion  161  In  this  territorial  thesis,  I s e t o u t t o d e s c r i b e and c h a r a c t e r i z e t h e  behaviour o f Barrow's  significance and function.  Goldeneye  and t o e v a l u a t e i t s  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 t h a t  territorial  behaviour i s w e l l  Barrow's Goldeneye and i t s congeners.  I found no major  developed i n 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 B u f f l e h e a d drakes d u r i n g the b r e e d i n g season. T e r r i t o r i a l behaviour of f e m a l e s w i t h broods was s i m i l a r f o r Barrow's Goldeneye and B u f f l e h e a d , but was not s t u d i e d i n the Common Goldeneye. However, descriptive accounts i n l i t e r a t u r e indicate that  territoriality  i n Common Goldeneye i s probably s i m i l a r t o the other species (Carter 1958, S i r e n 1952, Gibbs 1961). territorial  I have shown t h a t some Barrow's Goldeneye a r e  i n winter, but I could not e s t a b l i s h i f Common Goldeneye and  Bufflehead were t e r r i t o r i a l  a t 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 e a s i l y defendable resource, whereas Common Goldeneye and Bufflehead feed mainly on free-swimming i n v e r t e b r a t e s E r s k i n e 197 2, Palmer 1976, Vermeer 1982). model  of t e r r i t o r i a l i t y ,  territorial  (Wiemeyer 1967,  A c c o r d i n g t o Brown's (1964)  we would expect Barrow's Goldeneye  i n winter but not Common Goldeneye and Bufflehead.  o b s e r v a t i o n s by N i l s s o n  (196 9)  indicate  that  aggressive i n winter and protect t h e i r mates.  However,  Common Goldeneye a r e  The behaviour described i s  s i m i l a r t o t h a t 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 o be  T e r r i t o r i a l behaviour may have evolved as an e x t e n s i o n of mate defense to include defense of an area f o r 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  a g g r e s s i v e n e s s of neighbouring i n t r u d e r s from the area.  from  the  p a i r s i n terms of e x c l u d i n g u n p a i r e d  They c o u l d a l s o develop a knowledge of the  resources of the area which may  increase t h e i r a b i l i t y to defend the area  r e l a t i v e to an intruder (Petrie 1984,  F i g l e r and Einhorn 1983).  Also, as  I have indicated i n Chapter I I I , exclusion of conspecifics and congeners from an area can enhance the f o r a g i n g o p p o r t u n i t i e s of the  territory  holder. We should not expect t o 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 s i z e and food r e s o u r c e s boundaries  are  set d i r e c t l y  by  (Gauthier 1985), because  pair  d e n s i t y and  not  food  territory density.  Therefore, a non-significant c o r r e l a t i o n between t e r r i t o r y size and food abundance (Gauthier 1985) an important aspect of I contend  does not necessarily indicate that food i s not  territoriality.  t h a t the main b e n e f i t of t e r r i t o r i a l i t y  i n the genus  Bucephala i s to p r o v i d e an e x c l u s i v e f e e d i n g area f o r the f e m a l e i n the s p r i n g and w i n t e r and f o r the young i n summer.  The importance of t h i s  f u n c t i o n has been s t r e s s e d i n other s t u d i e s 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).  I n t e r s p e c i f i c aggression i n Barrow's Goldeneye i s correlated with the degree of food competition, Barrow's Goldeneye being most aggressive toward congeners and more a g g r e s s i v e toward d i v i n g ducks than d a b b l i n g ducks.  I n t e r s p e c i f i c aggression has been reported i n two other species of  t e r r i t o r i a l waterfowl:  the A f r i c a n Black Duck (McKinney e i a l . 1978) 163  and  steamer-ducks (Nuechterlein and Storer 1985a, Livezey and Humphrey 1985a). The s i g n i f i c a n c e of t h i s a g g r e s s i o n i n steamer-ducks i s s t i l l  unclear  (Murray 1985). Murray  (1981), i n a c o m p r e h e n s i v e  territoriality  i n a variety  interspecific territoriality  of animals,  review  of  interspecific  r e j e c t e d the view  that  i s an adaptation that allows competitors for  f o o d t o occupy a common h a b i t a t (Simmons 1951, O r i a n s and W i l l s o n 1964, Cody 1974, Davies 1978) and argued t h a t i t l e a d s t o s e g r e g a t i o n and not coexistence. The r e s t r i c t e d area of sympatry of Barrow's Goldeneye and Common Goldeneye and t h e apparent avoidance of p r o d u c t i v e ponds by Common Goldeneye may be an example of such segregation.  More detailed studies of  Barrow's Goldeneye and Common Goldeneye i n 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 t o be r i g h t i n cases where one of the s p e c i e s dominates t h e other, eg. Barrow's Goldeneye v e r s u s B u f f l e h e a d . examples of i n t e r s p e c i f i c  territoriality  subordinate species (Orians and Willson 1964,  Most  i n v o l v e a dominant and a Murray 1981).  Murray (1981)  states 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 s m can be adaptive t o the dominant species i f i t r e s t r i c t s intruders.  t h e a c t i v i t i e s of p o t e n t i a l l y  competitive  I have shown that Barrow's Goldeneye aggression excludes other  species from the t e r r i t o r y and therefore may improve feeding conditions. Dhondt (1977) and Minot (1981) showed t h a t Great T i t s (Parus major) and Blue T i t s  (Parus caeruleus) compete for foods during the breeding  season  and t h a t the s m a l l e r Blue T i t i s the s u p e r i o r c o m p e t i t o r , i . e . reaches a h i g h e r d e n s i t y than Great T i t s . territorial  Neither species i s i n t e r s p e c i f i c a l l y  but Great T i t s are i n t r 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 .  164  Possibly,  B u f f l e h e a d would have a s i m i l a r advantage over Barrow's Goldeneye i n e x p l o i t a t i o n competition.  