Giant sea eagle

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Giant sea eagle
Giant sea eagle (Haliaeetus pelagicus)

Giant sea eagle ( Haliaeetus pelagicus )

Systematics
Class : Birds (aves)
Order : Birds of prey (Accipitriformes)
Family : Hawk species (Accipitridae)
Genre : White-tailed eagle ( Haliaeetus )
Type : Giant sea eagle
Scientific name
Haliaeetus pelagicus
( Pallas , 1811)

The giant sea eagle ( Haliaeetus pelagicus ) is a bird of prey from the sea ​​eagle genus . It is the largest white-tailed eagle and is characterized by its black and white plumage, its extraordinarily large and powerful orange-yellow beak and its paddle-shaped wings. Giant sea eagles live on the rivers and coasts of near-Pacific Russia. Depending on their geographical location, they are resident or migratory birds , the most important wintering areas are in Japan. Giant sea eagles feed on fish, waterfowl, and carrion . The inventory comprises about 5000 copies and continues to decline; therefore the IUCN classifies the giant sea eagle as vulnerable (endangered).

features

Detail of the head.

The species can be easily distinguished from other sea eagles by its proportions: the paddle-shaped wings appear relatively short due to their width and in comparison to the body length, the wedge-shaped tail quite long. The sexes are colored the same, in terms of size there is a moderate and in terms of weight a very pronounced sexual dimorphism : on average, females reach 11% more body size and 43% more weight than males. The body length is 85 to 105 centimeters, the wingspan 1.95 to 2.80 meters, the tail length 32 to 36 centimeters. Males weigh 4.9 to 6.0 kilograms, females 6.8 to 9.0 kilograms. The giant sea eagle is the largest species of the genus Haliaeetus and one of the largest birds of prey.

Giant sea eagle, cub

The plumage is predominantly dark brown to black; Forehead, shoulders, the very thick spring pants and the tail are sharply set off white. At the back of the head there are some lighter, grayish feathers, the legs and beak are orange-yellow. The iris is yellow and there is orange-yellow skin around the eyes. With the exception of the lighter tail feathers with dark tips, young animals have completely black-brown plumage. Greyish drawings can be seen on the head and chest. Some coverts of the shoulder area are colored whitish. The plumage of three-year-old animals is in a stage between juvenile and adult plumage . The first white color appears on the shoulders and the tail is almost completely white. In younger birds, the skin around the eyes is still pale yellow, and the beak and legs are also lighter than in adults.

Except for the white tail, completely dark feathered individuals appear very rarely, in the past especially on the Korean Peninsula .

The giant sea eagle flies comparatively slowly with strong, flat wing beats and interspersed with short gliding phases. It glides with almost straight wings and extended flight and control feathers. In flight , the adult giant sea eagles are almost completely dark in color, to which the white of the feather trousers, the wedge-shaped control feathers and the cover feathers of the front wing edge stand in clear contrast. Some feathers on the dark dressing gown also show white tips, and there are also light pen shafts on the head and neck. Young animals are mostly dark brown in flight, except for the white tail with dark tips, a grayish markings on the chest and head and whitish markings on the front wing edges. The flight image of subadult animals from the age of three mediates between juvenile and adult dress. The birds molt into the adult dress in the fourth year of life.

Calls

Sounds are mostly heard at the beginning of the breeding season and as part of the expressive behavior; the calls are similar to those of other sea eagles. Seagull- like calls were described during courtship; deep barking ( kyow-kyow-kyow ) and a louder, higher kra-kra-kra can also be heard .

Systematics

Haliaeetus pelagicus is a well-defined species within the genus of white-tailed eagles ( Haliaeetus ). The German naturalist Georg Wilhelm Steller brought the holotype to Europe after an expedition in the 1760s. In the English-speaking world, it is therefore called Steller's Sea Eagle . The first description was written by Peter Simon Pallas in 1811 . According to DNA analyzes , he is more closely related to sea eagles ( white- tailed eagles , bald eagles ) distributed in the northern hemisphere than to tropical species of the same genus.

No subspecies are recognized today. The systematic position of the dark morph was unclear for a long time, since until recently the last reliable sightings dated to 1968. It was occasionally treated as a separate species H. niger or as a subspecies H. pelagicus niger . However, the morphing theory is supported by a melanistic giant sea eagle, which hatched in 2001 in the Bavarian Hunting Falconry and now lives in the Berlin zoo . It was created by artificially bringing together germ cells from normally colored parent birds, and its own offspring were also normally colored.

distribution and habitat

Pacific coast from the Chukchi Sea to the East China Sea
green: resident birds
orange: mostly summer birds
blue: wintering areas
purple: occasional occurrences of non-breeding, roaming birds

The giant sea eagle lives in northern East Asia near the Pacific. Today the animals breed only in eastern Russia on the coast of the Bering Sea , the northern coasts of Kamchatka , on the northern Kuriles , on the Sea of ​​Okhotsk , on the Amur , on the Shantar Islands and on Sakhalin . The former breeding populations of South Korea are considered extinct; the same is assumed for North Korea despite the lack of data.

The species is seldom found far from larger bodies of water and inhabits both flat and rocky coasts, coastal lagoons and estuarine landscapes as well as larger lakes and rivers further inland in more montane regions up to 1000 meters above sea level.

hikes

In areas where the waters remain ice-free all year round, giant sea eagles are resident birds , the remaining populations are migratory birds. Animals from the breeding areas further north move to southern areas from October and winter in Kamchatka , on the southern Kuriles, in South Sakhalin, on the southern coasts of the Sea of ​​Okhotsk and occasionally in Korea, but mainly on Hokkaidō , the northernmost island Japan . At times over 2000 specimens, more than a third of the world's population, collect on the associated Shiretoko Peninsula . Hokkaidō is also drawn to the ready availability of artificial food sources such as bycatch from fisheries and carrion from hunter-killed animals. They return to the northern areas in March and April. The migration behavior results in a horizontal distribution area between 62 ° N and 50 ° N in summer and between 58 ° N and 42 ° N in winter.

As part of a study, nine giant sea eagles were equipped with transmitters in their winter quarters on Hokkaidō. Eight of them moved to Sakhalin, one to Onekotan (northern Kuril Islands). The young birds needed 31 to 61 days for the flight from Hokkaidō to the northern regions and thus far more time than adult birds (21 to 25 days). Another study on migration into the breeding areas produced a similar result for four 2 to 3 year old and four adult specimens. These differences are justified, among other things, with the energy balance: Since young animals have few fat reserves, they have to increase their fat reserves by taking longer breaks. Adult birds, on the other hand, are likely to begin their migration under better conditions, and pairs arriving earlier in the breeding areas can, among other things, occupy better territories and thus increase the likelihood of successful reproduction.

Occasional sightings were made north to the Anadyr , south to Beijing and the Ryūkyū Islands , west to Yakutsk and east to the Pribilof Islands , the Aleutian Islands and as far as the vicinity of Juneau in southeastern Alaska . Exceptionally, individual giant sea eagles reached Hawaii . The observation of a white- tailed eagle on the Wake Atoll in the winter of 1997 may have affected this species, but this is not considered certain.

Way of life

nutrition

Giant sea eagle with a captured fish on Hokkaido

The giant sea eagle feeds mainly on fish, especially salmon fish (Salmonidae, up to 7 kg in weight), sea birds and carrion. Occasionally he hunts chickens and land-dwelling mammals of appropriate size. The beak, which is unique for birds of prey and the strong muscles attached to it, developed in adaptation to this food in order to tear open the tough skin of the salmon and to chop meat from carcasses into bite-sized pieces. The food spectrum of the giant sea eagle is strongly dependent on the season and the habitat; A study of giant sea eagles from the Sea of ​​Okhotsk provided specific data: in spring and summer, giant sea eagles were observed catching prey and remains of prey in and under clumps were analyzed. Eagles living on coasts had a significantly higher proportion of seabirds of up to 73% in the food spectrum, in the vicinity of seabird colonies up to 91%. This proportion was much lower for eagles in the rivers, at 0 to 11%. In spring, carrion made up 83% of the food in the pairs nesting on rivers; in summer, when the young were rearing, fish made up 77% of the prey.

Giant sea eagles catch fish from the edge of the bank or wading in the shallow water, from a hide up to 30 meters in height in a swoop, or spot their prey from a slow search flight, usually at a height of six to seven meters. They grab the fish without submerging the rest of the body in the water. On Hokkaidō, bycatch from fishing boats is an important source of food. Giant sea eagles also hunt slowly-flying, common seabirds such as guillemots and prey on juveniles and eggs in colonies of seabirds. As opportunistic scavengers , they are also observed on the carcasses of mammals such as seals and on smaller mammals in the traps of trappers as well as on dead birds and fish. If several animals gather around a carcass, disputes over food can arise.

Social behavior and reproduction

Giant sea eagles live in pairs in territories during the breeding season. In the winter months, however, especially on Hokkaidō, several hundred individuals can gather at suitable resting places.

Giant sea eagle

Giant sea eagles are monogamous and likely mated for life. The animals usually nest in low density. The breeding season is between the end of April and mid-September, depending on the geographic location. The courtship and territory behavior include sliding together while shouting near the breeding site, as well as spectacular flight maneuvers and pursuit flights, which are also accompanied by calls. The giant sea eagle builds clumps with a diameter of up to 2.5 meters and a height of up to 4 meters, usually up to 30 meters above the ground in hard-to-reach places such as in the crowns of large trees and on ledges. Giant sea eagles lay one to three, usually two eggs, from which the young birds hatch after 38 to 45 days of incubation. Depending on external conditions, they gain an average of 77 to 92 grams per day. In the first 15 to 20 days, the ability to thermoregulate in the young is not yet sufficiently developed; therefore they are huddled . Older young animals, on the other hand, are not rowed at all in good weather. Often only one young animal survives due to adverse environmental conditions; Cainism , however, is rare in giant sea eagles. The young birds fledge after around 70 days and are then dependent on their parents for another two to three months.

Existence and endangerment

Haliaeetus pelagicus is listed as endangered ( vulnerable ) in the IUCN Red List , the population is estimated by BirdLife International at 5000 specimens and continues to decline. The main risk factors are the destruction of the habitat through the construction of hydropower plants, through the planned extensive development measures for the oil industry both on the coasts and offshore and through logging. Due to the deforestation of large trees in the breeding areas, giant sea eagles are forced to look for less suitable nesting sites. There the clumps are in danger of falling. In addition, there is a lack of food due to overfishing and environmental pollution . Currently, there are low reproductive rates and high juvenile mortality rates .

Frequent flying up due to disturbances increases the animals' energy requirements. Presumably, the predators who depend on efficiency avoid the vicinity of settlements. The pollution from industrial wastewater and especially from organochlorine compounds such as the insecticide DDT , its degradation product DDE and polychlorinated biphenyls (PCB) have a direct impact on the success of reproduction and the population . In seven deaths found on Hokkaidō between 1986 and 1998, considerable concentrations of pollutants were found: The highest value of DDT was measured with 17 micrograms per gram in a chest muscle, the highest of PCB with 41 micrograms per gram in a liver. The large quantities of poisons in giant sea eagles can also be attributed to their high position in the food chain , as the level of trophies also increases the toxin levels ( bioaccumulation ). DDT and DDE lead to thinner eggshells and reduce the breeding success as the eggs break or die. Higher concentrations of PCB can cause various symptoms of poisoning. Although DDT is already banned, high levels of exposure can still be measured.

Giant sea eagle on Hokkaido

In 1996, lead poisoning was first identified as the cause of death of a giant sea eagle. The birds ingest the lead mostly through carrion, either from water birds that died from swallowed lead weights from fishing, but mostly from the carcasses of larger mammals shot by hunters (usually Sika deer ). Until 2003, Japanese law allowed hunters to separate the desired body parts from hunted animals on site and leave the remaining body parts behind. The mostly used lead ammunition or its fragments remain in the carcass. Also shot animals that later perish and are not found during the search lead to carrion contaminated with lead. As the fish stocks before Hokkaidō have declined, giant sea eagles continue to move inland, where they find the carcasses of the sika deer, which is often the cause of game damage . Older giant sea eagles are usually dominant on the carcasses, begin to feed at the exposed point of the bullet, and so quickly ingest lead. Lead poisoning causes severe weight loss, damage to the liver, gall bladder and kidneys , diarrhea , sometimes shrinking of the pectoral muscles necessary for flying, anemia caused by a drop in hemoglobin and damage to the nervous system that can lead to complete blindness. Even non-immediately lethal doses of lead can later lead to death from long-term damage. Since 1996, 92 cases of fatal lead poisoning have been recorded, the actual number is likely to be significantly higher as only a fraction of the poisoned eagles are found. In 2000, the use of lead bullets was banned and since 2003, killed animals are no longer allowed to be left in the wild. However, compliance with these measures is difficult to control in the winter of the Japanese highlands and the success of the protective measures therefore depends heavily on the willingness of the hunters to cooperate.

Occasionally, the eggs and young of the giant sea eagle are taken from nature by animal dealers. Haliaeetus pelagicus is listed in Appendix II of the Washington Convention on Endangered Species (CITES), permits and proof of harmlessness for the population are required for catching and trading. Targeted shooting could also be a problem locally.

The species is protected by law in Russia, Japan, China and South Korea. There are a number of nature reserves in the habitat of the giant sea eagle, the main wintering quarters in Japan are designated as National Wildlife Protection Areas . The IUCN also proposes special protection for salmonid spawning areas.

The world's first breeding of the giant sea eagle in captivity was achieved in 1987 at Moscow Zoo.

swell

literature

Further reading:

Individual evidence

  1. ↑ E. Potapov, I. Utekhina & MJ McGrady (2000): Steller's Sea Eagle in Magadan District and in the North of Khabarovsk District . First Symposium on Steller's and White-tailed Sea Eagles in East Asia, pp. 29–44 ( full text ; PDF; 398 kB)
  2. ↑ HRL Lerner & DP Mindell (2005): Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA . Molecular Phylogenetics and Evolution 37, pp. 327–346 ( full text ; PDF; 1.1 MB)
  3. ^ MEJ Gore & PO Won (1971): The birds of Korea . Royal Asiatic Society, Seoul, Tokyo; quoted in Kaiser (2010)
  4. ↑ M. Kaiser (2010): A living specimen of the dark form of Steller's Sea Eagle, Haliaeetus pelagicus (`` niger '') in captivity . Journal of Ornithology 151 (Online), doi: 10.1007 / s10336-010-0580-2 .
  5. ↑ a b c Based on Ferguson-Lees & Christie (2001)
  6. ↑ M. Ueta & H. Higuchi (2002): Difference in Migration Pattern Between Adult and Immature Birds Using Satellites . The Auk 119 (3), pp. 832-835
  7. ↑ Steller Sea-Eagle ( full text ; PDF; 14 kB). In: RL Pyle & P. ​​Pyle (2009): The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status . BP Bishop Museum, Honolulu, HI, USA Version 1
  8. ↑ MJ Rauzon, D. Boyle, WT Everett & J. Gilardi (2008): The Status of Birds of Wake Atoll. Atoll Research Bulletin No. 561, Smithsonian Institution, p. 33 ( full text ; PDF; 5.3 MB)
  9. ↑ a b A. Ladyguin (2000): The morphology of the bill apparatus in the Steller's Sea Eagle . First Symposium on Steller's and White-tailed Sea Eagles in East Asia S- 1-10 ( full text ; PDF; 104 kB)
  10. ^ A b M. Ueta, E. Popatov & MJ McGrady (2000): Diet of the Steller's Sea Eagle in the Northern Sea of ​​Okhotsk . First Symposium on Steller's and White-tailed Sea Eagles in East Asia, pp. 71–82 ( full text ; PDF; 49 kB)
  11. ↑ a b VB Masterov (2000): Postnatal development of Steller's Sea Eagles sexing and aging techniques . First Symposium on Steller's and White-tailed Sea Eagles in East Asia, pp. 17–28 ( full text ; PDF; 87 kB)
  12. ↑ M. Ueta & VB Masterov (2000): Estimation by a computer simulation of population trend of Steller's Sea Eagles . First Symposium on Steller's and White-tailed Sea Eagles in East Asia, pp. 111–116 ( full text ; PDF; 109 kB)
  13. ↑ a b Sea of ​​Okhotsk and Sea of ​​Japan Coasts ( full text ( memento from November 30, 2010 in the Internet Archive ); PDF; 454 kB). In: BirdLife International (2003): Saving Asia's Threatened Birds . ISBN 0-946888-47-7
  14. ↑ a b c d Haliaeetus pelagicus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed November 25 of 2010.
  15. ↑ H. Iwata, M. Watanabe, E.-Y. Kim, R. Gotoh, G. Yasunaga, S. Tanabe, Y. Masuda & S. Fujita (2000): Contamination by chlorinated hydrocarbons and lead in Steller's Sea Eagle and White-tailed Sea Eagle from Hokkaido, Japan. First Symposium on Steller's and White-tailed Sea Eagles in East Asia, pp. 91–106 ( full text ; PDF; 51 kB)
  16. ↑ K. Saito (2009): Lead poisoning of Steller's Sea-Eagle (Haliaeetus pelagicus) and White-tailed Eagle (Haliaeetus albicilla) caused by the ingestion of lead bullets and slugs, in Hokkaido Japan ( full text ; PDF; 370 kB). In: RT Watson, M. Fuller, M. Pokras & WG Hunt (Eds.): Ingestion of Lead from Spent Ammunition: Implications for Wildlife and Humans . The Peregrine Fund, Boise, Idaho
  17. ↑ Martin Kaiser: Breeding success of the giant sea eagle, Haliaeetus pelagicus, in the Berlin zoo with a female of the dark morph

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This version was added to the list of articles worth reading on December 29, 2010 .