Food Habits of the Whiskered Auklet at Buldir Island, Alaska

Abstract

We studied the food habits of Whiskered Auklets (Aethia pygmaea) at Buldir Island, western Aleutian Islands, Alaska, during the summer of 1976. At Buldir, these birds fed primarily in and near convergent tidal fronts in the passes between three islets just offshore; feeding occurred throughout the day. Whiskered Auklets ate at least 10 different species of zooplanktonic prey, of which the copepod Neocalanus plumchrus was the most important. Next in importance were chaetognaths (probably Sagitta elegans), the amphipod Parathemisto pacifica, megalopae of the crab Erimacrus isenbeckii, and an unidentified amphipod. Pteropods (probably Limacina helicina), larval cephalopods, and a larval fish occurred in trace amounts. During most of the summer, Whiskered Auklets were nearly monophagous on N. plumchrus; we do not consider a difference in prey during late incubation/early chick rearing to represent a biologically-significant trend. We collected Least (A. pusilla), Crested (A. cristatella), and Parakeet (Cyclorrhynchus psittacula) auklets during late chick rearing, to compare their food habits with those of Whiskered Auklets. At this time, both Least and Whiskered auklets were monophagous on smaller N. plumchrus, whereas Crested and Parakeet auklets mainly ate larger N. cristatus and P. pacifica; Parakeet Auklets ate the widest diversity of zooplankton. Selection of prey by the four auklet species appeared to occur in relation to size, with the smaller auklets eating smaller zooplankters.