Wedge-tailed Shearwater

Wedge-tailed Shearwater (Puffinus pacificus) is a large tropical shearwater with a long wedge-shaped tail and both pale-bellied and uniformly dark plumage forms. Body shape, bill structure, plumage pattern and voice provide the strongest field characters. Age, sex and season may alter its appearance, so identification should combine several features and careful direct field comparisons with similar species in the same habitat (Wikipedia, general species account).

It feeds on fish and squid across warm oceans, often associating with feeding schools, and nests in burrows at island colonies. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds gathering where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant or visitor (Wikipedia, general species account; Wildlife of Japan occurrence records).