Eastern imperial eagle

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Eastern imperial eagle
Eastern imperial eagle (Aquila heliaca)

Eastern imperial eagle ( Aquila heliaca )

Systematics
Class : Birds (aves)
Order : Birds of prey (Accipitriformes)
Family : Hawk species (Accipitridae)
Subfamily : Aquilinae
Genre : Real eagle ( Aquila )
Type : Eastern imperial eagle
Scientific name
Aquila heliaca
Savigny , 1809

The eastern imperial eagle ( Aquila heliaca ) is a species of bird in the hawk family (Accipitridae). The distribution area of ​​this large representative of the subfamily Aquilinae extends from south-eastern Central Europe to the east to China . The Spanish Imperial Eagle of the Iberian Peninsula , which was previously considered a subspecies of the Eastern Imperial Eagle, is now listed as a separate species ( Aquila adalberti ).

The species inhabits steppes and structurally similar, open agricultural landscapes. The diet consists mainly of small to medium-sized, ground-dwelling mammals. Despite an increase in the population in Southeastern Europe in recent decades, the IUCN classifies the world population as VU IUCN 3 1st svg( vulnerable "endangered").

description

Eastern imperial eagles are among the largest representatives of the subfamily Aquilinae, they appear very large, heavy and powerful, but somewhat more plump compared to the similar golden eagle . They reach a body length of 68 to 84 cm and a wingspan of 1.76 to 2.16 m and are therefore only slightly smaller than golden eagles. The sexual dimorphism is clearly pronounced in terms of size and weight, males reach an average of about 83% of the size of females. Males weigh 2.45 to 2.72 kg and have a wing length of 540 to 622 mm, females reach a weight of 3.16 to 4.53 kg and a wing length of 565 to 661 mm. As with all representatives of the Aquila genus , the tips of the hand wings are heavily fingered and the legs are feathered up to the toes. In flight, the wings appear long and quite narrow, the relatively long tail is almost straight at the end.

Overall, adult birds are almost monochrome, very dark black-brown. Sharply set off from this is a white markings in the shoulder area, and the back of the head and neck are light beige to gold in color. The entire trunk, the forehead and the upper and lower wing coverts are dark black-brown and in the flying bird only form a weak contrast to the somewhat lighter, single-colored, dark-gray wing feathers . The tail feathers are basally below and above silvery gray and finely dark banded transversely and show a wide, black subterminal band and a narrow white end band.

The iris is light yellow-gray, the wax skin and the toes are yellow in color. The beak is broadly gray at the base and black towards the tip.

Eastern Imperial Eagle, portrait of an immature bird

The juvenile plumage differs considerably from that of the adult birds. The neck, chest and front abdomen as well as the under wing coverts are uniformly light reddish beige and show strong brown longitudinal stripes on this basis. The dark dashed lines are missing on the lower abdomen, on the upper and lower tail ceilings and on the legs. The back and the small and middle upper wing-coverts are brown and lightly dashed lengthways. The large upper wing-coverts show broad, light beige pointy spots.

The wings are on a dark brown-gray background, especially finely lightly banded at the base, the 3–4 inner hand wings are usually clearly lightened compared to the other hand wings. The joint is a single color, dark brown-gray. The inner hand wings , the arm wings and the tail feathers show a distinct whitish end band. The iris is gray to brown. The young birds are colored after 6–7 years.

Vocalizations

The courtship call consists of lined up, deep and rough, barking calls, which can be reproduced with “rhä-rhä-rhä”, “krau-krau-krau” or “krock-krock-krock”. When threatened at the nest, both partners utter a muffled "ko-gok, vk vk ok". Such or similar calls , some of which are reminiscent of ravens , such as "krä" or "gäk" are occasionally uttered on other occasions. The call constantly used by young birds when begging is two-syllable and is circumscribed as "stiarb".

distribution and habitat

Eastern Imperial Eagle:
  • Breeding areas
  • Year-round occurrence
  • migration
  • Wintering areas

    • The distribution area of ​​the species includes large parts of the forest steppe and steppe zone as well as the "cultural steppe" of the Palearctic and extends from southeastern Central Europe to Lake Baikal in Siberia . The eastern imperial eagle reaches its north-westerly distribution limit in Europe in the east of Austria and the Czech Republic as well as in Slovakia . In addition to Russia and Ukraine , Hungary , Romania and various countries on the Balkan Peninsula also have other occurrences in Europe . The distribution in Europe is disjoint and fragmented into numerous individual occurrences.

