The gadwalls are primarily herbivore, though they do boost their protein when breeding. Like other dabbling ducks, they feed primarily at the surface of the water.
Rather than diving for food, they easily tip over with their feet in the air and grab underwater vegetation with their long necks and bills. Aquatic vegetation is their favorite food, although the female and/or young gadwalls eat insect larvae, insects, shrimp, crabs, frogs and small fish.
The gadwalls are astonishingly social, and flocks can total to thousands while migrating. They spend most of their time foraging for food, mostly in close association with other water birds, but not cooperating in any way.
In fact, they often pilfer food from other ducks and other species. Their foraging happens during the day, but they migrate at night to evade from predators like hawks and eagles.
While the females look identical to female mallards, the males don an intricate pattern. Though they don't have dramatic colours, their feathers have intricate colours and designs on the breast and sides. As ducks go, they are comparably large. Most individuals are a little under 2 ft (0.61 m) long and weigh 2-3 lbs (0.9-1.36 kg).