Dynamics of species structure of birds in the step ecosystems of the angara region under modern conditions

Abstract

For a long period (1968-2022), the species structure of the bird population of the northern steppes of the Angara steppe district was studied. They have a small area, are represented by several sites, are part of the Euro-Siberian subregion and form the Priangarsky forest-steppe district. Most of them are plowed up or used for intensive grazing and hayfields (in floodplains). Due to the severe degradation of agriculture, the main part of the former arable land is represented by fallow lands, weeds and young, sparse steppe pine forests. This territory has large lake-marsh ecosystems that attract birds for nesting and rest stops during migrations. 317 species of birds have been recorded on this territory, and the proportion of typically steppe birds is small, which is typical for marginal steppes, in different areas - 37-40 species. Compared to the zonal steppes, which are inhabited by forks more adapted to arid conditions, bird species are found here with a wider norm of reaction to natural conditions. Therefore, the proportion of specific steppe species from the south (zonal steppes) to the north is significantly reduced. The main response to climate warming is the expansion of bird ranges to the north. It is most typical for birds of intrazonal habitats - wetland ecosystems, which are the first to respond to changes in habitat conditions. Native steppe bird species are the last to react to strong climate warming. Until now, only a few vagrants of individual typical steppe bird species have been recorded in the northern areas of their distribution, and cases of their episodic nesting have been noted. The main core of species in the northern parts of the steppe and in the central parts of this natural zone is formed by birds of the same systematic genera. The marginal steppes are inhabited by steppe species that obviously do not have such deep adaptations to existence in conditions of moisture deficiency, as true representatives of the zonal steppe. A detailed study of the ecological structure of birds in all areas of the Priangarsky steppe district over a long period of climate change makes it possible to find out the features of the formation of the bird fauna at the border of the focal distribution of the Asian steppes.