Fall Distribution of Pelagic Birds over the Shelf off SW Vancouver Island

Abstract

-The distribution of pelagic birds was investigated over the continental shelf off southwestern Vancouver Island in September and October of 1986 and 1987. The California Gull (Larus californicus) had higher densities (average 61 birds/km) than all other birds combined and most gulls occurred in few but relatively large flocks near fish trawlers over offshore banks and the outer continental shelf. California Gulls were seen at more locations and in much smaller flocks in nearshore waters than further seaward. Glaucouswinged Gulls (L. glaucescens), Cassin's Auklets (Ptychoramphus aleuticus) and Common Murres (Uria aalge) occurred more in nearshore waters, while Sabine's Gulls (Xema sabini) and Sooty Shearwaters (Puffinus griseus) occurred mostly over the mid shelf. Pink-footed Shearwaters (P. creatopus) were generally observed to be further from shore than were Sooty Shearwaters. Northern Fulmars (Fulmarus glacialis) were most abundant in the deepest waters (100-200 m) and Common Murres in the most shallow waters (<60 m). The distribution of pelagic birds over the shelf is discussed in relation to that of their diet and the presence of trawlers. Received 4 November 1988, accepted 31 March 1989.