The role of tropical rainfall in driving range dynamics for a long-distance migratory bird

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence range dynamics across the lifecycle of a migratory songbird, the American redstart (Setophaga ruticilla). Using long-term data from the nonbreeding grounds and breeding origin estimated from stable hydrogen isotopes in tail feathers, we found that the relationship between nonbreeding season survival and migration distance is mediated by precipitation, but only during dry years. A long-term drying trend throughout the Caribbean is associated with higher mortality for individuals from the northern portion of the species’ breeding range, resulting in an approximate 500 km southward shift in breeding origins of this Jamaican population over the pa..., See the manuscript and supplementary materials for further details on model formulation. The data included here include BBS and environmental data for the abundance and occupancy analysis. Geolocator data can be found in https://doi.org/10.1002/ecy.3938. , , # The role of tropical rainfall in driving range dynamics for a long-distance migratory bird

*Hierarchical Breeding Bird Survey Abundance Model*
To evaluate the effect of winter rainfall on population abundances of American redstarts on the breeding grounds we relied on 30 years (1990-2019) years of the long-term Breeding Bird Survey (BBS) data to coincide with our 30-year banding and isotope dataset. Data from 554 BBS routes included in this analysis were selected based on the likely breeding origins of this population (*SI Appendix,* Figure S4). Stable-hydrogen isotope analysis indicated that this wintering population originates from a broad latitudinal band (35 to 50 °N). To determine the longitudinal band of our population we calculated the 95% CI of breeding longitude estimated from a sample of geolocator tagged individuals (-93 to -83 °W).

The model includes estimates of log-linear population trends (![]()).  ![]()represents the effect of week-of-year on abundance, *β*3 accoun...