ACKNOWLEDGEMENT
We thank all fieldworkers who collected data for this study, the island inhabitants, laboratory technician Randi Røsbak (NTNU, Trondheim) for extracting DNA and genotyping procedures, and Håkon Holand for help with parentage analyses. This work was funded by the Research Council of Norway (Centre for Biodiversity Dynamics 223257 and 274930). MLP also thanks “Forsknings- og undervisningsfondet i Trondheim ” for financial support. The study design was subject to review by the Norwegian Environment Agency (permits 2001/6427-ARTS/VI/ARE and 2004/1671-ARTS-VI-ID) and complied with the laws of animal welfare in Norway (permits S-2603-01, S-204-8032-1, and S-2007/1482 from the Norwegian Animal Research Authority and the Bird Ringing Centre at Museum Stavanger, Norway). The authors have no conflicts of interest to declare.