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Species Guide

Comb Duck

Sarkidiornis sylvicola

The comb duck, or American comb duck (Sarkidiornis sylvicola), presents a striking figure with its large size and distinctive markings. This species is one of the largest ducks, with lengths ranging from 56 to 76 cm, wingspans from 116 to 145 cm, and weights between 1.03 and 2.9 kg. The adult comb duck features a white head speckled with dark spots, a pure white neck, and underparts. The upperparts are a glossy blue-black with iridescent hues of blue and green, particularly noticeable on the secondaries. Males are significantly larger than females and sport a prominent black knob on their bills.

Identification Tips

When identifying the comb duck, look for the unique combination of a white head with dark flecks and the contrasting glossy blue-black upperparts. The male's bill knob is a key feature, distinguishing it from other species. Immature comb ducks may resemble the fulvous whistling duck but are generally seen with adults, aiding in their identification.


The comb duck favors tropical wetlands, thriving in still freshwater environments such as swamps and lakes.


This species is indigenous to continental South America, extending south to the Paraguay River region in eastern Paraguay, southeastern Brazil, and extreme northeastern Argentina. It has also been recorded as a vagrant on Trinidad.


Comb ducks are largely sedentary, dispersing only during the wet season. They are often observed perching in trees and typically form flocks—small during the wet season and up to 100 individuals in the dry season. Flocks may segregate by sex. They can pose challenges for rice farmers when foraging.

Diet and Feeding

These ducks are primarily herbivorous, grazing or dabbling for vegetation. They also consume small fish, invertebrates, and seeds to a lesser extent.


Nesting mainly occurs in tree holes, with nests lined with reeds, grass, or feathers. Males may be polygynous, having multiple mates either simultaneously or consecutively, and defend their young but not the nesting sites. Unmated males perch in trees, awaiting mating opportunities. Females lay 7 to 15 yellowish-white eggs, and "dump nests" with eggs from multiple females may contain up to 50 eggs.

Conservation status

The comb duck is currently classified as Least Concern on the IUCN Red List, indicating a stable population without significant immediate threats to its survival.

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Comb Ducks on Birda

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Chris Bell
12 Mar 2024 - 9:49pm

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