I n t e r s p e c i f i c aggression by Barrow's Goldeneye  possibly reduces e x p l o i t a t i o n competition and thus i s advantageous t o the goldeneye. I suggest that the high l e v e l of i n t r a s p e c i f i c aggression i n Barrow's Goldeneye has f a c i l i t a t e d  the evolution of i n t e r s p e c i f i c  territorialism,  and that the feeding advantages gained maintain;. i t . Whether i n t e r s p e c i f i c a g g r e s s i o n o r i g i n a t e d f i r s t as m i s d i r e c t e d i n t r a s p e c i f i c a g g r e s s i o n and was l a t e r maintained because i t conferred some a d a p t i v e advantages ( r e d u c t i o n of f o o d competition) o r whether i t o r i g i n a t e d as a response t o c o m p e t i t i o n i s unknown.  Losey (1981, 1982)  showed e x p e r i m e n t a l l y t h a t d a m s e l f i s h , w i t h experience and e c o l o g i c a l cues, can p e r c e i v e a new s p e c i e s as a c o m p e t i t o r . p r o c e s s i s p o s s i b l e i n Barrow's Goldeneye.  A similar learning  D e t a i l e d s t u d i e s on t h e  factors e l i c i t i n g i n t e r s p e c i f i c aggression may help resolve the question, i.e. whether i t o r i g i n a t e d because of c o m p e t i t i o n  or a c c i d e n t a l l y .  Experiments w i t h t h e I c e l a n d i c p o p u l a t i o n which i s a l l o p a t r i c with the Bufflehead may permit us t o answer i t .  2) Competition between Barrow's Goldeneye and Bufflehead B i r c h (1957) i n d i c a t e d t h a t c o m p e t i t i o n o c c u r s when two s p e c i e s u t i l i z e common resources i n short supply; or i f the resources are not i n short supply, c o m p e t i t i o n o c c u r s when t h e a n i m a l seeking t h a t r e s o u r c e harms another  i n the p r o c e s s .  Pianka  (197 8)  s t a t e d as a c o n d i t i o n  necessary f o r the coexistence of two populations that each population must i n h i b i t i t s own growth more than t h a t of t h e other s p e c i e s .  Several  f a c t o r s i n t h i s study show t h a t c o m p e t i t i o n i s s t r o n g between Barrow's Goldeneye and Bufflehead and that the Barrow's Goldeneye i s the dominant  165  species:  1) Breeding d e n s i t y of Barrow's Goldeneye i s almost t w i c e a s  high as that of Bufflehead when the reverse should be expected considering body  size  and a v a i l a b i l i t y  of nesting c a v i t i e s  (Gauthier  1985).  2) Barrow's Goldeneye dominate B u f f l e h e a d i n t e r r i t o r i a l encounters and exclude  them  from  their  territories.  t e r r i t o r i a l goldeneyes from their t e r r i t o r y .  3) B u f f l e h e a d  exclude  non-  4) Bufflehead avoid nesting  c a v i t i e s w i t h l a r g e e n t r a n c e s p o s s i b l y because of Barrow's Goldeneye. 5) M o r t a l i t y rate of Bufflehead young increased following an increase i n Barrow's Goldeneye density. These s p e c i e s compete f o r n e s t i n g c a v i t i e s , territories.  food r e s o u r c e s ,  and  How do Bufflehead manage t o coexist with Barrow's Goldeneye?  This study has i d e n t i f i e d adaptations that may permit Bufflehead t o coexist, and a t t a i n high d e n s i t i e s i n the presence of Barrow's Goldeneye. 1. Difference i n size. Several authors have argued that d i f f e r e n c e s i n beak and body s i z e s between s p e c i e s f a c i l i t a t e c o e x i s t e n c e by p e r m i t t i n g e x p l o i t a t i o n o f d i f f e r e n t f o o d r e s o u r c e s (Orians and W i l l s o n 1964, Cody 1974).  This i s  u n l i k e l y for these two species on the breeding grounds as their d i e t s are similar  (Munro 1939, 1942, Erskine 1972, Palmer 1976).  be more important  I t may, however,  i n winter when both species occupy d i f f e r e n t 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 l e s s abundant then.  Schoener (1982)  has argued t h a t reduced o v e r l a p d u r i n g l e a n t i m e s i s a g e n e r a l , but not i n v a r i a b l e , f e a t u r e of c o m p e t i t i v e i n t e r a c t i o n s .  Smith e_£ a l . (1978)  showed that i n times of reduced food abundance, d i e t s i m i l a r i t y i n groups of species with s i m i l a r feeding methods decreases.  The smaller size of  the B u f f l e h e a d a l l o w s i t t o use s m a l l e r n e s t c a v i t i e s than Barrow's  166  Goldeneye with these possible advantages:  1) Bufflehead are l e s s l i k e l y  than Barrow's Goldeneye to be l i m i t e d by n e s t s i t e a v a i l a b i l i t y .  Nest  p a r a s i t i s m i s l e s s f r e q u e n t i n B u f f l e h e a d (Erskine 197 2, Donaghey 197 5, G a u t h i e r 1985)  than i n Barrow's Goldeneye ( t h i s study).  In wood ducks  nest parasitism has been shown to be greater when nest s i t e a v a i l a b i l i t y i s reduced and/or nest conspicuousness been  shown t o  increase  nest  increased.  d e s e r t i o n rate, adversely  reproductive success (Jones and Leopold 1967, 1979,  P a r a s i t i s m has a l s o  Eriksson and Andersson 1982).  affecting  Morse and Wight 1969,  Zipko  2) Bufflehead are more l i k e l y to f i n d  nesting c a v i t i e s closer to their breeding ponds than Barrow's Goldeneye. This should greatly reduce overland t r a v e l for Bufflehead, reducing r i s k s of predation or l o s s .  3) Smaller cavity entrances exclude more predators  than l a r g e r entrances would, again r e d u c i n g r i s k s of p r e d a t i o n .  A l l of  t h i s should t r a n s l a t e into higher s u r v i v a l f o r Bufflehead, and may explain i n part the lower brood m o r t a l i t y of Bufflehead versus Barrow's Goldeneye in this  study.  Other p o s s i b l e advantages of a s m a l l e r s i z e are: requirements for growth which may  1) Lower f o o d  allow Bufflehead to occupy small shallow  l a k e s avoided by goldeneyes, and t o s u r v i v e b e t t e r i n t i m e s of shortage.  2) Superior a g i l i t y compared to the goldeneye.  food  This explains  the a b i l i t y of B u f f l e h e a d t o decoy a g g r e s s i v e Barrow's Goldeneye from t h e i r mate or brood, staying j u s t out of reach.  Barrow's Goldeneye cannot  decoy other goldeneye e f f e c t i v e l y and must f i g h t or retreat. (1952) d e s c r i b e s s i m i l a r  r e l a t i o n s h i p s between  the  Armstrong  Ringed  Plover  (Charadius hiaticula) and the L i t t l e Ringed Plover (C. dubius), the l a t t e r decoying aggressive Ringed Plover away from h i s mate i n s i m i l a r fashion to the  Bufflehead.  