Spectacled eiders (Somateria fischeri) winter among leads in the Bering Sea pack ice, where they dive 40-70 m for benthic prey. During the first icebreaker cruises into that area, esophagi of collected eiders contained only clams, mostly Nuculana radiata, with no trace of the once-dominant Macoma calcarea. Alternative prey used elsewhere (snails, amphipods, other bivalves) were available but not eaten. Eiders ate mainly N. radiata 18-24 mm long, although M. calcarea of this length contained 62% more energy. Percent body lipid of eiders averaged 12+/-3% (SD) for 26 adult males and 14+/-3% for 12 adult females. Mean body mass (+/-SE) of these males in late March (1,688+/-21 g) was higher than reported for 53 males after arriving at breeding areas in late May (1,494+/-14 g). Body mass of these females (1,550+/-35 g) was lower (but not significantly) than reported for 11 females upon arrival at breeding sites (1,623+/-46 g). In 1999, the last spectacled eiders left the wintering area on 21 April, 4-8 weeks before their typical arrival at breeding sites. Their location is unknown in the interim, when habitats used appear critical to acquiring reserves for reproduction.
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