1. Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands
2. Resource Ecology Group, Wageningen University, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands
3. Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand
4. Department of Vertebrate Zoology, Faculty of Biology, Moscow State University, Moscow, Russia
5. Centre for Isotope Research, Nijenborgh 6, Faculty of Science and Engineering. University of Groningen, Groningen, The Netherlands