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Comb Duck Picture

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The Comb Duck (Sarkidiornis melanotos), formerly known as the Knob-billed Duck, is an unusual, pan-tropical duck, found in tropical wetlands in South America, sub-Saharan Africa, Madagascar and south Asia from Pakistan to Laos and extreme southern China. It is a vagrant to Trinidad.

It is the only species of the genus Sarkidiornis (the supposed "Mauritian Comb Duck" was a misidentification of the Mauritian Shelduck).

Description Female at Santragachi in Kolkata, West Bengal, India. Female at Santragachi in Kolkata, West Bengal, India.

This common species is unmistakable. Adults have a white neck, head and underparts, and glossy blue-black upperparts. The head is freckled with dark spots. The male is larger than the female, and has a large black knob on the bill. Young birds are brown above and buff below (Madge and Burn 1987, Zimmerman et al. 1999).

South American birds, S. m. sylvicola, are smaller and have black flanks; Old World birds, S. m. melanotos, have light grey flanks (Madge and Burn 1987).

The Comb Duck is silent except for a low croak when flushed (Zimmerman et al. 1999).

Range and habitat

It breeds in still freshwater swamps and lakes the tropics. It is largely resident, apart from dispersion in the wet season. (Madge and Burn 1987).

The Comb Duck is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

Feeding and behavior

This duck feeds on vegetation by grazing or dabbling (Madge and Burn 1987) and to a lesser extent on small fish, invertebrates, and seeds. It can become a problem to rice farmers (Honolulu Zoo).

In addition to feeding in shallow water and on land, Comb Ducks often perch in trees. They are typically seen in flocks (Zimmerman et al. 1999, Honolulu Zoo), small in the wet season, up to 100 in the dry season. Sometimes they separate according to sex (Honolulu Zoo).

Reproduction Male Common Comb Duck

African birds breed during and after the rainy season and may not breed if the rain is scanty (Honolulu Zoo). Comb Ducks nest mainly in tree holes (Madge and Burn 1987), also in tall grass. They line their nests with reeds, grass, or feathers, but not down (Honolulu Zoo).

Males may have two mates at once or up to five in succession. They defend the females and young but not the nest sites. Unmated males perch in trees and wait for opportunities to mate (Honolulu Zoo).

Females lay 7 to 15 (Madge and Burn 1987) yellowish-white eggs. Several females may lay in a single "dump nest" containing up to 50 eggs (Honolulu Zoo).


Uncertainty surrounds the correct systematic placement of this species. Initially, it was placed in the dabbling duck subfamily Anatinae. Later, it was assigned to the "perching ducks", a paraphyletic assemblage of waterfowl most of which are intermediate between dabbling ducks and shelducks. As the "perching ducks" were split up, the Comb Duck was moved to the Tadorninae or shelduck subfamily. Analysis of mtDNA sequences of the cytochrome b and NADH dehydrogenase subunit 2 genes (Johnson & Sorenson, 1999), however, suggests that it is a basal member of the Anatidae, vindicating the earliest placement, but the issue cannot be resolved to satisfaction without further study.


In Kolkata, West Bengal, India.

Male at Sultanpur National Park in Gurgaon District of Haryana, India.

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