in driftlines (Naumann 1896-1905 in Cramp et al. 1977). They feed largely by 

 day but apparently sometimes feed at night and at dawn and dusk (Palmer 1976b). 



Like the Black Scoter, White-winged Scoters feed primarily on animal life, 

 principally molluscs and crustaceans. Cottam (1939 jLn Palmer 1976b) summarized 

 food habits in North America and found that this scoter ate about 75% molluscs 

 and about 13% crustaceans. Molluscs eaten include olive shells ( Olivella pycna ) , 

 dog whelks ( Nassarius fossatus ), blue mussels ( Mytilus edulis ), jacknife clams 

 ( Solon solarius ) , cockles ( Cardium ) , snails ( Physa ) , scallops, and oysters. 

 Crustaceans eaten include crabs (e.g., Cancer , Carcinus ) , isopods, amphipods, 

 shrimp, and crayfish. 



White-winged Scoters also eat insects (e.g., caddisfly larvae, grasshop- 

 pers), echinoderms (sand dollars, sea-urchins, brittle stars, starfish, heart- 

 urchin), annelids (Polychaetes) , and fish and their eggs. They have also been 

 known to eat frogs but apparently eat these, as well as fish, relatively rare- 

 ly (authors cited in Bellrose 1976, Palmer 1976b, Cramp et al. 1977). 



Which foods are most important in the diet varies from area to area. In 

 different studies, blue mussels, rock clams ( Cancer irroratus ), Atlantic dog- 

 winkle, ( Thais or Nucella lapillus ) , Atlantic razor clams ( Ensis or Siliqua 

 costata ) , and Arctic wedge clams ( Mesodesma arctatum ) , cockles ( Cardium edulis ) 

 (authors cited in Bellrose 1976, Palmer 1976b), and slipper shells ( Crepidula 

 f ornicata ) (Hof f 1977) have been the principal foods eaten. 



Plants eaten include pondweeds (e.g., Zostera , Potamogeton , Ruppia , Val - 

 lisneria ) , and sea lettuce ( Ulva ) (Palmer 1976b). 



We have no quantitative information on the food habits of White-winged 

 Scoters in southeastern waters. They presumably feed on the foods indicated 

 above. Palmer (1976b) and Cramp et al. (1977) provided more extensive lists 

 of foods eaten, as well as references to the primary literature dealing with 

 the food habits of the White-winged Scoter. 



SUSCEPTIBILITY TO OIL POLLUTION 



White-winged Scoters appear to be highly susceptible to oil pollution. In 

 North America, oil-related deaths of these ducks have been recorded since the 

 1930's. In 1937, they were among the most frequently encountered victims of an 

 oil pollution incident in San Francisco Bay, California (Aldrich 1938, Moffitt 

 and Orr 1938, both Ln Vermeer and Vermeer 1974). It was also one of the most 

 numerous victims of an oil spill in the same area in 1971 (Small et al. 1972, 

 Table 10). Following the grounding of the freighter SEAGATE off the Olympic 

 Peninsula in Washington, White-winged Scoters and Common Murres were the two 

 species hardest hit by the subsequent oil spill (Richardson 1956, LaFave 1957, 

 both ^n Vermeer and Vermeer 1974). There is also evidence of high oil-related 

 mortality in the Old World. In a review of oil spills in Danish waters from 

 1953 to 1968, Joensen (1972a) listed this species as one of the most frequent 

 victims; in the same area, most of the world's largest wintering population was 

 lost to oil pollution in 1972 (Joensen 1972a). 



382 



