Male (left) and female mallards, worldwide, 50–65 cm (20–26 inches) longDucks, geese and swans are all birds that live in fresh- or saltwater habitats, feeding in the water and nesting on land, on reed platforms or even holes in trees. They feed on grasses, water plants, fish, insects and worms, using their wide flat beaks to dredge muddy riverbeds for worms, molluscs and insect larvae, and to pull up waterweeds. Ducks swim along the surface using their feet, which are webbed, as paddles. Swans and geese are larger than ducks, and have long, elegant necks. Geese also have notched bills, for pulling up grass.
The duck family is divided between shelducks, dabbling ducks, diving ducks and sea ducks. The shelducks are a group of larger ducks, halfway between geese and ducks.
Dabbling ducks, or “puddle ducks", feed on the surface of water or on land, or as deep as they can reach by up-ending without submerging completely. The group includes the pintails, teals and mallards. Dabblers have a comb-like structure called a pecten along either edge of their beak. It strains the water inside beak, trapping any food. The ducks also use it to preen their feathers.
Swans have small "teeth" in their beaks—actually jagged edges—which they use for snapping leaves and combing small creatures off water plants.
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