Numerous studies undertaken since 1940 document seasonal abundance patterns of aquatic birds in California wetlands. Many of these studies focus only on shorebirds at a single site (e.g., R. W. Storer 1951, Recher 1966, Jehl and Craig 1970, and Gerstenberg 1972) but together they span the length of the state from San Diego Bay (Jehl and Craig 1970) to Humboldt Bay (Gerstenberg 1972). The most ambitious shorebird census study is that of Jurek (1972, 1973, 1974), who used volunteer observers to count shorebirds in wetlands throughout the state. State and federal agencies have also conducted waterfowl censuses throughout California. Some researchers have attempted to quantify the seasonal abundance patterns of all aquatic birds in wetland habitat: Gerdes (1970) at Morro Bay, Winkler et al. (1977) at Mono Lake, Bollman et al. (1970) and Gill (1972a) in San Francisco Bay, Swarth et al. (1982) in salt ponds in south San Francisco Bay, King et al. (1987) at San Elijo Lagoon, and Funderburk and Springer (1989) at lakes Earl and Talawa. Collectively, these studies and the more general accounts of Grinnell and Miller (1944), Cogswell (1977), McCaskie et al. (1979), and Garrett and Dunn (1981) provide a very useful description of the seasonal use patterns of aquatic birds in California.