Regional drivers of seabird population change: understanding interacting pressures to predict future resilience

Supervisor: Catherine Horswill

Co-supervisor: Andrea Manica

Project Summary (PhD):

Seabird populations are changing rapidly, but the causes of these changes vary markedly across regions. Climate change, fisheries, disease outbreaks and habitat conditions can act together, creating complex patterns of population decline, stability or recovery. Understanding how these interacting pressures shape demographic rates, such as survival and breeding success, is essential for predicting future population trajectories and informing conservation action.

This project will combine long-term demographic datasets, environmental information and advanced statistical models to investigate why seabird populations respond differently across space and time. By identifying the processes driving regional variation in population dynamics, the student will develop models that can forecast future change under alternative environmental scenarios and support evidence-based management of marine ecosystems.

Type of Work: 

The student will analyse long-term datasets on seabird survival, reproduction and abundance alongside environmental data on climate, fisheries and other human pressures. They will develop quantitative models to investigate spatial variation in demographic processes and identify how multiple drivers combine to influence population change. The project is primarily computational and is best suited to students with a good working knowledge of statistical analysis in R. It will provide advanced training in Bayesian statistical modelling. The student will work within a collaborative marine ecology research group and engage with conservation organisations and policy stakeholders to ensure that the research has real-world impact.

Importance of the area of research concerned:

Seabirds are among the most threatened groups of marine animals and are widely recognised as indicators of ocean health. Effective conservation and sustainable marine management require an understanding of how multiple environmental pressures interact to influence populations across large spatial scales.
 

References:

Merrall, E. S., Green, J. A., Robinson, L. A., Butler, A., Wood, M. J., Newell, M. A., Black, J., Daunt, F., & Horswill, C. (2024). Incorporating density-dependent regulation into impact assessments for seabirds. Journal of Applied Ecology, 61, 2510–2524. https://doi.org/10.1111/1365-2664.14750 Horswill, C., Wood, M. J., & Manica, A. (2022). Temporal change in the contribution of immigration to population growth in a wild seabird experiencing rapid population decline. Ecography, 2022(11), e05846. https://doi.org/10.1111/ecog.05846 K. Layton-Matthews, C.E. Regan, M. Ballesteros, K. Hodges, S. Descamps, T. Anker-Nilssen, S. Benjaminsen, F. Daunt, R.T. Barrett, L. Buckingham, V.S. Bråthen, S. Christensen-Dalsgaard, N. Dehnhard, K.E. Erikstad, A.L. Fayet, H.H. Helgason, M.K. Johansen, S. Lorentsen, E. Lorentzen, B. Moe, G.H. Systad, H. Strøm, K.R. Searle, & T.K. Reiertsen, Demographic responses of North Atlantic seabirds to seasonal ocean warming, Proc. Natl. Acad. Sci. U.S.A. 122 (50) e2507531122, https://doi.org/10.1073/pnas.2507531122 (2025). Schatz, C., Delord, K., Joubert, D., Peroteau, S., Sun, R. and Barbraud, C. (2025), Inter-population variation in demographic responses to environmental changes: insights from four seabird populations. Oikos, 2025: e11364. https://doi.org/10.1002/oik.11364