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Annual variation in the foraging behaviour of thick-billed murres in relation to upper-ocean thermal structure around St. George Island, Bering Sea

TitleAnnual variation in the foraging behaviour of thick-billed murres in relation to upper-ocean thermal structure around St. George Island, Bering Sea
Publication TypeJournal Article
Year of Publication2010
AuthorsKokubun, N, Takahashi, A, Ito, M, Matsumoto, K, Kitaysky, AS, Watanuki, Y
JournalAquatic Biology
Volume8
Pagination289–298
Abstract

We studied the foraging behaviour of adult thick-billed murres Uria lomvia as theyreared their chicks at St. George Island, Alaska, USA, relative to the thermal structure of the nearbyocean water column in the summers 2004, 2006, and 2007 using data recorders attached to the birds.The thermal structure of the upper ocean varied substantially among the years. Satellite-derived seasurface temperature (SST) and water temperature at depths >40 m were higher in 2004 than in 2006and 2007 (9.1, 8.3 and 7.8°C for mean SST; 5.1, 4.4, and 2.2°C for median bottom temperature, respectively).We recorded a strong thermocline in 2004 and 2007, but not in 2006. Nonetheless, the thermoclinewas one of the important foraging habitats in all years. The foraging behaviour of thick-billedmurres appeared to vary with annual variation in the intensity of the thermocline and water temperatureat depth and evidently with associated vertical distribution of prey. Birds spent more time foragingin stratified waters and dived to around thermocline depth (and deeper in 2007) in 2004 and 2007.However, the birds used both stratified and mixed waters in 2006 and were less likely to dive to thermoclinedepth. Main prey items delivered to chicks varied among years. Sandlance (53% of observeditems) and pollock (23%) predominated in 2004, compared with cephalopods (23%), flatfishes

DOI10.3354/ab00243
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