1. Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
2. School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
3. School of Psychology and Neuroscience, University of St. Andrews, St Andrews KY16 9JP, UK
4. Department of Biology, Pacific University, Forest Grove, OR 97116, USA
5. Department of Collective Behaviour, Max Planck Institute for Ornithology, Radolfzell 78315, Germany
6. Chair of Biodiversity and Collective Behaviour, Department of Biology, University of Konstanz, Konstanz 78464, Germany