1. Dept of Biology; Section for Evolutionary Ecology, Lund Univ.; Ecology Building SE-223 62 Lund Sweden
2. Dept of Arctic and Marine Biology; Arctic Animal Physiology, Arctic Biology Building, Univ. of Tromsø; NO-9037 Tromsø Norway
3. Inst. of Biodiversity; Animal Health and Comparative Medicine, Graham Kerr Building, Univ. of Glasgow; Glasgow G12 8QQ UK
4. Dept of Biology; Univ. of Konstanz and Max Planck Inst. for Ornithology; PO Box 616 DE-78457 Konstanz Germany