1. Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland
2. Student Scientific Society for Ornithology, University of Wrocław, Wrocław, Poland
3. Faculty of Biological Sciences, University of Zielona Góra, Zielona Góra, Poland
4. Lesista 3, Kraków, Poland
5. Laboratory of Forest Biology, University of Wrocław, Wrocław, Poland