    The eastern imperial eagle probably originally only inhabited semi-open and open steppes with at least individual groups of trees. However, the species also inhabits agricultural areas with a comparable structure in south-eastern Europe.

    Systematics

    No subspecies are recognized for the species today. The Spanish Imperial Eagle of the Iberian Peninsula , formerly considered a subspecies of the Eastern Imperial Eagle, is now listed as a separate species ( Aquila adalberti ). Molecular genetic studies have confirmed the species status of both taxa and their close relationship as sister taxa . According to these studies, the closest relative of the two species is the predatory eagle ( Aquila rapax ).

    Way of hunting and food

    The ground squirrel is one of the most important prey of the Eastern Imperial Eagle in Southeastern Europe and Turkey

    The species uses different methods to hunt ground-dwelling animals. The most common are hide hunting from a low vantage point, for example a haystack, fence posts or low, bare trees, as well as shock flights from a circling search flight. Larger prey animals are, however, often captured from the ground-level search flight. Hunting on foot for small prey such as insects is less common.

    The basis of the diet are usually only a few species of small to medium-sized, ground-living mammals, in large parts of the distribution area ground squirrels and / or hamsters are the main prey. In addition, mainly young birds up to the size of young bustards and cranes , but also adult medium-sized birds such as pigeons , hen birds and corvids are captured. Carrion is apparently used regularly, and frogs and insects are also eaten less often .

    Reproduction

    Egg,     Museum Wiesbaden collection

    The courtship usually begins immediately after arriving at the breeding site. It usually consists of the high circles of one or both couple partners above the breeding site, with intense calls. Occasionally the partners playfully fly mock attacks on each other.

    The nests are mainly built on deciduous trees. The trees used are often more or less free, in densely populated areas but also hidden in larger forest areas and then sometimes far away from the habitats . In the substructure, the nests consist of branches as thick as a thumb, the nest hollow is laid out with thinner branches, scraps of fur and usually also with green twigs. The nest diameter is usually between 100 and 130 cm. The nests are often used several times.

    In southeastern Europe, eggs are seldom laid as early as mid-March, but mostly from the end of March to the end of April at the latest. The clutches usually consist of two to three eggs, rarely just one egg. The eggs are pale brownish or mottled purple on a white background. They measure an average of 73.3 × 56.5 mm.

    The breeding season is about 43 days. Cainism occurs when there is a lack of food, but it is not mandatory and more than one young bird regularly fledges. For example, 78 times 1, 67 times 2 and 7 times 3 nestlings were found in 152 nests in Slovakia . The nestling period lasts 62 to 67 days; the young birds usually fly out in late July to early August.

    hikes

    The migration from the narrower breeding grounds often already takes place at the end of August or beginning of September, the actual migration mostly begins at the end of October to the beginning of November. The migration strategies are evidently individual and very different depending on the population. Individual birds overwinter in the extended breeding area, but the majority of the population is migratory , with the spectrum ranging from short to long-distance migrants. The main wintering areas are north-east Africa, parts of the Arabian Peninsula , the north-west of the Indian subcontinent and south-east China . The birds return to their breeding sites in early March to early April.

    Individual migration routes have been explored in the last 15 years or so by catching and broadcasting with satellite transmitters. Two adult birds caught in winter near Taif in Saudi Arabia migrated to breeding areas west of the Urals in Russia in spring . A four-year-old bird that was also caught there surprisingly moved to northern China not far from the Mongolian border during the summer ; the migration of this bird was almost in an east-west direction.

    Young imperial eagle in Seewinkel (Austria)

    Existence and endangerment

    The population in Europe was estimated by the IUCN in 2007 at 1051 to 1619 pairs, the majority of which live in the European part of Russia with 600 to 900 pairs alone. According to the IUCN, Kazakhstan also has a large population with 750 to 800 pairs. The world population is estimated by the IUCN at a few thousand pairs.

    In the past, the imperial eagle profited from human activity, especially from the opening up of the landscape, and expanded its area to the west, so the Carpathian Basin was only settled around 150 years ago. In the 20th century the population declined dramatically, at least in south-eastern Europe, the species has now probably become extinct in Greece , in Hungary the population had shrunk to around 15 pairs by 1980 and for Bulgaria the population was still 15 for 1980 to 1993 estimated up to 20 pairs.

    The main cause of the decline was the extensive application of poison bait to exterminate wolves and other predators as well as corvids and direct human pursuit. Other causes of the decline were the extensive felling of individual trees and groups of trees in the agricultural landscape, which deprived the imperial eagle of nesting opportunities, as well as the conversion of agricultural use, which led to the decline of important prey animals such as the ground squirrel.

    Intensive conservation programs for the species were started in Hungary and Slovakia around the end of the 1970s. In addition to the comprehensive coverage of all breeding pairs as possible, the programs include agreements with the landowners to avoid disruption to the eyrie by agriculture and forestry, the guarding of eyrie to prevent disruption by onlookers and the robbery of eggs or young birds, and the construction of artificial nests the securing of existing clumps in danger of falling.

    These programs were and are very successful, the population in Hungary increased from 14 pairs in 1985 to 61 to 65 pairs in 2002, in Slovakia from 12 pairs in 1981 to 40 to 45 in 2004. In the course of this population recovery, the species its distribution area also extended to the west, in 1998 the Czech Republic was settled (2004 2 pairs) and in 1999 the eastern Austrian Burgenland (2004 also 2 pairs). For the first time in 200 years was in the Donauauen a breeding pair observed after the imperial eagle had previously taken root already back in the Danube-Auen March at the Austrian-Slovakian border several years in Austria in 2011 again. In 2014, there was also a report of an imperial eagle pair with a boy in the Neusiedlersee-Seewinkel National Park in Hanság . In spring 2019, 22 breeding pairs with 29 young birds were counted again in Austria.

    Different data on population development are available from the Asian part of the distribution area. The population on the eastern border of the total distribution area in the vicinity of Lake Baikal decreased by more than 40 percent from 1982/83 to 1998/99, the reasons for this decrease are unclear. In contrast, the population in the 877 square kilometer Naurzum reserve in northwestern Kazakhstan has apparently increased since 1946 and was stable or slightly increased in the period from 1990 to 2002. The IUCN classifies the world population of the imperial eagle as endangered ("vulnerable") .

    Eponyms

    The asteroid (8980) Heliaca is named after Aquila heliaca .

    swell

    Individual evidence

    1. ^ J. Ferguson-Lees, DA Christie: Raptors of the World. Christopher Helm, London, 2001, ISBN 0-7136-8026-1 , p. 740.
    2. ^ D. Forsman: The Raptors of Europe and the Middle East - A Handbook of Field Identification . T & AD Poyser, London, 1999: pp. 378-382
    3. ↑ UN Glutz v. Blotzheim, KM Bauer & E. Bezzel: Handbook of the birds of Central Europe . Vol. 4, 2nd edition, AULA-Verlag, Wiesbaden 1989, ISBN 3-89104-460-7 , p. 624.
    4. ↑ HRL Lerner, DP Mindell: Phylogeny of eagles, Old World vultures and other Accipitridae based on nuclear and mitochondrial DNA . Molecular Phylogenetics and Evolution 37; 2005: pp. 327-346.
    5. ↑ M. Wink, H. Sauer-Gürth: Phylogenetic Relationships in Diurnal Raptors based on nucleotide sequences of mitochondrial and nuclear marker genes . In: RD Chancellor, B.-U. Meyburg (Ed.): Raptors Worldwide . Berlin, Budapest, 2004: pp. 483–498.
    6. ↑ UN Glutz v. Blotzheim, KM Bauer & E. Bezzel: Handbook of the birds of Central Europe . Vol. 4, 2nd edition, AULA-Verlag, Wiesbaden 1989, ISBN 3-89104-460-7 , p. 634.
    7. ^ A b c S. Danko and J. Chavko: Breeding of the Imperial Eagle Aquila heliaca in Slovakia. In: Meyburg, B.-U. & Chancellor, RD (eds.): Eagle Studies. WWGBP, Berlin, London, Paris 1996, ISBN 3-9801961-1-9 , pp. 415-423.
    8. ^ S. Danko: Ringing results on the imperial eagle Aquila heliaca in the northwest of the breeding area. In: Meyburg, B.-U. & Chancellor, RD (eds): Eagle Studies. WWGBP, Berlin, London, Paris 1996, ISBN 3-9801961-1-9 , pp. 389-403.
    9. ^ B. Hallmann: The decline of the Imperial Eagle Aquila heliaca in Greece. In: Meyburg, B.-U. & Chancellor, RD (eds): Eagle Studies. WWGBP, Berlin, London, Paris 1996, ISBN 3-9801961-1-9 , pp. 439-442.
    10. ↑ a b c L. Haraszthy, J. Bagyura, T. Szitta, Z. Petrovits and L. Viszló: Biology, Status and Conservation of the Imperial Eagle Aquila heliaca in Hungary. In: Meyburg, B.-U. & Chancellor, RD (eds): Eagle Studies. WWGBP, Berlin, London, Paris 1996, ISBN 3-9801961-1-9 , pp. 425-428.
    11. ↑ T. Petrov, P. Iankov, A. Darakchiev, K. Nikolov, T. Michev, L. Profirov and B. Milchev: Status of the Imperial Eagle Aquila heliaca in Bulgaria in the period between 1980 and 1993. In: Meyburg, B.-U. & Chancellor, RD (eds): Eagle Studies. WWGBP, Berlin, London, Paris 1996, ISBN 3-9801961-1-9 , pp. 429-438.
    12. ↑ T. Mebs & D. Schmidt: The birds of prey in Europe, North Africa and the Middle East. Franckh-Kosmos, Stuttgart 2006, ISBN 3-440-09585-1 , pp. 240-241.
    13. ↑ A. Ranner: The current situation of the imperial eagle (Aquila heliaca) in Austria. In: A. Gamauf and H.-M. Berg (Ed.): Birds of prey and owls in Austria. Vienna 2006, ISBN 3-902421-15-0 , pp. 27–35.
    14. ^ Donau-Auen: Pair of imperial eagles newly moved in on ORF -NÖ from June 3, 2011, accessed on June 3, 2011.
    15. ↑ ORF ON, November 9, 2014
    16. ^ A (reasonably) good year for Austria's imperial eagle. In: The Standard. August 21, 2019, accessed on August 21, 2019 (German).
    17. ↑ VV Rybatsev and TE Katzner: Severe declines of Eastern Imperial Eagle Aquila heliaca populations in the Baikal region, Russia: a modern and historical perspective. Bird Conservation International 17, 2007: pp. 197-209. Full text as pdf
    18. ↑ E. Bragin and TE Katzner: Long-term population trends and nesting success of Imperial Eagle, Golden Eagle and White-tailed Sea Eagle in North-West Kazakhstan in 1990 and 2002. In: RD Chancellor, B.-U. Meyburg (eds.): Raptors Worldwide. WWGBP / MME, Budapest, 2004: pp. 551-556

    literature

    • J. Ferguson-Lees, DA Christie: Raptors of the World. Christopher Helm, London 2001, ISBN 0-7136-8026-1 .
    • D. Forsman: The Raptors of Europe and the Middle East - A Handbook of Field Identification . T & AD Poyser, London 1999, ISBN 0-85661-098-4 .
    • Urs N. Glutz von Blotzheim , Kurt M. Bauer and E. Bezzel: Handbook of the birds of Central Europe. Volume 4, 2nd edition, AULA-Verlag, Wiesbaden 1989, ISBN 3-89104-460-7 .
    • T. Mebs & D. Schmidt: The birds of prey in Europe, North Africa and the Middle East. Franckh-Kosmos, Stuttgart 2006, ISBN 3-440-09585-1 .

    Web links

    Wiktionary: Imperial Eagle  - explanations of meanings, word origins, synonyms, translations
    Commons : Eastern Imperial Eagle  - Collection of images, videos and audio files
    This version was added to the list of articles worth reading on October 8, 2008 .