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A study of the distribution of some members of the Nyrocinae wintering on the coastal waters of southern… Mitchell, George Joseph 1952

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A STUDY OF THE DISTRIBUTION OF SOME MEMBERS OF THE NYROCINAE WINTERING- ON THE COASTAL WATERS OF SOUTHERN BRITISH COLUMBIA by GEORGE JOSEPH MITCHELL A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of Zoology We accept t h i s t h e s i s as conforming to the standard r e q u i r e d from candidates f o r the degree of MASTER OF ARTS. Members of the Department o f Zoology THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1952 ABSTRACT From September, 1 9 5 1 ,'until March 195 2 , f i e l d work was c a r r i e d on to determine the d i s t r i b u t i o n of w i n t e r i n g d i v i n g ducks on the c o a s t a l waters of southern B r i t i s h Columbia, and an attempt was made to d i s c o v e r and e v a l u a t e the f a c t o r s caus-i n g d i s t r i b u t i o n and movement. D i v i n g ducks are i n f l u e n c e d by the a v a i l a b i l i t y of food and other f a c t o r s r e l a t e d to t h i s a v a i l a b i l i t y . These f a c t o r s i n c l u d e salmon and h e r r i n g spawning, g r a i n e l e v a t o r s , sewer out-f a l l s , and changing t i d e s . L o c a l movements r e s u l t from c o u r t -s h i p a c t i v i t y , d l e l p e r i o d i c i t y and d i s t u r b i n g a g e n c i e s . M o r t a l i t y f a c t o r s , i n c l u d i n g hunting, o i l i n g , p r e d a t i o n and l e a d p o i s o n i n g d i d not cause s e r i o u s Inroads i n the w i n t e r -i n g d i v i n g duck p o p u l a t i o n d u r i n g the study. Lake, and bay and e s t u a r l n e h a b i t a t s were found to be l e s s important w i n t e r i n g areas than h a b i t a t s a l o n g p r o t e c t e d and unprotected c o a s t l i n e . A l l s p e c i e s of d i v i n g ducks showed pr e f e r e n c e f o r c e r t a i n h a b i t a t s and r e g i o n s i n the study area, and were absent or uncommon i n o t h e r s . During the w i n t e r , the drakes and hens of most s p e c i e s were d i s t r i b u t e d non-randomly because of the preponderance of males and t h e i r tendency to f l o c k t o g e t h e r . In e a r l y s p r i n g the sexes were d i s t r i b u t e d non-randomly due to p a i r f o r m a t i o n and predominance of drakes. A d i f f e r e n t i a l sex m i g r a t i o n was evident i n most species of ducks d u r i n g l a t e f a l l and e a r l y s p r i n g . Only a small percentage of j u v e n i l e s of a l l s p e c i e s were w i n t e r i n g on the study area, I n d i c a t i n g that they p o s s i b l y win-t e r i n other l o c a l i t i e s . i TABLE OF CONTENTS Page INTRODUCTION 1 ACKNOWLEDGEMENT S DESCRIPTION OF STUDY AREA, HABITATS, AND OBSERVATIONAL AREAS PROCEDURE .......................................... l 4 FACTORS INFLUENCING SEASONAL DISTRIBUTION AND MOVEMENT Climate l 6 Land and Shore Topography 17 Food A v a i l a b i l i t y and Preference 17 I n v e r t e b r a t e s 17 Salmon Spawn » 24 H e r r i n g Spawn 25 G r a i n E l e v a t o r s 2? Sewer O u t f a l l s 28 FACTORS INFLUENCING DAILY DISTRIBUTION AND MOVEMENT Weather J>1 T i d e s 33 D i s p l a y and C o u r t s h i p 34 D i e l P e r i o d i c i t y 36 D i s t u r b a n c e s 39 FACTORS OF MORTALITY 40 Hunting 40 O i l i n g 42 Lead P o i s o n i n g 44 P r e d a t i o n 44 i i DISTRIBUTION OF THE SPECIES .. 4-5 Redhead (Nyroca americana) * 4-5 Ring-necked duck (Nyroca c o l l a r l s ) 4-9. Canvas-back (Nyroca y a l i s l n e r l a ) 4-9 Greater Scaup Duck (Nyroca m a r i j a ) 50 L e s s e r Scaup Duck (Nyroca a f f i n i s ) 51 American Golden-eye (Glaucionetta,, c l a n g u l a americana) .............. 52 Barrow's Golden-eye ( G l a u c i q n e t t a l s l a n d l o a ) . . . . 52 B u f f l e - h e a d ( C h a r l t o n e t t a a l b e o l a ) .............. 53 Old-squaw ( C l a n g u l a hyemalls) 55 H a r l e q u i n Duck. ( H i s t r i o n i c u s h i s t r l o n l c u s ) 55 White-winged Scoter ( M e l a n l t t a degland1) ...-.'v; 5^ Surf Scoter ( M e l a n l t t a p e r s p i c l l l a t a ) .......... 5& American Scoter (Oldemia americana) ............ 57 STRUCTURE OF THE POPULATION 60 Sex S t r u c t u r e ..... ^  60 Age S t r u c t u r e 80 DISCUSSION 83 CONCLUSIONS 90 LITERATURE CITED 92 i i i TABLE • Page I. Food, by volume percentages, taken by nine s p e c i e s of d i v i n g ducks d u r i n g p e r i o d September 1951 to March 1952. . 21 I I . D e l t a M u n i c i p a l i t y bag check of d i v i n g ducks shot by hunters d u r i n g open seasons, 1949-1951.. 4l I I I . Number of dead b i r d s found on a two mile sample of beach at Boundary bay, February 7 and 24, 1952 42 IV. P r o b a b i l i t y v a l u e s f o r u n i f o r m i t y of d i s t r i -b u t i o n with r e s p e c t to.sex and sex r a t i o d u r i n g p e r i o d September 195.1 - March 1952. . . . . . . . . . . . . 63 V Percentage j u v e n i l e s , by s p e c i e s , observed d u r i n g p e r i o d , September 1951 - March 1952 SI i v FIGURE Page 1. A e r i a l photograph of Vancouver and adjacent waters. Note the sandy shore at the l o n a I s l a n d j e t t y (lower r i g h t c orner) and West P o i n t Grey (lower l e f t ) 10 2. Low t i d e at O b s e r v a t i o n a l Area 3, K i t s i l a n o beach. Unprotected-sandy h a b i t a t ....» 11 3. Low t i d e at O b s e r v a t i o n a l Area 4, J e r i c h o beach. Unprotected-rocky h a b i t a t . ......... .11 4-. Low t i d e at O b s e r v a t i o n a l Area 5> E n g l i s h Bay beach. Unprotected-rocky h a b i t a t 12 5« Low t i d e at Observational, Area 6, Second beach. Unprotected-rocky h a b i t a t 12 6. Low t i d e at O b s e r v a t i o n a l Area 7> Prospect P o i n t . P r o t e c t e d - r o c k y h a b i t a t . ............ 13 7. Low t i d e at O b s e r v a t i o n a l Area 2>, North arm of F r a s e r r i v e r . Bay and e s t u a r l n e h a b i t a t . . 13 g. South end of A n v i l i s l a n d , Howe sound, showing abrupt and rocky shore t y p i c a l of t h i s region.1 9 9. A e r i a l photograph of the P a s l e y i s l a n d group. The p r o t e c t e d i n t e r - i s l a n d a r e a o f f e r s sanc-t u a r y to d i v i n g ducks at n i g h t . .............37 10. Percentage number of d i v i n g ducks counted per o b s e r v a t i o n a l mile on i n d i v i d u a l h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952. ..4-6 11. Percentage number of d i v i n g ducks counted per o b s e r v a t i o n a l mile on i n d i v i d u a l h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952....4-7 12. T o t a l number of d i v i n g ducks counted, by sp e c i e s , on O b s e r v a t i o n a l Areas 1 - 9 d u r i n g , p e r i o d September 1951 to March 1952. (Repre-s e n t i n g cumulative t o t a l s of average number counted per observation? d u r i n g t h i s p e r i o d . ) . 46 V FIGURE Page 13* A e r i a l photograph of Ganges harbour, S a l t S p r i n g i s l a n d , and the northwest end of Prevost i s l a n d . The narrow i n l e t s on P r e v o s t i s l a n d are f a v o u r i t e f e e d i n g areas f o r b u f f l e - h e a d and golden-eyes. T h i s r e -g i o n i s an important h e r r i n g spawning 14-. Average number of a l l s p e c i e s of d i v i n g ducks counted per o b s e r v a t i o n a l mile by h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952. (Representing cumulative t o t a l s of average number counted per o b s e r v a t i o n a l m i l e d u r i n g t h i s p e r i o d . ) 59 15« Percentage p a i r e d by s p e c i e s , observed i n study area d u r i n g p e r i o d September 1951 to March 1952 66 16. Percentage p a i r e d , b y . s p e c i e s , observed i n study area d u r i n g p e r i o d September 1951 -March 1952 67 17. Percentage males, by s p e c i e s , observed i n study area d u r i n g p e r i o d September 1951 -March 1952. . . . . . 6g l g . Percentage males, by s p e c i e s , observed i n study area d u r i n g p e r i o d September 1951 -March 1952. 69 19. D i s t r i b u t i o n and d e n s i t y o f w i n t e r i n g d i v i n g ducks i n study area, southern B r i t i s h Columbia ' 94-20. D i s t r i b u t i o n and d e n s i t y of w i n t e r i n g d i v i n g ducks i n study area, southern B r i t i s h Columbia 95 INTRODUCTION The d i v i n g , bay or sea ducks have, f o r many years been recorded as t r a n s i e n t s on the P a c i f i c seabord d u r i n g s p r i n g and f a l l m i g r a t i o n s , and as r e s i d e n t s d u r i n g the w i n t e r . The re c o r d s of Munro and Cowan (194-7) show t h a t a l l the s p e c i e s o f Nyrocinae, w i t h the e x c e p t i o n of the e i d e r s and l e s s e r scaup duck; (Nyroca  a f f i n i s ) , w i n t e r on the marine waters adjacent to southern B r i t i s h Columbia. Munro (1939, 194-1, 194-2), i n h i s s t u d i e s on the American golden-eye ( G l a u c l o n e t t a c l a n g u l a americana),. Barrow*s golden-eye ( G l a u c l o n e t t a l s l a n d l c a ) , g r e a t e r scaup duck (Nyroca m a r i l a ) , l e s s e r scaup duck and b u f f l e - h e a d (Char 1 -t o n e t t a a l b e o l a ) , observed these ducks on t h e i r c o a s t a l w i n t e r -i n g grounds and made c o n c l u s i o n s r e g a r d i n g t h e i r d i s t r i b u t i o n and movement. U n t i l September, 1951> when the present study was i n i t i a t e d , l i t t l e attempt had been made to s y s t e m a t i c a l l y observe d i v i n g ducks throughout the e n t i r e winter p e r i o d on an are a s u i t -a b l y l a r g e and e c o l o g i c a l l y v a r i e d t o i n c l u d e a l l s p e c i e s of Nyrocinae w i n t e r i n g i n t h i s l a t i t u d e * , In w i n t e r , most species o f d i v i n g ducks l i v e on the c o a s t a l marine waters. In the study area, the ducks showing t h i s h a b i t were g r e a t e r scaup duck, American golden-eye, Barrow 1s golden-eye, b u f f l e h e a d , h a r l e q u i n ( H l s t r l o n l c u s h l s t r i o n l c u s ) , white-winged s c o t e r ( M e l a n l t t a deglandi),, s u r f s c o t e r ( M e l a n l t t a p e r s p l c l l l a t a ) , American s c o t e r (Oidemla americana), and, to a l e s s e r degree, canvas-back (Nyroca v a l i s l n e r l a ) . During the study, an attempt was made to observe a l l e x i s t i n g shore l i n e w i t h i n the study area. T h i s was not p o s s i b l e owing to l i m i t e d time and t r a n s p o r t a t i o n f a c i l i t i e s a v a i l a b l e . However, the s h o r e l i n e and lak e s observed r e p r e s e n t the v a r i e d a r r a y o f e c o l o g i c a l h a b i t a t s that e x i s t . When i t i s i m p r a c t i c a l to mark a s u f f i c i e n t l y l a r g e number of animals f o r r e c o g n i t i o n a t a l a t e r date, a l l c o n c l u s -i o n s r e g a r d i n g seasonal and d a i l y movement must be made by a n a l y s i n g a s e r i e s of o b s e r v a t i o n a l data on the s p e c i e s , r a t h e r than the i n d i v i d u a l . T h i s method has been used i n the present study. Because the many f a c t o r s i n f l u e n c i n g the w i n t e r i n g ducks c o u l d not be c o n t r o l l e d , i t has been necessary t o i n d i c a t e the e f f e c t s of these f a c t o r s r a t h e r than draw d e f i n i t e c o n c l u s i o n s . 3 ACKNOWLEDGEMENTS The w r i t e r wishes to express h i s a p p r e c i a t i o n to Dr. I. MoT, Cowan of the Department of Zoology, who suggested t h i s i n v e s t i g a t i o n and under whose d i r e c t i o n , t h e work has been c a r r i e d out, and to Dr. W. A. Clemens of the same Department f o r g r a n t i n g f i n a n c i a l a s s i s t a n c e from the Department's funds f o r t r a n s p o r t a t i o n purposes, and f o r h i s h e l p i n i d e n t i f i c a t i o n of the i n v e r t e b r a t e animals. G r a t e f u l acknowledgement i s made to Dr. P, A. L a r k i n , C h i e f F i s h e r i e s B i o l o g i s t , B r i t i s h Columbia Game Commission and Department of Zoology, f o r a d v i c e and h e l p w i t h the s t a t i s t i c a l a n a l y s e s ; to Mr. J . H a t t e r , C h i e f Game B i o l o g i s t , B r i t i s h Columbia Game Commission and Department of Zoology, and Dr. W. M. Cameron of the same Department f o r t h e i r suggestions and a d v i c e . Thanks are a l s o extended to Miss M« H a r r i n g t o n , Department of B i o l o g y and Botany, f o r help i n i d e n t i f i c a t i o n of p l a n t foods, and to Mr. E. W. T a y l o r and Mr. D. J . Robinson, B i o l o g i s t s , B r i t i s h Columbia Game Commission, and Mr. C. J . Guiguet, B i o l o g i s t , P r o v i n c i a l Museum, V i c t o r i a , f o r t h e i r winter water-fowl r e c o r d s and suggestions, accommodation and t r a n s p o r t a t i o n i n the f i e l d ; to I n s p e c t o r A. A, Sherman, Department of F i s h e r i e s , Duncan, f o r water t r a n s p o r t a t i o n at Cowichan bay and S a l t S p r i n g i s l a n d . The author i s indebted to the, f o l l o w i n g men whose co-o p e r a t i o n and f i e l d o b s e r v a t i o n s have made i t p o s s i b l e to i n c l u d e 4 much of the s h o r e l i n e i n the present study: Dr. M. Y. W i l l i a m s , Department of Geology; Mr. D. A. Munro, Canadian W i l d l i f e S e r v i c e , Vancouver; Mr. E. D. Wood, V i c t o r i a ; Mr. D. F. Winteringham, S a l t S p r i n g i s l a n d ; Mr. W. A. McKay, Department of F i s h e r i e s , Vancouver; C p l . L. R. Lane and Mr. H. D. M u l l i g a n , Game Wardens, B r i t i s h Columbia Game Commission, Vancouver; M r . G. W. Smith and Mr. R» Webb, f e l l o w students. F i n a l thanks go to Mr. K. Racey, Vancouver, f o r h i s reco r d s of wint e r d i v i n g duck m o r t a l i t y , and P o r t Hardy r e c o r d s ; Canadian W i l d l i f e S e r v i c e f o r the D e l t a bag-check r e c o r d s ; Inspector. R. E. A l l e n and the B r i t i s h Columbia Game Commission f o r p e r m i s s i o n to use t h e i r motor launch; Dr. G. C. C a r l , D i r e c t o r , P r o v i n c i a l Museum, V i c t o r i a , f o r t r a n s p o r t a t i o n i n tha t area, and Mr. G. W. Anderson f o r h i s a e r i a l photograph of Pa s l e y i s l a n d . 