Matsudaira's Storm Petrel

Matsudaira's Storm Petrel (Oceanodroma matsudairae) is a large dark storm petrel with long pointed wings, a forked tail and pale shafts showing on the outer primaries. 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 forages over the north-western Pacific for planktonic animals, fish and squid, and returns to the Bonin Islands to breed in burrows and rocky cavities. 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).