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Foraging behavior of incubating and chick-rearing thick-billed murres Uria lomvia

TitleForaging behavior of incubating and chick-rearing thick-billed murres Uria lomvia
Publication TypeJournal Article
Year of Publication2010
AuthorsIto, M, Takahashi, A, Kokubun, N, Kitaysky, AS, Watanuki, Y
JournalAquatic Biology

The varying demands associated with egg incubation and chick-rearing are known tohave a corresponding effect on the foraging behavior of seabirds. We deployed data loggers on incubatingand chick-rearing thick-billed murres Uria lomvia to examine differences in their divingbehavior and characteristics of habitats used for foraging. To compare diets of incubating and chickrearingbirds we collected their stomach contents using a water offloading technique. We found thatincubating birds performed longer foraging trips than chick-rearing birds (incubating: 19.0 ± 7.2 h;chick-rearing: 9.9 ± 5.6 h). Incubating birds foraged in the offshore stratified water masses (sea surfacetemperature [SST] > 9°C) and frequently dived to the depth of the thermocline (20 to 50 m).Chick-rearing birds spent more time foraging in the inshore, well-mixed water masses (SST < 8°C),and at depths >60 m. Small juvenile walleye pollock Theragra chalcogramma, squid and euphausiidswere the dominant prey of incubating and chick-rearing birds. Distributions of these small preywere commonly associated with the thermocline, while larger fish, which parents brought back tofeed their chicks, were distributed below the thermocline. Results suggest that incubating murresmainly foraged at shallow depths near the thermocline with higher concentrations of small prey,while chick-rearing murres feed their chicks large prey caught on deep dives while feeding themselveson small prey caught on shallow dives.

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