Steppe Russian-Kazakh border zone as an area of increased mortality of red book diurnal birds of prey on powerlines (on the example of administrative provinces of the Volga-Ural region)

The work is devoted to the problem of the death of rare diurnal birds of prey on low-voltage power transmission lines in the steppe and semi-desert Volga-Ural region within the Astrakhan, Volgograd, Saratov, Samara and Orenburg regions of the Russian Federation. In the period from 2010 to 2021, it was possible to collect data on the death of more than 200 diurnal feathered predators in the study area and to establish accurate GPS coordinates for 136 electrocution victims. Representatives of seven species of Red Book birds of prey are dying on power lines in the Volga-Ural region that are not equipped with bird protection devices. They include long-legged buzzard Buteo rufinus, short-toed eagle Circaetus gallicus, imperial eagle Aquila heliacal, steppe eagle Aquila nipalensis, white-tailed eagle Haliaeetus albicilla, red-footed falcon Falco vespertinus and lesser kestrel Falco naumanni. An extremely uneven distribution of dead birds in the study area was revealed and a fairly clear binding of dead birds to the border with the Republic of Kazakhstan was found. Red Book eagles, buzzards and small falcons died from electric shock within 0.78-114.96 km from the border with Kazakhstan, on average at a distance of 18.29 ± 1.64 km (n = 136). At the same time, 90% of all birds died within a relatively narrow border strip 40 km wide. The total number of dead birds in the ranges 0-20, 20-40, 40-60, 60-80, 80-100 and 100-120 km significantly differed by the average values of the ranks (Friedman's test: χ2 = 26.15, df = 5, p = 0.00008, n = 7). When comparing the ranges of distances in pairs, significant differences in the number of dead birds appeared already between the intervals of 0-20 km and 40-60 km (Wilcoxon test: Z = 2.37, p = 0.02, n = 7) and then remained at the level of p = 0.02 with increasing distance to the border. Such attraction of birds to the Kazakh border within the Russian territory can be explained by a decrease in anthropogenic load and the anxiety factor against the background of an improvement in the food supply (an increase in the number of rodents and locusts in pastures and fallow lands) in the border zone. The obtained data allow us to recommend priority isolation of bird-hazardous power transmission lines, primarily located within 0-20 and 0-40 km from the border.