White-winged Scoter

White-winged Scoter (Melanitta deglandi) is a large sea duck with bold white wing patches; males also show a white eye mark and swollen orange-tipped bill. The combination of body shape, bill structure, plumage pattern and voice provides the most useful field characters. Age, sex and season can alter its appearance, so identification should use several features rather than colour alone. This supports comparison with similar species in the field (Wikipedia, general species account).

It breeds on boreal lakes and winters along coasts, diving for molluscs, crustaceans and other benthic prey. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds more likely to gather where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant, visitor or introduced bird (Wikipedia, general species account; Wildlife of Japan occurrence records).