Associations of extreme weather, El Niño events, and streamflow with the annual apparent survival of a migratory riparian bird in the western United States

Neotropical avian migrants are affected by environmental change throughout their full annual cycles. In the southwestern United States, these species rely on riparian corridors for food and water, for migration stopover sites, and as breeding grounds. Climate change imperils these essential ecosystems, with the southwest predicted to become hotter and more arid, thus resulting in more frequent extreme heat and drought. The tropical forests of Latin America, where many Neotropical migrants overwinter, face similar threats. The impacts of these changes on the demography of migratory riparian species remains poorly understood. We analysed 13 years of capture–mark–recapture bird banding data (2011–2023) from southern Utah to examine the effects of age-class and a range of environmental variables on the survival of a common migratory and riparian breeding bird, the Western Yellow-breasted Chat Icteria virens auricollis. We found that adult chats had a significantly greater probability of survival than first-year birds (mean survival adults: 0.53 ± 0.11; juveniles: 0.12 ± 0.07). While rates of survival differed for the two age-classes, the variability was closely matched across years, indicating that both adults and juveniles are impacted similarly by ecological factors. We also found that annual survival rates were particularly sensitive to the El Niño-Southern Oscillation (ENSO) cycle, with El Niño events being associated with reduced chat survival. This suggests a key negative impact of drier, hotter conditions during migration and on the wintering grounds in Central America—conditions that may become increasingly extreme with future climate change. We also found near-significant negative effects of breeding season heat events (% of days with maximum temperature exceeding the 90th percentile of a 30-year baseline) and spring precipitation, as well as a potential positive association between chat survival and breeding season streamflow. Our results not only demonstrate the importance of environmental variation across the full annual cycle of chats in driving variation in survival, but also highlight how future climate change may impact the demography of a key riparian species.