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[1], worms, and small molluscs. Diving ducks and sea ducks forage deep underwater; Dabbling ducks feed on the surface of water or on land. Dabbling ducks have in their beaks special plates called lamellae[1] similar to a whale's baleen. These tiny rows of plates along the inside of the beak let them filter water out of the side of their beaks and keep food inside. To be able to submerge more easily, the diving ducks are heavier than dabbling ducks, and therefore have more difficulty taking off to fly. A few specialized species such as the Smew, Goosander, and the mergansers are adapted to catch large fish.
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. Many species of ducks are temporarily flightless while moulting; they seek out protected habitat with good food supplies during this period. This moult typically precedes migration.
