1. Section of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
2. Department of Migration and Immunoecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany
3. Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
4. Smithsonian Tropical Research Institute, P.O. Box 0843-03092, Balboa Ancón, Panama