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Photo by Glen Smart
Photo Courtesy of U. S. Fish and Wildlife Service
Gadwall
Mareca strepera
NatureServe conservation status
Global (G-rank): G5
State (S-rank): S4S5B,S4N
External links
General information
The gadwall, Anas strepera, is a dabbling duck that breeds in North America and Eurasia. North American populations breed in Canada and much of the United States. Populations in the northern portion of the species' breeding range migrate south for winter; main North American wintering areas include southern Canada, the United States, and Mexico. The gadwall is a common duck in Utah, where it occurs statewide in appropriate habitat. Some gadwalls are year-round residents of Utah, some breed in Utah and winter in Mexico and California, and some breed in northern North America and winter in Utah.
Similar to other species of waterfowl, gadwalls prefer ponds, lakes, and marshes. Nests are constructed on dry areas near water, often near the base of a shrub, or within thick vegetation. Nine to eleven eggs are laid in the spring and then incubated by the female alone for about one month. The female tends the young, which can fly at about two months of age. Gadwalls eat primarily aquatic plants and aquatic invertebrates, although grains and fishes are also occasionally consumed. North American gadwall populations are currently doing extremely well, having grown a great deal during the past decade.
Species range
BREEDS: North America: southern Alaska, southern Yukon, southern Mackenzie (north to near Yellowknife; Can. Field-Nat. 106:254-256), northern Saskatchewan, central Manitoba, southern Ontario, southwestern Quebec, Prince Edward Island, Anticosti Island (rarely), and the New Brunswick-Nova Scotia border south locally to southern California, southern Nevada, northern Arizona, southern New Mexico, northern Texas, southern Kansas, Iowa, centralMinnesota, southern Wisconsin, northern Ohio, northern Pennsylvania (formerly), and, on the Atlantic coast, to North Carolina (one isolated breeding area in northern Alabama); also in the Old World (AOU 1983). Highest breeding densities occur in the northern Great Plains and intermountain valleys of the western U.S.; some portions of Alaskan, Pacific, and Atlantic coasts also have important breeding populations (Ringelman 1990). Range may be expanding eastward. WINTERS: North America: southern Alaska, southern British Columbia, Idaho, Colorado, southern South Dakota, Iowa, the southern Great Lakes, and Chesapeake Bay on the Atlantic coast (rarely from New Brunswick and Nova Scotia) south to northern Baja California, Oaxaca, the state of Mexico, Puebla, Veracruz, Tabasco, Yucatan, the Gulf Coast, Florida, the Bahamas, western Cuba, and (formerly) Jamaica; also in Old World (AOU 1983). Major wintering areas include coastal Louisiana and Texas, Gulf Coast of Mexico to Yucatan Peninsula, central and southern Atlantic coast of U.S., Central Valley of California, and much of the west coast of Mexico (Ringelman 1990); also northwestern Utah (Bear River refuge) and southeastern Missouri (Mingo refuge) (Root 1988). Formerly resident (COUESI group) in the northern Line Islands (Washington and New York islands); now extinct (AOU 1983).
Migration
Partially migratory. Migratory populations move northward in spring, departing wintering areas by March or early April, usually arriving at northernmost breeding grounds late April-early May; move southward September-October (sometimes later) (Ringelman 1990, Terres 1980). Primary migration corridor originates in the prairies and extends through the low plains region of the central and south-central U.S. and into Mexico; secondary migration routes link the prairies with the Pacific Northwest, northern and central California, and northern Utah; Utah breeders winter in central and southern California and Mexico; migrates also along diagonal routes from Great Plains to central and southern Atlantic coast (Ringelman 1990). Gadwalls banded in breeding areas in north-central Colorado were recovered primarily near the banding areas and in central and coastal Texas, northern Utah, along the east and west coast of Mexico, and in the Interior Highlands of Mexico (Szymczak and Rexstad 1991).
Habitat
Lakes, ponds, rivers, marshes. Prefers freshwater but may be found on any open water during migration and winter. Moderate- to large-sized wetland of a permanent or semipermanent nature, expanses of open water with submersed vegetation, and open undisturbed shorelines are important molting habitats (Ringelman 1990). Nests in thick vegetation near freshwater lakes, ponds, or streams, including open brackish or alkaline waters. Nests usually in dry upland site under clump of shrubs or in herbaceous vegetation, average of 300 m from water. Tends to nest near semipermanent wetlands that are relatively resistant to drought (Ringelman 1990). Commonly uses man-made ponds. May nest on island, upland meadow or grassland. Suitable nesting islands should be 0.1-0.5 ha in size, elongate, and separated from mainland by at least 150 m of water that remains 0.9 m deep in nesting season (Ringelman 1990). Successful breeders usually return to nesting area used the previous year (Szymczak and Rexstad 1991). A diversity of wetland types is required for successful reproduction, so that brood-rearing habitat is near nesting habitat; females will move brood up to 1.9 km to brood habitat (Ringelman 1990).
Food habits
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 (e.g., insects, crustaceans). Aquatic invertebrates comprise about half the diet in spring and summer; eats green portions of aquatic plants in non-nesting season; feeds generally in water 15-66 cm deep (Ringelman 1990). Juveniles intitally eat equal amount of animal and plant food; plant food begins to dominate after 2 weeks (Ringelman 1990).
Ecology
Molting males may form groups of hundreds or thousands in mid-summer. Annual survivorship of adults banded in Colorado was 69-75% (Szymczak and Rexstad 1991).
Reproductive characteristics
Breeding usually begins in mid-April in the south to early June in the north. Clutch size: usually about 9-11. Incubation: about 4 weeks, by female. Young are tended by female, can fly at 49-63 days. Relatively high percentage of yearlings do not breed. Up to at least a few hundred nests/ha on islands lacking mammalian predators.
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
- Peterson, R. T., and V. M. Peterson. 1990. A field guide to western birds, 3rd ed. Houghton Mifflin, Boston. 432 pp.
