Mateusz Gutowski, Damian Ostrowski
Ornis Polonica 2022, 63: 115–129
https://doi.org/10.12657/ornis.2022.2.3
Abstract: The population size and distribution of the Boreal Owl Aegolius funereus were studied in 2012–2021 in forest of the SPA Natura 2000 Puszcza nad Gwdą (776.8 km2, NW Poland) dominated by the Scots Pine Pinus sylvestris. In 2013, 92 sample plots 1 x 1 km were surveyed twice between mid April and late May. In 2020 and 2021 two point counts were performed during night-time at 72 observations point located within 3 sample plots (30 km2 each) and at 45 observation points located in >100 old-year stands outside the plots, first in March and second in April each year. In 2012–2021 61 territories of the Boreal Owl were found in the SPA area, 44 of which were calling males, 3 pairs and 14 occupied hollows. Total density of the Boreal Owl in 2020–2021 was estimated at 0.8 territory/10 km2 of overall area and 0.9 of forest area. The total males density on three sample plots was estimated at 1.7 in 2020 and 1.1 territory/10 km2 forest area in 2021. The Boreal Owl occurred in dense stands (63% of all analysed stands; N=47), the Scots Pine dominated (96%) and mostly aged >100 years (41–147 years; mean 104 years). The understory layer of trees were represented by Norway Spruce Picea abies (35%) and European Beech Fagus sylvatica (17% of occupied stands). The Boreal Owl was also recorded in microhabitats characterized by old pines left on clearcut (37% of stands; N=28), aged 96–150 years (mean 122 years). The Norway Spruce occurred in 57% of microhabitats inhabited by Boreal Owls. Hollows of the Boreal Owl were detected mostly in stands with old Scots Pines (93%; N=13; 90–171 years, mean 126 years). Population size in the studied area was estimated at 55–65 males, roughly 3–5% of the national population, which makes SPA Natura 2000 Puszcza nad Gwdą one of the most important area for the species in Poland.
Keywords: Aegolius funereus, Boreal Owl, forest management, Puszcza nad Gwdą, SPA Natura 2000
