Using song dialects to reveal migratory patterns of Ruby-crowned Kinglet populations

. Conservation of a migratory species requires knowledge not only of its breeding range, but also of its migratory path and non-breeding range. Except for timing, other aspects of the migration of the Ruby-crowned Kinglet ( Corthylio calendula ) remain largely unstudied, with no published data on migration routes. Breeding populations of this species in the Sierra Nevada and Cascades mountain ranges, as well as those in eastern Canada and the northeastern U.S., have experienced significant declines, whereas Rocky Mountain breeders have increased. Understanding the winter range and migratory pathways used by different breeding populations may be key to explaining these contrasting population trends. Song dialects of the Ruby-crowned Kinglet differ regionally among various breeding populations, and these dialect regions were previously mapped. Because this kinglet sings during spring migration and winter, we obtained archived, non-breeding-season recordings of song and assigned each to one of those regional song dialects. This allowed us to assess the likely winter ranges and migration pathways of different breeding populations. This approach offers some advantages over typical methods of tracking movements. Birds do not need to be captured; one can easily obtain data over large ranges and from many individuals; and it can be applied to species, such as this kinglet, that are too small to permit use of most tracking devices. We were able to assess likely winter range and spring migration routes for populations that breed in the eastern U.S. and Canada, the interior of Alaska, and for the subspecies C c. grinnelli that breeds along the Gulf of Alaska and western British Columbia