Epsilon Archive for Student Projects

Abstract

Seabirds are facing immense pressures, primarily induced by competition with commercial fisheries; this is of considerable concern due to the critical role that they play in marine food webs and their invaluable function as bioindicators. In this thesis, I studied the temporal change in trip duration for the Common Guillemot Uria aalge, a circum-arctic seabird species. Pre-recorded video footage that focused on a group of guillemot pairs residing on the Swedish island of Stora Karlsö during the 2021 breeding season served as the basis for this study. Five pairs were observed from egg-laying in May to chick-fledging in July. I hypothesized that there would be distinct shifts in trip duration and frequency following egg hatching, compared to egg incubation. Moreover, I investigated the possible development of a Storer Ashmole’s Halo around the breeding colony; this would likely be evident due to an increase in trip duration as the season progressed and fish stocks near the colony progressively depleted. I found a significant increase in trip frequency following egg hatching. However, total time spent away from the nest did not appear to change; individual trips were, therefore, shorter once the chicks had hatched. The quantity of fish delivered to the chick fluctuated but did not show a clear correlation with chick age, or seasonal effects. Furthermore, the size of the fish delivered to the nest remained relatively stable throughout the breeding season. The results indicate that a Storer Ashmole’s Halo most likely does not develop around the Stora Karlsö breeding colony; however, more research surrounding the topic is ultimately needed. The data that I collected allows for the investigation of potential variations in feeding rates leading up to chick fledging.