5 DESCRIPTION OF STUDY AREA, HABITATS, AND OBSERVATIONAL AREAS The waters of the S/trait of Georgia, Burrard i n l e t , and Howe sound adjacent to the coast of southern B r i t i s h Columbia, and the i n l a n d lakes i n th$s r e g i o n , are probably the most n o r t h -e r l y c o a s t a l wintering grounds of the redhead (Nyroca americana), r ing-necked duck (Nyroca c o l l a r i s ) , canvas back, and l e s s e r scaup duck. To the greater scaup duck, American golden-eye, Barrow's golden-eye, b u f f l e - h e a d , h a r l e q u i n , white-winged s c o t e r , and surf s c o t e r , these waters are the approximate mid-points of t h e i r c o a s t a l winter ranges. Dhring September, October and November large numbers of d i v i n g ducks a r r i v e on these w i n t e r i n g grounds from t h e i r more n o r t h e r l y breeding range. According to Munro and Cowan (194-7), some species, such as the h a r l e q u i n and non-breeding white-winged s c o t e r s , surf s c o t e r s , and American scoters summer i n small numbers on the B r i t i s h Columbia coast . The s a l t water study area i s bounded on the west by the east coast of Vancouver i s l a n d , and extends from Oyster bay i n the n o r t h , southeast to V i c t o r i a . The eastern boundary i s formed by the mainland coast l i n e and extends from the 4-9th p a r a l l e l north to McNab creek, Howe sound* The freshwater lakes i n c l u d e d i n the study are St . Mary l a k e , S a l t Spring i s l a n d , and Langford, E l k , Durrance, Sooke, 6 Wolf, Quamichan, Somenos l a k e s , and i n p a r t , Cowichan and Comox la k e s , Vancouver i s l a n d . On the mainland, o b s e r v a t i o n s were made at Beaver l a k e and Lost Lagoon, Vancouver. The study r e g i o n i s c h a r a c t e r i z e d by m i l d w i n t e r s and h i g h p r e c i p i t a t i o n . At Comox, near the n o r t h e r n boundary of the study area, the lowest temperature recorded ( M e t e o r o l o g i c a l D i v i s i o n , Department of T r a n s p o r t ) i n January 1952, was 7°F. The lowest r e c o r d e d temperature a t V i c t o r i a was l S ^ F . , and a t Vancouver, l 4°F. Highest p r e c i p i t a t i o n occurs d u r i n g December, and the average monthly p r e c i p i t a t i o n d u r i n g t h i s month at Cumberland ( 4 l y e a r s 1 o b s e r v a t i o n s ) i s 10.87 i n c h e s , a t V i c t o r i a (58 y e a r s 1 o b s e r v a t i o n s ) , 4.67 inches, and at Vancouver ( 4 l y e a r s ' o b s e r v a -t i o n s ) , 8.76 i n c h e s . The marine waters seldom freeze, over ex-cept i n the marshy areas, and some p r o t e c t e d bays. Even here the i c e soon r o t s or i s broken up by wind and wave a c t i o n . F r e s h -water l a k e s u s u a l l y f r e e z e over completely or p a r t i a l l y d u r i n g the l a t t e r p a r t of December and e a r l y January. On the P a c i f i c coast, t h r e e major f a c t o r s operate to determine the d i s t r i b u t i o n of shore i n v e r t e b r a t e s . These have been d e s c r i b e d by R l c k e t t s and C a l v i n (1939), as the degree of wave shock, the type of shore bottom, and the t i d a l exposure. These f a c t o r s suggested the c l a s s i f i c a t i o n of h a b i t a t s used by these workers, and a s i m i l a r but m o d i f i e d system has been adopted f o r the present study. Cottam (1939), has shown, and the r e s u l t s of the food a n a l y s i s made by the author i n d i c a t e , that many s p e c i e s of 7 I n v e r t e b r a t e s are u t i l i z e d as food by d i v i n g ducks. I t i s r e a -sonable to assume then, t h a t those f a c t o r s which I n f l u e n c e I n -v e r t e b r a t e d i s t r i b u t i o n a l s o a f f e c t the d i s t r i b u t i o n of d i v i n g ducks. The c l a s s i f i c a t i o n of marine h a b i t a t s adopted i s based on the exposure of the s h o r e l i n e to h i g h winds and wave shock, and the type of bottom, whether.rocky or sandy. The e f f e c t of wave shock i s c o n s i d e r e d n e g l i g i b l e i n the freshwater h a b i t a t , and no d i s t i n c t i o n between d i f f e r e n t types of bottom has been made. C o n s i d e r i n g degree of exposure and type of bottom, the f o l l o w i n g g e n e r a l i z a t i o n s can be made: Unprotected coast? The s h o r e l i n e i n t h i s r e g i o n , be-cause o f i t s p o s i t i o n and exposure to frequent strong winds, Is sub j e c t e d to heavy s u r f . Many g r a d i e n t stages occur and o c c a -s i o n a l l y , a s t r i p o f unprotected beach i s broken by a p r o j e c t i n g p o i n t o r p i e r which p r o v i d e s p r o t e c t i o n to the leeward s h o r e l i n e . However, the m a j o r i t y o f s h o r e l i n e i n t h i s category i s pervaded by a h i g h degree of wave shock. P r o t e c t e d c o a s t : Wave shock i s minimized i n t h i s r e g i o n because o f n a t u r a l and a r t i f i c i a l o b s t r u c t i o n to heavy waves and str o n g winds. Again, many g r a d i e n t stages of wave , shock e x i s t , but heavy s u r f on t h i s shore i s uncommon. Sandy shore and rocky shore: Along a s t r i p o f coast l i n e , much l n t e r g r a d a t i o n o f types o f bottom e x i s t , r a n g i n g from muddy, muddy-sandy, to rocky. In the Greater Vancouver area, much o f the bottom i s sandy, due to the d e p o s i t i o n of s i l t by the F r a s e r r i v e r . Often, rocks are present on the sandy bottom, and a change from a sandy, sandy-rocky, to a rocky bottom occurs almost i m p e r c e p t i b l y . The author has attempted c l a s s i f i c a t i o n a f t e r d e t e r m i n i n g which element, whether rock or sand, was p r e -dominant, and has e s t a b l i s h e d o b s e r v a t i o n a l areas to c o i n c i d e approximately w i t h these bottom t y p e s . Bay and e s t u a r i n e ; The s h o r e l i n e i n t h i s h a b i t a t i s almost completely p r o t e c t e d from s u r f , and the water s a l i n i t y , because of the i n f l u e n c e o f r i v e r s and streams, i s lower than i n other r e g i o n s . In the Greater Vancouver a r e a , o n l y one such h a b i -t a t e x i s t s , and, o c c u r r i n g at the mouth of the North arm of the F r a s e r r i v e r , Includes the waters from the H. R». McMillan.;, boom-i n g ground n o r t h to West P o i n t Grey and west t o the Iona I s l a n d j e t t y . The shore Is p r o t e c t e d from heavy wave a c t i o n by the j e t t y , and the many l o g booms which are p r e s e n t . The combined e f f e c t o f these two f a c t o r s r e s u l t s i n quiescent waters. ^ n e m a j o r i t y of bottom c o n s i s t s of sand and mud, alth o u g h some rocks are pr e s e n t , e s p e c i a l l y a t the northern end i n the v i c i n i t y of West P o i n t Grey. At low t i d e , v a s t expanses of shore are exposed l i m i t i n g the d i v i n g ducks to the narrow dredged channel j u s t east o f the J e t t y . C Lake: The onl y lake i n t e n s i v e l y s t u d i e d was St. Mary l a k e , S a l t S p r i n g i s l a n d . Small a l d e r (Alnus s p . ) , w i l l o w s ( S a l i x s p . ) , and western s p i r a e a ( S p i r a e a d o u g l a s s l Hook), are 9 present a l o n g the s h o r e l i n e , and sedges (Carex sp.) and water l o b e l i a ( L o b e l i a dortaaanna L,) grow i n the water near the shore. Low-lying wooded h i l l s on a l l s i d e s serve to p r o t e c t the lake from strong winds. The s h o r e l i n e i n the Greater Vancouver a r e a can be c l a s s i f i e d i n t o four h a b i t a t s , v i z ; I. Unprotected coast-sand bottom, I I . Unprotected coast-rock bottom, I I I . P r o t e c t e d c o a s t - r o c k bottom, IV. Bay and estuarine-mud-sand bottom. The f i r s t two h a b i t a t s are r e p r e s e n t e d by three i n d i v i -d u a l and separate u n i t s of shore ( F i g u r e s 1-5). H a b i t a t s three and f o u r are represented by one u n i t of s h o r e l i n e each ( F i g u r e s 6-7) and the lake h a b i t a t , i s t y p i f i e d by St. Mary l a k e , S a l t S p r i n g i s l a n d . The separate u n i t s of s h o r e l i n e r e p r e s e n t i n g the unpro-tected-sandy and unprotected-rocky h a b i t a t s are q u i t e d i s t a n t from one another, and i t was not p o s s i b l e to cover a l l these u n i t s on the same day. For t h i s reason each of the three u n i t s of shore w i t h i n these two h a b i t a t s was e s t a b l i s h e d as an obser-v a t i o n a l a r e a . The o b s e r v a t i o n a l areas i n each type and t h e i r s i z e and l o c a t i o n Is as f o l l o w s : 10 Observational Habitat Size Area (Miles) 1 I 3.5 3 6 7 g 9 I II II l l III IV V 3.9 .4 1.2 .7 1.8 2.6 3.5 1.6 Location West of Jetty, North arm of Fraser r i v e r , West Point Grey to the Royal Vancouver Yacht Club, K i t s i l a n o beach, Royal Vancouver Yacht Club to K i t s i l a n o beach, English Bay beach, Second beach to Siwash rock, Prospect point to Coal harbour, North arm of Fraser r i v e r , St. Mary lake. Photographic Surveys Ltd. Figure 1. A e r i a l photograph of Vancouver and adjacent waters. Note the sandy shore at the Iona Island Jetty (lower right corner) and West Point Grey (lower l e f t ) . 11 F i g u r e 2. Low t i d e at O b s e r v a t i o n a l Area 3* K i t s i l a n o beach. Unprotected-sandy h a b i t a t . Figure 3» Low t i d e at O b s e r v a t i o n a l Area 4, J e r i c h o beach. Unprotected-rocky h a b i t a t . 12 F i g u r e Low t i d e at O b s e r v a t i o n a l Area 5, E n g l i s h Bay beach. Unprotected-rocky h a b i t a t . F i g u r e 5« Low t i d e at O b s e r v a t i o n a l Area 6, Second beach. Unprotected-rocky h a b i t a t . 13 F i g u r e 6. Low t i d e at O b s e r v a t i o n a l Area 1, Prospect p o i n t . P r o t e c t e d - r o c k y h a b i t a t . F i g u r e 7» Low t i d e a t O b s e r v a t i o n a l Area S, North arm of F r a s e r r i v e r . Bay and e s t u a r i n e h a b i t a t . Ik PROCEDURE In the m a j o r i t y o f cases, a l l counts were made w i t h b i n o c u l a r s and a twenty-power t e l e s c o p e . Observers i n the f i e l d were s u p p l i e d w i t h p o c k e t - s i z e d census books i n which p e r t i n e n t data such as s p e c i e s , numbers p r e s e n t , sex and age of the d i v i n g ducks were r e c o r d e d . P l a c e , time, weather, wind v e l o c i t y , c o n d i t i o n of water and d i s t a n c e from shore were a l s o noted, and i n each case an attempt was made to determine the a c t i v i t y of a l l b i r d s observed. Those d i v i n g c o n t i n u o u s l y were recorded as f e e d i n g , whether or not food m a t e r i a l c o u l d a c t u a l l y be seen i n the b i l l * ' Those ducks s i t t i n g on the water, showing l i t t l e o r no movement were r e c o r d e d as r e s t i n g or, l o a f i n g . Other a c t i v i t i e s noted were f l y i n g , d i s p l a y i n g and c o u r t i n g , and attempts a t c o i t u s . Observations were made by walking a l o n g the beaches, d r i v i n g a l o n g roads i n c l o s e p r o x i m i t y to the shore, and t r a -v e l l i n g by open boat and motor l a u n c h . When o b s e r v i n g by boat, every attempt was made to a v o i d d i s t u r b i n g the ducks i n order to i n s u r e a g a i n s t c ounting the same ducks r e p e a t e d l y . To determine how the numbers and s p e c i e s of ducks changed or v a r i e d , a r b i t r a r y time p e r i o d s were e s t a b l i s h e d . Each month contained two time p e r i o d s , v i z . from the f i r s t day of the month to the f i f t e e n t h , i n c l u s i v e , and from the 15 s i x t e e n t h day to the l a s t day of the month, i n c l u s i v e * I t i s seen t h a t u n l e s s a month has e x a c t l y t h i r t y days, the time p e r i o d s w i l l vary s l i g h t l y i n l e n g t h . However, i t i s f e l t t h a t t h i s i n t r o d u c e s no b i a s to the o b s e r v a t i o n s because a l l time p e r i o d s c o n s i s t o f f o u r t e e n to s i x t e e n days. Only the r e c o r d s f o r those h a b i t a t s on which o b s e r v a t i o n s have been made r e p e a t -e d l y throughout the winter are used to draw comparisons r e g a r d -i n g h a b i t a t p r e f e r e n c e and r e l a t i v e abundance, although counts made on a l l s h o r e l i n e covered are used to determine o v e r a l l d i s t r i b u t i o n and sex and age s t r u c t u r e of the v a r i o u s s p e c i e s . An attempt was made to o b t a i n d a t a a t l e a s t onceevery two weeks on o b s e r v a t i o n a l areas one to nine , and whenever p o s s i b l e , a t l e a s t f o u r o b s e r v a t i o n a l areas were covered on the same day., 16 FACTORS INFLUENCING- SEASONAL DISTRIBUTION AND MOVEMENT CLIMATE The w i n t e r c l i m a t e i n the S t r a i t of Georgia, a l r e a d y mentioned, can be d e s c r i b e d as m i l d with h i g h . p r e c i p i t a t i o n . Temperatures normally f a l l below f r e e z i n g d u r i n g December and January, and many of the small shallow l a k e s on Vancouver i s l a n d , and the mainland f r e e z e over. Ice may form on s m a l l areas of calm s a l t water, but t h i s temporary c o n d i t i o n i n no way pre v e n t s the ducks from f e e d i n g , nor does i t act to d e l i m i t t h e i r a v a i l a b l e f e e d i n g area. During l a t e December, 1951, and e a r l y January, 1952, Somenos and Quamichan la k e s were completely f r o z e n and suppor-ted no d i v i n g ducks. S t . Mary l a k e was p a r t i a l l y f r o z e n , but t h i s c o n d i t i o n d i d not a f f e c t the f e e d i n g a c t i v i t y o f the smal l p o p u l a t i o n o f ducks w i n t e r i n g t h e r e . K o r t r i g h t (1943), demonstrated that the g r e a t e r scaup duck, American golden-eye. Barrow's golden-eye, b u f f l e - h e a d , h a r l e q u i n , old-squaw ( C l a n g u l a h y e m a l l s ) , and the three s p e c i e s of s c o t e r s , commonly w i n t e r n o r t h of the study a r e a . T h i s would i n d i c a t e t h a t the temperature extremes i n the S t r a i t o f Georgia 17 are w i t h i n the l i m i t s of t o l e r a n c e o f these ducks. Although no d e f i n i t e data are a v a i l a b l e , i t would seem t h a t low temperatures may l i m i t the northern w i n t e r d i s t r i b u t i o n o f the redhead, r i n g -necked duck, canvas-back and l e s s e r scaup duck. LAND AND SHORE TOPOGRAPHY I t i s c o n c e i v a b l e that o n l y a s m a l l number of d i v i n g ducks would win t e r on southern B r i t i s h Columbian waters i f the c o a s t l i n e was r e g u l a r and not p r o t e c t e d from heavy s u r f by the o u t l y i n g i s l a n d s . However, the s h o r e l i n e i s very i r r e g u l a r and c h a r a c t e r i z e d by numerous bays, sounds and i n l e t s , and the Jux-t a p o s i t i o n o f the many smal l e r i s l a n d s and Vancouver i s l a n d w i t h the mainland r e s u l t s i n a h i g h degree of wind and wave p r o t e c t -i o n . Large waves s i m i l a r to those o c c u r r i n g on the west coast of Vancouver i s l a n d are not experienced i n the s t r a i t . F i e l d o b s e r v a t i o n s i n d i c a t e that enough s h o r e l i n e i s . a v a i l a b l e to o f f e r sanctuary to a l l ducks d u r i n g storms. FOOD AVAILABILITY ANE PREFERENCE I n v e r t e b r a t e s I t was not p o s s i b l e to o b t a i n q u a n t i t a t i v e and q u a l i -t a t i v e d a t a on the d i s t r i b u t i o n o f i n v e r t e b r a t e s i n the study a r e a . However, a r i c h supply o f many s p e c i e s of I n v e r t e b r a t e s occurs i n the i n t e r - t l d a l zone. R i c k e t t s and C a l v i n (1939), IS have shown how i n v e r t e b r a t e s are d i s t r i b u t e d i n the t i d a l zones on the P a c i f i c c oast, and P a r i z e a u (194-1), working on the east coast of Vancouver i s l a n d , found the g r e a t e s t wealth and v a r i e t y of i n v e r t e b r a t e fauna o c c u r r e d i n the lower h a l f of the t i d a l zone. I n v e r t e b r a t e s are I n f l u e n c e d by the type of shore and exposure, w i t h the r e s u l t that an uneven d i s t r i b u t i o n o ccurs over a l a r g e and v a r i e d c o a s t l i n e , Cottara (1939), has shown that d i v i n g ducks eat a v a r i e t y of i n v e r t e b r a t e s and p l a n t food, but u s u a l l y there Is one food that i s taken i n g r e a t e r q u a n t i t i e s than o t h e r s . The ducks probably have a p r e f e r e n c e f o r a c e r t a i n food and w i l l gorge themselves with t h i s food when I t i s a v a i l a b l e . When non-a v a i l a b l e , other more a v a i l a b l e foods are eaten In g r e a t e r q u a n t i t i e s . The food study made by Cottam (1939) has shown t h a t 44.07$ of the food eaten by 819 white^wlnged s c o t e r s c o n s i s t e d of clams, o y s t e r s and pectens, and 11.98$ blue mussels ( M y t l l u s  e d u l l s ) . For l68 s u r f s c o t e r s , 13.04-$ of the food was clams and 28.74-$ was blue mussels. T h i s would i n d i c a t e t h a t w h i t e -winged s c o t e r s showed a p r e f e r e n c e f o r clams, o y s t e r s and pec-tens, whereas the s u r f s c o t e r s p r e f e r r e d blue mussels. The former I n v e r t e b r a t e s are most commonly found pn sandy bottom, while the mussels are most abundant on rocky bottom. I f I t Is true t h a t these two s p e c i e s of d i v i n g ducks do show p r e f e r e n c e f o r c e r t a i n foods, i t should be expected they would be most common In areas where these foods were a v a i l -a b l e . In order to test- t h i s , the numbers of white-winged 19 s c o t e r s and s u r f s c o t e r s were compared on two areas which showed d i f f e r e n c e s In type of bottom, and presumably c o n t a i n e d d i f f e r e n t q u a n t i t y and v a r i e t y of i n v e r t e b r a t e s . One of these areas extends from Qualicum r i v e r to Courtenay, Vancouver i s l a n d . There are s e v e r a l commercial o y s t e r beds In t h i s area, and probably o y s t e r s and clams are g e n e r a l l y abundant. The second a r e a extends from Gibsons, Howe sound, n o r t h to McNab creek and south along the west s i d e of A n v i l , Gambler and Keats i s l a n d s . Most of the s h o r e l i n e i s rocky and abrupt ( F i g u r e g) and blue mussels are very abundant. F i g u r e g. South end of A n v i l i s l a n d , Howe sound, showing abrupt and rocky shore t y p i c a l of t h i s r e g i o n . In two o b s e r v a t i o n s , 1 5 . 4 white-winged s c o t e r s per mile and 4.4- s u r f s c o t e r s per mile were seen from Qualicum r i v e r to Courtenay. The two obs e r v a t i o n s i n Howe sound showed that 0 . 