1. Institute of Animal Ecology and Nature Education, Hauptstraße 30, 35321 Gonterskirchen, Germany
2. Frankfurt Zoological Society, Bernhard-Grzimek-Allee 1, 60316 Frankfurt, Germany
3. Department of Plant Ecology and Ecosystems Research, University Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
4. APB-BirdLife Belarus, Parnikovaya Street 11-4, 220114 Minsk, Belarus