From past change to future risk: Population dynamics of Atlantic Puffins (Fratercula arctica) and Razorbills (Alca torda) in the rapidly warming Gulf of Maine

Abstract

Rapidly warming global temperatures are having a widespread influence on wildlife communities, with southern-edge populations often experiencing the greatest negative impacts. The Gulf of Maine is warming faster than most of the global ocean and has experienced shifts in the abundance, distribution, and quality of marine prey communities. These shifts can cascade up the food web and ultimately affect the fitness and viability of marine top predators such as seabirds. Using integrated population models, I jointly analyzed population count, capture-mark-recapture, and productivity data for Atlantic Puffins (Fratercula arctica) and Razorbills (Alca torda) breeding at the southern edge of their range in the Gulf of Maine to quantify their population dynamics and explore the environmental and demographic drivers that explain key demographic vital rates. Additionally, I conducted a Bayesian population viability analysis to project the population for 15 years (2025-2039) to predict how these populations may respond to future change given their response to past changes. Overall, I found divergent population trends between the two species despite similar demographic rate estimates. The puffin population remained relatively stable while the Razorbill population largely increased. Interannual variation in productivity was much higher in puffins than Razorbills, and adult survival was found to be the primary driver of population dynamics for both species. Key demographic rates in both species were negatively associated with warming-related stressors. Finally, my projections suggest that the puffin population is at greater risk of decline than the Razorbill population however neither population is likely to fall below 50% or 30% of the 2024 population size within 15 years. Overall, my results suggest that the study species are not at immediate risk of decline though early demographic signs of climate stress suggest that climate change may already be shaping population dynamics. These findings highlight the potential threat of climate change processes on range-edge seabird populations in the rapidly warming Gulf of Maine and the need for conservation strategies that consider both current and future environmental conditions.