Size: 18.5-23" (47-58 cm). A very nondescript dabbling duck. Males grayish brown mottled. Some brown on head and black undertail coverts. Females mottled brown. The key to identification of this species is its white speculum, unique to the Gadwall.
Similar Species- Almost all female ducks look similar to the Gadwall; however, no other duck has a white speculum.
Male has a series of low rrebb-rrebb notes and various whistles. Females give a soft quack.
Breeds from southern Alaska and southwestern and south-central Canada, south to southern Wisconsin, southern Kansas, northern New Mexico, central California, and locally on parts of East Coast. Winters from southern Alaska to central California, across portions of middle U.S. to central Florida and Gulf Coast, and south into south-central Mexico.
Feeds on leaves, stems, and tubers of aquatic plants. Also eats algae and seeds of sedges and grasses. Occasionally grazes in pastures and grain fields; may feed on acorns. Eats some small fishes and aquatic invertebrates, which comprise about half spring and summer diet; eats green portions of aquatic plants in non-nesting season. Juveniles initially eat equal amounts of animal and plant food; plant food begins to dominate after 2 wk.
Feeds generally in water 15- 66 cm deep. Builds concealed nest on ground. One study found that few hundred nests/ha are possible on islands lacking mammalian predators. An Idaho study suggested that mammalian and avian predators may significantly affect nest success in some wildlife management areas. Highest breeding densities occur in northern Great Plains and intermountain valleys of western United States. Molting males may form groups of hundreds or thousands in midsummer
Breeding usually begins in mid-April in southern range, early June in north. Female incubates about 9-11 eggs for 4 wk. Female tends young, which fly at 49-63 days. Species breeds later than most other ducks. Relatively high percentage of yearlings do not breed.
Gazda, R.J. 1994. Duck productivity and nest predation in southeastern Idaho. M.S. Thesis, Univ. of Montana, Missoula. 61pp.