1. Research Group Evolutionary Ecology of Variation, Max Planck Institute for Ornithology, Seewiesen, Germany
2. Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany
3. Department of Biology, Center for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
4. Department of Biology, Behavioural Ecology, Ludwig Maximilian University of Munich (LMU), Planegg-Martinsried, Germany