Authors: Edward R. Pandolfino and Lily A. Douglas
Year: 2023
Publication: Avian Behavior, Ecology, and Evolution
Publication Link: https://journal.afonet.org/vol94/iss3/art10/
Keywords: Corthylio calendula; distribution; migration; migration route; Ruby-crowned Kinglet; song; song dialect; winter range
Abstract: 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. We
found that kinglets breeding in the eastern portions of the range wintered in the southeastern and south-central U.S., and that their
spring migrations occurred across a broad swath of the eastern U.S. Interior Alaska breeders wintered mostly in California, and the
subspecies C. c. grinnelli wintered from the southernmost parts of their breeding range, south as far as northwestern California. We
obtained too few winter recordings from birds using the dialects of kinglets breeding in the interior west (Rocky Mountains and the
Sierra Nevada and Cascades ranges) to determine their winter range, and spring recordings were also sparse from those regions. It is
likely that those interior-west breeders winter mainly in Mexico, an area with very few archived recordings. We also analyzed unpublished
banding data for the Ruby-crowned Kinglet that, although providing little information about breeding-wintering range connectivity,
were consistent with the migratory pathways we determined from song dialects.