Knob-billed Duck

The knob-billed duck, or African comb duck, is a distinctive species, one of the largest ducks, with a length ranging from 56 to 76 cm, a wingspan of 116 to 145 cm, and a weight between 1.03 to 2.9 kg. The adult's head is white with dark spots, and it has a pure white neck and underparts. The upperparts are a glossy blue-black with iridescent blue and green on the secondaries. The male is notably larger than the female and sports a prominent black knob on the bill.

Identification Tips

When identifying the knob-billed duck, look for the unique black knob on the male's bill and the size difference between sexes. The white head with dark spots, white neck, and underparts, as well as the iridescent blue-black upperparts, are key features. Juveniles present a duller buff coloration below with brown upperparts and are often seen with adults, aiding identification.

Habitat

This species thrives in still freshwater environments such as swamps and lakes within tropical regions. It is largely sedentary, dispersing only in response to the wet season's conditions.

Distribution

The knob-billed duck is found across the tropical and subtropical wetlands and waterways of Sub-Saharan Africa, Madagascar, South Asia, and mainland Indochina.

Behaviour

These ducks are often seen in flocks, which can number up to 100 in the dry season. They may separate by sex and are known to perch in trees. They feed on vegetation, small fish, invertebrates, and seeds, sometimes becoming a nuisance to rice farmers.

Song & Calls

The knob-billed duck is typically silent, but may emit a low croak when disturbed or flushed.

Breeding

Breeding occurs during or after the rainy season, with nesting primarily in tree holes or tall grass. Males may be polygynous, defending females and young but not the nest sites. Clutches consist of 7 to 15 yellowish-white eggs.

Similar Species

The knob-billed duck can be confused with the comb duck, but it is generally larger with lighter flanks. The immature plumage may resemble that of the cotton pygmy goose, but size and hue differences, as well as the presence of adults, aid in differentiation.

Diet and Feeding

Knob-billed ducks graze or dabble for vegetation and also consume small fish, invertebrates, and seeds. They can adapt to various feeding environments but may impact rice cultivation.

Conservation status

Although local populations may be declining, the knob-billed duck's extensive range keeps it from being globally threatened. It is classified as Least Concern by the IUCN and is protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds.