The Role of the Arctic Fox in the Breeding Success of the Snow Bunting

Abstract

The reproductive success of breeding birds can be determined by many different factors. One factor often associated with the failure of a brood is nest depredation. To avoid depredation, different bird species implement different adaptations. Some species have evolved a specific nesting-strategy, for example cavity-nesting. In addition to the top-down regulation by predators, breeding birds are also subjected to changing climatic conditions. Bird species which are breeding in the high Arctic, where the breeding season is short and the effects of Arctic warming have already led to changes in the local climate, can be very sensitive to those factors. In this thesis, I explore the role of the Arctic fox (Vulpes lagopus) and its top-down effect on the fledging success of a population of migratory snow buntings (Plectrophenax nivalis) on Svalbard. First, I investigated how the nest’s accessibility influences the daily probability of snow bunting broods being depredated by the Arctic fox and how the predation pressure changes on snow bunting nests throughout the season. Then, I investigated the role of fox abundance in the reproduction of the snow bunting in comparison to weather factors, which have previously been found to impact the breeding success significantly. I used a 22-year long time series from 1998 to 2020 of monitored snow bunting nests in Adventdalen. My analysis revealed nest height to be the dominating factor influencing the daily probability of a nest being depredated. In addition, I found a tendency of broods that were started later in the season to be more depredated than earlier broods. Arctic fox abundance had a rather small effect on the snow buntings’ fledging success in comparison to the local climate. The mean temperature had a strong impact on the fledging success, as well as the timing of breeding. This study shows the Arctic fox might not play an essential role in the snow bunting population’s breeding success at present. However, there are implications that future warming will impact both the snow bunting and the Arctic fox and might therefore also alter their interactions with each other.