Consecration of spots
| Consecration of spots | ||||||||||||
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Spot consecration ( Circus assimilis ) |
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| Scientific name | ||||||||||||
| Circus assimilis | ||||||||||||
| Jardine & Selby , 1828 |
The Fleckenweihe ( Circus assimilis ) is a bird of prey from the genus of the consecration ( Circus ). Unlike the rest of the species of this genus, it nests in trees and inhabits mostly semi-arid areas with sparse tree growth. Their distribution area includes all of Australia , Sulawesi , Timor , Sumba and the Lesser Sunda Islands .
features
anatomy
Spot harriers are medium-sized birds of prey with long, broad wings, a slender body, a narrow, elongated tail, and long legs and toes. They do show a clear sexual dimorphism in their physique, whereby the female becomes significantly heavier and larger than the male: Female spotted harriers weigh between 530 and 745 g. They reach a body length of 50–62 cm and a wing length of 414–467 mm, which corresponds to a wingspan of 120–150 cm. The tail of female birds is 266–297 mm long, their tarsus measures 85–107 mm. The male, however, is smaller and, above all, lighter. It weighs 412–537 g and reaches about the same body length as the female, but has significantly shorter wings with 368–412 mm. The tail also usually does not reach the same length as the female with 232–273 mm.
Overall, the Spotted Harrier is therefore indeed a relatively large but rather lean representative of its genus, which clearly weighs less than the sympatric marsh harrier ( C. assimilis ) or neuginensische Papuan Harrier ( C. spilothorax ).
Coloring and drawing
Adult birds
Females and males of the spotted harrier show the same plumage, which not only makes it difficult to identify the sex, but also represents an exceptional case, since the sexes in most species of the genus Circus have different colors.
The head of the adult spotted harrier is light to slate gray in color. The red-brown veil clearly stands out on the face and forms a contrast to the rest of the head. The upper wing coverts are divided into two areas in terms of color: the small arm coverts are reddish with white pits, the rest of the upper wing coverts, like the back, are interspersed with a dark, bluish gray and black spots. These spots can also be clearly seen when sitting. Hand and arm wings are also gray; they have several thin, black bands and are bordered by a black end band. The tips of the hand wings are also colored black. Broad black ribbons stretch across the tail feathers on a gray background; the edge of the tail is white or cream colored.
From the throat up to the pants and the rump , a white spot pattern on red-brown base, which gives the Spotted Harrier her name runs through the body bottom. It extends both over the underside of the trunk and the under wing-coverts, towards the rump it sometimes appears as a sparrow-hawk . The underside of the arm and hand wings has a whitish-gray tone, and the feathers are very thin and banded in black; as on the top, they are lined with a black end band and black wing tips. The control springs are also broadly banded on the underside in black on a white background, with the subterminal band being the widest.
The color of the wax skin ranges between yellow and pale yellow; the iris of adult animals is orange to light yellow. The skin of the legs also has a yellowish hue. The claws are black, the beak is bluish gray with a black or dark tip.
Immatur
Immature spotted harriers already resemble the adult animals in their plumage, but the basic color of the upper side is gray-brown, while the underside is more matt. The face and head are striped brown, the underside has white stripes.
Juvenile
Juvenile animals differ noticeably from adults: the upper part of the head is red-brown and interspersed with dark brown, wedge-shaped or arrow-shaped longitudinal stripes. Chin, throat and ear-covers are reddish-yellow-brown; here, too, narrow, dark stripes run around the face in a star shape. The face itself is filled with the sand or light rust brown face veil. This veil extends behind the ear covers in the neck and is also traversed by dark, albeit shorter and much finer, wedge-shaped stripes that extend radially from the beak. The coat is yellow-brown to chestnut-colored. The jacket feathers have black, wedge-shaped drawings that taper towards the tip of the nib. Back, rump feathers and most of the shoulder feathers have a black-brown tone and lighter, rust- or sand-brown tips and a black wedge in the middle. With increasing age these feathers become paler and the drawing becomes less distinct.
Flight image
The hunting flight of the Fleckenweihe is characterized by a juggling at low altitude. In flight juggling, the bird lets both legs hang down to grab the prey (see also the section on hunting behavior ). The wingspan of the spotted harrier is roughly 2.4 times its body length.
In terms of flight and size, the spotted harrier is similar to the marsh harrier, but can be distinguished from it by its slimmer build and longer tail.
Vocalizations
Spot harriers are acoustically rather inconspicuous outside of courtship and breeding season. The call consists of a screeching, high- pitched wik wik wik , as well as a quick rattle ( kikikiki ... ).
habitat
The species inhabits open and semi-open landscapes such as grasslands, semi-deserts and very light forests, but also grain fields with hedges and trees. Occasionally she also hunts in swamp and coastal areas, but otherwise avoids wetlands.
distribution
The distribution of the spot consecration includes Australia and the islands of Wallacea ( Sulawesi , Timor , Sumba , Lesser Sunda Islands ). It is widespread, but rarely found in most of its range. The main focus is on Southeast Australia and some smaller areas in the Outback and Sulawesi. For Timor and the Lesser Sunda Islands, breeding occurrences are assumed to be likely, but have not been proven.
hikes
Spot orders are sorted by diffusion and populated habitats highly variable resident birds , nomadic or migratory . In areas with little drought, the harlot tends to be sedentary, while highly arid areas usually only seek out after the rainy season in the Australian summer or when there is a large food supply. From August to April, especially from October to February, a southward migration can be observed, which then reverses again in winter. The longest hike distance recorded so far is 1650 km.
