1. Department of Zoology, University of Melbourne; Parkville Victoria 3010 Australia
2. Advanced Facility for Avian Research; University of Western Ontario; London Ontario N6A 5B7 Canada
3. Department of Zoology, Edward Grey Institute; University of Oxford; Oxford OS1 3PS United Kingdom
4. Griffith School of Environment and Environmental Futures Research Institute, Griffith University; Gold Coast; Queensland 4222 Australia