1. Department of Theoretical Ecology, Ecology Building, Lund University, SE-22362 Lund, Sweden.
2. Department of Biological and Environmental Sciences, Integrative Ecology Unit; Post Office Box 65 (Viikinkaari 1), FIN-00014, Helsinki University, Finland.
3. Department of Biological and Environmental Sciences, Bird Ecology Unit; Post Office Box 65 (Viikinkaari 1), FIN-00014, Helsinki University, Finland.
4. Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Post Office Box 1066, Blindern, N-0316 Oslo, Norway.
5. Dipartimento di Biologia Animale, Università degli Studi di Pavia, Piazza Botta 9, I-27100 Pavia, Italy.