Wedge tail
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Wedge-tailed harrier ( Haliastur sphenurus ) |
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| ( Vieillot , 1818) |
The wedge-tailed harrier ( Haliastur sphenurus ) is a medium-sized bird of prey from the hawk-like family that is native to New Guinea and Australia. The sandy-brown to red-brown feathered species feeds primarily on carrion and vertebrates and colonizes a wide range of different habitats in the tropics and subtropics. It is only absent in regions with very dense forests. During the breeding season, the wedge-tailed harrier is shy and lives solitary or in pairs.
The IUCN classifies the stock situation of the wedge tailed Weihs as safe ( least concern ). No subspecies are distinguished.
features
The wedge-tailed Weih reaches a body length of 50 to 60 centimeters and has a wingspan of 120 to 145 centimeters. Males weigh an average of 700 grams, the females are significantly heavier at 850 grams. It has a strong, slightly squat rump, small head, relatively short and broad wings, a medium-long, rounded tail and short but strong legs and toes.
Adult birds
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Adult wedge-tailed harriers have a sand-brown head and lower body with dense dotted lines. On the belly the dotted line changes into a dark brown spot. The rump and the underside of the tail are somewhat paler than the rest of the underside of the body and almost without markings. On the upper side of the body, the small wing-coverts and the shoulders are also sand-brown, the remaining wing-coverts and the wings are black. The rest of the top of the body is dark brown. The upper tail-coverts and the tail plumage are pale brown-gray, on the tail feathers there is a diffuse black end band. Before moulting, when the plumage is severely worn, the birds are a little lighter. During the moult, when the birds have partly old and partly new plumage, they appear spotted.
The beak is dark gray, the wax skin is also gray in color. The iris is dark brown, the legs and feet are cream colored.
Fledglings
Fledglings have plumage similar to that of the adult birds. With them, however, the dotted lines on the head and front underside of the body are more pronounced. On the other hand, they appear darker on the upper side of the body. The contrast between the lighter shoulders and the wing covers is less pronounced in them. They have cream-colored to reddish-brown spots on the wing covers, the rump and the upper tail coverts. The control springs are narrowly pale in color.
Possible confusion
During field observations, the wedge-tailed Weih can be confused with very light-colored rabbit eagles or young birds of the Brahmin Weih belonging to the same genus . Compared to both species, the body of the wedge-tailed harlequin is stronger and the wings are shorter and narrower in relation to the body size. The tail plumage is also shorter compared to the total length, which leads to a more compact appearance of the wedge-tailed harrier. The top of the body of the wedge-tailed eagle is also distinctly reddish-brown with less contrast to the blackish wings and the tail plumage.
Distribution area
The distribution area of the wedge-tailed Weih extends from Cenderawasih Bay in western New Guinea to Goodenough Island in the Solomon Sea off the east coast of New Guinea. For distribution area also includes the Solomon Islands east of New Guinea and New Caledonia before the Australian northeast coast.
In Australia the wedge-tailed harrier is a very widespread species. It is only absent in parts of the Great Sand Desert . the Nullarbor Desert , the Great Victoria Desert, and the Gibson Desert . The population numbers vary depending on the circumstances of the respective distribution area. It is comparatively rare in the Flinders Range , on the Eyre Peninsula , on Lake Torrens and in the southwest of the state of Western Australia . The wedge-tailed harlequin is also very rare in Tasmania.
The wedge-tailed harrier is a breeding bird in its entire range. The populations in the southeast and east of Australia are migratory birds, while the other Australian populations are usually resident birds. During the winter months, the populations in the southeast and southwest increase. Individual individuals also roam a very large area nomadically.
habitat
The wedge-tailed fairy can be found in a wide range of habitats in the tropics, subtropics and the temperate climate zone. It is only absent in very dense forest areas and can often be seen near water. In Australia, its height distribution extends from the lowlands to altitudes of 1400 m in the high plateaus of New South Wales.
Typical habitats include open forest areas, agricultural landscapes and wetlands both inland and on the coast. In Australia, the wedge-tailed harrier can be found almost all over the continent. It is only missing in desert regions that have hardly any precipitation. However, it populates the Mallee and arid scrubland, which is loosely made up of bushes and individual trees. The wedge-tailed fairy is one of the species that benefit from clearing forests. However, it is dependent on individual tall trees being able to serve as a nest location. It is therefore often found on agricultural land in Australia. The establishment of water points in Australia as part of the expansion of the agricultural land in the 20th century probably led to the fact that it was able to expand its range further into the interior of Australia. On the other hand, draining wetlands has a negative effect, so that in regions in which this has occurred, the population figures decline. There are various reports from the beginning of the 20th century that suggest that wedge-tailed harriers occurred in far greater numbers earlier.
General way of life
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The wedge-tailed Weih lives solitary or in pairs. Larger gatherings of birds of this type can be observed especially when there is a very plentiful supply of food. Occasionally, however, several wedge-tail harriers gather in common resting places. From the beginning of the 20th century, however, there are reports from Australia that each year at the beginning of the breeding season, larger groups of wedge-tailed harriers gathered for two or three weeks and then left these gatherings in pairs. There are no recent observations of this behavior.
A typical behavioral characteristic is leisurely gliding over treetops or at low altitude over farm buildings, pastures or bodies of water. He often sits in a very characteristic, steeply upright posture on exposed branches near water or in forest clearings. He can also be seen regularly on boat masts.