6 l white-winged s c o t e r s per mile and 1 9 * 7 5 s u r f s c o t e r s per mile were f e e d i n g here. These o b s e r v a t i o n s i n d i c a t e that 20 i n v e r t e b r a t e d i s t r i b u t i o n and waterfowl p r e f e r e n c e f o r these food organisms i s a f a c t o r a f f e c t i n g the d i s t r i b u t i o n of w i n t e r -i n g d i v i n g ducks. A v a i l a b i l i t y of food, d i s c u s s e d i n the f o l l o w i n g sec-t i o n s , a l s o a f f e c t s d i s t r i b u t i o n . M o f f l t t (1938), found that canvas-backs i h the Suisun area, C a l i f o r n i a , f e d i n the marshes d u r i n g the f a l l , and when the food supply became exhausted, moved to the open bays to consume animal food. A small sample of g i z z a r d s , obtained d u r i n g the winter, was examined and the percentage volume of food eaten by the nine s p e c i e s of d i v i n g ducks considered, i s p r e s e n t e d i n Table I . No c o n c l u s i o n s can be drawn from such an Inadequate sample, but the r e s u l t s i n d i c a t e that the canvas-back i s predominantly a p l a n t f e e d e r . Undoubtedly, the presence of p l a n t food a f f e c t s the d i s -t r i b u t i o n of these ducks. They were most common i n bay and e s t u a r i n e h a b i t a t where an abundant supply o f p l a n t food i s found. The g r e a t e r scaup duck, American golden-eye, b u f f l e -head, old-squaw, h a r l e q u i n duck, white-winged s c o t e r , s u r f sco-t e r and American s c o t e r are predominantly animal f e e d e r s . A l l areas on which these ducks were seen f e e d i n g have an abundant supply of t h i s p r e f e r r e d animal food. The r e s u l t s a l s o I n d i c a t e that s u r f s c o t e r s show a p r e f e r e n c e f o r blue mussels, and that clams and crustaceans, are p r e f e r r e d by white-winged s c p t e r s . T h i s i s s u b s t a n t i a t e d by Cottam (1939) i n h i s d i v i n g duck food study. The presence of more white-winged s c o t e r s on the east Table I." Food, by volume percentages, taken by nine s p e c i e s o f d i v i n g ducks d u r i n g p e r i o d September 1951 to March 1952. Canvas- Greater Ameri- B u f f l e - O ld Har- White- Surf Ameri-back scaup can head Squaw l e - winged Scoter can duck golden- quln s c o t e r Scoter eye duck ' Number of g i z z a r d s examined 6 3 1. 4 2 2 5 & 1 P l a n t food Pondweeds Potomogeton p e c t l n -atus 2.7S Potomogeton sp. 100.00 15.97 T Sedges "Cyperaceae" T .69 T Sc i r p u s sp. T 10.00 Carex sp. T T T Smartweeds Polygonum sp. ' T T T Crowfoot Ranunculus sp. T Dock Rumex sp. T iRose Rosa sp. . T Algae T T Table I . Cont'd. Food, by volume percentages, taken by nine s p e c i e s o f d i v i n g ducks d u r i n g p e r i o d September 1951 "to March 1952. Canvas- Greater Ameri- B u f f l e -back scaup can head duck golden-eye O l d - Har- White- Surf American squaw l e - winged s c o t e r s c o t e r quin s c o t e r duck Animal food M o l l u s c a Blue mussel, M y t l l u s e d u l l s Clam, Protothaca, stamlnea Clam, Protothaca.sp. Clam, undetermined Pecten, Pecten hinds11 S n a i l , C a l l l s t o m a costatum S n a i l , C a l l j s t o m a sp. S n a i l , T hais sp. S n a i l , L i t t o r i n a sp. S n a i l , C e r t h l o p s l s sp. S n a i l , Odostomia sp.(?) S n a i l , undetermined Arthropoda Crustacea Crab, Hemlgrapsus nudus 3.-47 50.00 50.00 T 30.00 77.09 IOO.OO 4 0 . 0 0 1.42 15.74 30.73 35.52 17.22 2.22 3.07 3.52 2,59 77.75 32*90 5.56 .65 55.54 Table I . Cont'd,, Food, by volume percentages, taken by nine s p e c i e s of d i v i n g ducks d u r i n g p e r i o d September 1951 t'o March 1952. Canvas- Greater Amerl- B u f f l e -back scaup can head duck • golden-eye O l d - Har-squaw l e -quin duck White- Surf Ameri-winged s c o t e r can s c o t e r s c o t e r Animal Food Arthropoda Crustacea Crab, Hemlgrapsus sp. Hermit Crab, - Pagurus. sp. Crab, Oregonia g r a c i l i s Amphipoda In s e c t a , Aphrosylus sp.(?) D i p t e r a C o e l e n t e r a t a Hydrozoa, A b l e t -e n a r i a sp.(?) Chordata P i s c e s , Clupea p a l l a s i 2 0 . 0 0 T T 6 6 o 2 0 7.03 3«>52 21.60 Undetermined 11,10 Lead shot 2k coast o f Vancouver i s l a n d than i n Howe sound, and the rev e r s e s i t u a t i o n w i t h s u r f s c o t e r s , may he, as a l r e a d y mentioned, due to t h i s p r e f e r e n c e . D i v i n g ducks were u s u a l l y observed f e e d i n g i n water depths o f from s i x to e i g h t fathoms. Depth d a t a were obtained by e s t i m a t i n g the d i s t a n c e from shore a t which the ducks were f e e d i n g , and then c a l c u l a t i n g depth by means of Hydrographic maps. Schorger (194-7), r e p o r t s t h a t old-squaws have been taken i n g i l l nets a t from 12 to 27 fathoms, but a l l b i r d s seen d u r i n g the study were e i t h e r f e e d i n g i n waters not deeper than s i x to eight fathoms, or r e s t i n g on deeper water i n c l o s e p r o x i m i t y to la n d . The l i t e r a t u r e and f i e l d o b s e r v a t i o n s i n d i c a t e t h a t a r i c h i n v e r t e b r a t e fauna i s present on the i n t e r - t i d a l shores w i t h i n the study a r e a . Salmon Spawn Salmon ova, which become a v a i l a b l e i n the c o a s t a l streams i n October, appear to have a d e f i n i t e b e a r i n g on the winter d i s t r i b u t i o n of some s p e c i e s of d i v i n g ducks. Although the author was unable to f i n d evidence of t h i s i n the wi n t e r o f 1951-52, Munro (1923) found t h a t Barrow 1s golden-eyes were f e e d -i n g e x t e n s i v e l y on the spawn of sockeye salmon (Oncorhynchus  nerka). T h i s f o o d formed the p r i n c i p a l food d u r i n g November and December. Evidence has a l s o been o b t a i n e d by Munro (1939) that 25 salmon eggs form the main food f o r the American golden-eye d u r i n g December and January. A s i m i l a r s i t u a t i o n has been r e -p o r t e d by Wright (1944), who has observed American golden-eyes e a t i n g sockeye spawn i n October, November, and December on F l a t h e a d l a k e , Montana. Greater scaup ducks have been recorded by Munro ( l 9 4 l ) f e e d i n g on salmon ova and the r o t t e d f l e s h o f dead salmon a t t h i s season. Mr. A. A. Sherman, ( p e r s o n a l communication) r e -p o r t s v e r y few golden-eyes and mergansers on the Cowlchan r i v e r over the win t e r p e r i o d 1951-52, and, as s t a t e d e a r l i e r , no e v i -dence of d i v i n g ducks u t i l i z i n g salmon ova has been o b t a i n e d d u r i n g the present study. The l i t e r a t u r e i n d i c a t e s t h a t some s p e c i e s , namely the golden-eyes and g r e a t e r scaup ducks, do feed on salmon ova and consequently t h e i r d i s t r i b u t i o n i s i n f l u e n c e d by the presence of t h i s food. H e r r i n g Spawn, The ova of the P a c i f i c h e r r i n g (Clupea p a l l a s l l ) , form the seasonal food f o r many s p e c i e s o f d i v i n g ducks w i n t e r i n g i n the S t r a i t of Georgia, as shown by Munro and Clemens (1931) i n t h e i r study of t h e . r e l a t i o n of waterfowl to h e r r i n g spawn i n B r i t i s h Columbia. These authors found that the American g o l d e n -eyes, old-squaws, h a r l e q u i n ducks, white-winged s c o t e r s , s u r f s c o t e r s and American s c o t e r s were u t i l i z i n g h e r r i n g spawn as food, and as a r e s u l t , moving to areas of spawn abundance to 26 feed. In two separate s t u d i e s , Munro (1939, 1941) found that h e r r i n g ova were consumed by Barrow 1s golden-eyes and perhaps formed the most important seasonal food of the g r e a t e r scaup duck. One s u r f s c o t e r shot and examined by the author at Ganges harbour, S a l t S p r i n g i s l a n d on March 26, 1952, had f e d e n t i r e l y on h e r r i n g ova. The stomach and g i z z a r d c o n t a i n e d 19 o c of t h i s f o o d. Observations show t h a t i n March, when h e r r i n g spawning i s at i t s peak, l a r g e numbers of d i v i n g ducks concentrate over areas o f spawn abundance. T h i s i n f l u x and c o n c e n t r a t i o n of ducks was seen i n two l o c a l i t i e s d u r i n g the study. Mr. D. J . Robinson ( l e t t e r ) on March 22, 1952, observed and estimated 2,800 to 3,400 g r e a t e r scaup ducks and a s m a l l e r number of golden-eyes, white-winged s c o t e r s and s u r f s c o t e r s at Nanoose bay, Vancouver i s l a n d . The t o t a l number of d i v i n g ducks was estimated to be between 4,000 and 5>000. In t h i s same area, from November, 1951 to e a r l y March, 1952, o n l y 225 d i v i n g ducks per o b s e r v a t i o n were seen. A p a r a l l e l s i t u a t i o n was observed a t t h i s bs"yby Munro (1941) on March 12, 1934. On t h i s date a r a f t of s e v e r a l thou-sand g r e a t e r scaup ducks and s m a l l e r f l o c k s of white-winged s c o t e r s and s u r f s c o t e r s were f e e d i n g on h e r r i n g ova.. Again, on March 26, 1936, Munro (I94l) estimated 3,000 g r e a t e r scaup ducks t o g e t h e r w i t h a s m a l l e r number of white-winged s c o t e r s and American s c o t e r s f e e d i n g i n t h i s bay. A d d i t i o n a l evidence showing t h a t h e r r i n g spawn 27 I n f l u e n c e s waterfowl d i s t r i b u t i o n i s presented by Mr. K. Racey ( p e r s o n a l communication), who r e c o r d e d the numbers of d i v i n g ducks seen between F o r t Rupert and P o r t Hardy, Vancouver i s l a n d , from October, 1950, to May, 1951. Throughout the f a l l and win-t e r American golden-eyes, Barrow's golden-eyes, whlte-wlnged s c o t e r s , s u r f s c o t e r s and American s c o t e r s were p r e s e n t , but not common i n t h i s a r e a . During l a t e March and A p r i l , when h e r r i n g spawn was a v a i l a b l e , l a r g e c o n c e n t r a t i o n s of golden-eyes and s c o t e r s , as w e l l as a few g r e a t e r scaup ducks were seen f e e d i n g on h e r r i n g ova i n Hardy bay. L a t e r i n May when no ova were a v a i l a b l e , o n l y a few d i v i n g ducks were p r e s e n t and f e e d i n g In the a r e a . Although t h i s f l o c k i n g h a b i t may be c h a r a c t e r i s t i c of these ducks p r i o r to s p r i n g m i g r a t i o n , i t i s b e l i e v e d t h a t the presence o f h e r r i n g spawn i s an important f a c t o r i n f l u e n c i n g waterfowl d i s t r i b u t i o n and movement. Gra i n Elevators^ D i v i n g ducks are a l s o i n f l u e n c e d by the presence of g r a i n p o o l e l e v a t o r s i n Vancouver harbour. T h i s i n f l u e n c e i s r e l a t e d to the f a c t o r of food a v a i l a b i l i t y and appears to a f f e c t g r e a t e r scaup ducks, American golden-eyes and Barrow's golden-eyes more than the other s p e c i e s of d i v i n g ducks. At the No, 1 P o o l E l e v a t o r on November 23, 1951, a l a r g e r a f t of approximately 150 g r e a t e r scaup ducks and 150 2g American golden-eyes and Barrow 1s golden-eyes were seen a c t i v e l y d i v i n g , and, presumably f e e d i n g . H. D. M u l l i g a n ( p e r s o n a l com-munication), observed these s p e c i e s i n s m a l l e r numbers on December 13, 1951, f e e d i n g on g r a i n c h a f f . Cottam (1939), s t a t e s t h a t g r a i n s o f v a r i o u s kinds are taken by American golden-eyes at b a i t s t a t i o n s where these foods are consumed i n p r e f e r e n c e to most n a t u r a l foods because of a v a i l a b i l i t y . f h e r e are oi l l y a few p o o l e l e v a t o r s i n Vancouver har-bour and probably only a few ducks are i n f l u e n c e d by t h i s source of food. However, the a v a i l a b l e g r a i n c h a f f does a f f e c t d i s -t r i b u t i o n o f a smal l percentage o f g r e a t e r scaup ducks and golden-eyes. Sewer O u t f a l l s S e v e r a l other f a c t o r s were found to i n f l u e n c e seasonal d i s t r i b u t i o n and movement of d i v i n g ducks. In the Gr e a t e r Vancouver area, many sewer o u t f a l l s are l o c a t e d i n E n g l i s h bay, F a l s e creek, Vancouver harbour and Burrard i n l e t . During the study g r e a t e r scaup ducks, American golden-eyes and s u r f s c o t e r s , i n a s s o c i a t i o n w i t h g u l l s , were seen many times i n compact r a f t s scavenging over the Brockton p o i n t and J e r i c h o beach sewer o u t f a l l s . Cottam (1939), has observed l e s s e r scaup ducks f e e d i n g i n s i m i l a r s i t u a t i o n s on the e a s t e r n seaboard, and h i s stomach 29 analyses f u r t h e r i n d i c a t e that these b i r d s were consuming sewage m a t e r i a l * He a l s o c i t e s the case (p.4-0) of l e s s e r scaup ducks c o n c e n t r a t i n g over the sewer o u t f a l l s i n Santa Barbara, C a l i f o r n i a , i n order to feed on sewage. Four l a r g e r a f t s of g r e a t e r scaup ducks of 700, 375, 350, and 200 b i r d s , approximately, and many s m a l l e r r a f t s , were seen between Vancouver harbour and the Second Narrows b r i d g e , Burrard i n l e t on February 24, 1952, E i g h t sewer o u t f a l l s are l o c a t e d i n t h i s area, and the ducks, r a f t e d and d i v i n g over these p o s i t i o n s , were presumably f e e d i n g on the sewer f l o t s a m . On December 9, 1951, approximately 500 g r e a t e r scaup ducks were seen f e e d i n g over the s e v e r a l sewer o u t f a l l s east of the Second Narrows b r i d g e , and presumably, were f e e d i n g on sewage at that time. Mr. A. Dzubin ( p e r s o n a l communication) r e p o r t s a s i m i l a r s i t u a t i o n was observed on January 5, 1952, a t which time an unestimated number of g r e a t e r scaup ducks were seen between Second Narrows bridge and Vancouver harbour. A comparable s i t u a t i o n was observed at C l o v e r p o i n t , V i c t o r i a , on March 15, 1952. In t h i s l o c a l i t y approximately 250 g r e a t e r scaup ducks, 35 s u r f s c o t e r s and a few American golden-eyes were a c t i v e l y f e e d i n g over the sewer o u t f a l l i n t h i s area. C. J . Suiguet ( p e r s o n a l communication) has seen l a r g e r a f t s of d i v i n g ducks i n t h i s a r e a at numerous times d u r i n g the winter. R. Webb ( l e t t e r ) observed approximately 300 g r e a t e r scaup ducks, and a s m a l l e r number of s u r f s c o t e r s and g u l l s f e e d i n g around C l o v e r p o i n t on February 7, 1952, 30 The f o r e g o i n g o b s e r v a t i o n s would seem to i n d i c a t e that g r e a t e r scaup ducks, and to a l e s s e r degree, s u r f s c o t e r s and American golden-eyes, commonly f e e d on sewage>. . and consequent-l y , spend much of t h e i r time i n the v i c i n i t y of sewer o u t f a l l s 0 The d i s t r i b u t i o n of sewers i n the Vancouver and V i c t o r i a areas probably d i r e c t l y i n f l u e n c e s ithe d i s t r i b u t i o n of these s p e c i e s . In c o n s i d e r i n g a l l the f o r e g o i n g f a c t o r s which i n f l u e n c e seasonal d i s t r i b u t i o n and movement, i t can be concluded t h a t food a v a i l a b i l i t y and p r e f e r e n c e appear to be the two c h i e f f a c t o r s governing t h i s d i s t r i b u t i o n and movement. C o t t l e (194-9), drew s i m i l a r c o n c l u s i o n s In his. study of the f e e d i n g behaviour of d a b b l i n g ducks i n the lower F r a s e r v a l l e y , and Cottam (1939), s t a t e s t hat food a v a i l a b i l i t y and p r e f e r e n c e are the two prime f a c t o r s r e s p o n s i b l e f o r d i v i n g duck d i s t r i b u t i o n . 31 FACTORS. INFLUENCING DAILY DISTRIBUTION AND MOVEMENT As mentioned e a r l i e r , an attempt was made to determine the a c t i v i t y of a l l ducks seen d u r i n g the s t u d y , and, when pos-s i b l e , to draw c o n c l u s i o n s r e g a r d i n g the reasons f o r t h i s mani-f e s t a t i o n o f movemento The f o l l o w i n g f a c t o r s , most of which are r e l a t e d to food a v a i l a b i l i t y , are c o n s i d e r e d r e s p o n s i b l e f o r d a i l y movement and d i s t r i b u t i o n . WEATHER Severe weather and very rough water, sometimes exper-ienced i n the S t r a i t o f Georgia, appears i n some i n s t a n c e s to > f o r c e numbers of ducks from the exposed f e e d i n g grounds to c a l -mer waters. T h i s was I n d i c a t e d by two separate counts made from Cowlchan bay, Vancouver i s l a n d , to Ganges harbour, S a l t S p r i n g I s l a n d , immediately before and a f t e r a storm on January 13, 1952. The, t o t a l d i v i n g duck count on January 12, when the water was very calm and there was no a p p r e c i a b l e wind, exceeded 900 ducks. On January l 4 , f o l l o w i n g a severe storm, the same, area was covered. In t h i s second count, only 535 d i v i n g ducks were seen. Quite probably some ducks were overlooked because of the rough c o n d i t i o n of the water. N e v e r t h e l e s s , I t i s 32 b e l i e v e d that fewer ducks were a c t u a l l y p r e s e n t at t h i s time. No d e f i n i t e c o n c l u s i o n s c o u l d be drawn r e g a r d i n g where the ducks had gone, but presumably they had l e f t the area f o r q u i e t e r waters. I t has been observed, t h a t l a r g e numbers of d i v i n g ducks f e e d and r e s t i n Hammond bay, Vancouver i s l a n d . T h i s bay i s p r o t e c t e d d u r i n g most stormy weather, and on February 9» 1952, when water c o n d i t i o n s on the east c o a s t o f Vancouver i s l a n d were very rough, 655 ducks were seen here. On January 17, 1952, when water c o n d i t i o n s were g e n e r a l l y calm, o n l y 4-2 d i v i n g ducks were observed i n t h i s bay. Counts made on the same days at the more exposed Departure bay, a few m i l e s to the south, showed t h a t fewer b i r d s were u s i n g t h i s a r e a d u r i n g stormy weather, although the d i f f e r e n c e does not appear too s i g n i f i c a n t . Although i n some i n s t a n c e s waterfowl are d i s t u r b e d by rough water and seek more s h e l t e r e d waters, o b s e r v a t i o n s i n f e r that these c o n d i t i o n s do not always r e s u l t i n movement. Perhaps the degree of storminess i s the o p e r a t i v e f a c t o r d e t e r m i n i n g the response o f the waterfowl, f o r on December 21, 1951, a r a f t of approximately 200 s u r f s c o t e r s were observed f e e d i n g a t the entrance to Horseshoe bay, Howe sound. At t h i s time, a. moderately str o n g n o r t h e r l y wind was sending l a r g e breakers i n t o the bay. Another set of data are presented which a l s o show t h a t d i v i n g ducks are not a f f e c t e d by moderate wave a c t i o n . At J e r i c h o beach, on March 17, 1952, 4-37 d i v i n g ducks were seen f e e d i n g , a p p a r e n t l y u n a f f e c t e d by the d r i v i n g r a i n and rough 33 water. Two days l a t e r , when the waters were extremely calm 4-34 d i v i n g ducks were counted on the same a r e a . E v i d e n t l y the con-d i t i o n s of the former day d i d not a f f e c t the ducks or cause them to s h i f t to calmer waters. The above o b s e r v a t i o n s i n f e r that a l t h o u g h waterfowl are o r d i n a r i l y u n a f f e c t e d by stormy weather, there are Instances where severe storms cause movement to p r o t e c t e d bays. TIDES F l u c t u a t i n g t i d e s have, on s e v e r a l o c c a s i o n s , appeared to be a f a c t o r c a using duck movement and f l o c k i n g ^ l n the v i c i n i t y " of the Iona I s l a n d J e t t y . T h i s i s probably due to the t u r b u -lence caused by the r i v e r water, which i s at a h i g h e r l e v e l than the s a l t water a t t h i s time, p o u r i n g over the n o r t h end o f the J e t t y on the out-going t i d e . On November 3, 1951» a t 1 p.m., G-. W. Smith ( p e r s o n a l communication) observed an estimated 3>5°0 waterfowl, mostly d i v i n g ducks, f e e d i n g v i g o r o u s l y a t a d i s t a n c e of 500 yards west of the j e t t y . These ducks, forming a long dense r a f t p a r a l l e l to the shore, were f e e d i n g In what appeared to be a zone of d r i f t m a t e r i a l r e s u l t i n g from the r e c e d i n g t i d e and t u r b u l e n t waters. . Surf s c o t e r s formed the g r e a t e s t p a r t of t h i s r a f t , w hile white-winged s c o t e r s , American s c o t e r s , b u f f l e - h e a d s , g r e a t e r scaup ducks, and some pond ducks (baldpate (Mareca 34 americana)), were a l s o p r e s e n t . One week l a t e r , a t 2 p.m. on November 9, only 21 d i v i n g ducks were seen i n t h i s a r e a . At t h i s time the t i d e was h i g h and there was no evidence of t u r -bulence o r r u s h i n g water. I t i s p o s s i b l e t h a t many i n v e r t e -b r a t e s are d i s l o d g e d from the bottom when the F r a s e r r i v e r water i s p o u r i n g over the J e t t y and the ducks a t such times congregate here to u t i l i z e the a v a i l a b l e f o o d . G-riscom (1945), r e p o r t s t h a t American golden-eyes are a f f e c t e d by t i d e s i n Newburyport harbour, Massachusetts where, two hours a f t e r h i g h t i d e , these ducks move i n to feed a t the mouth of the sewer. DISPLAY AND COURTSHIP A great amount of sexual a c t i v i t y i s d i s p l a y e d by the d i v i n g ducks a f t e r the c o u r t s h i p has begun i n e a r l y s p r i n g . Munro (1939), and Munro and Clemens (1931), have d e s c r i b e d the d i s p l a y s o f the golden-eyes d u r i n g c o u r t s h i p i n February and March. American golden-eyes and Barrow's golden-eyes were seen i n c o u r t s h i p a c t i v i t y i n January i n the Vancouver area, and on February 22, 1952, a male American golden-eye was seen attempt-i n g c o i t u s w i t h a female of the same s p e c i e s which had been p r e -v i o u s l y swimming at h i s side w i t h body low i n the water and neck o u t s t r e t c h e d . S e v e r a l groups of three males and one female h a r l e q u i n duck were seen a c t i v e l y c o u r t i n g on February 10, 1952, a t B i g 35 Qualicum r i v e r , Vancouver i s l a n d * The males q u i c k l y flew a f t e r the female when she took f l i g h t , and f o l l o w e d her when she d i v e d i n t o the water. Old-squaws were seen c o u r t i n g i n the North Arm of the F r a s e r r i v e r i n l a t e February, No f l i g h t s were made by the two males and one female, but much d i v i n g a c t i v i t y was shown. In the same area on March 14-, 1952, three male b u f f l e - h e a d s were • d i s p l a y i n g before a hen, Munro (194-2) d e s c r i b e s the c o u r t s h i p behaviour of the b u f f l e - h e a d on the coast and s t a t e s that t h i s a c t i v i t y , r e a c h i n g i t s g r e a t e s t i n t e n s i t y on the i n t e r i o r breed-i n g ground i n A p r i l , i s i n i t i a t e d on the w i n t e r i n g grounds i n l a t e January and e a r l y February. Surf s c o t e r drakes were seen v i g o r o u s l y d i s p l a y i n g before a hen on March 15, 1952, at Oak bay, Vancouver i s l a n d . At t h i s time the males appeared v e r y h o s t i l e towards one another. Redheads, ring-necked ducks, canvas-backs, g r e a t e r scaup ducks, and white-winged s c o t e r s were not seen d i s p l a y i n g d u r i n g the study. However, ducks of these s p e c i e s were seen p a i r e d d u r i n g most of the winter. I f the p a i r i n g i n e a r l y s p r i n g was a t r u e sexual a s s o c i a t i o n , i t i s f e a s i b l e that c o u r t s h i p had taken p l a c e . The p a i r i n g seen i n October, November and December may have been the r e s u l t of chance a s s o c i a t i o n which had taken p l a c e i n the i n t e r i o r breeding a r e a s where p o s t - b r e e d i n g males o f t e n a s s o c i a t e w i t h moulting females. T h i s a s s o c i a t i o n has been r e p o r t e d by Munro (194-2), who s t a t e s t h a t moulting a d u l t and y e a r l i n g female b u f f l e - h e a d s are j o i n e d i n August and 36 September by f l y i n g young and a few a d u l t males and second year males i n a d u l t plumage. Munro (1939), has observed the a s s o -e l a t i o n of male and female American golden-eyes d u r i n g l a t e f a l l , and s t a t e s that at t h i s time the a d u l t males, accompanying females, young of the. year, and a few y e a r l i n g s , appear i n the i n t e r i o r of B r i t i s h Columbia. With the advancement of s p r i n g , c o u r t s h i p was seen to be p r e v a l e n t i n some species of d i v i n g ducks, and appeared to be an important f a c t o r c a u s i n g l o c a l movements and s h i f t s o f c o u r t i n g i n d i v i d u a l s . DIEL PERIODICITY A l l e e , et a l (1949), s t a t e that the m a j o r i t y of animals have a d i e l p e r i o d i c i t y i n t h e i r g e n e r a l behaviour, and mention that most animals show a w e l l d e f i n e d d i u r n a l p e r i o d of r e l a t i v e a c t i v i t y and n o c t u r n a l p e r i o d of r e l a t i v e I n a c t i v i t y . I t was not p o s s i b l e to study the n o c t u r n a l h a b i t s o f the d i v i n g ducks d u r i n g the study, or determine t h e i r a c t i v i t y at t h i s time, but o b s e r v a t i o n s a t P a s l e y i s l a n d on November 17 and 1$, 1951, showed that a great; amount of waterfowl movement occ u r r e d a t dawn and dusk. The J u x t a p o s i t i o n of P a s l e y I s l a n d , Popham i s l a n d , and Colby i s l a n d ( F i g u r e 9) forms an area of water which i s almost completely p r o t e c t e d from wind. F i g u r e 9. A e r i a l p h o t o g r a p h o f t h e P a s l e y i s l a n d g r o u p . The p r o t e c t e d i n t e r - i s l a n d a r e a o f f e r s s a n c -t u a r y t o d i v i n g d u c k s a t n i g h t . 38 A l a r g e c o n c e n t r a t i o n of s u r f s c o t e r s , Barrow's golden-eyes, b u f f l e h e a d s , and white-winged s c o t e r s was seen i n t h i s i n t e r - i s l a n d a r e a on the evening o f November 17. The f o l l o w i n g morning a t dawn t h i s c o n c e n t r a t i o n was a g a i n observed, and a t t h i s time, many groups of from f i v e to t h i r t y ducks were s t a r t -i n g to depart i n a s o u t h - e a s t e r l y d i r e c t i o n . A few b i r d s f l e w and swam to the nearby i s l a n d s and began f e e d i n g . At 8 a.m. t h i s l a r g e r a f t of ducks had completely d i s a p p e a r e d . L a t e r that day, a t about k p.m., groups of the same sp e c i e s of ducks began f l y i n g i n t o t h i s area i n s m a l l f l o c k s of from two to f i f t y . By 4;30 p.m. an estimated 800 ducks were again r e s t i n g approximately midway between these I s l a n d s . The water depth at t h i s p o s i t i o n v a r i e d from 13 to 25 fathoms. Although no d e f i n i t e c o n c l u s i o n s can be drawn from these o b s e r v a t i o n s , i t can be §peculated that these ducks were r e t u r n i n g to t h i s p r o t e c t e d a r e a to r e s t d u r i n g the n i g h t . No f e e d i n g a c t i v i t y was noted, and the deepness of the water would i n d i c a t e t h a t the s c o t e r s and golden-eyes c o u l d not feed here. Perhaps those b i r d s f l y i n g southeast from t h i s a r e a i n the e a r l y morning were d i s p e r s i n g to t h e i r f e e d i n g grounds In the Greater Vancouver a r e a . A r e t u r n v i s i t to these i s l a n d s on February 27, 1952, showed t h a t Barrow's- golden-eyes and s u r f s c o t e r s were, r e s t i n g there i n a s i m i l a r f a s h i o n . The f o l l o w i n g day, at 2 p.m. no. ducks were pr e s e n t . S i m i l a r d i e l p e r i o d i c i t y may e x i s t l o c a l l y i n a l l 39 s p e c i e s o f waterfowl, but remained undetected d u r i n g the study. DISTURBANCES Many agencies operate to d i s t u r b and move d i v i n g ducks o f f t h e i r f e e d i n g grounds. A l l Instances o f d i s t u r b a n c e noted were r e l a t e d to human presence i n the, v i c i n i t y . Commonly, they are f o r c e d to f l y or d i v e to a v o i d motor launches and f i s h boats. F r e q u e n t l y , when f e e d i n g c l o s e to the shore, the ducks take wing when approached by persons on the beach. I l l e g a l h u n t i n g was seen to cause r a p i d d i s p e r s i o n of ducks i n the North Arm of the F r a s e r r i v e r . At t h i s time, three gunners on the bow of a f i s h boat were seen s h o o t i n g i n d l s c r i -m i nantly i n t o f l o c k s of white-winged s c o t e r s and s u r f s c o t e r s , and ducks of these s p e c i e s were f l y i n g out o f the l o c a l i t y i n a l l . d i r e c t i o n s . Most d i s t u r b i n g agencies are harmless, however, and o n l y cause s m a l l movements i n the form o f short f l i g h t s or r a p i d d i v e s . FACTORS OF MORTALITY The agencies r e s p o n s i b l e f o r d i v i n g duck m o r t a l i t y on the w i n t e r i n g grounds were found to be hunting, and o i l i n g . These f a c t o r s vary i n t h e i r r e l a t i v e importance from year to year, and, d u r i n g the present study, an attempt was made to evaluate t h e i r combined e f f e c t s on the d i v i n g dtick p o p u l a t i o n . HUNTING Some s p e c i e s of d i v i n g ducks, such as the redhead., ring-necked duck, canvas-back, and scaups, are c o n s i d e r e d to be choice game b i r d s and are h e a v i l y hunted. The golden-eyes and sc o t e r s are b e l i e v e d to be u n p a l a t a b l e and " f i s h y " by many hun-t e r s and f o r t h i s reason are not shot. Table I I shows the num-ber and k i n d s of d i v i n g ducks k i l l e d by hunters d u r i n g the open seasons 1949 to 1951, a t the D e l t a M u n i c i p a l i t y and checked at the bag checking s t a t i o n s . Only 291 d i v i n g ducks of a l l s p e c i e s were k i l l e d d u r i n g three years of h u n t i n g . T h i s i s a s m a l l number compared to the 7,5^5 m a l l a r d s (Anas p_. pla t y r h y n c h u s ) shot i n t h i s same ar e a d u r i n g the same p e r i o d . A d d i t i o n a l ducks are k i l l e d by f i s h e r -men a f t e r the hunting season has c l o s e d , but i t i s b e l i e v e d 41 Table I I . D e l t a M u n i c i p a l i t y bag check of d i v i n g ducks shot by hunters d u r i n g open seasons, 1949 - 1951* Species Number shot 1949 1950 I95I T o t a l Redhead 1 1 2 Ring-necked duck 1 1 Canvas-back 25 14 9 48 "Scaup" 31 61 21 113 "Golden-eye" 7 11 1 19 B u f f l e - h e a d 31 49 16 96 Old-squaw 1 1 "Scoter" 6 5 11 T o t a l 94 143 54 291 that o n l y a small number of d i v i n g ducks are k i l l e d i n t h i s manner. The h a b i t of f l o c k i n g on open water prevents many hun-t e r s from sh o o t i n g d i v i n g ducks, and t h i s p robably i s an impor-tant reason f o r so few ducks being shot. I t i s c o n c l u s i v e t h a t hunting i s not an important f a c t o r causing d i v i n g duck m o r t a l -i t y . 42 OILING On February 17, and 24, 1952, the d e b r i s l i n e on the Boundary Bay beach was sampled and a l l dead b i r d s and the cause of death were re c o r d e d . The sample Included two m i l e s of beach. Table I I I shows the r e s u l t s of t h i s sampling. Table I I I . Number of dead b i r d s found on a two mile sample of beach at Boundary bay, February 7 and 24, 1952. Species Cause of M o r t a l i t y O i l e d Shot Unknown T o t a l "Scaup" 3 3 American golden-eye 1 1 B u f f l e - h e a d 3 3 6 Old-squaw 1 1 White-winged s c o t e r 3 4 1 8 Dabbling duck 1 9 10 Black b r a n t 3 3 " G u l l " 2 2 3 7 Common l o o n 1 1 Western grebe 1 1 2 Eared grebe 2 2 T o t a l 11 7 26 44 43 During the study only 11 b i r d s were found dead as a r e s u l t of o i l i n g . I t appears that o i l i n g has not been as s e r i o u s a f a c t o r of m o r t a l i t y as i n p r e v i o u s y e a r s . The e f f e c t of o i l p o l l u t i o n v a r i e s each year. In 1947* Mr. K. Racey ( p e r s o n a l communication) made o b s e r v a t i o n s on February 12, l 6 , and l g , at the s h o r e l i n e of West P o i n t Grey, Vancouver. The f o l l o w i n g s p e c i e s o f b i r d s were found dead as a r e s u l t o f o i l i n g : g r e a t e r scaup duck, huffier-head, old-squaw, s u r f s c o t e r , American s c o t e r , p i n t a i l ( D a f i l a a c u t a t z l t z l h o a ) , r e d - b r e a s t e d merganser (Mergus s e r r a t o r ) and horned grebe (Colymbus a u r l t u s ) . No a c t u a l count was made, but m o r t a l i t y was e s p e c i a l l y great among the American s c o t e r s and old-squaw ducks. L i n c o l n (1936), i n re v i e w i n g the e f f e c t of o i l p o l l u -t i o n on waterfowl, c i t e s examples of l a r g e numbers of ducks being k i l l e d i n d i r e c t l y by o i l a t many l o c a l i t i e s on the A t l a n t i c and P a c i f i c c o a s t s , and Racey (1930), .found 14 p l i e d dead b i r d s a t Crescent beach i n May, 1929, on a q u a r t e r mile sample of beach. He concludes t h a t much damage i s done t o l o c a l water b i r d s by o i l . Undoubtedly many b i r d s are k i l l e d each winter as a r e s u l t of o i l i n g , and t h i s i s pro b a b l y an important f a c t o r of m o r t a l i t y i n some years. O i l i n g d i d not appear to be as s e r i o u s i n the study area d u r i n g the w i n t e r of 1951-52, as i t has been i n o t h e r l o c a l i t i e s i n other y e a r s . The t o t a l number of deaths by t h i s cause could not be determined. 