Eagle owl (Bubo bubo L.) (Strigiformes, Aves) in the clay semi-desert of the Trans-Volga region

Nesting features and the ecology of the eagle owl ( Bubo bubo L.) in the northwestern part of the Trans-Volga clay semi-desert were studied in 1980–2024. Here, during the breeding season, the eagle owl is associated with local habitats of lake depressions and river valleys, and its nests are confined to steep slopes. Our main material was collected in a deep depression of the lake Elton (mainly on the territory of the Elton Nature Park), where 232 nesting cases were recorded in 1980–2024. 9 resident breeding sites have been identified there, where eagle owls have been nesting for many years in succession. With the development of farm cattle breeding, additional ones began to arise in the vicinity of some resident sites, forming a united nesting group with the resident. They were inhabited by couples disturbed in the residential areas, and, after their departure, young birds. All the nesting groups represented by resident and additional nesting sites were no longer functioning by the 2010s. When there were 5 to 9 breeding sites in the Elton region in 1980–2017 and 3 to 9 pairs nested annually, then only 2 breeding sites were noted in 2018–2023, almost all the nests of these pairs having been destroyed by cattle. The eagle owl population group, confined to the Elton Lake depression, is the core of the Elton–Khara population, since the conditions for eagle owl nesting are poor in the middle and upper reaches of the Khara River and the gullies flowing therein. For 45 years, an average of 5.2 pairs per year nested there and more than 19 birds (about 14 mature individuals) were present in the population annually. It is obvious that it is the Elton–Khara population that constantly “feeds” the eagle owl groups around the lakes Botkul, Bulukhta and Sorkul, which largely ensures the preservation of the species throughout the northwestern Trans-Volga region.