1. Institute of Biology, Leiden University, 2333 BE, Leiden, The Netherlands
2. Cornell Lab of Ornithology and Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14850, USA
3. Research School of Biology, Australian National University, Canberra, Australian Capital Territory 0200, Australia
4. School of BioSciences, University of Melbourne, Melbourne, Victoria 3010, Australia