Buller's Shearwater

Buller's Shearwater (Ardenna bulleri) is a grey-backed shearwater with a bold dark M-shaped upperwing pattern and contrasting white underparts. 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 breeds on islands near New Zealand, migrates widely through the Pacific and feeds on fish, squid and krill taken at the surface or during shallow dives. 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).