Pallas's Grasshopper Warbler

Pallas's Grasshopper Warbler (Locustella certhiola) is a streaked brown grasshopper warbler with a rufous rump, pale-tipped tail and strongly patterned upperparts. 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 central Asia east to the Sea of Okhotsk region, remains low in marsh and dense grass while hunting insects and migrates from the eastern Palearctic to India and Indonesia. 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).