1. Department of Ecology, Institute of Functional Biology and Ecology, Faculty of Biology, University of Warsaw, Biological and Chemical Research Centre, Warszawa, Poland; e-mail:
2. Roztocze National Park, Zwierzyniec, Poland
3. Faculty of Biology, Adam Mickiewicz University of Poznań, Poznań, Poland
4. Lublin Ornithological Society, Lublin, Poland
5. Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland