Knob-billed Duck

Identification

The knob-billed duck is one of the largest duck species and is unmistakable in adult plumage. Adults display striking white heads freckled with dark spots, pure white necks and underparts, contrasting sharply with glossy blue-black upperparts that shimmer with bluish and greenish iridescence, particularly visible on the secondary feathers. Males are considerably larger than females and feature a distinctive large black knob on the bill—the species' namesake feature. Length ranges from 56 to 76 centimetres with a wingspan of 116 to 145 centimetres.

Young birds are considerably duller, with buff-coloured faces and necks, dull brown upperparts, and greyish underparts. Immature knob-billed ducks may superficially resemble large female cotton pygmy geese, though they are rarely encountered without adults nearby, making field identification straightforward. The species is remarkably silent, producing only a low croak when flushed.

Range & Habitat

The knob-billed duck inhabits tropical and sub-tropical wetlands across Sub-Saharan Africa, Madagascar, most of South Asia, and mainland Indochina. This species favours still freshwater swamps and lakes in tropical regions and is largely resident throughout its range, though it disperses widely during the wet season.

Behaviour & Diet

Knob-billed ducks are highly social waterfowl, typically encountered in flocks that vary seasonally—small groups during the wet season swelling to flocks of up to 100 birds during the dry season, sometimes segregating by sex. These unusual ducks frequently perch in trees, an atypical behaviour among duck species. They feed primarily on vegetation through grazing and dabbling, supplemented by small fish, invertebrates, and seeds. In agricultural areas, they can become problematic for rice farmers due to their feeding habits.

Best Time & Places to See It

The knob-billed duck breeds during and after the rainy season across its range, with breeding success dependent on adequate rainfall. The best viewing opportunities occur during the dry season when birds congregate in larger flocks at traditional wetland sites. Look for them on still freshwater lakes and swamps, and scan nearby trees where they often perch. Birds are more dispersed during wet season months when breeding occurs.

Photography Tips

The bold contrast between the white head and neck and the glossy dark upperparts makes the knob-billed duck visually striking for photography. Males' prominent knobs are particularly photogenic and serve as useful identifying features. The iridescent sheen on the secondaries is best captured in good lighting conditions. Photograph flocking birds during the dry season from a distance to avoid flushing them, and watch for perching birds in emergent trees, which offer opportunities for unique compositional angles. Patience will reward you with images of these large, distinctive waterfowl in their natural habitat.