Knob-billed Duck

The Knob-billed Duck, also called the Comb Duck, is a large and widespread waterfowl species found across tropical wetlands in Africa, South Asia, and South America. Its striking black-and-white plumage and, in breeding males, an enlarged fleshy knob atop the bill make it one of the more distinctive ducks of its range.

Unlike many ducks, this species shows a marked size difference between the sexes, with males considerably larger and bearing the namesake knob, which becomes more prominent during the breeding season.

• Upperparts are glossy blackish with green and bronze iridescence on the back and wings
• Head and neck are white, densely speckled or spotted with black, especially on the crown
• Underparts are white, sometimes with a faint buff wash on the flanks
• Bill in breeding males has a large black fleshy knob at the base, absent or much reduced in females
• Distinguished from other African, Asian, and South American waterfowl by the combination of glossy black upperparts, speckled white head, and (in males) the bill knob

Adult males are notably larger than females and develop the characteristic bill knob, most pronounced during the breeding season, along with glossy black upperparts and a heavily speckled white head. Females are smaller, lack the bill knob, and show a somewhat duller version of the same black-and-white pattern. Juveniles are browner and less contrastingly patterned before molting into adult plumage.

This species inhabits freshwater wetlands, floodplains, slow rivers, and seasonal pools across sub-Saharan Africa, South and Southeast Asia, and parts of South America, favoring areas with nearby trees for roosting and nesting. It is largely resident but shows local and seasonal movements tied to water availability, particularly in monsoon and flood-pulse regions.

Knob-billed Ducks feed on seeds, aquatic vegetation, and invertebrates, dabbling and grazing in shallow water and on adjacent land. They nest in tree cavities or dense vegetation near water, sometimes using large stick nests built by other birds. The species is relatively quiet, with low grunting or whistling calls, and often roosts and forages in mixed flocks with other waterfowl.