Phylogenetic signature of uropygial gland size in a North American bird community
Description
The uropygial gland and the oils secreted from it have been shown to serve important functions in many bird species including plumage maintenance and chemical communication. Previous species comparisons of uropygial gland size have only been conducted in South American and European communities and have found little to no phylogenetic signature. Here, we document uropygial gland measurements of 36 different species in eastern Pennsylvania, many of which are reported for the first time. Uropygial gland size is related to overall body size and shows a complex relationship with species, sex, and season. We also found a significant phylogenetic signature of relative uropygial gland size. Clades with larger than expected gland size for their body mass included the Paridae and Passerellidae, members of which have been shown to particularly rely on olfactory cues in a variety of ecological contexts. In contrast, we found that the Turdidae have smaller than expected gland sizes. Our results are consistent with previous species-specific studies of olfactory-based behaviors and we believe that the size of the uropygial gland could be a good indicator of the degree of reliance on olfaction in individual bird species.
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All measurements were collected from wild-caught birds in eastern Pennsylvania. Phylogenetic data was obtained from BirdTree.org.