44 LEAD POISONING No evidence of l e a d p o i s o n i n g was found d u r i n g the study. The very nature of t h e i r f e e d i n g h a b i t s and p r e f e r e n c e f o r open water probably accounts f o r only s m a l l q u a n t i t i e s of l e a d shot being i n g e s t e d by d i v i n g ducks. The g i z z a r d of one canvas-back examined contained two l e a d p e l l e t s , and an American golden-eye and s u r f s c o t e r examined each had one p e l -l e t i n the g i z z a r d . The e f f e c t o f l e a d shot c o u l d not be d e t e r -mined, but probably i t i s an unimportant f a c t o r i n d i v i n g duck m o r t a l i t y , PREDATION On s e v e r a l occasions a b a l d eagle ( H a l l a e e t u s l e u c o c e -phalus) was seen making stoops at d i v i n g ducks at the Iona I s l a n d J e t t y . When approached by the eagle, the ducks would d i v e , and although the eagle made numerous attempts, i t was unable to c a t c h any ducks. In o t h e r s i t u a t i o n s some ducks are probably k i l l e d by ea g l e s , but t h i s i s probably an unimportant f a c t o r of m o r t a l i t y on the w i n t e r i n g grounds. 45 DISTRIBUTION OF THE SPECIES The data o b t a i n e d d u r i n g the winter on O b s e r v a t i o n a l Areas 1 to 9, were analysed i n order to determine i f d i f f e r e n t s p e c i e s of d i v i n g ducks showed p r e f e r e n c e f o r c e r t a i n h a b i t a t s . In F i g u r e 10 and 11 f o r each s p e c i e s , the percentage of the t o t a l number counted per o b s e r v a t i o n a l m i l e on each h a b i t a t over the wint e r p e r i o d i s shown. The cumulative t o t a l s of the average number counted by s p e c i e s on a l l h a b i t a t s ( O b s e r v a t i o n a l Areas 1 to 9) d u r i n g the study Is shown In F i g u r e 12. General d i s t r i b u t i o n over the e n t i r e study area, by s p e c i e s , i s d i s c u s s e d i n the f o l l o w i n g s e c t i o n s , and d i s t r i b u -t i o n and d e n s i t y (average number seen per o b s e r v a t i o n ) are shown In Fig u r e 19 and 20. . REDHEAD (Nyroca americana) Only a few ducks of t h i s s p e c i e s were w i n t e r i n g i n the study area, and a l l b i r d s , with one ex c e p t i o n , o c c u r r e d on lake h a b i t a t . One p a i r of redheads were counted a t E l k l a k e , V i c t o r i a , i n March 1952, but the g r e a t e s t number occu r r e d a t St. Mary l a k e , where i n January, 11 b i r d s were observed a t one time. One drake was seen f l y i n g over the Iona I s l a n d J e t t y i n November, 1951, hut t h i s was the onl y time t h i s s p e c i e s 46 REDHEAD RING-NECKED DUCK 100 ' U J <s U 50 u cc Ul a. 1 2 3 4 5 6 7 8 9 CANVAS-BACK 100-1 LU o < S 50H o ac U J a. — i — i — i — i — i — i — 1 2 3 4 5 6 7 8 9 AMERICAN GOLDEN-EYE 1001 ui CD < ui 50 H u OS U l a. 12 3 4 5 6 7 8 9 ' OBSERVATIONAL AREA 1001 50 — i i 1 1 1 1 1— I 2 3 4 5 6 7 8 9 GREATER SCAUP DUCK lOOn 504 J 2 3 4 5 6 7 8 9 BARROW'S GOLDEN-EYE 100 50H 1 2 3 4 5 6 7 8 9 OBSERVATIONAL AREA F i g u r e 10. Percentage number of d i v i n g ducks counted per o b s e r v a t i o n a l mile on i n d i v i d u a l h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952. 47 BUFFLE-HEAD l O O i UJ o < • h-i 5 0 H o 2 3 4 5 6 7 8 9 HARLEQUIN DUCK lOOn 5 6 7 8 9 SURF SCOTER 1001 < tr. Ul a. 50-\ 1 2 3 4 5 6 7 8 9 OBSERVATIONAL AREA OLD-SQUAW l O O l 5 0 H 1 2 3 4 6 7 8 9 WHITE-WINGED SCOTER I00i 5 0 H I 2 3 4 5 6 7 8 9 AMERICAN SCOTER 1 2 3 4 5 6 7 8 9 OBSERVATIONAL AREA F i g u r e 11. Percentage number of d i v i n g ducks counted per o b s e r v a t i o n a l mile on i n d i v i d u a l h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952. N U M B E R ro (7> a> <s> o — r\3 o O. o o o o o o o o o o o O o o o o o o o o o o J ... 1 , .. L _ . 1.. 1 L— 1 1 • 1 1 L m o m r REDHEAD RING-NECKED DUCK CANVAS-BACK GREATER SCAUP DUCK AMERICAN GOLDEN-EYE BARROW'S GOLDEN-EYE BUFFLE-HEAD OLD-SQUAW HARLEQUIN DUCK WHITE-WINGED SCOTER SURF SCOTER AMERICAN S C O T E R F i g u r e 12. T o t a l number of d i v i n g ducks counted, by s p e c i e s , on O b s e r v a t i o n a l Areas 1 - 9 d u r i n g p e r i o d September 1951 to March 1952. (Representing cumulative t o t a l s of average number counted per o b s e r v a t i o n d u r i n g t h i s p e r i o d . ) 49 o c c u r r e d on s a l t water h a b i t a t . Redheads were the l e a s t abundant d i v i n g duck on the study a r e a . I t showed a d e f i n i t e p r e f e r e n c e f o r lake h a b i t a t and was not observed f e e d i n g on s a l t water a r e a s . T h i s p r e -ference f o r lake h a b i t a t i s shown i n F i g u r e 10, where over 92$ o f the b i r d s observed per mile were on S t . Mary l a k e . RING-NECKED DUCK (Nyroca c o l l a r i s ) These b i r d s d i d not occur on s a l t water areas, and were seen o n l y on St. Mary l a k e . In December, 1951» "the l a r g e s t r a f t was observed and c o n s i s t e d of 22 males and 19 females. Very o f t e n , these ducks were f e e d i n g and r e s t i n g i n a s s o c i a t i o n with g r e a t e r scaup ducks. I t was not determined why these b i r d s d i d not occur at E l k l a k e , or other l a k e s i n the V i c t o r i a r e g i o n , where presum-a b l y , food a v a i l a b i l i t y i s s i m i l a r to t h a t found at St. Mary l a k e . CANVAS-BACK (Nyroca v a l l s l n e r l a ) Ducks of t h i s s p e c i e s were not g e n e r a l l y d i s t r i b u t e d over the study area, but appeared to p r e f e r S t . Mary lake and the bay and e s t u a r i n e h a b i t a t i n the North arm of the F r a s e r 50 r i v e r . The only other l o c a l i t i e s wherei;they were seen was at the mouth of the K o k s i l a h and Cowichan r i v e r s , Vancouver i s l a n d , and at the Gorge near V i c t o r i a . They were observed o n l y t o r e s t on S t . Mary lake where the g r e a t e s t number counted at one time was 5#o At the North arm of the F r a s e r r i v e r , canvas-backs were u s u a l l y f e e d i n g , but no more than H-l were seen a t one time. Canvas-backs showed d e f i n i t e p r e f e r e n c e f o r wind-pro-t e c t e d waters of low s a l i n i t y . They were not seen f e e d i n g along any s t r i p o f unprotected s h o r e l i n e i n the study a r e a . GREATER SCAUP DUCK (Nyroca mar11a) These ducks were g e n e r a l l y d i s t r i b u t e d over the study area, but l o c a l i t i e s of g r e a t e s t abundance were E n g l i s h bay, Vancouver harbour, Nanoose bay, Cowichan bay, Ganges harbour and V i c t o r i a . Sewer o u t f a l l s and abundant h e r r i n g spawn, r e s u l t -i n g i n a h i g h degree of food a v a i l a b i l i t y were the f a c t o r s r e s -p o n s i b l e f o r heavy c o n c e n t r a t i o n s i n these l o c a l i t i e s . Greater scaup ducks were present on a l l o b s e r v a t i o n a l areas i n the Vancouver area, but were most abundant at J e r i c h o beach ( O b s e r v a t i o n a l Area 4) and K i t s i l a n o beach ( O b s e r v a t i o n a l Area-3)• A small p o p u l a t i o n of from three t o ten b i r d s wintered on St. Mary l a k e , and groups of two and three b i r d s were seen at E l k l a k e , V i c t o r i a , and Beaver l a k e , Vancouver. O c c a s i o n a l l y 51 a l a r g e r a f t of 100 to 200 b i r d s were observed at Lost lagoon, Vancouver, and Langford l a k e , Vancouver i s l a n d , but? these d i d not occur i n the se l o c a l i t i e s d u r i n g the e n t i r e study p e r i o d . Food a v a i l a b i l i t y g r e a t l y i n f l u e n c e s the d i s t r i b u t i o n of g r e a t e r scaup ducks, f o r those areas not having sewer out-f a l l s or a v a i l a b l e h e r r i n g ova, such as Howe sound and Ind i a n arm, are not c h a r a c t e r i z e d by an abundance of t h i s s p e c i e s . On the ea s t coast of Vancouver i s l a n d between Qualicum r i v e r and Courtenay, t h i s s p e c i e s was second i n abundance. LESSER SCAUP DUCK (Nyroca a f f l n i s ) No b i r d s of t h i s s p e c i e s were seen on the study a r e a d u r i n g the wi n t e r . Evidence that small numbers of these b i r d s are p r e s e n t d u r i n g f a l l m i g r a t i o n and e a r l y w i n t e r has been obtained by Munro (1947), who counted a t o t a l of 21 l e s s e r scaup ducks on Burnaby l a k e d u r i n g September, October and November, 1946. Munro (1941), s t a t e s that i t seems f a i r l y w e l l e s t a b l i s h e d that the l e s s e r scaup duck i s a scarce w i n t e r v i s i -tant i n B r i t i s h Columbia. F a r t h e r south i n the P o r t l a n d r e g i o n , Oregon, t h i s b i r d i s the most abundant of the w i n t e r i n g d i v i n g ducks, but i n southern B r i t i s h Columbia, i t i s r a r e l y seen i n wi n t e r . 52 AMERICAN GOLDEN-EYE ( G l a u c l o n e t t a c l a n g u l a americana) Ducks of t h i s s p e c i es were seen on a l l o b s e r v a t i o n a l areas and d i d not show a marked p r e f e r e n c e f o r any one h a b i t a t "type, a l t h o u g h more were present In the p r o t e c t e d - r o c k y than other h a b i t a t s . American golden-eyes were most abundant on the east coast of Vancouver i s l a n d and the V i c t o r i a a r e a . Almost a l l the golden-eyes In these l o c a l i t i e s were of t h i s s p e c i e s . In the Greater Vancouver a r e a and i n Howe sound and Indian arm, t h i s s p e c i e s i s f a r outnumbered by Barrow's golden-eye. Lake h a b i t a t i s not p r e f e r r e d to marine h a b i t a t s , and only a sm a l l number of these b i r d s were seen on St. Mary lake d u r i n g e a r l y s p r i n g . BARROW*S GOLDEN-EYE ( G l a u c l o n e t t a i s l a n d l c a ) The d i s t r i b u t i o n of Barrow's golden-eye and American golden-eye i s s i m i l a r i n the study area, but many r e g i o n s w i t h l a r g e numbers of one sp e c i e s i s c h a r a c t e r i z e d by a p a u c i t y of the r e l a t e d s p e c i e s . Examples of t h i s s i t u a t i o n were c i t e d above, but can be emphasized a g a i n . In two counts between Qualicum r i v e r and the c i t y of Courtenay, o n l y f i v e Barrow*s golden-eyes were seen, whereas the number of American golden-eyes was more than f i f t y times g r e a t e r . In Howe sound, 53 Barrow's golden-eyes were found to be almost twenty times as numerous, and d u r i n g one o b s e r v a t i o n a t Ind i a n arm, only e i g h t American golden-eyes as opposed t o 3 H Barrow's golden-eyes were seen. T h i s s p e c i e s i s not commonly seen In the V i c t o r i a a r e a . Only one or two b i r d s were seen o c c a s i o n a l l y on f r e s h -water l a k e s , which i n d i c a t e s that t h i s h a b i t a t i s not p r e f e r r e d as f e e d i n g or r e s t i n g grounds. In the Vancouver a r e a they were more abundant on unprotected and p r o t e c t e d s h o r e l i n e than In bay and e s t u a r i n e h a b i t a t . BUFFLE-HEAD ( C h a r i t o n e t t a a l b e o l a ) These ducks were observed on a l l o b s e r v a t i o n a l areas i n the Vancouver r e g i o n except a t Spanish banks and E n g l i s h Bay beach ( O b s e r v a t i o n a l Areas 2 and 5)« They were common on the east coast of Vancouver i s l a n d , i n the V i c t o r i a r e g i o n , and i n Howe sound, but o n l y one drake was observed i n Ind i a n arm. Bu f f l e - h e a d s were not seen f e e d i n g In heavy s u r f , and appeared to p r e f e r p r o t e c t e d a r e a s . More than 4-00 were observed i n two counts a t Granges harbour and Prevost i s l a n d , where they congregate to fe e d i n the narrow p r o t e c t e d bays ( F i g u r e 13). One or two b i r d s were present on each sma l l l a k e and po t - h o l e examined In the V i c t o r i a r e g i o n , and o f t e n these were the onl y ducks u s i n g these f e e d i n g areas. 54 Department of Lands and F o r e s t s . F i g u r e 13. A e r i a l photograph of Ganges harbour, S a l t S p r i n g i s l a n d , and the northwest end of Prevost I s l a n d . The narrow I n l e t s on Prevost i s l a n d are f a v o u r i t e f e e d i n g areas f o r b u f f l e - h e a d s and golden-eyes. T h i s r e -gion i s an important h e r r i n g spawning ground. 55 OLD-SQUAW (C l a n g u l a hyemalis) These ducks were most abundant i n the V i c t o r i a r e g i o n and S a l t Spring i s l a n d . None was seen d u r i n g two counts on the east coast of Vancouver i s l a n d from Qualicum r i v e r to Courtenay, nor i n Howe sound, and only one drake was seen i n Indian arm. S a l t water areas are used e x t e n s i v e l y by t h i s s p e c i e s and none was seen on lake h a b i t a t . In the Vancouver r e g i o n , old-squaws were most numerous i n bay and e s t u a r i n e h a b i t a t . On March 23, 195 2 , t h i r t e e n p a i r s were seen at E n g l i s h Bay b e a c h — an area where none had been seen p r e v i o u s l y . T h i s f l o c k i n g may be concomitant w i t h t h e i r h a b i t of moving i n c l o s e r to the c o a s t -l i n e as s p r i n g advances. A s i m i l a r s i t u a t i o n was seen a t Ganges harbour, where i n March, 195 2 , the number of old-squaws had i n c r e a s e d f o u r f o l d s i n c e January. HARLEQUIN DUCK ( H l s t r l o n i c u s h l s t r l o n l c u s ) Only nine h a r l e q u i n ducks were seen i n , t h e Vancouver r e g i o n d u r i n g the study, and these were observed along unpro-t e c t e d s h o r e l i n e at J e r i c h o beach and the Iona I s l a n d J e t t y ( O b s e r v a t i o n a l Areas k- and l ) . Areas of g r e a t e s t abundance were i n the V i c t o r i a r e g i o n , between Qualicum r i v e r and Courtenay, and at S a l t Spring i s l a n d . Lake h a b i t a t was not used by t h i s s p e c i e s , and none was seen i n Indian arm. Only three p a i r were observed d u r i n g 56 two counts i n Howe sound. These ducks p r e f e r to fe e d along u n p r o t e c t e d c o a s t l i n e and p r e f e r r e d areas were the G-ulf i s l a n d s and the east c o a s t o f Vancouver i s l a n d . WHITE-WINGED SCOTER ( M e l a n l t t a d e g l a n d l ) The east coast of Vancouver I s l a n d , and the G u l f I s l a n d s are the areas of g r e a t e s t white-winged s c o t e r abundance. In the V i c t o r i a r e g i o n , t h i s s p e c i e s i s more abundant than the su r f s c o t e r . They were present on a l l r e g i o n s except I n d i a n arm, and only 39 were seen In two counts i n Howe sound. In the Vancouver r e g i o n , they u t i l i z e d a l l h a b i t a t types except bay and e s t u a r i n e h a b i t a t i n the North arm of the F r a s e r r i v e r . Although no white-winged s c o t e r s were observed on lake h a b i t a t d u r i n g the winte r , they d i d occur on St. M»ry lake s e v e r a l times d u r i n g September, 1951, and March, 195 2 -SURF SCOTER ( M e l a n l t t a p e r s p l c l l l a t a ) T h i s s p e c i e s d i d not occur $n lake h a b i t a t d u r i n g the s"t;udy, but was very common on a l l o t h e r a r e a s . Indian arm, Howe sound, and the Vancouver r e g i o n , where white-winged s c o t e r s were not abundant, were the r e g i o n s of g r e a t e s t s u r f s c o t e r concentration.. On the east coast of Vancouver i s l a n d , and a t 57 V i c t o r i a , the reverse s i t u a t i o n was seen where the p o p u l a t i o n of s u r f s c o t e r s was much sm a l l e r than the white-winged s c o t e r p o p u l a t i o n . In the Vancouver r e g i o n , s u r f s c o t e r s were abundant on a l l h a b i t a t s except bay and e s t u a r i n e , and they showed the tendency to aggregate i n l a r g e f l o c k s on these h a b i t a t s * AMERICAN SCOTER (Oldemla americana) A l l ducks counted i n the Vancouver r e g i o n were seen between the mouth of the F r a s e r r i v e r and E n g l i s h Bay beach. They were not observed i n the p r o t e c t e d waters between P r o s p e c t p o i n t and Coal harbour, nor d i d they occur on any lake h a b i t a t . Only a small p o p u l a t i o n wintered i n the V i c t o r i a r e g i o n and the east coast o f Vancouver i s l a n d , and In two counts a t Ganges harbour, only three American s c o t e r s were seen. They d i d not occur i n Howe sound or Indian arm d u r i n g the w i n t e r , and t h i s i s taken to i n d i c a t e t h a t f o r some undeter-mined reason, these areas are u r i p r e f e r r e d . The g r e a t e s t number oc c u r r e d along the unprotected s h o r e l i n e i n the Vancouver r e g i o n . In order to determine r e l a t i v e use, by a l l s p e c i e s , of the f i v e h a b i t a t s i n the Vancouver r e g i o n , the average number of a l l d i v i n g ducks counted per o b s e r v a t i o n a l mile f o r each h a b i t a t was c a l c u l a t e d and pre s e n t e d g r a p h i c a l l y i n F i g u r e 14-. The d i f f e r e n c e s between the numbers of ducks u s i n g 58 the unprotected-sandy, unprotected-rocky, and p r o t e c t e d - r p c k y h a b i t a t s are not g r e a t c o n s i d e r i n g the great v a r i e t y In counts from month to month, so that i t i s d o u b t f u l i f much s i g n i f i -cance can be att a c h e d to these d i f f e r e n c e s e In the case of bay and e s t u a r i n e and lake h a b i t a t s , the number of ducks vary g r e a t l y from those i n the f i r s t t h ree h a b i t a t s . T h i s i s taken to i n d i c a t e that these two h a b i t a t s are l e s s d e s i r a b l e w i n t e r -i n g a r e a s . 