Mallard ducks are omnivorous. The majority of what they eat is plant material, including the seeds, stems, and roots of sedges, grasses, pondweeds, and smartweeds. They also consume tree seeds like acorns and various types of waste grain along with small insects, crustaceans, mollusks, tadpoles, frogs, earthworms, and small fish. However, young ducklings have a far less varied diet than their adult counterparts and eat mostly aquatic insects.