Comments: Primarily shallow waters such as ponds, lakes, marshes, and flooded fields; in migration and in winter mostly in fresh water and cultivated fields, less commonly in brackish situations (AOU 1983). See Nichols et al. (1983). Adapted to dynamic wetland conditions that provide a variety of wetland types in relatively close proximity (Allen 1986, which see for details on winter habitat in Lower Mississippi Valley). In Maryland, breeding pairs and broods used stormwater-control basins, especially permanent ponds with gently sloping sides (Adams et al. 1985). In California and Oregon, molting areas were dominated by bulrush and cattail and were traditionally flooded in summer and often associated with lakes or rivers (Yarris et al. 1994). Usually nests on ground in concealing vegetation, sometimes in trees or in atypical situations. Nest usually within 0.8 km of water (Palmer 1976). Commonly uses man-made ponds. Successful nesters are more likely to return to the same nesting site in successive years than are unsuccessful nesters.