The Gulf of Maine is a dynamic ecosystem with rapidly warming sea surface temperatures (SSTs), therefore it is vital to understand how species interactions vary over time and space. In chapter two, I quantify and compare dietary differences among four tern species, across seven islands in the region, over a 32-year period. Multivariate statistical analyses were employed to discern spatial and temporal differences in foraging ecology. Findings suggest there are significant differences between species and islands; however, only three prey species comprise the majority of chick diet for all terns and islands. The reliance on only a few prey items led to narrow foraging niches, potentially increasing their vulnerability to climate change, fisheries practices, or other localized disturbances.
The third chapter characterizes long-term trends across nesting islands, describes within-season dietary phenology, and quantifies how warming SSTs may influence diet. Over time there was a declining trend in the occurrence of hake and increasing amounts of sand lance. In addition, hake and sand lance occur with higher frequency earlier in the season, while butterfish and “other fish” showed the opposite trend. Furthermore, results indicated that the within-season decline of hake occurs more rapidly in years with earlier spring thermal transition dates potentially indicating a phenological shift. Finally, warming SSTs were found to be negatively correlated with hake and positively correlated with the “other fish” prey group. Given projections of further warming in the region, understanding how the diet of these seabirds may be impacted in crucial to their conservation