3) B e t t e r  manoeuverability  i n submerged a q u a t i c  v e g e t a t i o n which would enable them t o e x p l o i t densely v e g e t a t e d ponds  167  better than Barrow's Goldeneye. Bufflehead  breed s u c c e s s f u l l y  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 t o confirm that. 2.  High l e v e l of i n t r a s p e c i f i c aggression i n Barrow's Goldeneye. Ripley (1961) described a phenomenon he c a l l e d aggressive neglect i n  which a dominant, a g g r e s s i v e s p e c i e s , exposes i t s nest o r young t o increased  mortality  because  of t h e t i m e  i t spends  i n aggressive  interactions. Several q u a l i t a t i v e observations suggest that t h i s may occur i n Barrow's Goldeneye.  Male and female B u f f l e h e a d sometimes  decoy  a t t a c k i n g goldeneye f o r 5 or even 10 minutes d u r i n g which t i m e t h e goldeneye does not protect i t s mate or brood.  3) Does t e r r i t o r i a l b e h a v i o u r l i m i t b r e e d i n g d e n s i t i e s i n t h e genus Bucephala? This i s a d i f f i c u l t question t o answer because of the diverse scales at  which t h e q u e s t i o n c o u l d be addressed (pond l e v e l ,  population l e v e l ) . to  region  level,  Watson and Moss (1970) l i s t three conditions necessary  show that s o c i a l interactions l i m i t breeding populations:  s u b s t a n t i a l p a r t of t h e p o p u l a t i o n does not breed; breeders are p h y s i o l o g i c a l l y capable of b r e e d i n g ;  a) that a  b) t h a t such non-  c) t h a t 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 t h a t some s p e c i e s can be and a r e  l i m i t e d by t e r r i t o r i a l  behaviour (Hilden 197 9, P a t t e r s o n 1980, Klomp  1980). There i s no doubt that i n the genus Bucephala t e r r i t o r i a l behaviour  168  of  both drakes and f e m a l e s w i t h broods can and does l i m i t d e n s i t i e s of  p a i r s and broods on i n d i v i d u a l ponds.  Whether t h i s a f f e c t s more than the  d i s t r i b u t i o n of p a i r s and broods remains to be shown.  This w i l l depend i n  p a r t on the a v a i l a b i l i t y of s u i t a b l e h a b i t a t nearby. t e r r i t o r i a l behaviour species.  I believe that  can l i m i t the p o p u l a t i o n of breeding Bucephala  However, I view t e r r i t o r i a l behaviour  as an a d a p t a t i o n t o  e x p l o i t resources optimally at medium population l e v e l s .  At low density  l e v e l s i t has l i t t l e advantages and a t v e r y high d e n s i t y 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 t h i s breakdown to occur are probably never i n natural conditions.  reached  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 d e n s i t i e s simply because Bufflehead must face both i n t r a and i n t e r s p e c i f i c competition f o r space. densities  of Barrow's Goldeneye are  availability.  Bengtson (197 2)  nest  site  season may  a f f e c t breeding  densities.  r e p o r t e d i n c r e a s e d m o r t a l i t y of ducklings when Barrow's  Goldeneye d e n s i t i e s were high.  Other studies indicate that t e r r i t o r i a l i t y  regulate t e r r i t o r i a l waterfowl species (Riggert 1977,  1978,  by  breeding  Once t h i s l i m i t i n g f a c t o r i s removed, i t i s l i k e l y t h a t  t e r r i t o r i a l i t y during the breeding  may  often controlled  Also,  Evans and Pienkowski 1982,  McKinney e± al*  Patterson 1982).  4) Management implications and research needs Most of the f i n d i n g s of t h i s study have management a p p l i c a t i o n s as little  was  known of the breeding  Goldeneye when t h i s study was  and  initiated.  w i n t e r i n g ecology  of Barrow's  However, l i k e most studies, t h i s  study revealed further needs for research. 1)  I have shown that Barrow's Goldeneye r e a d i l y use nest boxes and that breeding  d e n s i t i e s can be  i n c r e a s e d by  169  t h e i r use.  Two  factors  accounted for most of the nesting f a i l u r e s :  predation and desertion.  Research i s needed on ways of deterring predation by black bears, on the causes of nest desertion, and on i n t r a s p e c i f i c nest parasitism. 2)  The s t r o n g t e r r i t o r i a l behaviour considered density.  o f Barrow's Goldeneye should be  i n any management o r i e n t e d toward i n c r e a s i n g t h e i r  I have shown that pair density and e s p e c i a l l y 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 t h a t i n c r e a s e i n goldeneye d e n s i t y may have a negative impact on Bufflehead.  More research i s needed t o confirm  and quantify t h i s 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 t h i s , 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 s i z e , n e s t i n g chronology, young growth, young s u r v i v a l , would be enlightening. 4)  R e l a t i o n s h i p s between Barrow's Goldeneye and Common Goldeneye i n areas of sympatry need t o be q u a n t i f i e d f u r t h e r . Goldeneye r e a l l y superior competitors?  A r e Barrow's  Are Common Goldeneye slowly  invading the breeding range of Barrow's Goldeneye? 5)  S u r v i v a l of ducklings v a r i e d considerably between years. of  t h i s v a r i a t i o n needs t o be quantified.  that weather may be important. behaviour may be important.  The cause  My observations indicate  Also, a t high densities,  territorial  The impact of high d e n s i t i e s of Barrow's  Goldeneye on t h e s u r v i v a l of B u f f l e h e a d d u c k l i n g s needs f u r t h e r quantification.  The causes behind the higher survival of Bufflehead  170  ducklings compared t o Barrow's Goldeneye ducklings s t i l l have t o be identified. 6)  Waterfowl  have  usually  been  ignored  uninteresting from a t h e o r e t i c a l point been  management-oriented  concepts.  with  i n academic  of view.  little  concern  research  as  Most studies have for theoretical  I have shown here, not o n l y t h a t s t u d i e s o f w a t e r f o w l  ecology can address central t h e o r e t i c a l questions, i.e. competition, population  regulation,  territoriality,  etc., but a l s o , t h a t t h e  answer t o these t h e o r e t i c a l q u e s t i o n s have i m p o r t a n t management applications.  My message i s t h a t  possible, t o consider a study.  we  should  strive,  whenever  both t h e o r e t i c a l and p r a c t i c a l implications of  Both theory and management would benefit greatly from such  an approach.  171  LITERATURE CITED Afton, A.D. and R.D. 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Welty, j.C. 1982. The l i f e of birds. W.B. Saunders Company, Philadelphia. Wiemeyer, S.N. 1967. B u f f l e h e a d food h a b i t s , p a r a s i t e s , and b i o l o g y 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 , C a l i f o r n i a , 99pp. Williams, M. 1979. The s o c i a l structure, breeding and population dynamics of P a r a d i s e Shelduck i n the G i s b o r n e - e a s t c o a s t d i s t r i c t . N o t o r n i s 26:213-272. Williams, M.J. 1974. C r e c h i n g behaviour of the shelduck Tadorna tadorna (L.). O r n i s Scand. 5:131-143. Wittenberger, J.F. 1981. 722pp.  Animal  s o c i a l behaviour.  Duxbury Press, London,  Wittenberger, J.F. and R.L. T i l s o n . 1980. The e v o l u t i o n of monogamy: hypotheses and evidence. Ann. Rev. Ecol. Syst. 11:197-232. Wolff, J.O., M.H. F r e e b e r g and R.D. D u e s e r . 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 s y m p a t r i c s p e c i e s of Peromyscus (Rodentia: Cricetidae). Behav. Ecol. Sociobiol. 12:237-242. Young, CM. 1970. Territoriality tadorna). I b i s 112:230-33 5. 193  i n the Common Shelduck  (Tadorna  Zar, J.H. 1974. B i o s t a t i s t i c a l a n a l y s i s . P r e n t i c e - H a l l , Inc., Englewood C l i f f s , New Jersey. Zipko, S.J. 197 9. E f f e c t s of dump n e s t s and h a b i t a t on r e p r o d u c t i v e ecology of wood ducks, A j x sponsa (Linnaeus). Ph.D. D i s s e r t a t i o n , 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 p a r t of a study on the b r e e d i n g e c o l o g y of Barrow's Goldeneye (Bucephala islandica) i n central B r i t i s h Columbia, I wanted to capture and i n d i v i d u a l l y mark a d u l t drakes t o 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 c o u l d not o b t a i n hand-reared b i r d s t o use as decoys and  decided to t r y mirrors.  Instead of a clover-leaf trap with open entrances  as used by Donaghey (197 5), I used a spring-door decoy t r a p as d e s c r i b e d by Anderson e t a l . (1980).  I used f o l d i n g wire dog cages (0.5 x lm) which  I f i t t e d with a t r i p p i n g mechanism s i m i l a r to that described by Anderson et a l . (1980). A glass mirror (0.4 x 0.8m) the  trap.  was f i x e d with wires a t the closed end of  To reach the mirror, the b i r d had to swim over the treadle that  c l o s e d the t r a p door.  Each t r a p was p o s i t i o n e d i n open water w i t h i n a  Barrow's Goldeneye t e r r i t o r y i n lm of water. the  Four aluminium poles held  cage f i x e d and a t a h e i g h t so t h a t the t r e a d l e and t h e m i r r o r base  were under water.  I t took l e s s than 10 min t o i n s t a l l a t r a p .  Results  r e p o r t e d h e r e a r e from 519 t r a p hours ( d a y l i g h t o n l y ) : 12 h / t r a p i n 1982 (2 t r a p s ) , 35 h / t r a p i n 1983  (5 t r a p s ) , and 80h/trap i n 1984  (4 t r a p s ) .  Each trap was checked at l e a s t 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 c a p t u r e d 41 Barrow's Goldeneye, 27 males and 16 females, w i t h m i r r o r t r a p s (Table 40). captured, (n=25).  In t e r r i t o r i e s where a goldeneye drake  was  e f f o r t per t r a p averaged 10.7 h and ranged from 4 t o 28 h  In those where a female was captured, t r a p p i n g 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 t o attack other females.  196  Whenever a female goldeneye was captured, her mate swam around the trap and stayed close t o i t .  I f 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, t h e i r 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 a l s o c a p t u r e d other s p e c i e s (Table  40).  These s p e c i e s , w i t h the e x c e p t i o n of the American  Wigeon (Anas americana), are w e l l known f o r t h e i r a g g r e s s i v e  behavior  d u r i n g the breeding season ( F j e l d s a 1973 a, Donaghey 197 5, Titman and Seymour 1981). B i r d s must see t h e i r r e f l e c t i o n i n the m i r r o r b e f o r e e n t e r i n g t h e trap.  Improper o r i e n t a t i o n , wind, and sun o f t e n reduced t h e m i r r o r ' s  efficiency. mirrors. birds  In addition, i n d i v i d u a l birds may vary i n t h e i r reaction to  Although m i r r o r t r a p s cannot be used t o mark l a r g e numbers of  they  may prove u s e f u l  i n l o c a l i z e d studies,  e s p e c i a l l y when  a c c e s s i b i l i t y or costs p r o h i b i t the use of captive decoys.  197  Table  40.  Bird  species captured  using mirror traps. Year  Species  1982  1984  1983  3  Horned G r e b e (Podiceps a u r i t u s )  I/O  Gadwall  1  (Anas s t r e p e r a ) A m e r i c a n Wigeon (Anas amer,icana)  1/0  2/0  Blue-winged T e a l (Anas dj,scQfS)  6/2  Northern Shoveler (Ajijag c l y p e a t a >  1/0  0/1  Barrow's Goldeneye (Bucephala j s l a n d i c a )  7/0  8/6  12/10  Bufflehead (Bucephala  1/0  1/0  1/0  1  males/females  198  Appendix 2. Evidence of long-term pair bonds i n Barrow's Goldeneye  199  Geese, swans and ducks that cooperate i n r a i s i n g young maintain longterm pair bonds (Kear 1970,  Bolen 1971,  Weller 1976,  Patterson 1982).  most H o l a r c t i c ducks the female r a i s e s the young a l o n e , new  In  p a i r s are  formed every year on wintering and/or migration areas, and males follow t h e i r p h i l o p a t r i c female to breeding areas  (Hochbaum 1944,  Rowley  1983,  and o t h e r s ) . Female Barrow's Goldeneye (Bucephala  islandica) return to the same  b r e e d i n g area every year and o f t e n use the same n e s t i n g s i t e s 1976).  