Comb Duck

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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

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). They tolerate any other ducks in the same area, but they do not like to be anywhere near where there might be humans inhabiting the area.

Reproduction

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).

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