1. Department of Cognitive Science, Lund University, Helgonavägen 3, 22100 Lund, Sweden
2. Max-Planck-Institute for Ornithology, Eberhard-Gwinner-Strasse, 82319 Seewiesen, Germany
3. Max-Planck Comparative Cognition Research Station, Loro Parque Fundacíon, 38400 Puerto de la Cruz, Tenerife, Spain