Ducks are common water birds. Most domestic (farm) ducks were bred from mallards. The adult female duck is called a hen, the adult male is called a drake, and the young are called ducklings.

Breeds: The Pekin Duck is a common farm duck. The ducklings are bright yellow; adults are white. They were brought to America from China in the 1870's. Another popular farm duck is the Rouen duck, which was originally from France; this duck still has mallard-like coloring. The Muscovy is another popular farm duck; this American breed has dark feathers.

Diet: Ducks have a varied diet. They eat insects, worms, frogs, snails, slugs, small shellfish, grasses, and other plants.

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.

The word duck (from Anglo-Saxon duce), meaning the bird, came from the verb "to duck" (from Anglo-Saxon supposed *ducan) meaning "to bend down low as if to get under something" or "to dive", because of the way many species in the dabbling duck group feed by upending (compare Dutch duiken, German tauchen = "to dive").

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 ??ssa, ??tta (nessa, netta) = "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.

The drakes of northern species often have extravagant plumage, but that is moulted in summer to give a more female-like appearance, the "eclipse" plumage. Southern resident species typically show less sexual dimorphism, although there are exceptions like the Paradise Shelduck of New Zealand which is both strikingly sexually dimorphic and where the female's plumage is brighter than that of the male. The plumage of juvenile birds generally resembles that of the female.

Feeding
Ducks exploit a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small molluscs.

Diving ducks and sea ducks forage deep underwater. To be able to submerge more easily, the diving ducks are heavier than dabbling ducks, and therefore have more difficulty taking off to fly. Dabbling ducks feed on the surface of water or on land, or as deep as they can reach by up-ending without completely submerging. Along the inside of the beak they have tiny rows of plates called lamellae like a whale's baleen. These let them filter water out of the side of their beaks and keep food inside. A few specialized species such as the smew, goosander, and the mergansers are adapted to catch and swallow large fish.

Communication
Despite widespread misconceptions, most ducks other than female Mallards and domestic ducks do not "quack"; for example, the scaup makes a noise like "scaup", which its name came from. The ducks make a wide range of calls, ranging from whistles cooing, yodels and grunts. Calls may be loud displaying calls or quieter contact calls.

A common urban legend claims that duck quacks do not echo; however, this has been shown to be false. This myth was first debunked by the Acoustics Research Centre at the University of Salford in 2003 as part of the British Association's Festival of Science. It was also debunked in one of the earlier episodes of the popular Discovery Channel television show MythBusters.