1. Forest Research Institute, Department of Forest Ecology, Sękocin Stary, 3 Braci Leśnej; 05−090 Raszyn, Poland; e-mail j.gryz@ibles.waw.pl
2. Warsaw University of Life Sciences, Faculty of Forestry, Department of Forest Silviculture, 159 Nowoursynowska; 02−776 Warsaw, Poland; e-mail: longina_chojnacka_ozga@.sggw.pl
3. Warsaw University of Life Sciences, Faculty of Forestry, Department of Wildlife Management and Forest Zoology, 159 Nowoursynowska; 02−776 Warsaw, Poland