M. V. Flint1, 2 and A. N. Golovkin†
1Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, 117851 Russia
2 Institute of Marine Sciences, School of Fisheries and Ocean Sciences,
University of Alaska Fairbanks, Fairbanks, AK, USA
Received March 11, 2002
Abstract—The diet of Least Auklets, Aethia pusilla, was examined in two neighboring breeding colonies (Tol-
stoi Point and Zapadni Point) at Saint Paul Island, eastern Bering Sea. Different copepod species were the most
common prey of the birds from the two colonies. Neocalanus plumchrus s.l. CV predominated in birds at Tol-
stoi Point (85.0% of food mass) while N. cristatus CV predominated in birds at Zapadni Point (90.0% of food
mass). Comparisons with the results obtained from zooplankton sampling in the vicinity of Saint Paul Island suggest
that Least Auklets from the two neighboring colonies used different foraging sites. The birds from Tolstoi Point per-
formed shorter foraging flights to the outer shelf domain where they collected smaller copepods (5.3 mg of wet
weight) in larger numbers (556 copepods per bird). Least Auklets from Zapadni Point flew a longer distance to the
shelf break area. These birds preyed on copepods, which have a body mass three times bigger (18.5 mg of wet
weight), and collected smaller amounts of prey (168 copepods per bird) to obtain a full food load. The differences in
the feeding behavior of Least Auklets from the neighboring colonies allow spatial partitioning in the use of different
food resources and must result in the reduction of local intraspecific and interspecific competition for food.
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