Food and populations of Surf Scoters in British Columbia

Abstract

Population densities and the food of Surf Scoters Melanitta perspicillata were investigated on the British Columbia coast. Surf Scoters are the most numerous marine birds there in autumn and spring. Six hundred and fifty thousand were estimated in March 1978. The principal food is the mussel Mytilus edulis except for about three weeks in spring when herring eggs form the main diet. Many thousands of ducks, cormorants, gulls and grebes also feed on herring and their eggs. Other mussel-eating ducks in British Columbia are Black Scoters Melanitta nigra and Barrow's Goldeneyes Bucephala clangula. In the fjords Barrow's Goldeneyes and Surf Scoters feed chiefly upon 0.1-1 cm sized mussels attached to the fjord walls. Mussel and herring spawn daily intakes of Surf Scoters are estimated.