**1. Introduction**

The site Kamenný hrb – Bankov is situated near the town Košice, in Volovské mountains, in Eastern Slovakia, in elevation 420−550 m. Volovské mountain range belongs to W Carpathians. The study site can be characterised as a hilly, forested area, overgrown with most forests over 80 years of age (nowadays already over 100 years old). The size study area is approx. 5.2 km2 . Composition of forests is formed by naturally grown oak (*Quercus petraea*), horbeam (*Carpinus betulus*), beech (*Fagus silvatica*), fir (*Abies alba*) and lime (*Tilia crdata*) stands, with sycamore (*Acer pseudoplatanus*) in higher elevations and with planted stands of spruce (*Picea abies*) of the same age, as other trees. Coniferous and mixed forests (spruce and fir-beach) dominate the ridge and its northern slope and oak and horbeam forests dominate southern expositions and the lowest elevations, but even oak and fir stand to grow side-by-side naturally, and the site is one of the lowest areas with naturally growing fir in Slovakia. The forest is not homogenous, it is interrupted by smaller and middle-sized meadows, clear-cuts and forest nurseries. The forest is harvested in a moderate, sustainable way, mainly due to its proximity to the town and also due to its main function – to serve as a recreation area for people from the town, with a number of forest tracks. Guild of forest owls at the site consists of 4 species: Eurasian Pygmy Owl (*Glaucidium passerinum*), Ural Owl (*Strix uralensis*), Tawny Owl (*Strix aluco*), Boreal Owl (*Aegolius funereus*), while the last species is a newcomer at the site because in period 1989–1994, only a few data of the species were found and no territorial males. Eurasian Pygmy Owl and Boreal Owl is in Slovakia traditionally associated with coniferous and mixed forests in higher mountains from 400 m a.s.l. up to forest limit in 1500 m a.s.l. [1–5], while Ural Owl and Tawny Owl is associated mostly with mountains and beech or oak forests, rarely broad-leaved lowland floodplain forests [1, 6], even if in some areas they occupy also mixed or even coniferous stands in mountains [7]. Populations of owls are regularly monitored at the site. First ornithological data on the occurrence of Eurasian Pygmy Owl and Ural Owl in the area come from the 1970s years by Mošanský (1982) [8], Danko (1988) [9], Pačenovský (1981) [10] and of the Tawny Owl from 1980s years by Mošanský (1982) [8], Takáč (1982) [11] and occurrence of the Boreal Owl from the site was previously not known. The site is one of the lowest areas in Volovské mountains with distribution of Eurasian Pygmy Owl, where two nests situated in 520 and 470 m elevation found and checked in years 1989, 1990, 1991, 1994, 1997 and 2009 were regarded as the lowest known nest sites of the species for Slovakia [5]; as well as one of the lowest known areas with distribution of the Boreal Owl. Thirty-year-long observation of the site prepared a possibility to follow population trends of 4 owl species occupying the site and most of them have shown rather steep population changes within those periods.
