Data from: The breeding distribution of a migratory bird fluctuates with nonbreeding season rainfall over the last century

Species responses to climate change include shifts in distribution,
abundance, and range limits. Predicting such shifts for migratory birds is
inherently complex given the diversity of ways climate change can impact
species throughout their annual cycles. For example, recent findings
demonstrate that the breeding origin of a nonbreeding population of
American Redstarts (Setophaga ruticilla) in Jamaica is shifting southward
in response to prolonged drought on the nonbreeding grounds differentially
causing lower survival in longer migrating individuals. Here, we examine
how widespread this mechanism has operated over the past century and
across the range of this species. We sampled tail feathers from redstart
museum specimens and live birds from three time periods dating back to the
turn of the 20th century from 5 regions across their nonbreeding range
(Andean, Greater Antillean, Isthmian, Pacific Slope, and Yucatan) and used
stable hydrogen isotopes to estimate changes in breeding origins. We used
an ANCOVA to estimate the strength of the shift in mean breeding origin
for each population of nonbreeding redstarts since the turn of the 20th
century, and the role of nonbreeding season rainfall in driving observed
shifts. Populations of redstarts on their tropical nonbreeding grounds
experiencing a drying trend in rainfall showed a corresponding southward
shift in their mean breeding origin (and vice versa) in subsequent years.
The link between nonbreeding rainfall and mean breeding origin was most
pronounced in the modern time period, where nonbreeding rainfall has
decreased across most of the redstart nonbreeding range. Our findings
illustrate how complex mechanistic drivers operate over space and time to
help shape breeding range dynamics for a migratory bird, and emphasize how
climate impacts species distributions throughout the annual cycle.