Figure 2.

The number of breeding pairs recorded in the whole area of study (central Poland, vicinity of Rogów village, Experimental Forest Station of Warsaw University of Life Sciences) in the three compared periods: 1) 1982–1992 [19], 2) 2001–2003 [24], and 3) 2011–2018 (current study). The letters show the changes between the three study periods (a for 1982–1992, b for 2001–2003, and c for 2011–2018) as indicated by a Mann–Whitney post hoc test.