Canvasback

Canvasback (Aythya valisineria) is a large North American diving duck with a long sloping forehead; males have red heads, black chests and pale backs. 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 dives on deep marshes and lakes for tubers, seeds and aquatic animals, especially wild celery where available. 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).