1. Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark
2. Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
3. Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA
4. US Fish and Wildlife Service, Division of Migratory Bird Management, Juneau, AK 99801, USA