1. a Department of Silviculture, Forest Faculty , Lithuanian University of Agriculture , Kaunas, Lithuania
2. b Department of Ecology, Institute of Environment , Lithuanian University of Agriculture , Kaunas, Lithuania
3. c Grimsö Wildlife Research Station, Department of Conservation Biology, Faculty of Forest Sciences , Swedish University of Agricultural Sciences , Riddarhyttan, Sweden
4. d School for Forest Engineers, Faculty of Forest Sciences , Swedish University of Agricultural Sciences , Skinnskatteberg, Sweden