Food is basically aquatic plants. On brackish or freshwater estuaries where they often winter, gadwalls concentrate on vegetation such as widgeon grass, eelgrass, muskgrass and pondweeds. In Pennsylvania, gadwalls are uncommon. They are considered non-breeding residents, although they have nested in Crawford and Butler counties. They breed mainly in the western United States, Canada and Alaska.
Hens seek dense, dry weed cover, hiding the nest from above and all sides.
They lay about 10 eggs, which hatch in 26 days. Gadwall are most plentiful in the Dakotas and Canada's prairie provinces, less common on the Atlantic Flyway. They are often seen with pintails and wigeons, but they rarely congregate in large flocks. The gadwall dives more often than any other puddle duck. Among the most beautifully marked of our ducks, a pintail male in breeding plumage has a brown head, white neck and breast, and a gray back and sides.