Duck is the common name for a number of species in the Anatidae family of birds. The ducks are divided between several subfamilies listed in full in the Anatidae article. They do not represent a monophyletic group, but are instead the members of the family not otherwise considered swans and geese. Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water.

Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules, and coots.

Etymology

This happened because the older Anglo-Saxon words ened (= "duck") and ende (= "end") came to be pronounced the same: other Germanic languages still have similar words for "duck" and "end": for example, Dutch eend = "duck", eind = "end", German Ente = "duck", Ende = "end"; this similarity goes back to Indo-European: compare Latin anas (stem anat-) = "duck", Lithuanian antis = "duck", Ancient Greek νησσα, νηττα (nēssa, nētta) = "duck"; Sanskrit anta = "end".

Some people use "duck" specifically for adult females and "drake" for adult males, for the species described here; others use "hen" and "drake", respectively.

A duckling is a young duck in downy plumage or baby duck.; but in the food trade young adult ducks ready for roasting are sometimes labelled "duckling".

Morphology

The overall body plan of ducks is elongated and broad, and the ducks are also relatively long-necked, albeit not as long-necked as the geese and swans. The body shape of diving ducks varies somewhat from this in being more rounded. The bill is usually broad and contains serrated lamellae] which are particularly well defined in the filter-feeding species. In the case of some fishing species the bill is long and strongly serrated. The scaled legs are strong and well developed, and generally set far back on the body, more so in the highly aquatic species. The wings are very strong and are generally short and pointed, and the flight of ducks requires fast continuous strokes, requiring in turn strong wing muscles. Three species of steamer duck are almost flightless however. Many species of duck are temporarily flightless while moulting; they seek out protected habitat with good food supplies during this period. This moult typically precedes migration.