Knob-billed Duck

The knob-billed duck is one of the largest ducks, 56–76cm long with a wingspan of 116–145cm and a weight of 1.03–2.9kg. Adults have a white head freckled with dark spots, a pure white neck and underparts, and glossy blue-black upperparts with blue and green iridescence on the secondaries. The male is much larger than the female and carries a large black knob on the bill. Young birds are dull buff and brown and can look like a large, greyish female cotton pygmy goose (Wikipedia, general species account).

It breeds in still freshwater swamps and lakes in the tropics and is largely resident apart from dispersal in the wet season. It grazes or dabbles for plants and takes smaller amounts of small fish, invertebrates and seeds, and often perches in trees. Flocks are small in the wet season and larger in the dry season. Across its range it nests mainly in tree holes, a male may have several mates, and females lay 7–15 eggs. In India it is resident; SoIB 2023 finds its trends uncertain and rates it a Low conservation priority (Wikipedia, general species account; SoIB 2023).