1. R. P. Freckleton is in the Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
2. W. J. Sutherland is at the Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
3. A. R. Watkinson is at the Schools of Biological and Environmental Sciences, and Tyndall Centre for Climate Change Research, University of East Anglia, Norwich NR4 7TJ, UK.