Males  accompany  their  mates from  wintering  areas,  (Palmer defend  t e r r i t o r i e s on the breeding ground and then l e a v e f o r unknown m o l t i n g areas when the female i s i n c u b a t i n g .  They are not seen a g a i n on the  breeding ponds u n t i l the f o l l o w i n g s p r i n g .  In t h i s paper, I p r e s e n t  evidence i n d i c a t i n g that some Barrow's Goldeneye p a i r s remain intact from year to year i n spite of a long separation and that pair reunion occurs on the wintering areas. During a study of the b r e e d i n g 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 a d u l t drakes and adult females with nasal disks. area was  77%  (n=36) i n 1982  degree of s i t e f i d e l i t y .  81  The return rate of females to the study  and 7 5% (n=81) i n 1983,  i n d i c a t i n g a high  S i m i l a r r a t e s of r e t u r n f o r females have been  found i n other c a v i t y n e s t i n g ducks ( E r s k i n e 1961, Dow The r e t u r n r a t e of drakes was  71% (n=7)  i n 1982  and Fredga 1983).  and 63% (n=15) i n 1983.  Two of t h r e e p a i r s marked i n 1982 r e t u r n e d i n t a c t i n 1983 and the o t h e r d i d not r e t u r n .  The females of these two  r e t u r n i n g p a i r s had  raised  broods i n 1982, and were therefore separated from t h e i r mates for a t l e a s t four months.  The existence of long-term pair bonds was confirmed i n 1984,  when three of seven marked p a i r s returned intact.  Of the remaining four  p a i r s , one s p l i t and only one member returned i n the other three.  200  The  two females  t h a t had l o s t  r e s i g h t e d b u t the f o u r males had not.  their  mates had r e - p a i r e d when  These f o u r males r e t u r n e d t o the  same pond where they had been captured t h e p r e v i o u s year and one even defended a t e r r i t o r y f o r two days.  Usually, unpaired males do not defend  t e r r i t o r i e s . One Barrow's Goldeneye drake marked on h i s t e r r i t o r y i n 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 , t h r e e other p a i r e d males were r e s i g h t e d on t h e same t e r r i t o r y t h e f o l l o w i n g year. Although t h e females of these males were not marked, i t i s l i k e l y t h a t they retained t h e i r 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 w a t e r f o w l  (Hochbaum 1944, Young 1970,  Donaghey 1975). The preceding observations indicate that Barrow's Goldeneye p a i r s can remain i n t a c t from year t o year i n s p i t e of a l o n g s e p a r a t i o n and t h a t unpaired males home to t h e i r previous breeding area.  Homing of unpaired  drakes t o b r e e d i n g areas has been r e p o r t e d i n s e v e r a l d a b b l i n g ducks (Poston 1974, Blohm 197 8) and d i v i n g ducks (Bengtson 197 2, A l i s o n 197 5, Donaghey 1975).  Breeding p h i l o p a t r y i n u n p a i r e d males would i n c r e a s e  t h e i r chances of finding a mate, or of reuniting with a previous mate. I t could also enhance t h e i r s u r v i v a l because of t h e i r f a m i l i a r i t y with the resources of the area. I now c o n s i d e r where and how p a i r s r e - u n i t e . W i t h i n a week o f t h e a r r i v a l of Barrow's Goldeneye on t h e i r wintering areas i n southern coastal B r i t i s h Columbia, i n e a r l y November, some p a i r s a r e a l r e a d y defending territories.  From a t o t a l of 34 t e r r i t o r i e s defended along a 5km stretch  of shoreline i n Burrard Inlet near Vancouver, B.C., i n February and March 1983, 59% were established by mid-December and 85% by l a t e December.  This  rapid formation of p a i r s soon after a r r i v a l on the wintering areas, when  201  there i s l i t t l e courtship, suggests that p a i r s reunite then.  In 1983, 55%  of the 400 males present i n B u r r a r d I n l e t on November 17 had a r r i v e d by November 1 compared t o only 11% of the 200 females.  This e a r l i e r a r r i v a l  of t h e males supports the c o n t e n t i o n  t h a t most p a i r s r e u n i t e on t h e  wintering  s t a g i n g areas.  ground r a t h e r than on f a l l  (1976) found s i m i l a r p a i r f o r m a t i o n mollissima).  i n the Common E i d e r  This too involved l i t t l e courtship.  I was f o r t u n a t e  (Somateria  B u t t e r f i e l d (1970) also  observed that p a i r s of Zebra Finch (Poephila guttata) separation displayed l i t t l e  Spurr and M i l n e  that reunited a f t e r  courtship.  t o document t h e reunion  Goldeneye on the wintering area.  of one p a i r of Barrow's  A drake marked on h i s breeding t e r r i t o r y  i n 1982 was resighted near Vancouver, B.C, defending a winter at the t i p of a s m a l l j e t t y .  He was p a i r e d w i t h an unmarked f e m a l e and  they remained i n t h e i r t e r r i t o r y a l l w i n t e r . defended  t h e same breeding  territory  In A p r i l 1983 t h e male  a s i n 1982.  presumably with the female with whom he had wintered.  He was p a i r e d , We marked her that  summer and she r a i s e d a brood w h i l e the male departed f o r the grounds.  territory  molting  On October 29, 1983 we s i g h t e d the male i n a s m a l l group of  goldeneye (37 males, 3 f e m a l e s , 10 immatures), 2 km east of h i s 1982 winter t e r r i t o r y . November 12.  D a i l y checks i n d i c a t e d t h a t he remained t h e r e u n t i l  On November 8, we s i g h t e d h i s mate i n a l a r g e group o f  goldeneye (84 males, 39 females, 1 immature), 4 km from the l o c a t i o n of the male.  T h i s c o i n c i d e d w i t h the f i r s t b i g i n f l u x of a d u l t f e m a l e s on  the wintering  areas.  On the next day (November 9) the female had joined  her mate and the pair was i n a small goldeneye group (5 males, 2 females, 1 immature) 1.5 km from t h e i r 1982 winter t e r r i t o r y .  202  On  November 12  the p a i r  (175 males, 79 females, f i r s t saw  the female.  feeding and resting.  