Responses of a threatened seabird to degradation of its breeding environment: prospecting and dispersal in the context of global change

Understanding what factors are affecting the spatial dynamics of threatened populations is key for their conservation. In addition to effects on local demographic parameters, a degradation of the environmental conditions on the breeding colonies of threatened seabirds like Black-legged kittiwakes (Rissa tridacyla) can lead to the dispersal of individuals, potentially to places that they have prospected previously. Very little information is nevertheless available about dispersal behavior at large spatial scales, notably among colonies situated tens of kilometers apart. In the current context of environmental change in Eastern Finnmark, the project aims at exploring the effect of environmental variability on the movements of breeding kittiwakes during the breeding season via the use of GPS loggers. In addition to gathering information on the foraging areas used by the birds, the main hypothesis to be tested is whether and at what spatial scale unsuccessful breeders make prospecting movements. Those movements will be compared to those of successful breeders, which are expected to focus on foraging. By the gathering of data over years with different environmental conditions, the spatial extend of the prospecting movements will be related to the temporal and spatial variability of the quality of the environment on and in the surroundings of the breeding area (food availability, local exposure to predators). The kittiwake is on the red list of endangered species in Norway and the study will provide useful data for its conservation as it will provide information on the state of its environment and how it reponds to it. The study will involve a sample of a total of 40 breeding birds over two years (20/year). Care to adhere to the demands for replacement, reduction and improvements was taken for the design of the study and will be for its implementation, notably by using GPS loggers that do not require the recapture of the individuals for accessing the data. The birds will be subject to very limited distress as the manipulation will consist in the capture of the birds to equip them with a miniaturized GPS for the tracking of their movements over the following weeks. A small blood sample will be taken at first capture for assessment of their health. The study has implications for the understanding of the response of seabird populations to changes of the environment, notably for a species like the kittiwake which suffers repeated breeding failures and predation pressures in northern Norway.