1. Spatial Ecology Department, Netherlands Institute of Ecology (NIOO-KNAW), Post Office Box 140, 4400 AC Yerseke, Netherlands.
2. Theoretical Biology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Nijenborgh 7, 9747 AG Groningen, Netherlands.
3. Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Post Office Box 50, 6700 AB Wageningen, Netherlands.
4. Project Group Movement Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Post Office Box 50, 6700 AB Wageningen, Netherlands.