Sakhalin Leaf Warbler

Sakhalin Leaf Warbler (Phylloscopus borealoides) is a small olive-green leaf warbler with pale underparts, a strong pale eyebrow and two light wing bars. 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 temperate forest on Sakhalin, the Kuril Islands and Japan, gleaning insects from foliage and migrating south to the Amami and Okinawa islands and Indochina for winter. 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).