1. Graduate Degree Program in Ecology, Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado 80523, USA;
2. Department of Biological Sciences, University of Denver, Denver, Colorado 80208, USA
3. Department of Terrestrial Ecology, Netherlands Institute of Ecology, 6708 PB Wageningen, The Netherlands
4. Animal Ecology Section, Department of Ecological Sciences, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands