Class Year


Document Type

Student Research Paper

Date of Creation

Spring 2023

Department 1

Environmental Studies


This study examines fine-scale environmental changes and intraspecific variation in the diet and foraging behavior of two seabirds in the Gulf of Maine, one of the fastest-warming regions of the ocean. This variation on the individual level, or behavioral plasticity, may help long-lived species to persist in rapidly changing environments. As the water warms, seabirds’ preferred prey (hake and herring) follow cooler waters deeper and farther offshore. It is unlikely that all individuals respond to changing food availability in the same way. For common terns (Sterna hirundo) and Arctic terns (Sterna paradisaea) breeding on Petit Manan Island, I hypothesized that: H1: Preferred prey decline in the diet as sea surface temperature (SST) increases; H2: Individuals vary in their response to increasing SST; H3: Individual-level diet influences fitness. In June and July of 2022, we conducted daily chick provisioning watches and recorded prey size and species. While SST did not influence average feeding rate, increased SST drove declines in the average prey size and the proportion of hake and herring in the diet at the colony level (H1 supported). Slopes were similar across nests, suggesting no individual variation in diet plasticity with increasing SST (H2 not supported). At the nest level, a higher average proportion of herring and hake was associated with higher chick mortality and a declining growth rate. A higher average feeding rate was associated with an increase in growth rate while prey size did not impact chick growth rate (H3 not supported). Our findings suggest that individuals that try to maintain a diet of preferred prey may have lower fitness in a changing climate. However, individuals that decrease their foraging distance and prey switch to maintain a sufficient feeding rate are successful in raising chicks that reach fledging age.


Written for ES 460: Independent Research Project.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License