1. Department of Behavioral Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Postfach 1564, D‐82305 Starnberg (Seewiesen), Germany
2. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
3. Department of Animal Ecology, Ecology Building, Lund University, SE‐223 62 Lund, Sweden