Golden eagle
| Golden eagle | ||||||||||||
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Golden eagle ( Aquila chrysaetos ) |
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| Aquila chrysaetos | ||||||||||||
| ( Linnaeus , 1758) |
The golden eagle ( Aquila chrysaetos ) is a large bird of prey within the hawk family (Accipitridae). Golden eagles inhabit open and semi-open landscapes throughout the Holarctic . They mostly feed on medium-sized, ground-dwelling mammals . The species used to be widespread in Europe, but has been systematically pursued, so that today it is only found in mountainous areas in many parts of Europe. In Germany, golden eagles only breed in the Alps .
description
Golden eagles are among the largest members of the Aquila genus . The sexes of the golden eagle differ significantly in size and weight. The female can reach a body length of 90-100 cm; the male is on average around 10 cm smaller. The wingspan varies between 190 and 210 cm in the male and between 200 and 230 cm in the female. Females weigh 3.8 to 6.7 kg, the lighter males 2.8 to 4.6 kg. Golden eagles have 11 wings , but the outermost (11th) wing is very small. The sixth swing arm is the longest at almost 60 cm. The 17 arm wings are between 35 and 40 cm long. The tail is made up of 12 control feathers that are 34 to 42 cm long.
The basic color of the plumage is a uniform dark brown. The neck is golden yellow. The tail of the adult animals is brown and more or less clearly interspersed with a few lighter bands. The beak is dark gray, the iris of the eyes dark brown. As with all species of the subfamily Aquilinae, the legs are feathered up to the very strong yellow toes .
Golden eagles in the first year of life are generally darker brown and have conspicuous, white feathers on the inner hand and outer arm . The tail is white and has a sharply defined, broad black end band . Golden eagles are only fully colored from the age of 5 to 7.
Due to the different coloration, the term gold eagle was also used for adult golden eagles until around 1900 . Young animals were thought to be a different species.
In flight, the golden eagle usually looks very light and elegant, despite its size. In addition to the strong fingering of the hand wings typical of eagles, the relatively long, only slightly rounded tail is striking. In contrast to all other representatives of the genus, the golden eagle lifts its wings slightly in soaring flight , so that a slightly V-shaped flight pattern is created.
distribution and habitat
The golden eagle inhabits the boreal , temperate and Mediterranean zones of the entire Holarctic . This makes it the most widespread representative of the Aquila genus . In the Palearctic , the distribution extends in the west of Ireland over Scotland in a wide strip through Europe and Asia to Kamchatka and Japan . In addition, the north and west of North America are colonized by the species. Through centuries of massive persecution, the distribution in Europe is now strongly fragmented. In Central Europe the occurrence of the golden eagle is essentially limited to the Alpine arc and the Carpathian Mountains , in Germany it only lives in the Bavarian Alps . Apart from the Alps, the occurrences in Denmark and in eastern Poland are closest to Germany.
Golden eagles inhabit open and semi-open landscapes of all kinds that offer sufficient food and have rock walls or older trees for nesting. Its habitat ranges from alpine meadows to large moors with small forests in the Baltic states to semi-deserts in northern Africa. Large, closed forests are only populated at the edge. Today's strong focus on mountainous landscapes is a consequence of the intense persecution, at least in Europe.
Systematics
The species status of the golden eagle is undisputed, according to recent molecular genetic studies, the closest relative is the African coffee eagle . Depending on the author, five to six subspecies are recognized, the delimitation is based on small differences in size and color and the transitions are fluid:
- A. c. chrysaetos : Europe without the Iberian Peninsula , Western Siberia .
- A. c. homeyeri : Slightly smaller and darker than nominate form. South adjoining nominate form; Iberian Peninsula , North Africa, Asia Minor , Caucasus , Arabian Peninsula , from there to Iran .
- A. c. daphanea : Even darker than A. c. homeyeri , largest subspecies; from east Iran via Afghanistan , Pakistan , north India and Nepal to west and central China and Mongolia .
