One of our recently funded NSF grants was just featured in Colorado Arts and Sciences magazine. This project will explore the evolution of post-zygotic reproductive isolation using hybridizing Black-Capped and Carolina chickadees as a model system. Previous studies revealed that hybrids between the two taxa suffer from physiological disfunctions which might mean that they have reduced ability to survive in harsh winter conditions. However, the proximate mechanisms behind reduced hybrid fitness remain elusive. In this collaborative effort between the Taylor lab, Amber Rice (Lehigh University), Zac Cheviron (University of Montana) and Matthew Carling (University of Wyoming), we will collect data from Black-Capped and Carolina chickadees across North America to examine within and between species gradients in cold tolerance. Ultimately, this project will help to improve understanding of how local adaptation leads to the evolution of intrinsic reproductive barriers.