Pacific Swift

Pacific Swift (Apus pacificus) is a dark, sickle-winged swift with a white rump, scaled underparts and a slightly forked 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 spends most daylight hours airborne catching insects and nests colonially in cliff and building crevices across eastern Asia. 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).