1. aDepartment of Behavioural Biology, University of Vienna, Vienna, Austria
2. bComparative Cognition, Messerli Research Institute, University of Veterinary Medicine Vienna, Vienna, Austria
3. cDepartment of Zoology, University of Oxford, Oxford, UK
4. dDepartment of Behavioural Ecology and Evolutionary Genetics, Max-Planck-Institute of Ornithology, Seewiesen, Germany
5. eDepartment Biology II, Biozentrum, Ludwig-Maximilians-Universität München, Munich, Germany