59 3 0 0 n 2 0 0 -UJ CD 1 0 0 -UNPROTECTED UNPROTECTED PROTECTED BAY AND LAKE SANDY . ROCKY ROCKY ESTUARINE HABITAT F i g u r e lk. Average number of a l l s p e c i e s of d i v i n g ducks counted per o b s e r v a t i o n a l mile by h a b i t a t s d u r i n g p e r i o d September 1951 to March 1952. (Representing cumulative t o t a l s of average number counted per o b s e r v a t i o n a l m i l e during t h i s p e r i o d . ) 6 0 STRUCTURE OF THE POPULATION SEX STRUCTURE A l l data obtained d u r i n g the study were analysed by the 2 x n Chi-square t e s t adopted from Snedecor (1946), i n order to draw d e f i n i t e c o n c l u s i o n s r e g a r d i n g d i s t r i b u t i o n o f the sexes. Provided that the method of sampling Introduces no b i a s , then a Chi-square t e s t t h a t g i v e s e i t h e r a very h i g h or very low p r o b a b i l i t y value i n d i c a t e s a departure from the amount of v a r i a t i o n expected, i n sex r a t i o s , r e s u l t i n g from chance f a c t o r s a l o n e . For example: f o r American s c o t e r i n November 1951* 3°3 h i r d s were counted and the t o t a l counts were 202 males to 101 females. T h i s r e p r e s e n t s a s i g n i f i c a n t departure from a 1:1 sex r a t i o (Chi-square = 33*67) and the p r o b a b i l i t y that t h i s sample was drawn from a 1:1 sex r a t i o p o p u l a t i o n i s l e s e than f i v e chances i n one hundred. Each i n d i v i d u a l group or sub-sample of ducks observed was used i n the analyses o f the d a t a . Chi-square t e s t s of t h i s k i n d measure d e v i a t i o n from a t h e o r e t i c a l standard i n which there i s complete u n i f o r m i t y ( i . e . no v a r i a t i o n ) i n the sub-samples. I f the b i r d s aggregate i n groups a t random, w i t h r e s p e c t to sex, one would expect i 1 i 61 c o n s i d e r a b l e v a r i a t i o n i n the sex r a t i o s of the sub-samples ( i . e . v a r i a t i o n s about the average). Thus Chi-square would assume an i n t e r m e d i a t e value and the corresponding p r o b a b i l i t y value ( i . e . the p r o b a b i l i t y that the samples were drawn from a p o p u l a t i o n i n which a l l the sexes were always arranged i n a f i x e d p r o p o r t i o n ) would l i e between 0.95 and O.05. I f the b i r d s were arranged i n groups with a p a r t i c u -l a r sex r a t i o v ery f r e q u e n t l y ( i . e . i f v a r i a t i o n i n the sub-samples was s m a l l ) , then Chi-square would be low, and the c o r -responding p r o b a b i l i t y value would be g r e a t e r than 0«95» T h i s would i n d i c a t e a h i g h p r o b a b i l i t y that the sub-samples were taken from a p o p u l a t i o n i n which the b i r d s grouped i n p a r t i -c u l a r sex r a t i o s . S i m i l a r l y , i f the b i r d s are grouping i n such a way that males congregate, then the sub-sample sex r a t i o s w i l l show wide v a r i a t i o n s and Chi-square w i l l be h i g h . The c o r r e s p o n d i n g p r o b a b i l i t y value w i l l be l e s s than 0.05. T h i s would i n d i c a t e that the p o p u l a t i o n was not d i s t r i b u t e d at random with r e s p e c t to sex. The v a r i o u s v a l u e s of Chi-square might of course r e -f l e c t more complicated s i t u a t i o n s than those suggested. For example, the l a s t case of a h i g h Chi-square value might r e s u l t from a combination of l i m i t e d f l o c k s i z e with g r e g a r i o u s beha-v i o u r of males or non-gregarious t e n d e n c i e s of the females. I t c o u l d a l s o r e s u l t from a d i f f e r e n t i a l s e asonal m i g r a t i o n of the two sexes, or a d i f f e r e n t i a l d i s t r i b u t i o n on the study a r e a . 62 In the f o l l o w i n g account of sex s t r u c t u r e , c o n c l u s i o n s have been drawn on the b a s i s of the a n a l y s e s , the r e s u l t s of which are summarized i n Table IV. S i g n i f i c a n t v a l u e s are those i n which the p r o b a b i l i t y value i s g r e a t e r than 0.95 or l e s s than 0.05, and the meaning of these^ v a l u e s I s based on observa-t i o n s on l i f e h i s t o r y and behaviour. In order to determine d i f f e r e n t i a l sex m i g r a t i o n , the sex r a t i o s i n October and November and i n March were compared ( 2 x 2 Ghl-square t e s t ) with the true winter sex r a t i o o c c u r r i n g i n December, January and February. A s i g n i f i c a n t d i f f e r e n c e between the sex r a t i o s i n October and November, and the t r u e winter sex r a t i o i s i n t e r p r e t e d to mean that one sex was more abundant e a r l i e r i n the w i n t e r as a r e s u l t o f d i f f e r e n t i a l sex m i g r a t i o n . A s i g n i f i c a n t d i f f e r e n c e i n sex r a t i o s c o u l d occur because o f a d i f f e r e n t i a l d i s t r i b u t i o n on the two sexes on the study area, but i t has been assumed that both sexes are r a n -domly d i s t r i b u t e d over the study a r e a . In o t h e r words, a s i g -n i f i c a n t d i f f e r e n c e i n sex r a t i o i n October and November and i n the three winter months, i s taken to mean t h a t one sex i s an e a r l i e r f a l l migrant than the other, or, i n the case where there i s an i n c r e a s e d preponderance of the sex which was p r e -ponderant i n e a r l y f a l l , one sex continues t o immigrate i n t o the study area as winter advances. A f u r t h e r assumption i s made r e g a r d i n g the change i n sex r a t i o s , v i z . , i f one sex i s more abundant i n the t h r e e Table IV. P r o b a b i l i t y values f o r u n i f o r m i t y o f d i s t r i b u t i o n with r e s p e c t to sex and sex r a t i o d u r i n g p e r i o d September 1 9 5 1 - March 1 9 5 2 . October November December January February March Species A B A B A B A B >.99 .3-• 5 >.99 . 5 - . 8 - . 0 2 s -.7 . 9 . 0 5 Redhead Ring-necked duck Canvas-back Greater scaup duck . 2 American golden-eye <.01 Barrow 1s . 0 1 golden-eye . 0 2 B u f f l e - . 9 0 head . 9 5 Old-squaw <.01 <.01 <,01 <.oi* <.oi <.oi3 X . 0 5 V>J 5— 2— :.oiKK .V <.oi* . 3 <.oix >.99 <.ois . 0 5 - ^ . 0 5 -. 5 . 1 >.99 . 1 , 0 2 . 5 < . 0 1 K . 5 <-01 . 2 < . 0 1 K . 9 < . 0 1 * H a r l e q u i n . 9 8 -duck . 9 9 < . 0 1 A B A B . 9 0 -. 9 5 . 8 -. 9 .1-. 2 . 7 -. 8 .05-. 1 . 0 5 -. 1 <.01 < . 0 1 * . 0 5 <.oi* >.99 <\oix . 5 <.oiK .5 .5-.7 > . 9 9 , 0 5 -. 1 , 9 8 < . 0 1 * >.99 . 8 -. 9 > * 9 9 " . 5 -.7 > . 9 9 . 2 -.3 >*99 . 1 -. 2 >.99 . 1 -. 2 Table IV. Cont'd. P r o b a b i l i t y v a l u e s f o r u n i f o r m i t y of d i s t r i b u t i o n w i t h r e s p e c t to sex and sex r a t i o d u r i n g p e r i o d September 1951 - March 1952. October November December January February March Species - A B A B A B A B A B A B White-winged ¥ „ ^ s c o t e r .8 <.01 K .10 <.01K .3 .1 >.99 <.01 >.99 .5 >.99 »2 , 7 - . 0 5 - _ . 2 - , 0 5 - x . 1 -S u r f x - 0 2 - _ „ • s c o t e r <.01 <.01 x <.01 <.01 .05 <.01 x >.99 < . 0 1 . <,01 <.01* >,99 <.01 American . 2 - . _ »3- _ . 7 - . 0 1 - ..3- . 5 - .05 , 5 - . 0 5 -s c o t e r .3 <.6l* .5 <-Ql .8 . 0 2 * * .5 .7 >.99 .1 .7 .1 A - P r o b a b i l i t y of u n i f o r m i t y of d i s t r i b u t i o n . E * P r o b a b i l i t y that sample was taken from a 1:1 sex r a t i o p o p u l a t i o n . I n d i c a t e s a s i g n i f i c a n t preponderance of males, xx I n d i c a t e s a s i g n i f i c a n t preponderance of females. S i g n i f i c a n t v a l u e s = 0.95 or l a r g e r ; O.05 or s m a l l e r . 65 w i n t e r months than i n October and November, i t i s assumed t h a t t h i s r e s u l t s from an i n f l u x of the l e s s abundant sex, and not as a r e s u l t of e f f l u x of the sex which was more abundant e a r l i e r i n the f a l l . The percentage of p a i r e d i n d i v i d u a l s , by s p e c i e s , f o r each month has been c a l c u l a t e d and confidence l i m i t s a t the 0.^5 l e v e l of s i g n i f i c a n c e have been a p p l i e d i n each case. I t has been c o n s i d e r e d that a p a i r i s any two ducks, one of which i s a male and the other a female, which are detached from other ducks or are c l o s e l y a s s o c i a t e d when w i t h other ducks. Hochbaum (1944), s t a t e s t h a t i n a l l . s p e c i e s , c o u r t s h i p d i s p l a y s are i n f r e q u e n t , or cease e n t i r e l y immediately f o l l o w i n g the formation of the p a i r . During t h i s p e r i o d of n o n - d i s p l a y , p a i r s are g r e g a r i o u s . Males do not show b e l l i g e r e n c e to one another u n t i l c o u r t s h i p i s resumed on the breeding grounds. For t h i s reason, any group of b i r d s seen i n the f i e l d i n which the sex r a t i o was e x a c t l y 1:1 was c o n s i d e r e d to c o n s i s t o f p a i r e d b i r d s . ' The data f o r the percentage p a i r e d f o r each s p e c i e s i s presented i n F i g u r e s 15 and l6„ v. The percentage of males i n each s p e c i e s f o r each month has been c a l c u l a t e d i n a s i m i l a r manner, (Figures 17 and 18) and f i d u c i a l l i m i t s a t the 0.95 l e v e l of con f i d e n c e have, been app-l i e d to these percentages. S i g n i f i c a n t and n o n - s i g n i f i c a n t changes i n percentages can be r e a d i l y found by comparing the ranges of the f i d u c i a l l i m i t s f o r each month. I f one set of f i d u c i a l l i m i t s does not o v e r l a p another set of l i m i t s , then gure 1 5 . Percentage p a i r e d , by s p e c i e s , observed i n study area d u r i n g p e r i o d September 1 9 5 1 to March 1 9 5 2 . 67 1001 actual percentage • — fiducial l imits 0 . 9 5 confidence level BUFFLE-HEAD OLD-SQUAW 100 50H Feb! Mar. Oct. Nov. Dec. Jan. Feb. Mar. Oct. Nov. Dec. Jan. HARLEQUIN DUCK WHITE-WINGED SCOTER 100 < 50H 100 50 H Oct! Nov! Dec. J an . Feb. Mar. Oct. Nov. Dec. Jan. Feb. Mar. SURF SCOTER AMERICAN SCOTER 100' UJ < 5 0 100" 5 0 H Oct. N o v . D e c . J o n . F e b . MoT. Dec. Jan. Feb. Mar. * F i g u r e 1 6 . Percentage p a i r e d , by s p e c i e s , observed i n study area d u r i n g p e r i o d September 1951 - March 1 9 5 2 . 6 Figure 17. Percentage males, by s p e c i e s , observed i n studv area d u r i n g p e r i o d September 1951 - March 1952. v. 69 F i g u r e 18. Percentage males, by s p e c i e s , observed i n study a r e a " d u r i n g p e r i o d September 1951 - March 1952. 70 i t can be assumed with reasonable accuracy, that the two p e r -centages are s i g n i f i c a n t l y d i f f e r e n t . Thus i n the graph f o r percentage males f o r the American golden-eye, i t i s seen t h a t the percentage males i n November i s s i g n i f i c a n t l y g r e a t e r than the percentage i n October. The percentage i n January i s s i g n i f i c a n t l y d i f f e r e n t from that i n a l l other months, and the percentage males i n November i s not s i g n i f i c a n t l y d i f f e r e n t from t h a t i n December, February and March. A t r e n d i s i n d i c a t e d In which the p e r c e n t -age of males Increases from October to November; does not show s i g n i f i c a n t i n c r e a s e a g a i n u n t i l January; and then shows a s i g n i f i c a n t r e d u c t i o n i n February and March. S i g n i f i c a n t d i f -f e r e n c e s on a l l o t h e r graphs showing f i d u c i a l l i m i t s can be obtained i n the same manner. Redhead There are not s u f f i c i e n t d a t a to draw c o n c l u s i o n s r e g a r d i n g the sex r a t i o of the sub-samples, nor can d i f f e r e n -t i a l seasonal m i g r a t i o n be determined. The one p r o b a b i l i t y value o b t a i n e d i n January (Table I V ) , i n d i c a t e s a non-random d i s t r i b u t i o n of males and females r e s u l t i n g from p a i r f o r m a t i o n with the s p e c i e s . The sex r a t i o of January's p o p u l a t i o n was 1,26 males to 1.00 female, which shows moderate v a r i a t i o n from a 1:1 sex r a t i o . 71 Ring-necked Duck S u f f i c i e n t data are a l s o l a c k i n g f o r t h i s s p e c i e s , but a non-random d i s t r i b u t i o n o f the sexes o c c u r r e d i n December ( p r o b a b i l i t y value g r e a t e r than 0 . 9 9 ) as a r e s u l t of p a i r f o r -mation. There was a preponderance of males i n January (Figure 17) and the w i n t e r sex r a t i o was 1.28 males to 1.00 female. No evidence was o b t a i n e d to show t h a t m i g r a t i o n began i n March, but i f m i g r a t i o n had s t a r t e d , then the drakes and hens had l e f t i n equal numbers. Canvas-back ~i: In January there was a s i g n i f i c a n t preponderance o f males i n the study a r e a (1.82 males to 1.00 female), and these showed the tendency to f l o c k t o g e t h e r ( F i g u r e 17) w i t h the r e s u l t that the sexes were not randomly d i s t r i b u t e d . The winter sex r a t i o was 1.4-2 males to 1.00 female and d i d not change s i g n i -f i c a n t l y i n March. The percentage of p a i r e d i n d i v i d u a l s r e -mained low throughout the winter ( F i g u r e 15), and i n March, only a s m a l l percentage of the p o p u l a t i o n c o n s i s t e d of p a i r e d b i r d s . T h i s , and the f a c t that there was no s i g n i f i c a n t change i n the percentage of males i n March, i n d i c a t e s t h a t i f s p r i n g m i g r a t i o n had begun, only p a i r e d ducks had l e f t the w i n t e r i n g grounds. 