Booted Warbler

Booted Warbler (Iduna caligata) is a small plain sandy-brown warbler with pale underparts, a short pale eyebrow and a relatively flat forehead. 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 scrub and open country across eastern Europe and western Asia, searches low vegetation for insects and migrates to South Asia, with wandering birds occasionally reaching far beyond the normal route. 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).