Eastern Imperial Eagle, Aquila heliaca
Eastern Imperial Eagle, Austria, April 2009, © Markus Jais
Immature Eastern Imperial Eagle, Austria, January 2013, © Markus Jais
English: Eastern Imperial Eagle
Scientific: Aquila heliaca
German: Östlicher Kaiseradler
Spanish: Águila imperial oriental
French: Aigle impérial
Taxonomy and Subspecies
Closely related to the Spanish Imperial Eagle which was formerly considered a subspecies of the Eastern Imperial Eagle but is now treated as a separate species.
The two Imperial Eagles species are related to the Steppe Eagle and the Tawny Eagle Aquila rapax [GRIN 2009].
Length: 72-83 cm
Wingspan: Male 185-205, Female 200-220 cm
Weight: Male 2,450-2,720 g, Female 3,160-4,530 g
26 years in the wild, 44 years in captivity. [Mebs & Schmidt 2006]
Eastern Imperial Eagles live in open landscapes like forest-steppes, steppes and deserts with small forests or single trees, but also in agricultural areas when there is enough food and trees for building the large nests. During Winter often near water where there is a lot of waterfowl [Mebs & Schmidt 2006].
From central (most western pairs in the Czech Republic and Austria) and south-eastern Europe to central Asia. In Europe the species breeds in Austria, Czech Republic, Slovakia, Hungary, Bulgaria, Macedonia, Serbia, Croatia, Romania, Russia, Ukraine and maybe in Moldova.
Probably extinct as a breeding species in Greece [GRIN 2009].
In Asia, the Eastern Imperial Eagle breeds in southwestern Siberia, Kazakhstan, Armenia, Azerbaijan, northern Pakistan, Mongolia, India, Turkey and eastern China [GRIN 2009].
Asian birds spend the winter in South-East Asia, Northern India and the Middle-East. Many European birds spend the winter in north-east Africa and and Middle East, but also in Greece and Turkey [Mebs & Schmidt 2006].
Not all birds migrate. Many birds from Hungary, Slovakia and Austria (especially the adults) spend the winter in the breeding areas.
Breeding and Reproduction
Normally starts breeding with 4 or 5 years [Mebs & Schmidt 2006]. The female lays 2 or 3 eggs and incubation time is about 43 days. The young spend between 70 and 79 days in the nest [Mebs & Schmidt 2006].
The Eastern Imperial raises 2 chicks more often than other Aquila species like the Golden Eagle or the Lesser Spotted Eagle. Sometimes, even 3 chicks fledge. [Mebs & Schmidt 2006] report the following statistics for 473 breeding attempts from Hungary (between 1980 and 2000) of which 348 where successful:
- 188 pairs raised 1 young eagles
- 143 pairs raised 2 young eagles
- 17 pairs raised 3 young eagles
So, for almost 50% of all successful breeding attempts more than 1 eagle fledged. That is a very high number for such a large eagle.
In mountainous areas in Hungary the birds use mostly oak (Quercus petrea, Q. cerris), beech (Fagus sylvatica) and introduced pine (Pinus silvestris, P. nigra, Larix decidua) forests while in the lowlands small groups of poplars (Populus spp.) and black locust trees (Robinia pseudoacacia) are the most important nest habitats.
Food and hunting
Feeds on mammals and birds. Important prey species are the members of ground squirrels (susliks) like the European ground squirrel Spermophilus citellus (also known as the European Suslik). Also takes other small mammals like European Hamsters Cricetus cricetus, European Hares Lepus europaeus and even hedgehogs. In Austria the species takes a lot of European Hares (mostly young and as carrion) as the hares reach very high densities in that area.
Sousliks are still among the most important prey in Russia and but in many parts of Europe other species like European Hares or Pheasants are more important now due to a widespread decline of sousliks in many eastern European countries.
Bird species taken include pheasants, partridges, pigeons or waterfowl. Also takes carrion.
A study of two pairs in Central Kazakhstan (Nedyalkov et al. 2014) shows how flexible the Eastern Imperial Eagle is regarding its diet. In that study 2 pairs were monitored. One pair hunted mostly over the Balkhash lake and caught wetland species like Great Cormorants Phalacrocorax carbo, Great Egret Ardea alba, Grey Heron Ardea cinere and Muskrats Ondatra zibethicus. The 2nd pair was focusing on rodents with the Great Gerbil Rhombomys opimus being the most important prey species. This shows that the Eastern Imperial Eagle can take advantage of many different prey species and is not an extreme food specialist.
Hunts either from a perch of from flight [Mebs & Schmidt 2006]. Capable of fast stoops. Sometimes hunts walking (frogs, reptiles or even insects) [Mebs & Schmidt 2006].
A rare and endangered eagle in Europe (and worldwide). European population only a little more than a 1,000 pairs with the majority in Russia.
In Austria the species had been extinct for 200 years until 1999 when the first pair recolonised the country. [Wichmann 2011] and has since then been increasing. In 2009 there were already 4 pairs who raised 9 chicks [Wichmann 2009] und in 2012 11 pairs raised 16 chicks [Birdlife AT 2012].
In Hungary and Slovakia, the population has increased due to conservation programs.
In 2002, 61-65 pairs were counted in Hungary [Mebs & Schmidt 2006]. In 2009, 105 territories were known in Hungary and the total number was estimated to be between 105 and 115 territories. 95 pairs laid eggs, chicks hatched at with 74 pairs and in the end, 70 pairs were successful and raised 132 chicks. [Horvath 2009]. In 2010 the number of known nesting pairs was 119 and the number of known fledglings was 105. At 5 territories the breeding success could not be recorded [Marton Horvath, pers. comm.]
The population in Slovakia was estimated at between 40-45 pairs in 2004 [Mebs & Schmidt 2006]. A more recent estimate is 45-50 pairs [Demerdzhiev et al. 2011].
In Bulgaria, in 2009, 20 territories were occupied and 20 young fledged [Save Raptors 2009a].
In Romania there were more than 50 pairs in 2004 and in Turkey, the population was estimated at between 70 and 120 pairs in 2003 [Mebs & Schmidt 2006].
The Eastern Imperial Eagle faces many threats. The most important ones are illegal poisoning,electrocution and habitat destruction.
Illegal poisoning is a serious threat in some countries like Austria und Hungary. In Hungary, 37% of 113 dead eagles found between 2001 and 2009 were victims of poisoning [Horvath 2009].
Electrocution is the second most important cause of death in Hungary with 31%. In Bulgaria, the first recorded death because of electrocution has been document in 2009 [Save Raptors 2009b] (there are very likely more cases but not all birds are found).
Other threats include collision with vehicles and electric cables and in some cases even illegal shooting.
The lack of suitable nest trees is also a problem in several countries. The eagles often use young and unstable trees because there are no large and stable trees available. This can lead to increased destruction of nests by storms. In Hungary this is the case for 52% of all failed breeding attempts [Horvath 2009].
During the breeding season, human disturbance can cause breeding failure. In Hungary, 25% of all failed nesting attempts are because of human disturbance [Horvath 2009].
In the long term, habitat destruction because of intensification of agriculture can be a serious problem. This developments will increase disturbance and reduce prey availability which will often lead to the abandonment of a certain area by the eagles.
Construction of roads and other infrastructure can also reduce habitat quality.
The construction of more wind farms can make habitat unsuitable for breeding, hunting and dispersal and can also kill the birds.
The Eastern Imperial Eagle is a very rare species. It has a wide distribution but it is not common in most areas. The human caused mortality – mostly because of electrocution and poisoning is still too high. Reducing this mortality is of great importance in the conservation of this magnificent raptor.
Reducing mortality caused by electrocution is technically possible for almost all pylons. It is a matter of money. The energy companies often don’t want to pay for it and governments don’t provide enough money in many countries. But progress is being made here in some countries. In Hungary, Birdlife Hungary/MME, the Ministry of Environment and Water and electric companies signed an agreement called “Accessible Sky”, with the goal to modify dangerous powerlines until 2020 [Horvath 2009].
Fighting illegal poisoning is another important task. This can only be achieved through better education of people who still hate raptors and also by better enforcing existing laws – which are sufficient in many countries.
