@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Zoology, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Mitchell, George Joseph"@en ; dcterms:issued "2012-02-24T20:56:09Z"@en, "1952"@en ; vivo:relatedDegree "Master of Arts - MA"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """From September, 1951, until March 1952, field work was carried on to determine the distribution of wintering diving ducks on the coastal waters of southern British Columbia, and an attempt was made to discover and evaluate the factors causing distribution and movement. Diving ducks are influenced by the availability of food and other factors related to this availability. These factors include salmon and herring spawning, grain elevators, sewer outfalls, and changing tides. Local movements result from courtship activity, diel periodicity and disturbing agencies. Mortality factors, including hunting, oiling, predation and lead poisoning did not cause serious Inroads in the wintering diving duck population during the study. Lake, and bay and estuarine habitats were found to be less important wintering areas than habitats along protected and unprotected coastline. All species of diving ducks showed preference for certain habitats and regions in the study area, and were absent or uncommon in others. During the winter, the drakes and hens of most species were distributed non-randomly because of the preponderance of males and their tendency to flock together. In early spring the sexes were distributed non-randomly due to pair formation and predominance of drakes. A differential sex migration was evident in most species of ducks during late fall and early spring. Only a small percentage of juveniles of all species were wintering on the study area, indicating that they possibly winter in other localities."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/40912?expand=metadata"@en ; skos:note "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 a> 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 "@en ; edm:hasType "Thesis/Dissertation"@en ; edm:isShownAt "10.14288/1.0106560"@en ; dcterms:language "eng"@en ; ns0:degreeDiscipline "Zoology"@en ; edm:provider "Vancouver : University of British Columbia Library"@en ; dcterms:publisher "University of British Columbia"@en ; dcterms:rights "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en ; ns0:scholarLevel "Graduate"@en ; dcterms:title "A study of the distribution of some members of the Nyrocinae wintering on the coastal waters of southern British Columbia."@en ; dcterms:type "Text"@en ; ns0:identifierURI "http://hdl.handle.net/2429/40912"@en .