Winter ecology and diet of Ancient Murrelets off Victoria, British Columbia

We studied Ancient Murrelets (Synthliboramphus antiquus) in coastal areas near Victoria, British Columbia, by means of small-boat transects and collected birds to examine stomach contents and body weights during the winters of 1977–1979. The diet was composed almost entirely of adult Euphausia pacifica, except in November 1978, when herring were also common. Numbers of murrelets recorded on the water per kilometre travelled correlated with tidal amplitude, suggesting that tidal mixing affected prey availability. Body weights were high compared with those of breeding birds, peaking in January, when stomachs contained the maximum number of prey organisms. Dives were brief. Feeding intensity, or food availability, may reach a maximum in midwinter.