Adam Zbyryt, Edyta Kapowicz, Robert Kapowicz, Karol Zub
Ornis Polonica 2016, 57: 237–247
https://doi.org/10.12657/ornis.2016.4.0
Abstract: The objective of this study was to recognize distribution, number and breeding success of the Lesser Spotted Eagle Clanga pomarina in the Knyszyn Forest. The research was carried out on the study plot of 450 km2 in 1999–2015 , and in the whole Natura 2000 area SPA Puszcza Knyszyńska PLB200003 (1395 km2) in 2010–2014. We investigated the effect of year, nest tree species, nest site (forest interior, distance to the river valley or forest edge) and number of years the territory was occupied on breeding success. In 1999–2003 and 2010–2014 the number of breeding pairs of the Lesser Spotted Eagle varied between 46 and 58 in the whole Natura 2000 area. On the study plot we found 20 to 22 breeding pairs in 1999–2015, whose mean density reached 4.7 pairs/100 km2 (SD=0.1; range 4.7–4.9). The breeding success (percentage of nests with min one offspring fledged) varied from 33.3% (2007) to 70.5% (2006) (mean 53.9%; SD=8.8; Me=52.9). The number of nestlings per 100 km2 ranged from 1.11 juv./100 km2 (2009) to 2.67 juv./100 km2 (2002, 2006) (mean 2.07 juv./100 km2; SD=0.57). Breeding success was significantly affected by the year of the study (generalized linear mixed model, Z=10.18, P<0.001) and total rainfall in June (Z=3.06, P=0.002), while the remaining analysed factors were not significant. A single pair used on average 3.0 nests (SD=1.3; range 1–6; Me=3.0), each of them usually occupied for 4 consecutive years. During 27 years (data from 1989–2015), breeding territories were occupied for 21.9 years on average (SD=6.5; range 7–27; Me=23). The Lesser Spotted Eagle population makes up >2% of the Polish population, and it was stable during 17 years of monitoring.
Keywords: breeding density, breeding success, Lesser Spotted Eagle, Puszcza Knyszyńska, the Knyszyn Forest
