Band-rumped Storm Petrel

Band-rumped Storm Petrel (Hydrobates castro) is a dark oceanic storm petrel with a broad white rump and a square-ended or slightly notched tail. 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 over warm seas by taking planktonic animals and small fish near the surface, and nests in burrows or crevices on isolated 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).