Comb Duck is widespread throughout slow-moving fresh water in the lowlands of South America, north of the Southern Cone. It occurs in every mainland country except Suriname and Chile, but is restricted in Argentina to the northeast, is only a vagrant to French Guiana and Trinidad, and also occurs locally in eastern Panama. Comb Duck is large and very distinctive, and is unmistakable within the Neotropics. It often is seen flying over water, and is eye-catching and distinctive, with its broad wings and striking black-and-white plumage, especially when seen against a background of green vegetation. Comb Duck often grazes on small fish and invertebrates by swimming slowly and dabbling on the surface. Comb Duck is sexually dimorphic: the male is much larger than the female, and has a large, black, oblong crest above the bill. The genus Sarkidiornis is represented in the Old World by Knob-billed Duck (Sarkidiornis melanotos) of Africa and southern Asia, which some authorities consider to be conspecific with Comb Duck.