The year-round importance of breeding sites in common guillemots Uria aalge

• Main Author: Bennett, Sophie
• Other Authors: Daunt, Francis, Searle, Kate, Green, Jonathan
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: Uria aalge; uria
• Online Access: https://livrepository.liverpool.ac.uk/3170107/; https://livrepository.liverpool.ac.uk/3170107/1/201378344_Dec2022.pdf

As many natural populations are declining and facing increasing threats, understanding the mechanisms governing key demographic rates such as breeding success is increasingly critical. Across heterogeneous environments, animal breeding sites may differ in their quality such that some sites offer an intrinsically higher likelihood of breeding success than others. In declining populations, average quality of breeding sites used by the population is predicted to increase as individuals preferentially occupy the best locations (the ‘buffer effect’). However, we currently have limited understanding of whether this regulatory process operates in populations, or how its effects may vary in populations showing highly dynamic changes in density over time. Furthermore, the competition for higher quality breeding sites may often be intense such that individuals invest considerable time in site occupancy to protect higher quality breeding sites, even outside the breeding season. The site defence hypothesis predicts that occupancy should be positively correlated with breeding timing and success such that more successful sites are occupied earlier and/or more frequently, and result in higher breeding success. However, few studies test these predictions in populations where non-breeding season site occupancy dominates the annual cycle, limiting our understanding of potential fitness consequences. Even fewer studies investigate drivers and consequences of individual variation in site occupancy in the non-breeding season, hindering our understanding of how this behaviour may affect individual and population level fitness. In this thesis, I use a combination of long-term population demography data, time-lapse photography and novel inferences from biologging data to investigate how the quality of breeding sites may provide resilience to populations undergoing environmental change and drive the year-round behaviour of common guillemots, Uria aalge, a widespread colonial seabird species. The data in this thesis originate from a ...