Max Planck Institute of Animal Behavior - Department of Migration, Max Planck Institute of Animal Behavior - Department of Migration, The Academy of Natural Sciences of Drexel University - Ornithology Department, Montpellier University-CNRS - Centre for Evolutionary and Functional Ecology, University of Patras - Department of Biology, Keio University - Research and Education Centre for Natural Sciences, University of Patras - Department of Biology, University of Konstanz - Department of Biology, University of Moncton - Canada Research Chair in Polar and Boreal Ecology, University of Siena - Department of Physics, Earth and Environmental Sciences, Max Planck Institute of Animal Behavior - Department of Migration, Maremma Natural History Museum, Acopian Center for Conservation Learning - Hawk Mountain Sanctuary, Hellenic Ornithological Society/BirdLife, Nagasaki University - Graduate School of Fisheries and Environmental Sciences, Max Planck Institute of Animal Behavior - Department of Migration and Max Planck Institute of Animal Behavior - Department of Migration