72 Greater Scaup Duck In a l l months, there was a departure from a 1:1 sex r a t i o r e s u l t i n g from a preponderance of males ( F i g u r e 1.7). The d i s t r i b u t i o n of the sexes was s i g n i f i c a n t l y non-random from November to February due to the preponderance of males and t h e i r tendency to f l o c k t o g e t h e r . The sex r a t i o i n October and November (l . M J - males to 1,00 female) i n d i c a t e s more males than females on the s t u d y area-., The preponderance of males Increased u n t i l , d u r i n g the winter months, the r a t i o was 1.77 males to 1.00 female. T h i s i n d i c a t e s t h a t more males than females were moving i n t o the area as winter advanced. The percentage of p a i r e d ducks Increased i n March (Fi g u r e 15), but no evidence was obtained to i n d i c a t e that s p r i n g m i g r a t i o n had s t a r t e d . American G-olden-eye In a l l months there was a s i g n i f i c a n t departure from a 1:1 sex r a t i o r e s u l t i n g from a preponderance of females In October, and a preponderance of males d u r i n g the remainder o f the w i n t e r (Figure 17). The d i s t r i b u t i o n of the sexes was non-random i n October due to the f l o c k i n g t endencies of the females, and i n January and February, d i s t r i b u t i o n was non-random because many of the b i r d s had s t a r t e d to p a i r . In March, d i s t r i b u t i o n of the sexes was random and, because there was a s i g n i f i c a n t change i n the sex r a t i o a t t h i s time (1.72 males to 1„00 female 73 i n w i n t e r ) , i t i s construed that e i t h e r many males had l e f t the study area f o r the breeding grounds, or more p a i r e d ducks had a r r i v e d i n the study area from more s o u t h e r l y w i n t e r i n g grounds. There i s a s i g n i f i c a n t i n c r e a s e i n the number of p a i r e d ducks i n March (Figure 15)• The sex r a t i o i n October (0.25 males to 1.00 female) d i f f e r s from the w i n t e r sex r a t i o (2.6g males to 1,00 female), and a d i f f e r e n t i a l f a l l m i g r a t i o n i s i n d i c a t e d where females a r r i v e d on the w i n t e r i n g grounds before the bulk of the males a r r i v e d . A f t e r October, the p r o -p o r t i o n of males became i n c r e a s i n g l y g r e a t e r u n t i l January, i n d i c a t i n g a l a t e r m i g r a t i o n of the drakes. Barrow's Golden-eye In October and November there was a departure from a 1:1 sex r a t i o r e s u l t i n g from a preponderance of males (F i g u r e 17). During the remainder of the win t e r there was only a s m a l l preponderance of d r a k e s . The sex r a t i o i n °ctober (2.04- males to 1,00 female) shows that females remain longer on the i n t e r i o r l akes and are the l a s t to a r r i v e on the w i n t e r i n g grounds. T h i s i s f u r t h e r i n d i c a t e d d u r i n g the win-t e r when the number o f females became p r o p o r t i o n a t e l y g r e a t e r (winter sex r a t i o : 1.09 males to 1.00 female). In November the males tended to f l o c k t o g e t h e r , but t h i s became l e s s e v i -dent i n December. The s i t u a t i o n i n January when there was a preponderance of males i n most sub-samples, changed the 74 f o l l o w i n g month when the sexes were randomly d i s t r i b u t e d , i . e . showed more v a r i a t i o n from a 1:1 sex r a t i o . In March, the sexes were d i s t r i b u t e d non-randomly due to the preponderance of p a i r e d i n d i v i d u a l s ( Figure 15). Throughout the winter there was a preponderance of males i n the study area, and In March, t h i s preponderance became even g r e a t e r (1.25 males to 1.00 female). T h i s i n d i c a t e s t h a t e i t h e r more males had a r r i v e d i n the study area, or the p o p u l a t i o n which had l e f t the study area c o n s i s t e d o f a p p r o x i -mately equal numbers of males and females, thus l e a v i n g a popu-l a t i o n on the coast i n which there was an even g r e a t e r prepon-derance of males. B u f f l e - h e a d During the w i n t e r the sexes were d i s t r i b u t e d at r a n -dom, except i n March when, there was a h i g h p r o p o r t i o n of p a i r e d ducks on the study area ( F i g u r e l 6 ) . There was a marked preponderance of drakes i n a l l months except March (Fi g u r e IS) when presumably there was an I n f l u x of p a i r e d ducks from more s o u t h e r l y w i n t e r i n g grounds or an e f f l u x of more drakes than hens from the study a r e a . The preponderance of males i n October (I . 6 3 males to 1.00 female) became even l a r g e r In November (2.30 males to 1.00 female). T h i s Is not so marked i n December (I . 6 5 males to 1.00 female) when, i t i s b e l i e v e d , more females a r r i v e d In 75 the study a r e a . The data i n d i c a t e that males are the f i r s t to a r r i v e on the w i n t e r i n g grounds, and they form the b u l k of the popu-l a t i o n of e a r l y s p r i n g migrants. Old-squaw S u f f i c i e n t data are l a c k i n g f o r t h i s s p e c i e s to i n d i -cate trends i n d i s t r i b u t i o n and sex r a t i o d u r i n g the e n t i r e study. However, i n January the sexes were d i s t r i b u t e d at r a n -dom, when c o n s i d e r a b l e v a r i a t i o n o c c u r r e d i n the sex r a t i o of the sub-samples. In February and March, a non-random d i s t r i -b u t i o n o c c u r r e d as a r e s u l t of p a i r f o r m a t i o n ( F i g u r e l 6 ) . At t h i s time more than 75$ o r "the sub-samples were p a i r e d ducks. There was a preponderance of drakes i n January (1.95 males to 1.00 female) when most sub-samples contained more males than females ( F i g u r e 18). However, the p r o p o r t i o n of males d u r i n g January and February (1.51 male to 1.00 female) d i d not show a s i g n i f i c a n t change i n March (1.15 males to 1.00 female). T h i s i n d i c a t e s t h a t i f s p r i n g m i g r a t i o n began i n March, i t was not a d i f f e r e n t i a l sex m i g r a t i o n , but one where both males and females had l e f t i n equal numbers. Harlequin^ duck E a r l y w i n t e r data are a l s o l a c k i n g f o r t h i s s p e c i e s and i t i s seen that the p r o b a b i l i t y v a l u e s f o r sex r a t i o and d i s t r i b u t i o n of the sexes are very s i m i l a r to those f o r • 7 6 old-squaws. (Table IV) In January the sexes were d i s t r i b u t e d non-randomly owing to the presence of more drakes than hens i n a l l sub-samples ( F i g u r e 12>).. The sexes were d i s t r i b u t e d non-randomly i n February and March, but t h i s was due to p a i r f o r m a t i o n (Figure l 6 ) . At t h i s time, 55$ ' °f the sub-samples were p a i r e d ducks. A preponderance of drakes occurred i n January (2.33 males to 1.00 female) when there were more males than females i n a l l sub-samples. However, the p r o p o r t i o n of males d u r i n g January and February (2.13 males to 1.00 female) d i d not s i g n i -f i c a n t l y change i n March, when the sex r a t i o was 1.32 males to 1.00 female. T h i s i n d i c a t e s t h a t i f s p r i n g m i g r a t i o n began i n March, both drakes and hens had l e f t the w i n t e r i n g grounds i n equal numbers. Whlte-wlnged Scoter During October there was a h i g h p r o p o r t i o n of drakes i n the study area (Figure 16) when the sex r a t i o was 4.4-5 males to 1.00 female. T h i s p r o p o r t i o n decreased i n November (2.91 males to 1.00 female) and December (l . 2 4 males to 1B00 female), i n d i c a t i n g t h a t a d i f f e r e n t i a l sex m i g r a t i o n from the breeding grounds had taken p l a c e , and the males were the f i r s t to a r r i v e on the c o a s t a l waters. In October, November and December, the sexes were 77 d i s t r i b u t e d at random i n the sub^samples. Non-random d i s t r i -b u t i o n o c c u r r e d a f t e r December due to the preponderance of males i n most of the sub-samples, and i n March, non-randomness r e s u l t e d because more than 5 0 $ of the sub-samples were p a i r e d ducks ( F i g u r e l6). The winter sex r a t i o i n the study a r e a was males to 1 ,00 female, and no s i g n i f i c a n t change from t h i s r a t i o o c c u r r e d i n March (1.18S males to 1 ,00 female). T h i s i n d i c a t e d that s p r i n g m i g r a t i o n had not s t a r t e d i n March, or i f i t had, then the m a j o r i t y of the emmigrating ducks were p a i r e d and the m a j o r i t y of the migrants a r r i v i n g f r o g the south were a l s o p a i r e d . Surf S c o t e r During the e n t i r e study, the w i n t e r i n g p o p u l a t i o n con-s i s t e d of a preponderance of males (Figure I S ) , The g r e a t e s t preponderance of drakes occurred i n October, when the sex r a t i o was 5*46 males to 1 ,00 female. The p r o p o r t i o n of females became p r o g r e s s i v e l y g r e a t e r u n t i l , i n January, the sex r a t i o was 2.19 males to 1 ,00 female, A d i f f e r e n t i a l sex m i g r a t i o n i s i n d i c a t e d here, where the f i r s t f a l l migrants are predomin-a n t l y males, and the b u l k of the female p o p u l a t i o n a r r i v e s i n the study area d u r i n g November and December. A non-random d i s t r i b u t i o n of the sexes o c c u r r e d i n October, November and December when the drakes showed the 7 g tendency to f l o c k t o g e t h e r . In January, most of the sub-samples showed a sex r a t i o of from 2 males to 1 female, to 4- male to 1 female. The p r o p o r t i o n of males i n the sub-samples was g r e a t e r i n February (32 males to 1 female, to 1 male to 1 female) as a r e s u l t of non-random d i s t r i b u t i o n . In March, most sub-samples were e i t h e r p a i r e d ducks or c o u r t i n g p a r t i e s r e s u l t i n g i n a non-random d i s t r i b u t i o n . No s i g n i f i c a n t change from the w i n t e r sex r a t i o M 2.4-4-males to 1.00 female) o c c u r r e d i n March (2.31 males to 1.00 female). T h i s i n d i c a t e s that s p r i n g m i g r a t i o n had not yet s t a r -ted, or i f i t had, the m a j o r i t y of ducks which l e f t the study area were p a i r e d and the m a j o r i t y a r r i v i n g i n the study a r e a from the south were also p a i r e d . American S c o t e r During a l l winter months, except February, the sexes i n the sub-samples were d i s t r i b u t e d at random. In February, non-random d i s t r i b u t i o n o c c u r r e d because most of the sub-samples c o n s i s t e d of p a i r e d i n d i v i d u a l s ( F i g u r e 10). There was a preponderance of drakes i n October (5<»15 males to 1.00 female) which became p r o g r e s s i v e l y s m a l l e r u n t i l i n December ( F i g u r e 18), v; the sex r a t i o was 0 .52 males to 1.00 female. T h i s i n d i c a t e s t hat the e a r l y f a l l migrants were predominantly drakes which preceded the hens to the w i n t e r i n g grounds. The preponderance of females i n December cannot be e x p l a i n e d u n l e s s there were a c t u a l l y more females i n the 79 w i n t e r i n g p o p u l a t i o n . T h i s seems u n l i k e l y , however, because the w i n t e r sex r a t i o was 1.06 males to 1 .00 female. P o s s i b l y d i f f e r e n t i a l d i s t r i b u t i o n of the two sexes o c c u r r e d on the study area, although t h i s was not d e t e c t e d d u r i n g the study. No s i g n i f i c a n t change i n sex r a t i o o c c u r r e d i n March, i n d i c a t i n g t h a t i f m i g r a t i o n had s t a r t e d , the drakes and hens had departed i n equal numbers, and s i m i l a r l y , the migrants a r r i v i n g from the south were predominantly p a i r e d ducks. I t seems l i k e l y that some p a i r e d ducks had s t a r t e d m i g r a t i n g because there was n o . i n c r e a s e i n the percentage of p a i r e d American: s c o t e r s on the study area d u r i n g March ( F i g u r e l 6 ) . Before t h i s time, a s i g n i f i c a n t i n c r e a s e had o c c u r r e d each month a f t e r December. so AGE STRUCTURE Within the d i v i n g duck group, many s p e c i e s , such as the s c o t e r s , golden-eyes, b u f f l e h e a d s , h a r l e q u i n ducks, and old-squaws, do not mature and assume a d u l t plumage d u r i n g the f i r s t year, w i t h the r e s u l t t h a t s e v e r a l age c l a s s e s are p r e -sent on the w i n t e r i n g grounds. I t was very d i f f i c u l t d u r i n g the study to c o r r e c t l y i d e n t i f y J u v e n i l e s and y e a r l i n g b i r d s , and no attempt was made to sex the b i r d s i d e n t i f i e d as juven-i l e s . The d e s c r i p t i o n s of the sp e c i e s presented by K o r t r i g h t (19.43), were used to d i s t i n g u i s h j u v e n i l e s from a d u l t s , but these d e s c r i p t i o n s were not always s u f f i c i e n t l y complete to i n c l u d e a l l plumage p a t t e r n s encountered. E r r o r i s a l s o i n t r o -duced because of the manner i n which j u v e n i l e b i r d s , which c l o s e l y resemble the a d u l t female o f the s p e c i e s e a r l y i n the f a l l , g r a d u a l l y change t h e i r appearance d u r i n g the w i n t e r . More accurac y c o u l d have been o b t a i n e d i f a l l b i r d s had been observed a t c l o s e range, but o f t e n i t was necessary to s p e c i a t e , sex and age b i r d s w i t h b i n o c u l a r s at d i s t a n c e s exceeding 4-00 yards. With as much accuracy as c o u l d be o b t a i n e d i n the f i e l d , the percentage o f J u v e n i l e s seen each month f o r each sp e c i e s have been t a b u l a t e d , and f i d u c i a l l i m i t s at the 0 . 9 5 l e v e l o f confidence have been a p p l i e d (Table V ) . The percentage J u v e n i l e s In most s p e c i e s remained low 81 Table V„ Percentage J u v e n i l e s , by s p e c i e s , observed d u r i n g p e r i o d , September 1951 - March 1952. October November December January February March Redhead - 0 0 0 0 Ring-necked duck — 0 0 0 0 Canvas-back - - - 0 0 0 Greater scaup duck 0 0.8 0.1 0.3 1.0 0 American golden-eye 0 6.7 0 2.7 3.7 2.9 Barrow 1s goldenr»eye 0 0.4- 9.0 2.1 4-.0 1.9 B u f f l e - h e a d 0 0.3 0.5 1.0 0 1.3 Old-squaw - - - 0 0 0 H a r l e q u i n duck am* — 0 0 0 0 White-winged s c o t e r 4-.7 23.0 5.6 8.5 6.4- 4-.0 Surf s c o t e r 2.2 9.5 10.4- 5.5 5.0 1.6 American sc o t e r 0 0.7 0 0.5 1.8 ' ' 17.2 throughout the winter, and j u v e n i l e s of the redheads, r i n g -necked ducks, canvas-backs, old-squaws and h a r l e q u i n ducks were not seen. No s i g n i f i c a n t i n c r e a s e or decrease In percentages of j u v e n i l e s each month was noted i n the g r e a t e r scaup duck, American golden-eye, b u f f l e - h e a d and old-squaw s p e c i e s . There 52 was a s i g n i f i c a n t i n c r e a s e i n Barrow's golden-eye J u v e n i l e s i n December, and white-winged s c o t e r s i n November. There was a s i g n i f i c a n t i n c r e a s e i n the number of s u r f s c o t e r j u v e n i l e s i n November and December, and a f t e r t h i s time, the percentage decreased each month. From October to February, o n l y e i g h t j u v e n i l e American s c o t e r s were seen. In March, a sudden I n -f l u x of J u v e n i l e s o c c u r r e d , and 17 .2$ of the p o p u l a t i o n con-s i s t e d of young b i r d s . T h i s may be the r e s u l t of s p r i n g immigration i n t o the a r e a and r e p r e s e n t the beginning of migra-t i o n . F i e l d o b s e r v a t i o n s i n d i c a t e t h at o n l y a sma l l p e r c e n t -age of j u v e n i l e s of a l l s p e c i e s were present on the study area d u r i n g the w i n t e r . T h i s suggests t h a t p o s s i b l y , the bulk of the j u v e n i l e p o p u l a t i o n s concentrate i n ot h e r l o c a l i t i e s throughout the w i n t e r . S3 DISCUSSION Th i s i n v e s t i g a t i o n was made d n order to determine the d i s t r i b u t i o n of w i n t e r i n g ducks on the c o a s t a l waters of southern B r i t i s h Columbia. During the study, an attempt was made to d i s c o v e r and evaluate the f a c t o r s c a u s i n g d i s t r i b u t i o n and duck movement. Although d i s t r i b u t i o n has been determined throughout the e n t i r e study area, the main emphasis has been p l a c e d on d i s t r i b u t i o n on the f i v e e c o l o g i c a l h a b i t a t s i n the v i c i n i t y of Vancouver and S a l t S p r i n g i s l a n d , A study of the f a c t o r s i n f l u e n c i n g seasonal d i s t r i b u -t i o n of the d i v i n g ducks showed t h a t the wi n t e r c l i m a t e i n the area can be t o l e r a t e d by most s p e c i e s of ducks. The s c a r c i t y of redheads, ring-necked ducks, canvas-backs and l e s s e r scaup ducks may be due to lower t o l e r a n c e to f r e e z i n g temperatures. The I r r e g u l a r c o a s t l i n e and j u x t a p o s i t i o n of the many small i s l a n d s i n the S t r a i t of Georgia r e s u l t s i n numerous areas which are p r o t e c t e d from s t r o n g winds. There are a s u f -f i c i e n t number of these p r o t e c t e d areas to o f f e r sanctuary t o a l l ducks d u r i n g storms, although not a l l waterfowl leave the open waters at such times. Observations I n d i c a t e d t h a t d i v i n g ducks are i n f l u e n -ced by the d i s t r i b u t i o n of t h e i r p r e f e r r e d f o o d . I t was found that white-winged s c o t e r s are most abundant on the east coast o f Vancouver i s l a n d where there i s a r i c h supply o f t h e i r p r e f e r r e d food, v i z . clams and o y s t e r s . In Howe sound, white-winged s c o t e r s are uncommon, but s u r f s c o t e r s , which f e e d ex-t e n s i v e l y on the r i c h fauna of blue mussels, are v e r y abundant. Few s u r f s c o t e r s are found on the east coast of Vancouver i s l a n d , probably because t h e i r p r e f e r r e d f o o d — b l u e m u s s e l s — are not too abundant t h e r e . Other f a c t o r s , r e l a t e d to food a v a i l a b i l i t y , operate to i n f l u e n c e seasonal d i s t r i b u t i o n of the d i v i n g ducks. During the sockeye salmon and P a c i f i c h e r r i n g spawning p e r i o d s , l a r g e numbers of g r e a t e r scaup ducks, American golden-eyes, Barrow's golden-eyes, white-winged s c o t e r s , s u r f s c o t e r s and American s c o t e r s concentrate in. areas of spawn abundance i n order to . feed on the a v a i l a b l e ova. G r a i n e l e v a t o r s were found to a f f e c t the d i s t r i b u t i o n of the g r e a t e r scaup duck, American golden-eye, and Barrow's golden-eye i n Vancouver harbour, and c o n c e n t r a t i o n s of g r e a t e r scaup ducks, American golden-eyes and s u r f s c o t e r s were seen many times f e e d i n g over sewer o u t f