1. Evolutionary Behavioural Ecology Research Group, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
2. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
3. Chair in Global Flyway Ecology, Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
4. Department of Marine Ecology, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
5. Department of Biology and Center for Biodiversity, East Carolina University, Greenville, NC 27858-4353, USA