1. Bird Ecology Unit, Department of Biological and Environmental Sciences, University of HelsinkiPO Box 65, (Viikinkaari 1), 00014 Helsinki, Finland
2. Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences181 Riia Street, 51014 Tartu, Estonia
3. Ashworth Laboratories, Institute of Evolutionary Biology, School of Biological Sciences, The University of EdinburghThe King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK