Bubulcus ibis
Rare visitor: recorded only occasionally in this country
Western Cattle Egret (Bubulcus ibis) is a compact white heron with a short yellow bill and buff-orange plumes on the head, breast and back during breeding. 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 commonly forages in pasture and cultivated ground beside grazing animals, catching insects and other prey disturbed by their movement, and nests in mixed waterbird colonies. 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).