Qualitative and Quantitative Changes in a Guild of Forest Owls: Eurasian Pygmy Owl (Glaucidium passerinum), Ural Owl (Strix uralensis), Tawny Owl (Strix aluco), Boreal Owl (Aegolius funereus) at Kamenný Hrb – Bankov Site in Volovské Mountains Near Košice

A guild of forest owls was evaluated in 1989 − 2021 in a 5.2 km2 site in Slovakian Volovské mountains in Western Carpathians. Only the Eurasian Pygmy Owl (Glaucidium passerinum) declined in this near 30 year period from 8 to 5 territories and that local decline is referred to the increased presence of Tawny Owl (Strix aluco). Clear decline of calling activity of Eurasian Pygmy Owl in sympatric areas with Tawny Owls was also noted. Tawny Owl almost doubled its population from 3 to 5 territories occupied in 2017–2021 and the Boreal Owl (Aegolius funereus) was almost absent during 1989–1994 but occupied 8 breeding territories in years 2017–2021. Tawny Owl has a tendency of spreading to higher elevations, while Boreal Owl has an opposite tendency. Boreal Owl seeks suitable breeding habitats in old fir-beech forests with fir and oak stands and Black Woodpecker (Dryocopus martius) holes in old beeches as low as below 500 m a.s.l. Due to good populations of small mammals, Ural Owl (Strix uralensis) has been able to maintain stable populations with ca. 8 pairs in the study area between years 1989–2021. Good food situation also attracted some Boreal Owls to lowest known elevation limit of the species in Slovakia. Further research is needed, on a larger scale, to support the population trends documented in this paper.