The influence of migratory routes, breeding, and wintering grounds on cultural shifts in song of White-throated Sparrows ( Zonotrichia albicollis )

For song variants to spread among widely separated breeding populations by cultural evolution, song sharing would have to occur in locations where birds physically overlap in time and space, such as common wintering grounds and/or migratory routes. To identify such spatiotemporal links between populations, we used the Motus Wildlife Tracking System to investigate whether White-throated Sparrows (<em>Zonotrichia albicollis</em>) in three disparate breeding populations in British Columbia migrate to common wintering grounds and overlap on migration pathways. We also tracked sparrows overwintering in a single eastern region (Georgia, United States) to determine whether they disperse to multiple breeding regions. Except for a single sparrow that migrated to California, all other sparrows tagged on western breeding grounds (N = 23) were either detected in, or converging on, the south-central United States. Further, we detected a common migratory pathway tracking the southern edge of the boreal forests in Canada and the western edge of the Eastern Temperate Forests in the United States. This migratory route coincides with regions where previous studies have shown the rapid spread of novel song variants (doublet-ending songs) over short time scales; birds share not only a common wintering ground, but also a common migratory pathway that might reinforce song sharing if song learning extends into the bird’s first spring. Along with learning biases, this could explain the rapid, widespread adoption of novel song variants within the past two decades across western and central Canada. We confirmed that birds from a single wintering location in Georgia dispersed across a wide region during northward migration, which also corresponds to locations where other song variants (triplet-ending) have persisted.