Ducklings feed mainly on insects, particularly mosquito larvae, and also on crustaceans in addition to plant parts. When natural foods are plentiful and available, mallards prefer them, but when ice closes up marshes, lakes and ponds, they head for dry land and corn. Perhaps more than any other duck, however, mallards are notorious for feeding in farm fields where they search for grain in the remaining stubble of corn and sorghum fields. Mallards travel up to 25 miles for food. Often they make two feeding flights per day, one at dawn and the other in late afternoon.
Mallards mature sexually in their first year.
A period of social display begins in late fall and continues through winter into spring. Males grunt and whistle, swim, pump their heads, and preen in front of the females. The hens stimulate the courtship with calls and their own stylized body movements. Most pair-forming activities occur on the water, although chase flights in spring are prominent courtship rituals. Most hens have chosen their future mates by the time mallards arrive on the northern breeding grounds in spring.