Systematics
External system
The consecration of spots is one of the most original representatives of its genus, although not, as was sometimes assumed in the past, the ancestor of all consecrations. Genetically and ecologically, it belongs to the group of harriers inhabiting steppes and arid areas and developed earlier than all other species of this branch, as the phylogenetic family tree shows:
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Internal system
There are no recognized subspecies for the consecration of spots . Although birds from northern Australia, Sumba and Timor (“ rogersi ”) as well as Sulawesi and Taliabu (“ quirundus ”) are smaller in size and more diverse in color, these properties are also observed in animals from the rest of the range.
nutrition
During the day, the spotted harrier hunts small mammals (e.g. nasal sacs ), reptiles and birds living on the ground, especially quail and pipit, at low altitude . The blotched harrier glides over the ground in deep, rocking flight, only to then suddenly sink and grab the prey. The spotted harrier rarely eats carrion .
Reproduction
Courtship
The courtship is in the Spotted Harrier flying displays from one or both partners, however, be less spectacular than in other orders. The male circles either alone or together with the female at a great height, in conjunction with gentle pendulum movement at a height of around 100–200 m, with the bird performing a half roll or a sharp turn at the end of each swing. In contrast to harriers with pronounced sexual dimorphism in color, spotted harriers are monogamous .
Brood
The breeding season of the blotchless harrier in northern Australia is between July and September, in the south it lasts from September to October. Depending on the availability of food and weather conditions, it can nest in arid areas outside of this period. An accumulation of broods elsewhere between May and June makes two broods per year appear possible, provided the food supply is sufficient.
The spot consecration is the only representative of the genus circus that nests mainly in trees. If there is no natural nesting place in treeless areas, the spot consecration sometimes builds its nest on telegraph poles . The nest is a round, flat structure made up of a thin network of small twigs that are often loosely joined together. It is more similar in texture to those of ground breeders, so it is believed that spotted harriers did not originally breed in trees. The nest measures 40–70 cm in diameter and 16–39 cm in depth. The nesting height varies between two and 15 m. The clutch consists of two to four eggs (average: 3.0), a relatively low value for this species. However, the eggs are relatively large for consecration of this size (39.53 cm³ with an average weight of 671 g.
The incubation period is 32–34 days, the nestling period is 36–43 days. The young birds remain dependent on their parents for about six weeks. Occasionally observed groups of up to five birds point to family groups hunting together.
Existence and endangerment
There are apparently no data on large-scale stocks and long-term changes in stocks. Depending on the amount of precipitation, the stock can fluctuate considerably from region to region. The number of breeding pairs in the north-western part of the state of Victoria fell from 17 in 1980 to zero in the very dry 1982. In the almost treeless Nullarbor Desert , ten breeding pairs were recorded along a stretch of 140 km. In Sulawesi, the species has apparently benefited from the ongoing deforestation : If it was previously only a rarely seen bird, now sightings of spot harriers are increasing.
Due to its widespread distribution and its independence from wetlands, the spot consecration is considered by some authors to be less endangered than other consecrations. The IUCN classifies the worldwide existence of the spot consecration as not endangered ( Lower Risk ). On the other hand, sightings in Australia have decreased by 25% and in New South Wales by 55%. In the state of Victoria , the consecration of spots is on the early warning list ( Near Threatened ).
References
literature
- David Baker-Gabb : Comparative ecology and behavior of swamp harriers circus approximans, spotted harriers C. assimilis and other raptors in Australia and New Zealand. Ph.D. thesis, Monash University, Melbourne, Australia, 1982.
- David Baker-Gabb: The Evolution of Tree-nesting and the Origin of the Spotted Harrier. In: Corella 8 (3), September 1984. pp. 67-69.
- James Ferguson-Lees , David A. Christie: Raptors of the World. Houghton Mifflin Harcourt, 2001, ISBN 0618127623 , pp. 477-479.
- Stephen Marchant, Peter Higgins (Eds.): Handbook of Australian, New Zealand and Antarctic Birds. Vol. 2: Raptors to Lapwings. Oxford University Press: Melbourne, 1993. ISBN 0-19-553069-1 , pp. 98-103.
- Robert E. Simmons: Harriers of the World: Their Behavior and Ecology . Oxford University Press , 2000, ISBN 0198549644
Web links
- Circus assimilis on www.globalraptors.org
- Literature on the consecration of spots in the Global Raptor Information Network
- Circus assimilis onthe IUCN Red List of Threatened Species . Listed by: BirdLife International, 2008. Retrieved July 29, 2009.
- Videos, photos and sound recordings of Circus assimilis in the Internet Bird Collection
Individual evidence
- ^ John Barnard Dunning: CRC Handbook of Avian Body Masses CRC Press, 2007, ISBN 1420064444 , p. 53
- ↑ a b c d e f g h i j k l m n o p q r James Ferguson-Lees, David A. Christie: Raptors of the World Houghton Mifflin Harcourt, 2001, ISBN 0618127623 , pp. 477-479
- ↑ a b c d Stephen Marchant, Peter Higgins (Ed.): Handbook of Australian, New Zealand and Antarctic Birds. Vol. 2: Raptors to Lapwings. Oxford University Press: Melbourne, 1993. ISBN 0-19-553069-1 , pp. 98-103.
- ^ A b c Global Raptor Information Network: Species account: Spotted Harrier Circus assimilis. October 30, 2009. Retrieved April 4, 2009.
- ^ A b Robert E. Simmons: Harriers of the World: Their Behavior and Ecology Oxford University Press, 2000, ISBN 0198549644 , pp. 32-33
- ^ Robert E. Simmons: Harriers of the World: Their Behavior and Ecology Oxford University Press, 2000, ISBN 0198549644 , pp. 309-311
- ↑ www.birdlife.org , accessed July 29, 2009