had  j o i n e d a l a r g e group of goldeneye  30 immatures) and were at the l o c a t i o n where  we  They stayed f o r 11 days i n t h i s large group mainly On November 22 they l e f t the group and attempted to  establish a t e r r i t o r y 2 km east of t h e i r o l d t e r r i t o r y but were apparently u n s u c c e s s f u l because, on December 12, they were back on t h e i r o l d territory.  They defended the t e r r i t o r y a l l winter and were l a s t sighted  there on A p r i l 12, 1984 at 0715 h. on  their  1982  breeding  territory  The next day (April 13) they were seen  a t 1120  h. They had  distance i n one night and had apparently migrated  covered  the 320  km  alone, as they were not  seen i n any groups p r i o r to t h e i r departure from the wintering area. This observation indicates that f i d e l i t y Barrow's Goldeneye may  to w i n t e r i n g areas i n  be as strong as f i d e l i t y to breeding areas.  by members of a pair would f a c i l i t a t e  pair reunion.  Homing  Homing to wintering  areas has also been documented i n Bufflehead (Bucephala albeola) (Erskine 1961,  Limpert  1980), Oldsquaw (Clangula h i e m a l i s )  ( A l i s o n 1975), and  Common Eider (Spurr and Milne 1976), indicating that p a i r reunion may  also  occur i n these species. Pair  bonds i n Barrow's Goldeneye are  copulation i s common among waterfowl,  strong.  Although  forced  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 f o u r y e a r s of i n t e n s i v e s t u d i e s of Barrow's Goldeneye and Bufflehead.  Goldeneye drakes take several minutes before mounting a prone  female (Afton and S a y l e r 1982,  Savard unpub. data).  Such p h y s i o l o g i c a l  and/or b e h a v i o u r a l d e l a y would make forced copulation d i f f i c u l t . copulate  throughout w i n t e r  reinforce pair bonds as may  as w e l l as d u r i n g i n c u b a t i o n . territorial  203  defense.  Pairs  This  may  A few s t u d i e s on s e a b i r d s have shown t h a t p a i r s t h a t r e - u n i t e a r e more s u c c e s s f u l than p a i r s t h a t s p l i t (Coulson and Thomas 1983). (1980) and Hepp and Hair the  (1984) found that pairing i n waterfowl enhanced  dominance s t a t u s of both p a r t n e r s  opportunities.  Scott  and improved  their  foraging  Rowley (1983) l i s t s s e v e r a l possible advantages of p a i r  reunion over t h e f o r m a t i o n  o f new p a i r bonds.  The advantages o f p a i r  r e u n i o n i n Barrow's Goldeneye may i n c l u d e : 1) o b t a i n i n g an experienced mate, whose a b i l i t i e s a r e known; breeding and wintering  2) f a m i l i a r i t y of the male w i t h t h e  t e r r i t o r i e s which gives him a stronger  to defend them because of a p r e v i o u s  sense o f ownership.  motivation This  enhance the chances of the female to r e t a i n her previous t e r r i t o r y ;  will 3) a  reduction of the time and energy spent i n courtship. There i s also evidence i n the l i t e r a t u r e that other migrating diving ducks may have l o n g l a s t i n g p a i r bonds: H a r l e q u i n Ducks ( H i s t r i o n i c u s 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 o f p a i r bonds i s more common i n ducks than has been p r e v i o u s l y thought.  I t i s l i k e l y that t h i s w i l l be confirmed as more adult males are  i n d i v i d u a l l y marked i n 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 l i g h t 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,  t h e marked f e m a l e (M) was f i g h t i n g w i t h an  unmarked female (U). won  M had 3 young approximately  the f i g h t and M flew away.  In the next 10 min,  2 weeks old.  U  U swam away followed by M's young.  M made three unsuccessful attempts t o regain  her young, but each t i m e was chased away by U. M f l e w away. swam toward her 5 young, also approximately 0640 h: U attacked the three young of M.  U  2 weeks old.  The young had not mixed with U's  young and were a few meters away.  Following the attack, M's young  swam away and h i d 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 a i r f o r f i v e minutes. flew out of sight and U returned to her t e r r i t o r y . M's young, then swam toward her own young.  M again  U landed near  M's young f o l l o w e d U  swimming behind her, but a f t e r swimming a few meters U turned around and a t t a c k e d t h e young who f l e d back near shore among flooded trees.  U returned t o her young.  0654 h: M made another u n s u c c e s s f u l attempt t o r e g a i n her young and was chased o f f again by U.  U r e t u r n e d from her a e r i a l p u r s u i t a t  0657 h and, after she landed i n her t e r r i t o r y , 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 t o her young.  0659 h: M's young l e f t the f l o o d e d t r e e s and a g a i n swam toward U and her young.  U attacked them and they returned t o the flooded trees.  0703 h: U swam toward t h e f l o o d e d t r e e s and a t t a c k e d 206  M's young and  s u c c e s s f u l l y chased them o f f her t e r r i t o r y .  U stopped p u r s u i n g  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  calling  loudly.  However, her young had l e f t U's t e r r i t o r y and were swimming away. U was a t the border of her t e r r i t o r y threatening the young and had not  noticed M.  0714 h: U returned t o her young followed by M's young 20 m behind. 0715 h  M saw her young and f l e w t o the other s i d e o f U's t e r r i t o r y . She c a l l e d h e r young and they swam t o her.  M and her young swam  toward emergent vegetation. 0724 h: Brood M came out of emergent v e g e t a t i o n and swam away from U's territory.  U was feeding within her t e r r i t o r y 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 v i o l e n t f i g h t pursued her i n the air.  M flew out of sight and A landed near M's young.  confused. attract  She seemed  Her young were sleeping on a l o g 30 m away. A t r i e d t o M's young and swam behind them.  She d i d not appear  a g g r e s s i v e but t h e young, probably because of t h e i r encounter w i t h f e m a l e U, swam away and d i d not  previous  respond t o her  During the next hour, M's young remained alone on the water.  They  were v i s i t e d three times by A who d i d 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 l o g and s t a r t e d feeding.  