Gadwall Duck

Mareca strepera

When you visit the Refuge, a lot of the time it is easy to assume that the brown ducks you are seeing alongside the easily identifiable Mallard Duck are females, but that is not necessarily the case! Gadwall are about the same size as Mallards and have a fairly large, square head with a steep forehead. The main way to tell the differences between Mallards and Gadwall is that the Gadwall bill is noticeably thinner than a Mallards. In flight, the neck is slightly thinner and the wings slightly more slender than a Mallard’s. Male Gadwall are gray-brown with a black patch at the tail. Females are patterned with brown and buff. Females have a thin orange edge to their dark bills. In flight, both sexes have a white wing patch that is sometimes visible while swimming or resting, this is in contrast to the Mallard’s white-tipped blue patch in the same part of their secondary wing colors. Both Gadwalls and Mallards will have orange colored feet, with Gadwall feet looking a little more yellow.

Gadwall feed with other dabbling ducks, tipping forward to feed on submerged vegetation without diving. They sometimes steal food from flocks of diving ducks or coots. You’ll often see these ducks in pairs through the winter, because they select their mates for the breeding season as early as late fall. Female Gadwall produce an egg a day while they are laying their 7–12-egg clutches. To meet their demand for protein during this stressful time, female Gadwall eat more invertebrates than males during this period—in addition to using reserves of nutrients they’ve stored in their bodies during the winter. They typically choose dense brush or grasses at least a foot tall, usually within 200 yards of open water, and nest on islands when possible for greater safety from predators. In heavily cultivated areas, untilled land for nest sites can be a scarce resource. The female scrapes out a hollow, then settles into the nest and reaches out to grab twigs and leaves with her bill. She sets these against herself to form the base of a nest cup, then plucks her own down feathers to make an insulating lining. The finished nest is about a foot across with a cup 3 inches deep.

Like most ducks they often form flocks, and you may see them fidgeting as they swim about each other. These movements are actually a complex series of displays that communicate pair bonds, levels of aggression, and degrees of interest among potential mates. For example, Gadwall may send warnings to each other off by lifting their chin or opening their bill at another bird. A male may seek a female’s attention by ruffling his head feathers, drawing the head close to the body, and then rearing up out of the water and pushing his head forward. Further courtship displays include the male arching his head over his back and then jerking forward while raising his tail and wing coverts; pushing his bill underwater and then quickly tossing water into the air while whistling; and rearing up while raking his bill through the water and whistling. A female may show her interest by arching her head and neck and repeatedly moving it forward and then to the side away from the male. As the pair bond strengthens, the two birds face each other and raise and lower their heads, chins up; or turn their head and place the bill behind the wing, as if preening. Courtship happens in fall and early winter; virtually all females find mates by November. Gadwall are seasonally monogamous. Predators of eggs and young include California and Ring-billed gulls, Northern Harriers, foxes, weasels, mink, coyotes, and badgers.

Did You Know? Gadwall have increased in numbers since the 1980s, partly because of conservation of wetlands and adjacent uplands in their breeding habitat through the Conservation Reserve Program and the North American Waterfowl Management Plan. Their habit of nesting on islands within marshes gives them some protection from predators.