1. Evolutionary Ecology of Variation Group Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
2. Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
3. Behavioural Ecology Department Biology II Ludwig‐Maximilians University of Munich Groβhadener Straβe 2 DE‐ 82152 Planegg‐Martinsried Munich Germany