Temperature extremes across breeding and nonbreeding regions shape annual survival in a migratory bird

Abstract Migratory birds experience diverse ecological conditions throughout their migratory range that can influence survival, particularly during vulnerable life stages such as juveniles. Identifying the life stages and regions that constrain populations is therefore essential for migratory species of conservation concern, including aerial insectivores. Using a migratory population of red-necked nightjars (Caprimulgus ruficollis) as a model, we analyzed 12 years (2010–2021) of capture–recapture data to estimate sex- and age-specific annual survival probabilities and assessed the effects of time (year), vegetation development (normalized difference vegetation index [NDVI]), and land surface temperature (LST) in the breeding (Doñana) and nonbreeding staging areas (Mali and Guinea). Survival probabilities remained constant throughout the study period. Adults showed higher survival (females: 0.660 ± 0.038 standard error (SE), 95% confidence interval [CI]: 0.581–0.731; males: 0.677 ± 0.037 SE, 95% CI: 0.6–0.746) than juveniles (females: 0.398 ± 0.040 SE, 95% CI: 0.323–0.479; males: 0.352 ± 0.036 SE, 95% CI: 0.285–0.426), after accounting for age-specific differences in recapture probabilities. NDVI did not affect survival. In contrast, LST in both Doñana and Guinea was positively associated with survival in adults and juveniles. Our findings demonstrate that climatic factors operating in geographically distant regions can jointly shape red-necked nightjar demography and suggest that this species may be relatively resilient to projected increases in temperature.