Ducks eat a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small mollusks.

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 edge of the beak, there is a comb-like structure called a pectin. This strains the water squirting from the side of the beak and traps any food. The pectin is also used to preen feathers and to hold slippery food items. A few specialized species such as the mergansers are adapted to catch and swallow large fish.