Radde's Warbler

Radde's Warbler (Phylloscopus schwarzi) is a sturdy brownish leaf warbler with a long strong bill, prominent buff eyebrow and warm buff undertail coverts. 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 Siberian scrub and open forest, feeds on insects close to the ground in thick vegetation and migrates to Southeast Asia for winter, occasionally wandering far west. 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).