Duck — 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. Ducks are mostly aquatic birds, mostly smaller than their relatives the swans and geese, and may be found in both fresh water and sea water.
Most ducks have a wide flat beak adapted for dredging. They exploit a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small mollusks.
Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules, and coots.
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.
Some duck species, mainly those breeding in the temperate and Arctic Northern Hemisphere, are migratory; those in the tropics, however, are generally not. Some ducks, particularly in Australia where rainfall is patchy and erratic, are nomadic, seeking out the temporary lakes and pools that form after localized heavy rain.
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 large fish.
In the Mallard the tongue is a flat plate, and on the tongue’s back end is a short lift able flap with about 18 short spikes on for pushing struggling prey and other food down its throat.
The males (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.
Some people use “duck” specifically for adult females and “drake” for adult males, for the species described here; others use “hen” and “drake”, respectively.