Ducks make a "quack" sound and use their bills and webbed feet to find food in lakes, rivers, and ponds. Cows are called bulls when male and cows when female; they provide milk, leather, and meat and eat foods like corn and grass. Chickens say "cock-a-doodle-doo"; a rooster is larger and brighter than a hen, and hens sit on their eggs to keep them warm as they incubate.