The Comb Duck (Sarkidiornis melanotos) is an unusual duck, best placed in the shelduck subfamily Tadorninae, though it has formerly been included in the Anatinae. This duck breeds in the tropics of South America, sub-Saharan Africa and India. It is largely resident, apart from dispersion in the wet season, and it nests in tree holes usually, laying 7-15 eggs.
Its preferred habitat is freshwater swamps and lakes, where this duck feeds on vegetation by grazing or dabbling. Their diet consists of seeds, making them a problem to some farmers if they are in the area and are around their farms. It is very important for the comb ducks to have rain because it determines when they are going to mate and also if they are going to mate at all. This duck is not usually found in any public displays due to their special needs, such as warm weather. They are usually found in warm areas where there is rain from time to time.
This common species is unmistakable with its white neck, head and underparts, glossy blue-black upperparts, and freckled head dotted with dark spots. The male is larger than the female, and has a large black knob on the bill. Both sexes have white-colored bellies. The wingspan of the male is much larger than that of a female. Juveniles are brown above and buff below, their appearance changing as they age.
This species does not like to be anywhere near where there might be human habitation. Season and time of year determine flock size. The comb ducks usually fly together when they migrate. Sometimes the comb ducks may even separate themselves according to what sex they are into different groups. They do not have much of a problem with other ducks that might be in the same area as them. The sounds made by female and male comb ducks sound somewhat different. It is common for one male duck to have more than one mating female comb duck.
South American birds, S. m. sylvicola, are smaller and have black flanks (light grey in Old World birds).