COS 157-1 - The Effects of Climate on the Vital Rates of a Neotropical Migratory Songbird

Abstract: Climate change is one of the most pressing and complex challenges of the 21st century, with far-reaching impacts on global environments. Migratory species are considered to be particularly vulnerable to climate change, as they rely on specific climatic conditions at different stages of their annual cycle. However, predicting how demographic factors respond to global changes remains challenging due to the complex connections between vital rates and climate variables and the need for long-term datasets. Our study utilized a 27-year dataset to assess how local weather during the breeding season and climate patterns in the overwintering region impact the population demography of the Prothonotary Warbler, a Neotropical migratory songbird. They are considered a wetland indicator species that readily use nest boxes and have strong site fidelity, making them an excellent species for studying population demography. We used a female-based integrated population model and Bayesian population viability analysis (IPM-BPVA) to link vital rates to changes in climate and project future survival and reproductive success. The combination of IPMs and BPVAs has emerged as a powerful approach that accounts for the dependencies between different aspects of the population and provides reasonable predictions of future population trends.

We found that an increase in the frequency of local temperature anomalies (warmer than the 90th percentile and cooler than the 10th percentile) during the breeding season negatively affected juvenile and adult survival. Reproductive success was negatively affected by an increase in the Multivariate El Niño Southern Oscillation Index (MEI; i.e., stronger El Niño), a broad-scale climate index that reflects the conditions (e.g., a higher value indicates less rainfall in their winter range) during the preceding overwintering period. The impact of winter conditions on fecundity emphasizes the need to assess the influence of climate effects throughout the annual cycle.

We compared nine potential future scenarios involving differing degrees of increased temperature anomalies and stronger MEI conditions. We found that the Prothonotary Warbler population was predicted to decline in all scenarios, with the most severe declines projected under more frequent temperature anomalies. These findings suggest that increases in the frequency of temperature anomalies and MEI trends associated with climate change may threaten the long-term survival of Prothonotary Warblers. Our results underscore the need for continued individual-based long-term studies of migratory species to better understand how populations are affected by the changing climate and yield more precise projections of population trends due to climate change.