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1 June 2011 Sex and Age Ratios of Bicknell's Thrush Wintering in Hispaniola
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We investigated sex and age ratios of wintering Bicknell's Thrush (Catharus bicknelli) across a geographic gradient of sites on Hispaniola. The island-wide proportion male was 0.64 (n  =  127), which is comparable to the known male bias in breeding areas. The proportion male varied geographically on Hispaniola, suggesting some level of habitat segregation. Male-biased ratios occurred at two sites whereas sex ratios at five sites did not differ from parity. The island-wide proportion adult was 0.72 and age ratios were significantly adult-biased at two sites. We assessed vegetative structure at all sites and the proportion of male thrushes increased significantly with density of understory vegetation. Age ratios were not associated with vegetation characteristics. Neither sex nor age ratios varied significantly with elevation. Our data suggest the possibility of sexual habitat segregation with males preferentially occupying cloud forest sites characterized by a thick understory of vines and saplings occurring at densities >10,000 stems/ha.

Jason M. Townsend, Christopher C. Rimmer, Andrea K. Townsend, and Kent P. McFarland "Sex and Age Ratios of Bicknell's Thrush Wintering in Hispaniola," The Wilson Journal of Ornithology 123(2), 367-372, (1 June 2011).
Received: 19 April 2010; Accepted: 1 January 2011; Published: 1 June 2011

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