Black-winged Petrel

Black-winged Petrel (Pterodroma nigripennis) is a small grey-and-white gadfly petrel with a conspicuous dark diagonal bar across each upperwing. 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 ranges through tropical and subtropical Pacific waters, feeds on squid, fish and crustaceans and nests in burrows on oceanic islands. 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).