Mottled ducks are carnivors and herbivores. They eat aquatic invertebrates and small fish. They often eat snails, crayfish, beetles, dragonfly nymphs, fish and midge larvae. Invertebrates make up from 1 to 40 percent of their diet. They also eat seeds, grasses, aquatic vegetation and rice.
Mottled ducks usually feed in pairs in the fall and winter. During the summer, they may feed in small groups of about twenty. From August through October (especially in the rice fields) they often feed in flocks of around three thousand. When the ducks feed alone, they search the marshlands for seeds and invertebrates by sitting on the water and tipping their heads under water (a behavior called dabbling). They rarely dive for food, but when they do, it is for minnows.
Animal Foods: mammals; fish; eggs; insects; mollusks; aquatic or marine worms; aquatic crustaceans
Plant Foods: leaves; seeds, grains, and nuts
Primary Diet: omnivore