Wedge-tailed harriers are bullied by some species of birds . Species that exhibit this behavior include hawk falcon , masked lapwing , flute bird , thick-billed shrike crow, several species of crow, and the yellow-fronted babbler .
food
The wedge-tailed harlequin is an opportunistic omnivore that normally looks for prey at higher altitudes. During fishing flights it often flies at a height of 15 meters above the ground. Occasionally he scares up prey by falling down in a dive. He then kills living vertebrates with his claws. Occasionally, however, he also hunts from a raised hide. He can carry away prey up to 240 grams, he eats other prey on the ground. He catches fish by swooping down to 20 centimeters above the water surface and then grasping the fish with his claws. He then either eats the fish in flight or carries it to a nearby stand guard. The skin of a kangaroo is too tough for it to open. On the other hand, he is able to tear open rabbits. In those cases in which certain prey animals such as mice or grasshoppers multiply strongly, he switches his foraging to these abundant prey animals. In some areas of Kakadu National Park , young cleft-footed geese make up most of its diet at the end of the rainy season.
Like other birds of prey, wedge-tailed harriers follow the fire fronts of forest and steppe fires in order to pick up the fleeing or already dead animals. Occasionally they transport burning branches to prey by spreading the fires.
It also hunts prey from fellow birds and other large bird species. Among the birds that he robbed of their prey, including egrets , rabbit Eagle , Black Kite , Marsh Harrier , brown falcon and society Crow ( Corvus mellori ). It is also able to chase dingoes away from their prey. Compared to black kites, it is more assertive, especially on the ground. On the other hand, black kites can prevail against the wedge-tailed harrier in flight.
The wedge-tailed harrier often eats carrion outside of the breeding season, which is why it is more common at slaughterhouses. It grabs dead fish swimming on the water surface in flight from the water surface. Wherever carrion is found, larger numbers of wedge-tailed harriers can be found. In individual cases several dozen wedge-tailed harriers have been observed on carrion. It can also be found in large numbers near garbage dumps or comes in when a bush fire or freshly plowed arable land scares off a large number of prey.
Reproduction
The reproductive biology of the wedge-tailed harlequin has not yet been conclusively investigated. A large part of the knowledge gained so far has been gained through captive birds.
The wedge-tailed harrier is almost certainly a monogamous bird. However, there is no information on how long the pair bond exists in each case. In Mallacoota , however, a pair has been observed near their nesting site year-round, suggesting a longer relationship. The breeding season falls in the south of Australia in the period from July to January, in the north of Australia however in the period from March to October.
Breeding area and nest
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As a nesting tree, the Wedge-tailed Harrier uses tall, isolated trees in flood zones. In arid regions, its nesting tree is often located near artificial or natural water sources. Both parent birds are involved in building the nest.
The breeding area is vigorously defended against conspecifics and other bird species, especially at the beginning of the breeding season. According to observations, crows and white-bellied sea eagles in particular were not tolerated near the nest. However, foxes, dogs and Jägerliest are also attacked .
In some regions that offer very good living conditions, the nests of individual pairs are less than a kilometer apart. However, far greater distances are more typical. In the vicinity of Sydney the nest distance was 8 kilometers, in the region around the city of Mildura on the Murray River, however, 4.6 kilometers. However, there are reports, especially from the beginning of the 20th century, that in regions with a very large number of wedge-tailed harriers, these also brooded like colonies.
Raising the nestlings
The clutch comprises one to three eggs, typically a clutch size of two eggs. Both parent birds breed, but the female's share in the breeding business is somewhat larger. In captivity, the incubation period is 35 days, outdoor observations suggest 38 to 40 days. Both parent birds feed and row the young birds. Nestlings grown up in captivity fledged between the 47th and 52nd day of life.
Trivia
Both breeding females of the gray bower bird and males near their arbor imitate the calls of the wedge tailed harrier, who are among their predators. The drop arboreal bird, which belongs to the same family, also imitates the calls of the Kelischwanzweihs.
literature
- James Ferguson-Lees , David A. Christie: Raptors of the World. Helm Identification Guides, Christopher Helm, London 2001, ISBN 0-7136-8026-1 .
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 2, Raptors to Lapwings, Oxford University Press, Oxford 1993, ISBN 0-19-553069-1 .
Web links
Single receipts
- ↑ a b Handbook of the Birds of the World zum Keilschwanzweih , accessed on April 29, 2017
- ↑ a b c Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 71.
- ↑ a b c d e f Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 72.
- ↑ a b c d e Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 75.
- ↑ a b Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 76.
- ↑ a b c d e Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 74.
- ↑ Intentional Fire-Spreading by "Firehawk" Raptors in Northern Australia [1]
- Jump up ↑ Burn, Baby, Burn: Australian Birds Steal Fire to Smoke Out Prey [2]
- ↑ a b Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 77.
- ↑ a b Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds . Volume 2, p. 78.
- ↑ Clifford B. Frith, Dawn. W. Frith: The Bowerbirds - Ptilonorhynchidae . Oxford University Press, Oxford 2004, ISBN 0-19-854844-3 , p. 427
- ↑ Clifford B. Frith, Dawn. W. Frith: The Bowerbirds - Ptilonorhynchidae . Oxford University Press, Oxford 2004, ISBN 0-19-854844-3 , p. 419