In some parts of it’s range, the lack of suitable trees can be a serious problem. A long-term solution is to plant enough suitable trees in areas where there are not enough. A short-term solution is to build artificial platforms as it is done several countries, for example Hungary [Horvath 2009] or Bulgaria [Marin 2009].
Wind farms should not be build close to nesting areas including areas where it is likely that the eagles will make a comeback in the next years or decades. Wind farms should also not be built in known dispersal, wintering and migration areas.
Environmentally friendly agriculture is important for Eastern Imperial Eagles. Pesticides should be reduced to a minimum or avoided. Fallow land and other traditional farming practices that ensure a high diversity of prey species (susliks, hares, pheasants, partridges, etc) is important and should be encouraged.
More research about dispersal and mortality is necessary.
There are many conservation projects going on for the species in many countries. See interviews and websites below.
Status Global Raptor Information Network
Interviews about the Eastern Imperial Eagle
[Demerdzhiev et al. 2011]. Demerdzhiev, Dimitar; Horváth, Márton; Kovács, András; Stoychev, Stoycho and Karyakin, Igor (2011). Status and Population Trend of the Eastern Imperial Eagle (Aquila heliaca) in Europe in the Period 2000-2010. Acta zoologica bulgarica, Supplementum 3. Downloaded from http://saveraptors.org/en/news.php?id=191.[Birdlife AT 2012] Starker Aufwind für den weltweit bedrohten Kaiseradler: 16 Jungvögel in Österreich. Downloaded from http://www.birdlife.at/coro-skat/presse/starker-aufwind-fuer-den-weltweit-bedrohten-kaiseradler.html on 20. Jan. 2013.
[GRIN 2009] Global Raptor Information Network. 2009. Species account: Eastern Imperial Eagle Aquila heliaca. Downloaded from http://www.globalraptors.org on 18 Sep. 2009
[Horvath 2009]. Horváth, Marton. Interview on europeanraptors.org: Interview with Marton Horvath about the conservation of the Eastern Imperial Eagle Hungary.
[Horvath et al. 2010]. Horvát, M.; Szitta, T.; Firmánszky, G.; Solti, B.; Kovács, A and Moskát, C.5 (2010). Spatial variation in prey composition and it’s possible effect on reproductive succes in an expanding Eastern Imperial Eagle (Aquila heliaca) popuation). Acta Zoologica Academiae Scientiarum Hungaricae 56 (2), pp. 187–200, 2010.
[Marin 2009]. Marin, Simeon. Interview on europeanraptors.org: Interview with Simeon Marin from Green Balkans about the conservation of Eastern Imperial Eagles, Lesser Kestrels and Cinereous Vultures in Bulgaria
[Mebs & Schmidt 2006] Mebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.
[Nedyalkov et al. 2014] Nedko Nedyalkov, Anatoliy Levin, Andrew Dixon, Zlatozar Boev (2014). Diet of Saker Falcon (Falco cherrug) and Eastern Imperial Eagle (Aquila heliaca) from Central Kazakhstan. Ecologia Balkanica. 2014, Vol. 6, Issue 1.
[Save Raptors 2009a] Successful breeding season for Imperial Eagles in Bulgaria. Downloaded from http://www.saveraptors.org/en/news.php?pageNum_News0=&totalRows_News=23&id=27 on 18 Sep. 2009
[Save Raptors 2009b] Juvenile Imperial Eagle electrocuted by an electricity pole. Downloaded from http://www.saveraptors.org/en/news.php?pageNum_News0=&totalRows_News=23&id=27 on 08 Nov. 2009
[Wichmann 2009]. Wichmann, Gabor. Interview on europeanraptors.org: Interview with Gabor Wichmann from BirdLife Austria about the Conservation of the Eastern Imperial Eagle in Austria.
[Wichmann 2011]. Wichmann, Gabor. The situation of the Imperial Eagle Aquila heliaca in Austria. Acta zoologica bulgarica, Supplementum 3. Downloaded from http://saveraptors.org/en/news.php?id=191.
Forsman, Dick (1999). The Raptors of Europe and the Middle East A Handbook of Field Identification. PoyserMebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.