A swam toward M's young f o l l o w e d 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 t h i s display  by her young, A a t t a c k e d t h e t h r e e young o f M and chased them. A  207  attacked M's young twice but could not catch them. attacks and resumed feeding.  A stopped her  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 t h r e e f e m a l e s were marked  with nasal disks. 0750 h: Female C l e d her four newly hatched young t o t h e 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 a t t a c k e d one  of C's young, grabbed i t by t h e neck and shook i t under water. This prompted C to leave shore and attack A t o protect her young. A dominated C and drove her away.  Meanwhile, C's young escaped i n  emergent v e g e t a t i o n and became s e p a r a t e d from the other t h r e e young.  A returned t o her young and preened on shore.  While A was  r e s t i n g on shore, C regrouped h e r young and swam o u t of A's territory.  As C e n t e r e d t h e 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 l e a v i n g her young behind.  B then a t t a c k e d the young o f 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 o f f by B each time.  B k i l l e d the young.  The other young had sought r e f u g e 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 l e d her young t o a neighbouring lake 600 m away.  3rd encounter: 1328 h:  Ten days l a t e r a l l her young had died.  Lake 31 June 16, 1984. The two females were marked.  Female A had e s t a b l i s h e d her t e r r i t o r y e a r l i e r , after her 10 young had hatched.  on t h e l a k e 14 days  Female B's 11 young were  jumping out of the box. B l e d them toward the lake only 3 m away but was attacked on land by A who grabbed her r i g h t wing, climbed on her back b i t i n g her continuously.  This l a s t e d a t l e a s t 5 min.  A kept B from reaching t h e l a k e and B walked toward t h e f o r e s t with A s t i l l having hold of her wing. Female A r e l e a s e d B 40 m from shore and B went o f f w i t h her 11 young through the forest.  A returned t o her young on the lake but  remained c l o s e t o t h e a r e a where the f i r s t encounter o c c u r r e d . The v i o l e n t a t t a c k by A c o n t r a s t e d w i t h the s u b m i s s i o n o f B who d i d not f i g h t back but rather t r i e d to escape. The following day, B was located on a lake 700 m away with only 6 young.  The next day she had l o s t a l l her young who may have mixed  w i t h another brood on the l a k e .  A remained on her l a k e and  successfully raised a l l her young.  4th encounter:  Lake 106, June, 1981. Neither of the broods was marked.  When I a r r i v e d a t the lake, two female Barrow's Goldeneye were f i g h t i n g . The defeated female escaped to shore. one of t h e young and k i l l e d i t .  Then the v i c t o r i o u s female attacked  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 h i d i n g i n the grass.  There were no other b i r d s on the  pond besides the goldeneye.  I t i s clear from these examples that females do not attempt to steal other females' young. and  Females abandon t h e i r young o n l y a f t e r v i o l e n t f i g h t s ,  even make several attempts to regain them.  These four observations  suggest t h a t brood amalgamation i s not a s t r a t e g y used by the f e m a l e s 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 p a i r bond w i t h two or more f e m a l e s whose n e s t i n g c y c l e s o v e r l a p i n t i m e (Wittenberger 1981). T i l s o n 1980,  Polygyny i s r a r e i n w a t e r f o w l (Wittenberger and  Ford 1983) and commonly o c c u r s i n o n l y two s p e c i e s , the  M a g p i e Goose  (Anseranas semipalmata)  (Sarkidiornis melanotos)  and t h e A f r i c a n Comb Duck  (Frith and Davies 1961, S i e g f r i e d 1979).  Studies  of c a p t i v e b i r d s have i n d i c a t e d t h a t some southern hemisphere d a b b l i n g ducks may occasionally be polygynous (McKinney and Stolen 1982, Stolen and McKinney 1983, McKinney and Bruggers 1983).  S i m i l a r s t u d i e s 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 Common G o l d e n e y e  (Aythya v a l i s i n e r i a )  (Anderson,  M.  i n Ford  1983).  ( B u c e p h a l a c l a n g u l a ) and Barrow's Goldeneye  (£.  i s l a n d i c a ) have been observed defending two f e m a l e s and t h i s suggested that polygyny may occur i n these species (Eriksson, M. pers. comm., Savard per. obser.).  I d e s c r i b e here four cases of polygyny observed i n 1984  among 220 p a i r s of Barrow's Goldeneye  d u r i n g a study of  behaviour i n the i n t e r i o r of B r i t i s h Columbia,  territorial  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. A p r i l 15, two other p a i r s had established t e r r i t o r i e s .  By  Female B (marked)  was f i r s t seen A p r i l 17 on the pond and d i d not seem p a i r e d .  This  was  unusual as unpaired adult females are r a r e l y seen on the breeding areas. On A p r i l 18, male A was defending a t e r r i t o r y from which he excluded a l l goldeneyes but f e m a l e s A and B. territories  on  the l a k e and  Three monogamous males a l s o defended  t h e r e were  212  several  u n p a i r e d males  on  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 p r e v i o u s year. started incubation on May 3 and Female B on May 17. was  The nest of female A  destroyed by a Black Bear (Ursus americanus) on May 4 whereas that of  female B was Squirrel  deserted on May  27 because of egg predation by American Red  ( T a m i a s c i u r u s hudsonicus).  We  were a b l e t o i d e n t i f y  polygynous male after h i s capture on May 13. him  Female A  the  Both females remained with  i n the t e r r i t o r y u n t i l h i s departure on June 5. The two females then  spent most of t h e i r time on l a k e 13 a s s o c i a t i n g t e m p o r a r i l y w i t h other females but r a r e l y together.  They were l a s t seen on J u l y 5.  