Abstract
Abstract We analyzed distribution of Hermit Thrushes (Catharus guttatus faxoni) wintering in the eastern United States and northeastern Mexico using data from 2,077 specimens collected in winter or during migration. Hermit Thrushes collected in winter showed a sex-biased latitudinal distribution, with the female mean 1.2° south of the male mean. Three general, nonmutually exclusive hypotheses have been proposed to account for that pattern in other species: (1) dominance of males over females, which forces females to lower latitudes; (2) larger body size of males, which permits males to overwinter in colder areas; and (3) earlier arrival by males on breeding grounds, which selects for males to winter closer to the breeding grounds. The dominance hypothesis requires that females be subordinate, an assumption that is not supported by previous research with wintering Hermit Thrushes. We also found no difference in sex ratio among habitats, despite strong differences in habitat quality. The body-size hypothesi...
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