1. Department of Biology, Centre for Biodiversity Dynamics (CBD); Norwegian University of Science and Technology (NTNU); N-7491 Trondheim Norway
2. Norwegian Institute for Nature Research (NINA); N-7485 Trondheim Norway
3. Behavioural Ecology, Department of Biology; Ludwig Maximilian University of Munich (LMU); 82152 Planegg-Martinsried Germany