Gray headed eagle

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Gray headed eagle
Gray Headed Fish Eagle - Ichthyophaga ichthyaetus cropped.jpg

Gray head eagle ( Ichthyophaga ichthyaetus )

Systematics
Class : Birds (aves)
Order : Birds of prey (Accipitriformes)
Family : Hawk species (Accipitridae)
Genre : Ichthyophaga
Type : Gray headed eagle
Scientific name
Ichthyophaga ichthyaetus
( Horsfield , 1821)
Gray headed eagle in flight
The gray head eagle feeds mainly on fish that are captured from a raised hide.

The gray-headed eagle ( Ichthyophaga ichthyaetus ) is a species of raptor from the subfamily Haliaeetinae . Its patchy area of ​​distribution extends from India and Sri Lanka via rear India and the Malay Archipelago . Like other sea eagles, it builds large clumps in forests or on individual trees that are located on large rivers or lakes. It feeds mainly on fish, but occasionally also on reptiles or small mammals. The species has declined sharply in the last 30 years and is considered NT IUCN 3 1st svg(= Near Threatened - potentially endangered).

Together with the smaller brown- tailed sea eagle ( Ichthyophaga humilis ) it is in the genus Ichthyophaga (originally written Icthyophaga ) and is related to the genus Haliaeetus . According to genetic findings, this is polyphyletic and should actually also include the Ichthyophaga species. Some authors have therefore combined the two genera to form the genus Haliaeetus , but this has not yet been fully recognized.

description

With a body length of 61 to 75 cm, the gray head eagle is about the size of a steppe eagle , but is relatively short-winged at 155 to 170 cm. Its beak is strong, its body appears massive with a long neck and a small head. The wings are wide, the tail is rounded. The legs are relatively short with featherless tarsi and long claws on the toes. The species looks relatively clumsy and often sits upright for a long time on bare branches by rivers or lakes, with the tips of the hand wings barely reaching over half of the tail. The sexes only differ in size - the female is up to 23% larger and probably much heavier than the male. The youth dress looks significantly different. Immature birds are probably not colored until they are two or three years old. Subspecies are not recognized.

In adult birds, the head and neck are brown-gray to gray. The beak is gray, the wax skin gray-brown or blackish gray. The iris is yellow. The rest of the upper side is dark brown, slightly lighter on the upper back and darkest on the wings. The wings of the hand are almost blackish. The chest is brown and clearly set off from the white plumage of the lower abdomen, legs and tail. The control springs are white with a wide, offset black subterminal band . Legs and feet are grayish white to light yellowish gray.

In juvenile birds, the head is more or less brownish with whitish dashes. The sides of the head and throat are more gray, the stripes above the eyes are beige-brown. The warm brown color of the chest and flanks is interspersed with white vertical stripes and ends in the whitish, brownish faded, partly scrawled lower abdomen and leg plumage. The top is darker brown with gray edges and indistinctly banded arm wings. The control feathers are scribbled in brown on a white background, the scribbling forming indistinct bands. The clothes of immature birds are somewhere between youth and adult clothes. They are not exactly known or described.

  • Flying bird in youth dress, top

  • Flying bird in youthful dress, underside

voice

The gray-headed eagle is very shouting during the breeding season and can often be heard at night. The far-reaching screams sound peculiar and are reminiscent of the vocalizations of the wedge-tailed tokos ( Ocyceros birostris ). They are uttered individually or in rows, in flight or while waiting. High -pitched screams, an owl-like uh-wok or loud gurgling sounds are also described.

Distribution and existence

The scattered distribution of the gray-headed eagle lies in the orientalis and extends over 5 million km². It includes the north and east of Sri Lanka . In India, the species occurs in northern to eastern Rajasthan and on the southern west coast - but especially in the northeast in Uttar Pradesh , Bihar and Assam . They are available locally in Nepal and Bangladesh . From there the area extends over Indochina to the Malay Peninsula . The Great Sunda islands are Sumatra , including the Mentawai Islands and Lingga , Java and Borneo populated. There is evidence of 1990 from Sulawesi . In the Philippines there are deposits on Luzon , the Calamian Islands , Mindoro , Samar , Negros , Mindanao , Basilan and Bongao . The nature is everywhere sedentary , only in young birds there is Dismigrationen .

Previously, the gray-headed eagle was widespread and common. It is only moderately specialized in its habitat requirements. In the meantime, however, the species is usually only sparsely, rarely or very rarely. Only in northeast India do there seem to be larger local occurrences. Due to its large distribution area, the species is not yet seen as endangered, but is on the IUCN's warning list (“near threatened”) . There are no exact numbers, but it cannot be assumed that the number will exceed a five-digit number. BirdLife International estimates that there are 100,000 adult individuals and a total population of less than 150,000 birds.

Causes of decline include habitat destruction through deforestation , drainage or silting up of water bodies, disruption from human activities, overfishing , pollution and direct persecution. In some places the species competes with humans. For example, on the northern Tonle Sap it is heavily dependent on water snakes for food, which in turn are excessively hunted by humans. The construction of dams on the upper reaches of the river in the People's Republic of China , Laos , Thailand or Cambodia , which have a strong negative impact on the water regime downstream, may also pose a threat . Important conservation measures for the species would be the designation of protected areas, the general protection of remaining wetlands and regular monitoring.

Way of life

The gray-headed eagle predominantly inhabits forests of the lowlands below 300 m, occasionally the altitude ranges up to 1500 m. It is important to be close to slowly flowing or stagnant water. The species is also occasionally found in rivers and retention basins as well as in swamps and rice fields. In Cambodia it also inhabits riparian forests and on the coast mangrove swamps , lagoons and estuaries .

It feeds mainly on live or dead fish, and more rarely on reptiles, bottom-living birds (such as crested chickens ) and small mammals. In a study in Singapore , at least five fish species and one reptile species were found to be prey: four of the fish species were neozoa - two Pangasius species and the cichlids Cichla orinocensis and Geophagus altifrons ; the snakehead fish Channa striata and the white monitor monitor are native species. Most of the time, the prey is grabbed from a hide in the near-surface water. Sometimes the species searches for river sections or lake banks while hanging in the wind. Fish that are too heavy to carry are pulled out of the water and onto the bank.

The breeding season in Sri Lanka is between December and March, in India between November and January. In Myanmar, occupied nests were found in January and March, in Sumatra in April and in Borneo, apparently in August. In the riparian forests of Tonle Sap in Cambodia, the breeding season begins with the rising tide in September and ends in March, when the water has completely withdrawn.

The large nests can be up to 1.5 m wide and are between 8 and over 30 m high near the water in large trees with an open crown area. They are built from twigs and lined with green twigs at the beginning of each annual brood. After several years of use, they can be almost 2 m high. The clutch usually comprises one to two, rarely up to four eggs, which are incubated by both partners for 28–30 days. The nestling period is 10 weeks. It is not known when the boys will become independent.

literature

Individual evidence

  1. ↑ HRL Lerner, DP Mindell: Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA , Molecular phylogenetics and evolution, 2005
  2. ↑ F. Gill, D. Donsker (eds.): IOC World Bird List (v 4.4) , 2014, doi : 10.14344 / IOC.ML.4.4
  3. ↑ Clark et al. (2014), HBW Alive, see literature
  4. ↑ zoonomen.org , accessed December 14, 2014

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