Results of the monitoring of the Steppe Eagle population in Trans-Baikal Territory (Zabaikalsky Kray) in 2015, Russia

Ornithological survey was carried out in July–August 2015 in steppe areas of Russian part of Dauria (Trans-Baikal Territory, or Zabaikalsky Krai) in the frames of monitoring the population of the Steppe Eagle (Aquila nipalensis). Research was conducted at 13 study sites in 10 administrative districts of the region, including 11 study sites which were surveyed repeatedly (after first survey in 2010). A total of 57 nesting territories with 95 nest structures were identified in 2010 and 2015 together. Additionally adult birds were recorded in 24 points but nests were not found. In 2015 we checked 35 of 40 nesting territories that were identified in 2010 while other 35 nesting territories (including 17 ones with nest structures) are localized for the first time. A total of 27 nestlings and fledglings (1.4±0.5 nestlings and fledglings produced per successful nest) in 19 nests were recorded during the 2015 survey. In 2010, the status of Steppe Eagle in Dauria was assessed as extremely unfavorable. The main population characteristics had not essentially changed to 2015. Actual average nesting density slightly increased but still is close to 1 pair per 100 km2. An average distance between neighbor active nests in Dauria is unexpectedly long as comparing with such figures in other regions of the Steppe Eagle nesting. More than a half of potentially available nesting territories remain unoccupied, and the share of unoccupied nesting territories almost did not change. The productivity of successful nests (average brood size) remains low – on average 1.4±0.5 fledglings and nestlings per successful nest in 2015. The negative factors such as power lines that are dangerous for birds and steppe wild fires are still acting. More than 40 % of all the nesting territories were affected by fires in 2015; the nest structures were completely burnt at 17% of the known nesting territories visited in 2015. Meanwhile the following positive trends can be noted: the population number increased more than by 30 % (estimating 219 vs. 152 breeding pairs); breeding efficiency increased by 24 %; the breeding efficiency was 0.93 fledglings per 1 breeding pair in 2015 vs. 0.55 in 2010, which represents a 60 % increase; the share of successful pairs of potential population size increased from 20 % to 32 %; the share of subadults (under the age of 4–5 years) in the breeding pairs was reduced almost twofold – from 76 % to 35 % what means the mortality of adults significantly reduced. The population trend of the Steppe Eagle in Dauria should be considered in the framework of significant land use and climate changes that had a place and continue in the region