1. Nature Conservation and Plant Ecology Group, Wageningen University, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands
2. Tropical Nature Conservation and Vertebrate Ecology Group, Wageningen University, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands; Present adress: Community and Conservation Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O.Box 14, 9750 AA, Haren, The Netherlands; E‐mail