Ferruginous Duck

Ferruginous Duck (Aythya nyroca) is a compact diving duck, rich chestnut in males with a white eye and clean white undertail. 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 favours shallow, well-vegetated freshwater, diving for aquatic plants, seeds and invertebrates and nesting among reeds. 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. The Korean vertebrate catalogue used for this guide records the species in South Korea (Wikipedia, general species account; Wildlife of Korea occurrence records).