- A. c. kamtschatica : darkest subspecies, patch on the neck rather red-brown; Central Siberia to Kamchatka . Some authors do not recognize this subspecies, but rather combine it with A. c. canadensis .
- A. c. japonica : As dark as A. c. kamtschatica , but much smaller, smallest subspecies; Japan and Korea .
- A. c. canadensis : coloration as A. c. kamtschatica , but a little smaller; North America.
Hunting way
Golden eagles hunt mostly in open or semi-open landscapes in flight close to the ground, making optimal use of any cover. They slide close to the slopes, over knolls and small hills and try to surprise their prey at a short distance. Often they also hunt from a hide. The eagles usually grab their prey on the ground or in the air space close to the ground and kill it with their extraordinarily powerful toes and claws. Very large prey such as ibex fawns or young chamois grab them by the head. The golden eagle hits its claws through its skull and into the brain. In the few cases observed, these large prey were killed within seconds.
Hunting in open air is less common; however, the capture of migrating cormorants has already been observed several times. In view of their size, golden eagles move extremely agile and fast in the air. It has been observed several times how a golden eagle turned on its back in flight and thus preyed on a chasing raven , for example . Golden eagles cannot carry carcasses in flight that weigh more than their own body weight. Heavy prey therefore split them up and deposit them in portions, or they fly towards the carcass over several days.
food
Golden eagles are extraordinarily strong and very skilled. They regularly prey on animals that are considerably heavier than themselves. The maximum prey weight is around 15 kilograms. There is only one documented case in which an even heavier sika deer was hunted. Attack attempts on nearly full-grown chamois are documented. The chamois defense strategy is to jump down the slope and roll over, which means a significant risk of injury to both.
In the prey spectrum, ground-dwelling, small to medium-sized mammals from ground squirrel to ibex fawn size dominate, birds usually only play a smaller role. Usually a few mammalian species make up the main part of the diet. In addition, however, the golden eagle prey on almost all small and medium-sized mammals and birds that are found in the respective area. In the south of the distribution area in particular, it also regularly eats reptiles , where golden eagles, like bearded vultures, also drop tortoises on rocks in order to break their hard shells. Carrion plays an important role in nutrition, especially in winter, regionally but also in summer.
In the Swiss canton of Graubünden , Alpine marmots dominated the prey spectrum during the breeding season with 60.2% of all prey, followed by young chamois with 8.0%. This was followed by the mountain hare , ptarmigan and black grouse , each with 5.2%. In the Swiss foothills of the Alps, nestling food consisted primarily of brown hares (36.2% of all prey) in 4 territories , followed by domestic cats (27.5%), fawns (14.1%) and domestic chickens (8.1%). Populations in the Massif Central of France mainly hunt wild rabbits. In Scotland , depending on the region, rabbits were found in 10.7% to 46.9% of all tombs found in summer. Other important prey animals there were sheep and goats (in 0.6 to 26.8% of all vaults), grouse (5.4 to 47.8%) and red deer (as carrion) (1.2 to 22.3%).
Use of space and settlement density
Despite the large distribution area, there is so far only little data on the size of the action area , i.e. on the area used by a breeding pair. The values determined fluctuate considerably depending on the habitat and food supply. In the Swiss canton of Graubünden the size of the action area according to visual observations in 26 districts was between 29 and 88 km², with an average of 53 km². In Idaho , four pairs of golden eagles flew over areas between 11.6 and 49.0 km², also according to visual observations, with an average of 32.8 km². Due to the methodology, the values presented here probably represent the lower limit of the actual action area sizes. Golden eagles vehemently defend their entire action area against conspecifics all year round; a previously occasional separation between the defended area and the area used for foraging is therefore not justified.
The large-scale population density also shows significant differences, ranging from 1.9 breeding pairs (BP) / 1000 square kilometers around the Belarus Wizebsk up to 22.7 BP / 1000 square kilometers in parts of Scotland . Worldwide, the values are mostly between 5 and 20 BP / 1000 km². In the Alps , quite uniform values between 7.4 BP / 1000 km² in the Lower Tauern of Austria and 14.3 BP / 1000 km² in Graubünden were found.
Reproduction
Horst and nesting place
The golden eagle nests in rock faces and on tall trees. Nesting places on rocks are mostly in caves or under overhangs, exposures to the main wind direction (in Central Europe west and south-west sides) are clearly avoided. A (rock) eyrie is started flat and oval, clumps on trees are rounder and are built higher at the beginning. Rock nests in Scotland measured an average of 1.33 m × 1.06 m and were 0.79 m high, tree nests in Sweden had an average diameter of 1.4 m and were 1.1 m high. Depending on the duration of use, the clumps are constantly being expanded, supplemented and repaired, so that over the years mighty clumps, often more than two meters in height and width, are created. The nest is made from strong branches and twigs and padded with leafy twigs and tufts. This padding takes place throughout the breeding season. The nests built by both animals are used for several years, and usually a couple has several so-called alternating nests. In the mountains, the nesting sites are usually below the hunting areas, as the transport of the prey is easier down than up.
Brood and rearing of young
Golden eagles do not become sexually mature until they are around six years old. As far as is known, breeding pairs lead a monogamous permanent marriage. The courtship starts in January with sometimes spectacular courtship flights. The eggs are laid later and later at a higher latitude, in Oman on average at the beginning of December, in northern Alaska and Siberia at the beginning of May. The beginning of laying is fairly uniform throughout Europe between mid-March and mid-April and changes only marginally from north to south. The earliest egg-laying took place in Finland in early March and in Switzerland in late February.
The female usually lays two eggs every three to four days, less often only one or three. The short spindle-shaped eggs are dull and mostly off-white with brown, brown-purple or light gray speckles. If there is more than one egg, the others are usually no longer or only sparsely spotted. Eggs from the Alps measured an average of 76.4 × 58.0 mm. From the first egg onwards, the clutch is predominantly incubated by the female, while the male provides the female with food during the brood. The breeding season lasts 43 to 45 days.
The newly hatched eagles have a white down dress, the second down dress is put on at the age of 9 to 15 days, is dirty white and consists of denser and coarser feathers. The oldest boy often kills his younger siblings in the first few weeks of life. This so-called cainism is, however, in contrast to other representatives of the genus Aquila , such as the lesser spotted eagle , not obligatory, but occurs mainly when there is a food shortage. About seven weeks after hatching, the young birds can split up their prey themselves. Until then, the female feeds them with prey that has been felled by the male and brought to the eyrie. At the age of 74 to 80 days, the young birds complete their first successful short flights. The young birds spend the first 60 to 70 days after leaving the nest in the immediate vicinity of the nest; The young birds leave their parents' territory about 5 months after they leave.
Age
There is hardly any information on the average life expectancy of free-living golden eagles, but according to observations in Switzerland, territorial birds seem to regularly reach an age of> 20 years. The maximum values detected by bird ringing were 26 years (Switzerland) and 32 years (Sweden). A number of golden eagles are said to have lived to be over 40 years old in captivity, but many of these dates are considered questionable. The oldest golden eagle currently kept in Germany hatched on May 21, 1984. He lives in the Sababurg zoo in northern Hesse.
Population development and endangerment
Early on, people no longer saw the golden eagle just as the “king of the air”, but also as a hunting competitor and as an enemy of farm animals. The systematic persecution and extermination of the golden eagle began as early as the 17th century, parallel to the brown bear , wolf , lynx , bearded vulture and other predators. The eagles were shot in Europe or caught with iron and poison bait, the clumps were gutted and destroyed. The decline is quite well documented for Germany. As early as the 17th century, the last breeding pairs had disappeared from the Thuringian Forest , the Zittau Mountains and the Ore Mountains , around 1750 from the Harz Mountains and around 1800 from the Swabian Alb . The last broods were recorded for 1816 from the Black Forest and the Eifel , around 1840 near Celle , 1860 in Fläming , 1864 in the Giant Mountains , 1865 in Mecklenburg , around 1870 in East Prussia , 1876 in Brandenburg and 1887 in Pomerania . After that in Germany there were only golden eagles in the Bavarian Alps .
Despite the intense persecution in the entire Alpine region, the golden eagle survived there, as many eyries were inaccessible and inaccessible here. At the beginning of the 1920s, the hunt for golden eagles was restricted here, in 1925 it was granted year-round closed season in Bavaria and Tyrol, in Switzerland hunting was not completely prohibited until 1953. Intensive reenactments took place until the mid-1960s, with more than 100 specimens shot in Austria between 1959 and 1965 despite protection programs, legal protection measures and guarding. Kills were also approved, although the population of around 50 pairs at that time was classified as endangered.
From around the mid-1970s, there was a clear and sustained increase in populations in the entire Alpine region. For example, the population in Bavaria was estimated at 15 to 17 breeding pairs (BP) at the end of the 1960s, and in 1999 at 45–50 breeding pairs. In the Swiss canton of Graubünden, 42 BPs brooded on an area of 4585 km² in the years 1965–1971, and 105 BPs in the mid-1990s. In Austria, 300–350 BP brood in 2004, and in 2003 320–340 BP in Switzerland. The total population in the Alps is now estimated at 1100–1200 BP. Large populations in Europe are also home to Spain (approx. 1300 BP in 1998–2002), Norway (860–1040 BP, 2003) and Finland (300–350 BP, 2002).
In the United States , the species has been subject to the Bald and Golden Eagle Protection Act since 1952, and the keeping of live animals and the possession of dead eagles and their body parts are heavily regulated. The National Eagle Repository issues permits and distributes animals found dead to Indians for religious and cultural purposes.
Seen worldwide, the IUCN estimates the population of the golden eagle at around 250,000 animals and considers it stable. Therefore the species is classified as “not endangered”.
Situation in Bavaria
Up until the beginning of the 1990s, more and more pairs were observed in the Bavarian Alps that either did not start breeding at all or gave up breeding very early. In most cases, this was due to helicopters or paragliders who flew too close to the nests during the incubation phase or in the first weeks of life of the young birds, when they are not yet able to regulate their temperature independently and brought the adults to take off. Often the eggs then cooled down by the time the parents returned and died or the hatched young birds froze to death. Since the Golden Eagle species aid program has been closely monitoring almost all Bavarian breeding pairs in a monitoring system since the late 1990s , it has been able to prevent such anthropogenic disturbances since then. In 2016 there were again 50 breeding pairs in Bavaria.
literature
- Wolfgang Fischer: golden eagles, kaffir eagles and wedge-tailed eagles. 3. Edition. Westarp-Wissenschaft, Magdeburg 2006, ISBN 3-89432-223-3 ( Die Neue Brehm-Bücherei. Vol. 500).
- Dick Forsman: The Raptors of Europe and the Middle East. Poyser, London 1999, ISBN 0-85661-098-4 .
- Urs N. Glutz von Blotzheim , Kurt M. Bauer , E. Bezzel: Falconiformes. 2nd Edition. Aula, Wiesbaden 1989, ISBN 3-89104-460-7 ( Handbook of the birds of Central Europe. Vol. 4).
- H. Haller: The golden eagle (Aquila chrysaetos) as a breeding bird in the Swiss Alpine foothills: Propagation tendencies and their population-ecological basis. In: The Ornithological Observer. Vol. 91, 1994, pp. 237-254.
- H. Haller: The golden eagle in Graubünden. In: The Ornithological Observer. Supplement 9, 1996, ISBN 3-9521064-0-2 .
