1. Evolutionary Physiology Group, Max Planck Institute for Ornithology, Seewiesen, Germany
2. Department of Biology, Behavioural Ecology and Ecophysiology Group, University of Antwerp, Antwerp, Belgium
3. Faculty of Social Sciences, Antwerp School of Education, University of Antwerp, Antwerp, Belgium
4. Department of Zoology, School of Life Sciences, La Trobe University, Melbourne, Victoria, Australia