Japanese Bush Warbler

Japanese Bush Warbler (Horornis diphone) is a plain olive-brown warbler with a long pale eyebrow, rounded wings and a tail often held slightly raised. 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 stays low in dense scrub, bamboo and forest undergrowth, feeding on insects and remaining much easier to detect by the male's distinctive spring song than by sight across much of Japan. 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).