- Jeff Watson: The Golden Eagle. Poyser, London 1997, ISBN 0-85661-099-2 .
Web links
- Aquila chrysaetos in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed October 13 of 2008.
- Videos, photos and sound recordings for Aquila chrysaetos in the Internet Bird Collection
- International golden eagle monitoring in the Eastern Alps
- Age and gender characteristics (PDF; 5.7 MB) by J. Blasco-Zumeta and G.-M. Heinze (eng.)
- Spring selection
- Golden eagle protection project in the Allgäu
Individual evidence
- ^ RF Porter, I. Willis, S. Christensen, BP Nielsen: Flight Identification of European Raptors. T. & AD Poyser London 1981: p. 45
- ^ Dick Forsman: The Raptors of Europe and the Middle East. Poyser, London 1999, ISBN 0-85661-098-4 : p. 391
- ^ BirdWatch Ireland: Golden Eagle. Retrieved August 22, 2018 (American English).
- ↑ Golden eagle attacks deer in rare camera trap footage . ZSL Conservation. September 26, 2013. Retrieved August 2, 2014.
- ↑ https://www.youtube.com/watch?v=XRvmuvQab_Y
- ↑ http://www.redbull.com/at/de/adventure/stories/1331761889855/wie-brueder-im-wind-natur-und-fiktion-verschmelzen
- ^ H. Haller: The golden eagle in Graubünden. In: The Ornithological Observer. Supplement 9, 1996, p. 89
- ^ H. Haller: The golden eagle (Aquila chrysaetos) as a breeding bird in the Swiss Alpine foothills. Propagation tendencies and their population-ecological basis. In: The Ornithological Observer. Vol. 91, 1994, p. 243
- ↑ Watson 1997, p. 320
- ^ MW Collopy, TC Edwards: Territory size, activity budget, and role of undulating flight in nesting Golden Eagles. In: Journal of Field Ornithology. 60, pp. 43-51, cited in: J. Watson: The Golden Eagle. Poyser, London 1997, p. 92, incorrect references there corrected
- ^ H. Haller: The golden eagle in Graubünden. In: The Ornithological Observer. Supplement 9, 1996, p. 31
- ↑ Watson 1997, p. 331
- ↑ Sababurg Zoo | In the middle of the Reinhardswald: golden eagle (Aquila chrysaëtos). (No longer available online.) In: www.tierpark-sababurg.de. Archived from the original on August 12, 2016 ; accessed on August 12, 2016 .
- ↑ Glutz von Blotzheim u. a. 1989, p. 651
- ^ H. Haller: The golden eagle in Graubünden. In: The Ornithological Observer. Supplement 9, 1996, pp. 26-27
- ^ Theodor Mebs , Daniel Schmidt: The birds of prey in Europe, North Africa and the Middle East. Kosmos, Stuttgart 2006, ISBN 978-3-440-09585-0 , p. 208
- ^ H. Schöpf: Breeding biology and population dynamics of the golden eagle in Werdenfelser Land / Upper Bavaria. In: Ökologischer Jagdverein Bayern e. V. (Ed.): Feathered carnivores. 1998, pp. 47-52
- ↑ protection program | Steinadlerschutz.de. Retrieved August 11, 2016 .
Tree Frog (1998) | Beaver (1999) | Lynx (2000) | Golden Eagle (2001) | Wood ant (2002) | Swallowtail (2003) | Brown Hare (2004) | Sand lizard (2005) | Alpine Ibex (2006) | Grayling (2007) | Demoiselle (2008) | Brown Bear (2009) | Eucera longicornis (2010) | Earthworm (2011) | Brown Long-eared (2012) | Midwife Toad (2013) | Feldgrille (2014) | Grass snake (2015) | Water shrew (2016) | Red Deer (2017) | Ermine (2018) | Fireflies (2019)
