Abstract
An enduring problem in avian ecology and conservation is linking breeding and wintering grounds of migratory species. As migratory species and populations vary in the degree to which individuals from distinct breeding locales mix on stop-over sites and wintering grounds, establishing migratory connectivity informs our understanding of population demography and species management. We present a new Bayesian approach for inferring breeding grounds of wintering birds of unknown origins in North America. We incorporate prior information from analysis of genetic markers into geographic origin assignment based upon stable-hydrogen isotope analysis of feathers (δ2Hf), using the Loggerhead Shrike (Lanius ludovicianus). Likely geographic origins derived from analyses of DNA microsatellites were used as priors for Bayesian analyses in which birds were assigned to a breeding-ground origin using their δ2Hf values. As with most applications of Bayesian methods, our approach greatly improved the results (i.e. decreased the size of the potential area of origin). Area of origin decreased by 3 to 5-fold on average, but ranged up to a 10-fold improvement. We recommend this approach in future studies of migratory connectivity and suggest that our methodology could be applied more broadly to the study of dispersal, sources of productivity of migratory populations, and a range of evolutionary phenomena.
Highlights
Linking breeding and wintering grounds of populations, for declining or endangered migratory animals, is a major endeavor for conservation agencies and scientists, yet one fraught with technical and logistical challenges
Migratory species and populations vary in the degree to which individuals from distinct breeding locales mix on different stop-over sites and wintering grounds
Our aim was to develop an approach to assignment based on genetic admixture coefficients of Loggerhead Shrike (Lanius ludovicianus) derived from spatial analysis of nuclear DNA microsatellites as priors for Bayesian assignment based on d2Hf
Summary
Linking breeding and wintering grounds of populations, for declining or endangered migratory animals, is a major endeavor for conservation agencies and scientists, yet one fraught with technical and logistical challenges. To understand population demographics, local adaptation, and causes of diversification, the spatial characteristics (i.e. which populations mix on breeding and wintering grounds) and strength (i.e. proportion of individuals from distinct breeding areas on the wintering grounds, or vice versa) of migratory connectivity [1,2,3] must be quantified. This informs the effective, typically multinational, management strategies for migratory species [4] and provides insight into evolutionary trajectories [2]. Extrinsic markers (e.g. numbered leg bands) have provided the most direct empirical estimates of movements of migrants throughout the world [5,6], but often require both capture and recapture of individuals, which limits the amount of data collected.
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