Sex-ratio studies have received much attention from research workers in recent years. The contributions of Hochbaum (1944), Petrides (1944) and others have yielded considerable information on sex ratios in waterfowl; Beer (1945) and Yocom (1949) have presented data for the state of Washington. To interpret regional data on waterfowl sex ratios adequately, it is necessary to obtain a series of uninterrupted observations covering the entire migration period of the species concerned. In 1954, an ecologic study was conducted in the Potholes area, Grant County, central Washington (Johnsgard, 1956). During the period February 15 to May 16, sex-ratio data were collected for more than 15,000 ducks, including 17 species to be discussed in this paper. Nearly all these species wintered in the region and were present in small numbers when field work began in February (Johnsgard, 1954).
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