1. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK
2. Department of Biology, University of Haifa, Oranim, Tivon 36006, Israel
3. Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
4. Center for Behaviour and Neurosciences, University of Groningen, Groningen, The Netherlands
5. Nuffield Department of Clinical Neurosciences, Headington, Oxford OX3 9DU, UK
6. Department of Biology, University of Konstanz, Konstanz 78464, Germany
7. Department of Migration and Immuno-ecology, Max Planck Institute for Ornithology, Radolfzell 78315, Germany