I evaluated the use of various wetlands by wintering ducks in the Tulare Lake Basin (TLB), California, during October 1982 - April 1983 and September 1983 - March 1984. Aerial waterfowl counts of the TLB were used to document spacial use patterns by ducks. Ground surveys on evaporation ponds in the Tulare Lake Drainage District (TLDD) were used to evaluate duck use of specific ponds with varying chemical and biological parameters. During mid-winter, up to 300,000 ducks used the TLB. The most abundant species (northern pintail (Anas acuta), northern shoveler (Anas clvoeata), and green-winged teal (Anas crecca)) were found on freshwater habitats. Ruddy ducks (Oxvura jamaicensis) were the only species to extensively use the evaporation ponds. With the exception of ruddy ducks, the evaporation ponds did not appear to be valuable for feeding areas, but provided sanctuary during the hunting season. The use of evaporation ponds by waterfowl may be heavier in years without the extensive floodwater that was present during this study. / Graduation date: 1991