Both females had been marked i n e a r l i e r years so that their breeding history was p a r t i a l l y known. nest box she used i n 1984,  Female A nested i n 1982 and 1983 i n the same and r a i s e d a brood on Lake 13.  In 1983  breeding t e r r i t o r y was on Lake 13 and her mate was monogamous.  her  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  assumed t h a t she was p a i r e d w i t h a monogamous male.  i tis  I t i s also l i k e l y  that her mate's t e r r i t o r y was also on Lake 13. Case 2 In t h i s case, I w i t n e s s e d 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 a t 0500 h on A p r i l  4.  At 1600  challenged an established pair.  h, they landed on t h e i r breeding pond and After a v i o l e n t f i g h t i n which both sexes  p a r t i c i p a t e d , p a i r C took over the t e r r i t o r y . male was  observed  defending the t e r r i t o r y .  n e i g h o u r i n g p a i r , p a i r D, c o p u l a t e d .  213  On A p r i l  5, 6 and 7, the  A t 0645 h on A p r i l  8,  a  A t 06 55 h, male C a t t a c k e d male D  and a f t e r a v i o l e n t f i g h t male D l e f t the pond, abandoning h i s mate.  Male  C d i d not show any a g g r e s s i o n toward female D but female C d i d .  At  0710 h, male C approached f e m a l e D and both d i s p l a y e d t o each o t h e r . 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 h i s o r i g i n a l t e r r i t o r y by chasing  a l l goldeneyes that approached female C.  Both females remained with male  C and were observed copulating with him at l e a s t once. her c l u t c h on May  5 and hatched 14 young.  Female C i n i t i a t e d  I t i s not known i f f e m a l e D  nested.  Case 3 A male (G) w i t h two f e m a l e s was observed on A p r i l 30, d e f e n d i n g a t e r r i t o r y on a small pond which also supported another t e r r i t o r i a l On May 1 we captured and marked the polygynous male.  pair.  He was l a s t seen on  May 26. Case 4 On  May  2 a male w i t h two  f e m a l e s , 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 a l s o e s t a b l i s h e d territories.  Female H had bred on that pond i n 1982 and 1983.  we captured and marked the other female (I).  On May 11  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 d e s t r o y e d 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 p a i r s to see i f polygynous males tended to be more aggressive than monogamous males  (Table 41).  The r e s u l t s 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 i n Barrow's Goldeneye could be promoted by the 214  following factors: Scudder  197 8) so  (1) Breeding ponds are very productive (Cannings and that  the  resources of  the  territory  s i g n i f i c a n t l y a l t e r e d by the presence of a second female; not p r o v i d e p a r e n t a l a s s i s t a n c e (Munro 193 9);  females  toward  be  increases  However, s e v e r a l  They are (1) the existence of strong  and s t a b l e p a i r bonds (Appendix 2); males and  not  (2) Males do  (3) Polygyny  r e p r o d u c t i v e success of males (Wittenberger 1981). f a c t o r s also act to l i m i t polygyny.  may  (2) a g g r e s s i v e n e s s o f both p a i r e d  strange females  (Chapter I I I ) ;  (3) p a i r  formation occurring on the wintering ground and not related to t e r r i t o r y q u a l i t y (Palmer 1976, Appendix  2);  ( B e l l r o s e 197 8, Savard unpubl. data);  (4) sex r a t i o b i a s e d toward males (5) A b i l i t y of f e m a l e s to f i n d a  new mate more r e a d i l y than males (Savard unpubl. data). The low degree of polygyny observed i n the population studied  (<2%,  n=220 pairs) suggests that polygyny i n Barrow's Goldeneye i s not a common breeding s t r a t e g y but r a t h e r an unusual o c c u r r e n c e .  Models based on  habitat or male q u a l i t i e s to explain polygyny (Wittenberger 1981)  do not  apply here and have been questioned i n 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 n e s t s i t e s by females, l o s s of p r e v i o u s mate or the mate f a i l u r e t o establish or regain the female t e r r i t o r y ,  and f a m i l i a r i t y between b i r d s  i n v o l v e d , l e a d i n some c a s e s t o polygyny i n Barrow's Goldeneye.  These  factors have not always been considered i n previous studies of polygyny and may  prove important i n e x p l a i n i n g the o c c a s i o n a l o c c u r r e n c e of  polygyny i n other species.  215  Appendix 5.  Sexual dimorphism i n Barrow's Goldeneye  216  Livezey and Humphrey (1984) compared sexual dimorphism  (in weight)  of s e v e r a l s p e c i e s of w a t e r f o w l and showed t h a t s p e c i e s of the genus Bucephala were among the most d i m o r p h i c s p e c i e s .  Weights of Barrow's  Goldeneye are r a r e i n the l i t e r a t u r e ( B e l l r o s e 1978, Palmer 1976).  I  thus compare here weight of males and females captured during the study. In 1983 and 1984 males were r e s p e c t i v e l y 1.4 t i m e s and 1.6 t i m e s h e a v i e r than f e m a l e s (Table 42).  T h i s r a t i o may s l i g h t l y overestimate  the difference i n weight between males and females because most females were weighed l a t e i n t o i n c u b a t i o n .  Vermeer (1981) r e p o r t s an average  weight i n w i n t e r f o r males o f 1173 g (n=18) and of 823 g (n=13) f o r f e m a l e s f o r a weight r a t i o of 1.4.  Males' wings averaged 23 mm  than those of females i n both 1983 and 1984  217  (Table 42).  longer  Table 42.  Comparison of weight3 and wing length between male and female Barrow's Goldeneye. Weight (g) 1  Female  Male Female  Wing length (mm)  Male  1983  1002.8+26.3 n=9  717.6±5.1 n=69  1.4  237.3+2.0 n=7  214.7+0.5 n=68  1984  1121.9+23.9 n=13  703.8±4.2 n=59  1.6  238.8+1.3 n=12  215.0+0.5 n=57  2  Male  Female  Year  Male Female 1.1 1.1  1  D i f f e r e n c e s i n weight and wing l e n g t h between males and f e m a l e s were s t a t i s t i c a l l y s i g n i f i c a n t i n both years (T-test P<0.05).  2  standard e r r o r .  3  Males were weighed between May 1 and June 1. Most females were weighed i n the l a s t week of the incubation period between May 20 and June 20.  218  

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