Migratory divides represent the boundary between adjacent bird populations that migrate in different directions, and are of considerable interest to evolutionary biologists because of their potential role in speciation. Although migratory divides are typically defined based on indirect methods with limited spatial resolution, new technologies now allow greater precision for tracking small birds throughout their annual cycle. Here, we integrate geolocator, genetic, and morphological data to characterize a migratory divide. Hermit thrush ( Catharus guttatus ) populations on either side of this previously undescribed divide differ in migratory direction, migratory distance, and spring arrival times. Further, birds from the hybrid zone [...]
