Gadwall breed mainly in prairie potholes—small ponds scattered throughout the Great Plains and Canadian prairies. Some also breed on tundra, deltas, and wetlands in boreal forests of the far north. In developed areas with few natural ponds, Gadwall may use stock ponds. They choose well-vegetated wetlands with plenty of emergent plants to feed among and take cover in. Equally important for breeding are adjacent uplands with vegetation to conceal nests and for ducklings to hide in. On migration and in winter, look for Gadwalls in fresh and salt water marshes and well-vegetated reservoirs, beaver ponds, farm ponds, and streams. Back to top
Gadwall eat mostly submerged aquatic vegetation such as algae, grasses, rushes, sedges, pondweed, widgeon grass, and water milfoil, including leaves, stems, roots, and seeds. They also eat snails, midges, water beetles, and other invertebrates. During the breeding season, animal matter can account for nearly 50 percent of an adult Gadwall’s diet, but this proportion drops to only about 5 percent animal matter during winter. Back to top
Gadwall pairs form during fall migration. Once they return to their breeding grounds, they select their nest site while flying low over dry, grassy areas. The female makes a closer inspection on foot while the male stands guard near her. 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. It takes 5–7 days to go from looking for a nest site to having a finished nest ready for egg laying.
|Clutch Size:||7-12 eggs|
|Number of Broods:||1 brood|
|Egg Length:||1.9-2.4 in (4.9-6 cm)|
|Egg Width:||1.3-1.7 in (3.4-4.4 cm)|
|Incubation Period:||24-27 days|
|Nestling Period:||1-2 days|
|Condition at Hatching:||Alert, fully covered with down, eyes open, ready to leave the nest in a day or two.|
Gadwall are dabbling ducks—they ride fairly high in the water and they tip forward to graze on submerged plants that they can reach with their outstretched necks. They rarely dive. Gadwall sometimes steal food from American Coots. 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.Back to top
Gadwall populations increased by over 2.5 percent per year between 1966 and 2010, according to the North American Breeding Bird Survey. The species is not on the 2014 State of the Birds Watch List. Gadwall are the third most hunted duck species (after Mallard and Green-winged Teal), with some 1.7 million of them harvested in 2010. Slightly more than 1 in every 10 ducks shot by U.S. hunters is a Gadwall. Duck harvests are carefully managed, and Gadwall numbers are still strong in part because of the conservation of both wetlands and adjacent upland nesting habitat through the Conservation Reserve Program and the North American Waterfowl Management Plan, as well as the efforts of private conservation groups such as Ducks Unlimited.Back to top
Leschack, C. R., S. K. McKinght and Gary R. Hepp. (1997). Gadwall (Mareca strepera), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.
North American Bird Conservation Initiative. (2014). The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.
Raftovich, R. V., K. A. Wilkins, S. S. Williams and H. L. Spriggs. (2012a). Migratory bird hunting activity and harvest during the 2010 and 2011 hunting seasons. Laurel: US Fish and Wildlife Service.
Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, Jr. Ziolkowski, D. J. and W. A. Link. The North American Breeding Bird Survey, results and analysis 1966-2013 (Version 1.30.15). USGS Patuxtent Wildlife Research Center (2014b). Available from http://www.mbr-pwrc.usgs.gov/bbs/.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.