Imperial Eagle in the Republic of Tatarstan – Continuation of Research
Authors:   Kazan Federal University, Elabuga Institute, Bekmansurov R.H. ,   National Park “Nizhnyaya Kama”, Bekmansurova N.V. ,   Municipal budgetary institution of additional education, the Center for Children and Youth Tourism and Excursions “Yuldash”, Isakov G.N. ,   Directorate for Wildlife Conservation and Protected Areas of the Ministry of Natural Resources of Chuvashia
Published: October 2023

Eastern Imperial Eagle (EIE Aquila heliaca) biology has been continuously studied in the Republic of Tatarstan (area 68,000 km2) since autumn of 2011 and covered some habitats in cross-border areas. In general, this is the area around the confluence of two largest rivers of the Eastern Europe, the Volga and Kama, and a number of their tributaries, and also belongs to the northern part of EIE breeding range in the Volga region. Research results up to 2018 were briefly presented at the previous conference “Eagles of the Palearctic” in 2018. During the next five years, monitoring of known EIE breeding territories continued. Based on EIE nests being generally located in agrocenoses of river valleys, settlements with farms and pastures, we have decided to make changes to our monitoring system. Conditional boundaries of survey plots were drawn in GIS in a way for them to cover the entire river valley of one large Kama or Volga tributary or combine several small tributaries. The search for new nests has expanded the habitat database from 181 to 246. Nests found in territories that were not occupied by EIE in 2011–2014 are most likely the sign of young pairs spreading to new habitats, which is also shown by ringing results. We are cautious in estimating population growth, as the number of territories identified over the past 12–15 years does not correspond with a number of nesting pairs. As such, for at least 4% of territories where EIE was supposed to nest based on single bird observations, it was impossible to confirm their status as breeding territories. At least 15% of the territories require status confirmation, among them territories where nesting has been absent for more than 3–6 years or where nests have been lost altogether. Some breeding territories (about 1%) were abandoned by EIE due to changes in the quality of hunting grounds, mainly due to the cessation of agricultural land use and grazing. In 2023, we were able to check 180 territories where breeding has taken place at least once since 2011. Of these, 122 were reliably occupied by EIE, breeding began on 93 nests, and only on 78 it was successful. Based on the five-year research, we can reliably attribute 142 breeding territories in Tatarstan as occupied by EIE, not including cross-border nests. At the same time, nests might have been displaced over a considerable distance in some territories with an unconfirmed status. Additional studies confirmed the possibility of nests moving over 1.1–4 km, 2.7 km on average, 2.9 km median (n=11). It is noteworthy that in two breeding territories where nests were destroyed after the conflict with humans, nests were displaced by 1.1 and 4 km. Overall, we estimate the EIE abundance for known breeding territories at 142–170 pairs. But a significant area we consider being suitable as EIE habitat has not been surveyed, and we therefore assume that the current species abundance is higher. Nesting monitoring in recent years has not revealed a significant difference in breeding success and fecundity. We did not expect to regularly detect broods of three nestlings in northern nests of Pre-Kama region (Forest Transvolga), where worse food conditions were assumed when comparing with habitats in Trans-Kama region (Forest-steppe Transvolga). 2300 food remains have been identified at EIE nests during monitoring since 2012, with the leading position of corvids (Corvidae). Recently, an increase in the occurrence of European Hare (Lepus europaeus) has been noted in EIE diet; in 2023, remains of Roe Deer (Capreolus) were found at two nests for the first time. The increase of cickens (Gallus gallus domesticus) in EIE diet is a problem and leads to conflict with humans. Findings of the remains of Montagu's Harrier (Circus pygargus), Short-Eared Owl (Asio flammeus), Grey Partridge (Perdix perdix) we attribute to the commonness of these species in EIE feeding arears, and Common Kestrel (Falco tinnunculus) – to the continuing increase in its abundance in the region after depression that occurred after 2005. We consider nests with Russet Ground Squirrel (Spermophilus major) as a main prey in EIE diet to be food resource centers. One such nest has been monitored online for three breeding seasons. It has been established that, despite the large share of birds in the diet, the predominance of Ground Squirrel is obvious. Camera in this nest, visitation for ringing nestlings, and equipment maintenance showed that feeding on Ground Squirrel leaves minimal remains, and thus in other nests we do not always detect its presence in a diet during a single visit when ringing nestlings. This generally distorts the data on Ground Squirrel share in EIE diet for other pairs, specifically on the periphery of food centers. At the same time, we know that on individual nests at the range border EIE goes without Ground Squirrels. In 2023, we launched a project to install a video camera to study the diet at one of EIE nests in Pre-Volga area, where, according to the results of survey in 2022, Ground Squirrel was not found in the diet. Unfortunately, the project quickly ended after nestlings died because parents could not feed them. We also refined northern border of EIE breeding range during our research. In Pre-Volga region, the northernmost nest was found at a latitude 55.246270, and in Trans-Volga – 56.33994. However, photo observation (by N. Shemyakin) of EIE pair and their brood in the vicinity of the city of Izhevsk (Udmurtia) on August 23, 2021, at a latitude of 56.897006, shows that single pairs probably nest much further north. We specified the timing of the EIE arrival at breeding territories in spring: second half of March, which is much earlier than previous data (beginning of April).