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Marine Ecology Progress Series

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MEPS 424:191-204 (2011)  -  DOI: https://doi.org/10.3354/meps08973

Foraging areas of streaked shearwaters in relation to seasonal changes in the marine environment of the Northwestern Pacific: inter-colony and sex-related differences

Takashi Yamamoto1,*, Akinori Takahashi1,2, Nariko Oka3, Takahiro Iida1,2, Nobuhiro Katsumata4, Katsufumi Sato4, Philip N. Trathan5

1Department of Polar Science, The Graduate University for Advanced Studies, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
2National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
3Yamashina Institute for Ornithology, 115 Konoyama, Abiko, Chiba 270-1145, Japan
4International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo,
2-106-1 Akahama, Otsuchi, Iwate 028-1102, Japan
5British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK

ABSTRACT: As the spatial distribution of marine organisms is often affected by seasonal changes, pelagic seabirds may change their foraging areas in response to seasonal changes in the marine environment. Here, we examined the foraging area of streaked shearwaters Calonectris leucomelas, breeding at Sangan (SA) and Mikura Islands (MK), Japan, from spring to summer during pre-laying and incubation periods. Those colonies are located at the north and south of the Northwestern Pacific’s Kuroshio-Oyashio transition area where high seasonal temperature changes are observed, and where, consequently, birds may show comparable responses to such changes. Our results showed that streaked shearwaters from both colonies shifted their foraging areas northwards as the season progressed. The seasonal shift of foraging areas appeared to coincide with the movement pattern of pelagic fishes that migrate northward in association with the increase in water temperature. However, the pattern of seasonal movement differed between the 2 colonies; shearwaters from SA moved their foraging area along the coastal area of the Kuroshio-Oyashio transition, while those from MK moved along the Kuroshio Extension. Our results also indicated sex-related differences in this general pattern: females showed clear seasonal changes in foraging area, while males did not. During the pre-laying period males returned to the colony frequently to defend their nests or mates, and spent less time at sea. Our results suggest that streaked shearwaters changed their foraging areas in response to seasonal changes in the marine environment, although colony location and sex-related differences in reproductive roles may constrain the birds’ responses to seasonal change.


KEY WORDS: Streaked shearwaters · Northwestern Pacific · Seasonal change · Foraging · Kuroshio · Sex-related difference · Pre-laying


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Cite this article as: Yamamoto T, Takahashi A, Oka N, Iida T, Katsumata N, Sato K, Trathan PN (2011) Foraging areas of streaked shearwaters in relation to seasonal changes in the marine environment of the Northwestern Pacific: inter-colony and sex-related differences. Mar Ecol Prog Ser 424:191-204. https://doi.org/10.3354/meps08973

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