Reudink, Matthew W., Van Wilgenburg, Steven L., Steele, Lauren S., Pillar, Andrew G., Marra, Peter P., and McKellar, Ann E. 2015. "Patterns of migratory connectivity in Vaux's Swifts at a northern migratory roost: A multi-isotope approach." The Condor 117 (4):670-682. https://doi.org/10.1650/CONDOR-15-82.1
The strength of migratory connectivity between breeding, stopover, and wintering areas can have important implications for population dynamics, evolutionary processes, and conservation. For example, patterns of migratory connectivity may influence the vulnerability of species and populations to stochastic events. For many migratory songbirds, however, we are only beginning to understand patterns of migratory connectivity. We investigated the potential strength of migratory connectivity within a population of Vaux's Swifts (Chaetura vauxi). Like many aerial insectivores, this species is currently experiencing population declines. In 2012, a mass mortality event at a spring migratory roost on Vancouver Island, British Columbia, Canada, resulted in the deaths of >1,000 individuals (~2% of the British Columbia population). In these individuals, we examined variation in 3 stable isotopes (δ2H, δ13C, and δ15N) from claw samples to determine whether spring migrants showed inherent isotopic similarity in the habitats they used on their Mexican and Central American wintering grounds. Our results indicated the presence of 2 or 3 broad isotopic clusters, which suggests that Vaux's Swifts that migrated through Vancouver Island most likely originated from 2 or 3 overwintering locales or habitat types. We found no evidence of sex- or morphology-based segregation, which suggests that these groups likely share a similar overwintering ecology and, thus, may be equally vulnerable to stochastic events or habitat loss on the wintering grounds. Our results highlight the need for more studies on the nonbreeding-season ecology and migratory connectivity of this species.
