Lesser Scaup

Lesser Scaup (Aythya affinis) is a small North American diving duck; males have a peaked dark head, pale grey back and white flanks. 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 northern ponds and marshes and winters on lakes, reservoirs and coasts, diving for plants and invertebrates. 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).