Common Chiffchaff

Common Chiffchaff (Phylloscopus collybita) is a small greenish-brown leaf warbler with off-white underparts, a pale eyebrow and dark legs, named for its repeated chiff-chaff song. 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 breeds in open woodland across northern and temperate Eurasia, gleans insects from foliage, places a domed nest near the ground and migrates toward southern Europe, Asia and North Africa. 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).