Tracking climatic conditions throughout the year is often assumed to be an adaptive behavior underlying seasonal migration patterns in animal populations. In this study, we investigate this hypothesis using genetic markers data to map migratory connectivity for 22 genetically distinct bird populations across 6 species. We found that the variation in seasonal climate tracking at a continental scale is more likely a consequence, rather than an underlying driver, of migratory connectivity, which is itself largely shaped by energy efficiency -- i.e. optimizing the balance between accessing available resources and the cost of movement. However, our results also suggest that regional-scale seasonal precipitation tracking affects migration destinations, thus revealing a potential scale-dependency of ecological processes driving migration. Our results have implications for the conservation of migratory species under climate change, as populations that track climate seasonally are potentially at higher risk if they adapt to a narrow range of climatic conditions.

Understanding the geographic linkages among populations across the annual cycle is an essential component for understanding the ecology and evolution of migratory species and for facilitating their effective conservation. While genetic markers have been widely applied to describe migratory connections, the rapid development of new sequencing methods, such as low-coverage whole genome sequencing (lcWGS), provides new opportunities for improved estimates of migratory connectivity. Here, we use lcWGS to identify fine-scale population structure in a widespread songbird, the American Redstart (Setophaga ruticilla), and accurately assign individuals to genetically distinct breeding populations. Assignment of individuals from the nonbreeding range reveals population-specific patterns of varying migratory connectivity. By combining migratory connectivity results with demographic analysis of population abundance and trends, we consider full annual cycle conservation strategies for preserving numbers of individuals and genetic diversity. Notably, we highlight the importance of the Northern Temperate-Greater Antilles migratory population as containing the largest proportion of individuals in the species. Finally, we highlight valuable considerations for other population assignment studies aimed at using lcWGS. Our results have broad implications for improving our understanding of the ecology and evolution of migratory species through conservation genomics approaches.