Asian House Martin

Asian House Martin (Delichon dasypus) is a compact blue-black and white martin with a conspicuous white rump and pale grey 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 catches insects in flight over mountains and settlements and breeds colonially in enclosed mud nests beneath cliffs or buildings, migrating from central and eastern Asian breeding areas to lower latitudes or elevations. 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).