Abstract
Rapid warming in the Gulf of Maine (GoM) is contributing to widespread shifts in the abundance, distribution, and quality of marine prey communities. These shifts cascade up the food web and will ultimately affect the fitness and viability of seabirds, the impacts of which are expected to be especially pronounced at the southern edge of their ranges. Using integrated population models, we analyzed 26 years (1998–2023) of demographic data for Atlantic Puffins ( Fratercula arctica ; ATPU) and Razorbills ( Alca torda ; RAZO) nesting at the southern edge of their breeding range in the GoM. Additionally, we examined the environmental and demographic drivers of demographic rates and how these relationships may have changed over time. We found that key demographic rates in both species are linked to warming‐related stressors. In ATPU, adult survival declined with increasing summer length, and productivity was negatively associated with winter sea surface temperature anomalies. RAZO first‐year survival was positively associated with chick wing chord growth, which itself declined over time with a parallel increase in the proportion of lower‐quality prey in the diet. Summer length had a strong negative effect on productivity in this species. Finally, we found no evidence indicating that these climate‐demography relationships were changing over time, suggesting current stationarity in these species' responses to ocean warming. Our findings suggest that specific warming‐related factors, such as summer length and winter sea surface temperature anomalies have negatively impacted ATPU and RAZO demographic rates. Given the apparent stationarity of the identified climate–demography relationships over the study period, these relationships may be expected to persist under continued warming in the GoM. For cold‐adapted species like ATPU and RAZO that are already living close to their thermal limits in the GoM, these insights are especially urgent.