a l l s . D a i l y movement i s caused by changes i n weather c o n d i -t i o n s , a l t h o u g h not a l l waterfowl appear to be a f f e c t e d to the same degree. A count Immediately before and a f t e r a storm at Ganges harbour, S a l t S p r i n g I s l a n d , i n d i c a t e d t hat an emmigra-t i o n from the a r e a had taken p l a c e d u r i n g the. adverse weather c o n d i t i o n s . Surf s c o t e r s appear l e a s t a f f e c t e d by stormy weather. In some l o c a l i t i e s , v i z . the Iona I s l a n d J e t t y , t i d e s 85 appear to i n c r e a s e the a v a i l a b i l i t y of food, and t h i s i n t u r n a f f e c t s d i s t r i b u t i o n of waterfowl* Turbulent waters a t the J e t t y d u r i n g the outgoing t i d e s p o s s i b l y d i s l o d g e i n v e r t e b r a t e s from the bottom. T h i s i n c r e a s e d a v a i l a b i l i t y of food may be the reason f o r d i v i n g duck c o n c e n t r a t i o n a t t h i s time. L o c a l movements r e s u l t i n g from c o u r t s h i p a c t i v i t y are commonly seen d u r i n g e a r l y s p r i n g . During t h i s time, the drakes r a p i d l y pursue the hen when she takes wing, and the males appear b e l l i g e r e n t towards one another. Observations at P a s l e y I s l a n d I n d i c a t e that duck move-ment i s caused by d i u r n a l - n o c t u r n a l rhythm. T h i s d i e l p e r i o d -i c i t y a p p a r e n t l y causes changes i n l o c a l d i s t r i b u t i o n , as many ducks were seen to concentrate on p r o t e c t e d waters a t n i g h t , and depart from these waters i n e a r l y m o r n i n g — o n l y to r e t u r n the f o l l o w i n g evening. No d e f i n i t e c o n c l u s i o n s can be drawn, but I t i s p o s s i b l e that a s i m i l a r f l o c k i n g and d i s p e r s i o n of s p e c i e s of d i v i n g ducks takes p l a c e a t night and morning i n other a r e a s . D i s t u r b i n g agencies cause frequent l o c a l movements and d i s p e r s i o n of waterfowl f l o c k s . T h i s i s e s p e c i a l l y true i n the v i c i n i t y of Vancouver, where boats, and persons on the beach d i s t u r b the ducks. Bag-check r e c o r d s from the D e l t a M u n i c i p a l i t y i n d i c a t e that hunting i s not a s e r i o u s f a c t o r causing d i v i n g duck m o r t a l -i t y . T h i s i s probably due to the s m a l l degree of h u n t e r - e f f o r t , and the open water f l o c k i n g h a b i t of the ducks. g6 O i l on the s u r f a c e of the water, d i s c a r d e d by ships at sea, appears to k i l l many b i r d s i n some y e a r s . E l e v e n b i r d s were found dead as a r e s u l t of o i l i n g on a two-miie sample of beach at Boundary bay i n February, 1952, M o r t a l i t y appeared to be g r e a t e s t among old-squaws and American s c o t e r s i n the Vancouver a r e a i n 194-7. No evidence of death as a r e s u l t of l e a d p o i s o n i n g was found d u r i n g the study. Probably l i t t l e l e a d shot i s Ingested because of the deep water f e e d i n g h a b i t s of the d i v i n g ducks. P r e d a t i o n does not appear to be a s e r i o u s f a c t o r of m o r t a l i t y i n the study area d u r i n g the w i n t e r . R e l a t i v e use of f i v e h a b i t a t s by a l l s p e c i e s of d i v i n g ducks was determined, and no s i g n i f i c a n t d i f f e r e n c e i n use was seen on unprotected-sandy, unprotected-rocky and p r o t e c t e d -rocky h a b i t a t s . Bay and e s t u a r i n e , and lake h a b i t a t s appear l e s s important as w i n t e r i n g areas. The t o t a l number counted by s p e c i e s on a l l f i v e h a b i t a t s d u r i n g the study was determined, and i t was seen that s u r f s c o t e r s and g r e a t e r scaup ducks are the most abundant s p e c i e s on these h a b i t a t s . The percentage of the t o t a l number counted by s p e c i e s on each h a b i t a t i s p r e -sented g r a p h i c a l l y . Greater scaup ducks, American golden-eyes, and b u f f l e - h e a d s were found on a l l h a b i t a t s . Redheads, r i n g -necked ducks, danvas-backs, Barrow's golden-eyes, old-squaws, h a r l e q u i n ducks, white-winged s c o t e r s , s u r f s c o t e r s and American s c o t e r s , were c o n s p i c u o u s l y absent from some h a b i t a t s . 87 The data obtained on O b s e r v a t i o n a l Areas 1 to 9> r e p r e -s e n t i n g f i v e h a b i t a t types, were a n a l y s e d i n order to determine i f the d i f f e r e n t s p e c i e s of d i v i n g ducks showed a p r e f e r e n c e f o r c e r t a i n h a b i t a t s . I t was found that o n l y a small popula-t i o n of redheads and ring-necked ducks win t e r i n the study area, and were seen only on lake h a b i t a t . Canvas-backs were not abundant, but were observed on lake and bay and e s t u a r i n e h a b i -t a t s . Greater scaup ducks were abundant on a l l h a b i t a t s , but were not common i n Howe sound and Ind i a n arm. No l e s s e r scaup ducks were seen w i n t e r i n g i n the study area, although one author c i t e d has r e p o r t e d s m a l l numbers p r e s e n t d u r i n g e a r l y winter at Burnaby lake i n 1946. American golden-eyes were com-mon on a l l h a b i t a t s except l a k e s d u r i n g the winte r , and were not common i n Howe sound or Ind i a n arm. Although the d i s t r i b u -t i o n of Barrow's golden-eye i s somewhat s i m i l a r t o t h a t o f the American golden-eye, these b i r d s were not so abundant on the east coast of Vancouver i s l a n d . However, they were very com-mon i n Howe sound and Indian armj two areas where American golden-eyes are not common. P r o t e c t e d areas appear to be the p r e f e r r e d h a b i t a t s f o r b u f f l e - h e a d s . These b i r d s were common i n a l l areas except Indian arm. Old-squaws were not abundant during./the. winter and were most commonly seen i n bay and e s t u a r i n e h a b i t a t and along unprotected rocky shores a t Ganges harbour. H a r l e q u i n ducks were a l s o common a t Ganges harbour and along the east coast of Vancouver i s l a n d from Qualicum r i v e r to Courtenay, gg but o n l y a smal l p o p u l a t i o n was w i n t e r i n g i n the study a r e a . White-winged s c o t e r s and s u r f s c o t e r s were g e n e r a l l y d i s t r i b u t e d over the e n t i r e area, although t h e i r d e n s i t y v a r i e s i n l o c a l a r e a s . White-winged s c o t e r s were abundant i n a l l l o c a l i t i e s except Howe sound and Indian arm. Surf s c o t e r s were, on the other hand, very abundant i n these two i n l e t s , but not as abundant as on the east coast of Vancouver i s l a n d . American s c o t e r s were most common i n the Vancouver area, and were seen o n l y i n the unp r o t e c t e d coast h a b i t a t s . A l l data were analysed to determine the d i s t r i b u t i o n of the sexes f o r each s p e c i e s . The i n t e r p r e t a t i o n o f the p r o -b a b i l i t y v a l u e s obtained f o r the s p e c i e s i s based on observa-t i o n s on l i f e h i s t o r y and behaviour. S u f f i c i e n t data are l a c k i n g f o r redheads, ring-necked ducks, canvas-backs, o l d -squaws, and h a r l e q u i n ducks to i n d i c a t e trends over the e n t i r e w i n t e r . A f t e r December, most s p e c i e s showed s i g n i f i c a n t non-randomness i n the d i s t r i b u t i o n of males and females. T h i s occurred as a r e s u l t of the preponderance of males i n the canvas-back ducks, and a preponderance of p a i r e d ducks i n the other s p e c i e s . A d i f f e r e n t i a l sex m i g r a t i o n d u r i n g the f a l l was e v i -dent i n most s p e c i e s s t u d i e d . The males of Barrow's golden-eye, b u f f l e - h e a d , white-winged s c o t e r , s u r f s c o t e r and American s c o t e r formed the bulk of the e a r l y f a l l migrants. The r e v e r s e s i t u a t i o n was seen i n American golden-*eye, where 89 the females were the predominant' e a r l y f a l l migrants. During March, i t i s b e l i e v e d that some s p e c i e s had s t a r t e d to migrate to the breeding grounds. I t was found t h a t , i f m i g r a t i o n had a c t u a l l y s t a r t e d , o n l y p a i r e d i n d i v i d u a l s had emigrated i n the ring-necked duck, canvas-back, old-squaw, h a r l e q u i n duck, white-winged s c o t e r , s u r f s c o t e r and American s c o t e r s p e c i e s . The data i n d i c a t e that the b u l k of the b u f f l e -head s p r i n g migrants are males. A s i m i l a r s i t u a t i o n occurs i n the American golden-eye s p e c i e s , where e i t h e r dnakes had l e f t the study a r e a f i r s t or only p a i r e d ducks had a r r i v e d from the south. In the Barrow's golden-eye s p e c i e s , i t was i n d i c a t e d that only p a i r e d ducks had l e f t the study a r e a , or o n l y drakes had a r r i v e d from the more s o u t h e r l y w i n t e r i n g grounds. The d a t a d i d not i n d i c a t e t h a t g r e a t e r scaup ducks had s t a r t e d to emigrate i n March. The percentage of J u v e n i l e s i n each s p e c i e s remained low throughout the winter, and redhead, ring-necked duck, canvas-back, old-squaw and h a r l e q u i n duck J u v e n i l e s were not seen. No upward or downward trends i n the percentage of Juven-i l e s was e v i d e n t i n the g r e a t e r scaup duck, American golden-eye, b u f f l e - h e a d and old-squaw. S i g n i f i c a n t i n c r e a s e s and decreases i n the percentages of J u v e n i l e s are seen i n Barrow's golden-eye, white-winged s c o t e r , s u r f s c o t e r and American s c o t e r . The data i n d i c a t e that p o s s i b l y J u v e n i l e b i r d s con-c e n t r a t e i n other l o c a l i t i e s o u t s i d e the study area d u r i n g the w i n t e r . 90 CONCLUSIONS 1. The low winter temperatures i n the study a r e a are w i t h i n the t o l e r a n c e l i m i t s o f most s p e c i e s of d i v i n g ducks. The study area i s probably the no r t h e r n l i m i t of the win-t e r ranges of redheads, ring-necked ducks and canvas-backs. 2. Not a l l s p e c i e s o f d i v i n g ducks are a f f e c t e d by adverse weather c o n d i t i o n s . 3. Abundance and a v a i l a b i l i t y o f food appear to be the two c h i e f f a c t o r s i n f l u e n c i n g d i v i n g duck d i s t r i b u t i o n . Salmon and h e r r i n g spawning, g r a i n e l e v a t o r s and sewer out-f a l l s i n f l u e n c e seasonal d i s t r i b u t i o n of gr e a t e r scaup ducks, American golden-eyes, Barrow's golden-eyes, white-winged s c o t e r s , s u r f s c o t e r s and American s c o t e r s . 4. F a c t o r s r e s p o n s i b l e f o r d a i l y movement and d i s t r i b u t i o n are-weather, t i d e s , d i e l p e r i o d i c i t y , d i s t u r b a n c e s and . c o u r t s h i p a c t i v i t y . 5. The combined e f f e c t s of a l l agencies of m o r t a l i t y does not cause s e r i o u s inroads i n the w i n t e r i n g d i v i n g duck p o p u l a t i o n . 6. A l l s p e c i e s of d i v i n g ducks showed d i f f e r e n c e s i n t h e i r g e n e r a l d i s t r i b u t i o n on the study area, and the data i n d i -cate that they d i f f e r i n t h e i r h a b i t a t p r e f e r e n c e . 91 The sex and a g e . s t r u c t u r e d i f f e r e d i n each s p e c i e s , and j u v e n i l e s comprised o n l y a s m a l l percentage of the w i n t e r -i n g p o p u l a t i o n . A d i f f e r e n t i a l sex m i g r a t i o n occurs i n the f a l l when the bulk o f the migrants are males i n the Barrow's golden-eye, b u f f l e - h e a d , white-winged s c o t e r , s u r f s c o t e r and American s c o t e r s p e c i e s . The e a r l y f a l l American golden-eye mig-r a n t s are predominantly females. I f s p r i n g m i g r a t i o n commences i n March, then the m a j o r i t y of migrants of the ring-necked duck, canvas-back, Barrow's golden-eye, old-squaw, h a r l e q u i n duck, white-winged s c o t e r , s u r f scoter and American s c o t e r s p e c i e s are p a i r e d ducks. The data f o r the American golden-eye and b u f f l e -head i n March, I n d i c a t e that e i t h e r the drakes had l e f t the study area i n g r e a t e r numbdrs than the hens, or there had been a l a r g e i n f l u x o f p a i r e d ducks o f these s p e c i e s i n t o the study a r e a . 9? LITERATURE CITED A l l e e , W. C , A. E. Emerson, 0. Park, T. Park and K. P. Schmidt. 194-7. P r i n c i p l e s of Animal Ecology. P h i l a . and London, Saunders, pp. x i i . 837 i l l u s . Cottam, C. Food H a b i t s of North American D i v i n g Ducks. 1939. U.S.D.A. Tech. B u l l . 64-3. PP» 14-0. C o t t l e , W. H. A study of the Feeding Behaviour of Some Members 194-9. of the Anatinae W i n t e r i n g i n the Lower F r a s e r V a l l e y of B r i t i s h Columbia. Unpubl. B. A. T h e s i s , Univ. of B r i t i s h Columbia, pp. 65. G-riscom, L. Barrow's golden-eye i n Massachusettes. The Auk. 194-5. 62:401-4-05. Hochbaum, H. A. The Canvasback on a P r a i r i e Marsh. The 1944. American W i l d l i f e I n s t i t u t e , Washington, D. C , pp. x i i . 201 i l l u s . K o r t r l g h t , F. H. The Ducks, Geese and Swans of North America. 194-3. The American W i l d l i f e I n s t i t u t e , Washington, D. C., pp. v i i . 476 i l l u s . L i n c o l n , F. c. The E f f e c t of O i l P o l l u t i o n on Waterfowl. Trans. 1st. N. Amer. W i l d l i f e Conf.;555-564. M e t e o r o l o g i c a l D i v i s i o n . Department of T r a n s p o r t - Canada. C l i m a t i c Summaries f o r S e l e c t e d M e t e o r o l o g i c a l S t a t i o n s i n the Dominion of Canada. Volume I . 1952. Monthly Weather Map. January. M o f f i t t , J . 193^. Environmental F a c t o r s A f f e c t i n g Waterfowl i n the Suisun Area, C a l i f o r n i a . The Condor 40s76-84. Munro, D. A. A P r e l i m i n a r y Study qf the Waterfowl of Burnaby 1947. Lake, B r i t i s h Columbia. Unpubl. B. A. T h e s i s , Univ. of B r i t i s h Columbia, pp. 66. i l l u s . Munro,,J. A. 1923. A P r e l i m i n a r y Report on the R e l a t i o n of V a r i o u s Ducks and G u l l s to the Propagation of Sockeye Salmon a t Henderson Lake, Vancouver I s l a n d , B.C 0 The Canadian F i e l d N a t u r a l i s t , 37:107-116. 9S Munro, J . A. Studies of Waterfowl i n B r i t i s h Columbia, Barrow's 1 9 3 9 . Golden-eye, American Golden-eye, Trans, Royal Can. I n s t . 2 2 : 2 5 9 - 3 1 8 . Studies of Waterfowl i n B r i t i s h Columbia, G r e a t e r I 9 4 l . Scaup Duck, Lesser Scaup Duck. Canadian J o u r , Res. D, 1 9 : 1 1 3 - 1 3 8 . S t u d i e s of Waterfowl In B r i t i s h Columbia, B u f f l e -194-2. head. Canadian J o u r . Res. D, 2 0 : 1 3 3 - 1 6 0 . Munro, J . A. and W. A. Clemens. Waterfowl In R e l a t i o n to the 1 9 3 1 . • Spawning of H e r r i n g i n B r i t i s h Columbia. Canada B i o l . Bd, B u l l . 1 7 , pp. 46, i l l u s . Munro, J . A. and I. MoT. Cowan. A Review of the B i r d Fauna of 1 9 4 7 . B r i t i s h Columbia. B r i t i s h Columbia P r o v i n c i a l Museum, V i c t o r i a , S p e c i a l P u b l . No. 2 , pp. 2 8 5 . ' -i l l u s . P a r i z e a u , P. H. D. The E c o l o g i c a l D i s t r i b u t i o n of Marine I 9 4 l . Organisms at Gonzales P o i n t and P a c o f i on the B r i t i s h Columbia Coast. Unpubl. B. A. T h e s i s Univ. of B r i t i s h Columbia, pp. 1 3 9 . i l l u s . Racey, K. E f f e c t of F u e l O i l on Sea B i r d s . 1 9 3 0 . The M u r r e l e t . 1 1 : 2 2 . R i c k e t t s , E. F. and J . C a l v i n . Between P a c i f i c T i d e s . S t a n f o r d 1 9 3 9 . U n i v e r s i t y Press, pp. x x i l . 3 2 0 . i l l u s . Schorger, A. W, The Deep D i v i n g o f the Loon and Old-squaw and 1 9 4 7 . i t s Mechanism. Wilson B u l l . 5 9 : 1 5 1 - 1 5 9 . Snedecor, G. W. S t a t i s t i c a l Methods. The Iowa State C o l l e g e 1 9 4 6 . P r e s s , Ames, Iowa. pp. x v i . 4-85 i l l u s . Wright, P. L. American Goldeneye Feeding on Salmon Eggs, 1944-. The Condor. 4 - 6 : 1 2 6 - 1 2 7 . D I S T R I B U T I O N AND D E N S I T Y O F W I N T E R I N G DIVING D U C K S IN S T U D Y A R E A , S O U T H E R N B R I T I S H C O L U M B I A 1- lgure 20. O L D S Q U A W B U F F L E - H E A D R I N G - N E C K E D DUCK WHITE-WINGED S C O T E R S U R F S C O T E R A M E R I C A N S C O T E R sma l l s y m b o l s = 5 0 ducks large symbols = 3 0 0 ducks D I S T R I B U T I O N A N D D E N S I T Y * O F W I N T E R I N G DIVING D U C K S IN S T U D Y A R E A , S O U T H E R N B R I T I S H C O L U M B I A 

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