Common Yellowthroat

Common Yellowthroat (Geothlypis trichas) is a small New World warbler with olive upperparts and yellow throat; adult males have a broad black mask edged above with grey. 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 inhabits marshes, wet thickets and dense low vegetation across North America, gleaning insects close to the ground; northern birds migrate to the southern breeding range, Central America and the West Indies. 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).