title: Molecular sexing of prey remains permits a test of sex-biased predation in a wintering population of western sandpipers.
abstract: Population sex ratios in monogamous birds are often male biased. One factor that can affect population sex ratios is sex-biased predation. However, most estimates of sex-biased predation in birds have focused on species with obvious sexual colour dimorphism or body size dimorphism. Data on sexually monomorphic birds are generally lacking. In the present study, we adopt a PCR-based sexing procedure to help test for sex-biased predation in a wintering population of western sandpipers (Calidris mauri), a shorebird that shows only subtle sexual size dimorphism. Specifically, by comparing the a priori determined sex ratio of live birds wintering at a site in western Mexico to the molecular estimate obtained from depredated birds at this same site, we were able to perform a population-specific test for sex bias in predator-induced mortality. The proportion of females estimated from living (ca. 25%) versus dead (ca. 24%) individuals was in fact not significantly different, indicating that the strong male bias in this population is not due to differential predation. However, molecular sexing of prey remains is a hitherto unexploited test of sex-biased predation in birds, and is potentially applicable to any species for which prey remains can be gathered. We discuss our results in the context of alternate ecological hypotheses for population sex biases.
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. snebela@sfu.ca
authors.forename: Silke
authors.initials: S
authors.lastname: Nebel
authors.forename: Alison
authors.initials: A
authors.lastname: Cloutier
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Thompson
mesh_terms: D000818:Animals; D046091:Charadriiformes / Q000502:physiology*; D017931:DNA Primers; D004587:Electrophoresis, Agar Gel; D020387:Food Chain; D008800:Mexico; D016133:Polymerase Chain Reaction / Q000379:methods; D012732:Sex Determination Analysis / Q000379:methods*; D012744:Sex Ratio
chemical_list: D017931:DNA Primers