Black-browed Reed Warbler

Black-browed Reed Warbler (Acrocephalus bistrigiceps) is a small warm-brown reed warbler with a bold pale eyebrow topped by a narrow black stripe. 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 from eastern Mongolia and Russia through China to Japan, foraging low inside undisturbed reedbeds for insects and migrating to Southeast Asia for the non-breeding season. 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).