Eastern Imperial eagle

The Eastern Imperial eagle (Aquila heliaca heliaca) is a large bird of prey that breeds in southeastern Europe and extensively through West and Central Asia. Most populations are migratory and winter in northeastern Africa, the Middle East and South and East Asia. Like all eagles, the eastern imperial eagle is a member of the family Accipitridae. Furthermore, its feathered legs mark it as a member of the subfamily Aquilinae. It is a large, dark-colored eagle, with a resemblance to other members of the genus Aquila, but it is usually the darkest species in its range. It is an opportunistic predator that mostly selects smallish mammals as prey but also a fairly large proportion of birds, reptile and other prey types, including carrion. Compared to other Aquila eagles, it has a strong preference for the interface of tall woods with plains and other open, relatively flat habitats, including the wooded mosaics of the steppe.

Status

A juvenile eastern imperial eagle in Rajasthan, India

The eastern imperial eagle has declined greatly through history. At one time, people of eastern Europe and adjacent parts of Russia used to admire and even revere this eagle as a "sacred bird". It was widely referred to as the "cross-bearing eagle" (because of the shape of the white spots on its wings). According to folklore, the imperial eagle was able to divert the hailstorm clouds from the area it inhabited, and it was thus able to save farmers' crops. Therefore, the monarchy of Austria-Hungary once chose the imperial eagle to be its heraldic animal. Despite the historic reverence for the species, it was not spared the negative and hostile view of all birds of prey that arose throughout Europe and its colonies in the 17th century onwards, and the resulting persecution of essentially all birds of prey, including the eastern imperial eagle. However, almost certainly the leading cause of this species' decline was the practice of felling old trees on field boundaries that were the nest sites for the eagle. Among other reasons for its decline were the depletion (both incidental and intentional) of prey species and the incidental consumption by the eagles of poison baits, left out to eliminate wolves. As with other eagles in Eurasia, the Industrial Revolution allowed access to poisons and firearms, which made the killing of eagles far easier and hastened their decline. Towards the end of the 19th century, 1824 nests were recorded in Bulgaria, but by 1979 only 5 to 12 pairs remained in the country. Similarly, from a population once numbering in the thousands, the Hungarian population of imperial eagles was driven down to only 10-15 pairs by 1975-1980. In Greece, the eastern imperial eagle was extirpated altogether as a breeding species. While the declines further east in the species range have been less studied, more or less the same threats likely persist throughout the range. Some reserves in central Russia and Kazakhstan have retained semi-stable populations, due in no small part to their isolation. However, the eastern imperial eagle has also been extirpated as a breeding species from Pakistan and Afghanistan.

Today, dedicated conservationists and biologists are working extensively to remediate and reverse the decline of eastern imperial eagle. The species was uplisted to Vulnerable in 1994 and global protection initiatives were begun around this time. By 1996, it was estimated that there were 363-604 pairs in all of Europe (including European Russia). After a couple of decades of recovery efforts, by 2000-2010, the number of breeding pairs in Europe was estimated at up to 1800-2200, a significant increase. Peak numbers in Europe may fall along the European Green Belt. The strongest increases were in Hungary where from 10-15 pairs in the late 1970s an estimated total of 105 nesting pairs by the late 2000s. Conversions and conservation of lowland wildlands, has allowed the numbers of pairs using less ideal mountainous habitat decrease from 50% to 15% of breeding imperials, as they've shifted to more ideal lowland habitat. The nation's imperial eagle population has been continuously protected and monitored since 1975. Further efforts in Hungary were the mitigation of human-eagle conflicts through education in Hungary as poisoning (whether these eagles are the main target or not) continues, as well as general coordination with landowners and agricultural interests as the eastern imperial eagles are often required to forage in such areas. Other increases or returns to former parts of their range include have been noted in the Morava region of southwestern Slovakia as well as some parts of the Czech Republic, Serbia and Austria. However, overall 85% of the population in the Carpathian mountains region that forms the bulk of the land in eastern Europe was restricted to the Great Hungarian Plain, and were isolated from other populations. In Slovakia, the gap in the distribution in the Carpathian basin has led to concern about genetic isolation. Upon review, the genetic isolation of the two Slovakian populations was determined to be "marginally significant". The number of pairs of eastern imperial eagles increased in Bulgaria from 20 in 2009 to 24 in 2013. Among the efforts untaken to restore the Bulgarian populations were mitigating hazardous electrical poles, 608 were insulated within eagle territories, while also 483 supplemental feedings were given to 14 pairs from October to March. In Turkey, the number of imperial eagle pairs in recent estimates during the 21st century was widely placed at 35-150 pairs, probably closer to the higher number as there is evidence for there being 30-50 pairs in the East Thrace region alone.

Biologists working to place an artificial nests for imperial eagles to use.

In some areas of western Russia and in Kazakhstan, the eastern imperial eagle has maintained the nearest thing to a population stronghold. In 2011, the total estimated number of pairs was estimated at 3000-3500 in Russia and 3500-4000 in Kazakhstan. Though only 1534 breeding territories found firsthand, only some parts of the range were surveyed. According to Russian and Kazakh studies, cattle grazing in taiga forest edge appeared to benefit imperial eagles since they encourage habitat for prey, especially ground squirrels. In Kazakhstan moister conditions, possibly correlated with climate change seems to have increased populations of yellow ground squirrels and 2nd growth trees which both are likely to have caused a localized increase there. In Naurzum Nature Reserve alone nearly 300 imperial eagles may congregate in winter, making it a “critical refugium” for this species. On the other hand, precipitous decline has been detected in the Lake Baikal region of Russia and the species may be on its way to local extinction there. In the 1950s, imperial eagle pairs in the Baikal area numbered 250-300 strong. A strong decline was already noted by the mid-1980s when 150-200 pairs remained. However, the reduction hastened even more to merely 70 pairs in 1999. The Baikal imperial eagles during monitoring from 1950 to 1999 showed no overall changes in habitat or pair occupancy. In the 1998-1999 period, fledgling success was also found to drop considerably. Satellite study of migrating birds from Lake Baikal at migration stopovers and winter sites was reviewed but only 4 eagles were studied so results could not clearly determine whether depletions were mostly occurring at this time rather than during breeding. The reason for the sharp declines of the Baikal imperial eagles are not fully understood but are likely correlated with habitat destruction and human land use changes followed by pesticide use and other toxic threats through bioaccumulation. Reductions have also been reported in the lower Ural Mountains region of Russia with largely similar threats but it is not known what the exact rate of reduction is here. Although gone from Pakistan as a breeding species, it continues to be a key wintering site as around 150 eagles are estimated to winter in Pakistan.

References

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