Winterschlafplätze der Waldohreule (Asio otus) Ergebnisse eines 10-jährigen Monitorings und Empfehlungen für den Artenschutz

A characteristic feature of the strictly protected Long-eared Owl (Asio otus) is the formation of winter communities at shared roosting sites. These roosts often consist of coniferous trees in residential areas, some of which are used for many years or even decades. Since conifers are often considered to be of minor ecological importance and felling/pruning – especially for the protection of breeding birds – often takes place during the winter season, this can lead to con- flicts with the protection of this species. In order to expand local knowledge about the roosting sites of Long-eared Owls, and to increase general information about the characteristics of their roosts, systematic surveys were conducted in the southern part of the Hanover region over the past 10 years. This study summarizes the results of this monitoring and derives recommenda- tions for species protection that are highly relevant for the conservation of the Long-eared Owl beyond the area studied. A total of 13 roosting sites were recorded, mostly consisting of groups of conifers, where an average of 8 owls (min: 1, max: 35 owls) were observed. The trees used were mostly Spruce Picea spec. (54 %), followed by Thuja spec. (17%) and Yew Taxus baccata (12 %). Almost all trees were less than 15 m tall (97 %) and were located at a maximum distance of 10 m from a building (98 %). About 90 % of the trees were located 100–300 m away from the next open landscape as a potential hunting ground. At only two roosts Long-eared Owls were found in all five survey years, while the other roosts were only used in some years. Furthermore, within groups of trees, not every tree was used every year; instead, the owls alternated between different trees. In conjunction with the prior literature, the results show that Long-eared Owls regularly use relatively inconspicuous conifers as roosting sites, prefer groups of trees, and regularly switch between individual trees within a particular tree group, but also between different roosting sites that are further apart. For the protection of Long-eared Owls, this means that almost every conifer in residential areas can be a potential (part of a) roosting site and that it is not possible to rule out their use without prior inspection (e. g. before felling). In order to protect the Long-eared Owl and to prevent violations of species protection laws under Article 44 (1) Federal Nature Conservation Act (BNatSchG), we highly recommend i) recording and inventorying roosting sites as a means of protecting them, and ii) implementing measures for environmental education, information and awareness-raising among the general public/local residents. In addition, iii) tree protection statutes, which should refer to possible conflicts with species protection laws, are also an important tool to protect roosting sites of the Long-eared Owl. Furthermore, to protect winter roosts in the case of impacts, iv) the avoidance principle (“Vermeidungsgebot”) must be strictly applied and v) in the case of unavoidable felling, work should be carried out outside the owls' utilization period in winter wherever possible.