Inter-colony differences in the incubation pattern of streaked shearwaters in relation to the local marine environment

Foraging trip duratiom of breeding seabirds is affected by characteristics of available feeding habitat in the marine environment, which may in turn, generate inter-colony difference in the patterns of nest attendance. Here, nest attendance patterns and foraging areas of Streaked Shearwaters (Calonectris leucomelas) during their incubation period were examined using global location sensors. The study was conducted at Sangan (SI) and Mikura Islands (MI) in the northwstern Pacific, and Awa Island (AI) in the Japan Sea during 2006-2009. The duration of incubation shifts showed significant inter-colony difference, but no sex-related difference. Shearwaters from SI had shorter mean incubation shifts (5.6 days on average; range 3.0-8.0 days) than those from MI (7.2 days; range 4.8-10.7 days) adn AI (6.9 days;range 6.0-9.7 days). During the incubation period, Si adn MI shearwaters foraged in the northwestern Pacific's Kuroshio-Oyashio transition area, while shearwaters from AI mostly foraged in the Japan Sea.