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 semi-permanent 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 semi-permanent 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). In B.C., this species is found from sea level to 1,300 m in wet areas in the interior and in estuaries, brackish and freshwater marshes, mudflats, and sewage lagoons in coastal areas (Campbell et al. 1990).
Campbell, R. W., N. K. Dawe, I. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, and M. C. E. McNall. 1990. The Birds of British Columbia. Vol. 1 and 2, Nonpasserines. UBC Press, Vancouver, B.C.
Ringelman, J. K. 1990. Life history traits and management of the gadwall. U.S. Fish & Wildl. Serv., Fish and Wildlife Leaflet 13.1.2. 6 pp.