In the Arctic, polar bears (Ursus maritimus) rely on sea ice to hunt seals. However, sea ice is decreasing due to climate warming, and bears are changing their foraging behavior, increasing egg consumption. This shift in diet can put ground-nesting bird species, such as common eiders (Somateria mollissima), at risk. The aim of this project, as a part of my PhD, is to understand how prey can cope with novel stressors, such as the appearance of a new predator they have not coevolved with, by studying Kongsfjorden eider population. To assess behavioral and physiological stress-coping strategies, we will measure flight initiation distance, as well as blood levels of two main hormones mediating stress and parental care in birds: corticosterone and prolactin. This project will improve knowledge about how individuals respond to predation threat induced by a new egg predator: the polar bear. As eiders may respond differently to a native predator they have co-evolved with, we will compare stress-coping strategies measured in Svalbard with the ones measured on a Finnish eider population facing the recovery of its natural avian predator: the white-tailed eagle (Haliaeetus albicilla).