Class Year

2024

Document Type

Student Research Paper

Date of Creation

Spring 2024

Department 1

Environmental Studies

Abstract

Climate change is resulting in ecosystem-wide consequences, including shifts in the geographical distribution of species and the timing of biological events, or phenology. The rapidly warming Gulf of Maine hosts breeding populations of migratory common terns (Sterna hirundo) and Arctic terns (Sterna paradisaea). I used nest check data (2013-2022) and eggshell membrane stable isotope data (2022) from Petit Manan Island in the Gulf of Maine to examine the causes and consequences of variation in phenology in common and Arctic terns. I hypothesized that the timing of an individual’s breeding was impacted by their foraging behavior and that female terns that foraged more inshore and at higher trophic levels would have chicks with earlier hatch dates. Further, I hypothesized that chicks that hatched earlier would have a greater chance of survival, would grow faster, and would fledge at a larger size. I used linear models and stable isotope analysis to test these hypotheses. I found that, since 2013, mean hatch dates have decreased by 0.6 days/year and that breeding has become less synchronous and more variable for both tern species. Arctic terns had significantly lower δ13C and δ15N values than did common terns and a significantly smaller isotope niche. I found a relationship between hatch date δ15N values, but not with δ13C. There was no relationship between chick hatch date and survival; the impacts of hatch date on growth rate varied across years, species, and chick hatch order. Second-hatched (“B”) chicks were most impacted, particularly in 2022, when later-hatched B chicks had slower mass and wing chord growth rates and fledged at a smaller size. Fledging size can affect juvenile survival rates in seabirds, so my study may suggest impacts of hatch date on fitness in these two species of tern. Future research should repeat these analyses across years to determine how relationships between hatch date and fitness vary with environmental conditions.

Comments

Written for ES 460: Individualized Study-Research

Creative Commons License

Creative Commons Attribution-Share Alike 4.0 License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License.

Download

Share

COinS