This project will (a) continue genomic analyses of differentially migrating populations of the willow warbler and (b) expand the analyses to its closest relative, the chiffchaff. The ultimate goal is to identifying genes that underlie variation in migratory traits. We have used the latest technologies to assemble high quality reference genomes for these species that will be the used to analyze whole-genome resequencing data from a number of samples from different populations, including 100 samples for which there is detailed data on their migratory routes from geolocator tracks.