A number of studies have shown sex and age-based habitat segregation to be an important component of winter season population limitations among migrant songbirds. In this study, we investigate the age and gender distribution of wintering Bicknell’s Thrushes in the Dominican Republic. Between 2000 and 2008 we focused on two floristically and climatically distinct sites: one in high elevation cloud forest, and the other in mid elevation rainforest. We found the cloud forest site to be significantly male-biased in comparison to the rainforest site. The mean cloud forest proportion male was 74% ± 11%. In contrast, the rainforest site did not differ significantly from a 1:1 male to female ratio and, rather than being characterized as a “female” site, is best labeled as having an equal sex ratio. The mean proportion male at this site was 53% ± 2%. The distribution of juvenile birds did not differ between the sites. We identified several differences in the spatial behavior, diet, and body condition of birds at the two sites and we discuss these in the context of the differing gender distributions.
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