Long-billed harrier

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Long-billed harrier
Male long-billed harrier (Chondrohierax uncinatus)

Male long-billed harrier ( Chondrohierax uncinatus )

Systematics
Class : Birds (aves)
Order : Birds of prey (Accipitriformes)
Family : Hawk species (Accipitridae)
Subfamily : Honey buzzards (Perninae)
Genre : Long-billed harrier ( Chondrohierax )
Type : Long-billed harrier
Scientific name
Chondrohierax uncinatus
( Temminck , 1822)

The Langschnabelweih ( Chondrohierax uncinatus ) is a medium-sized bird of prey from the family of Accipitridae , which has specialized in the hunt for tree-dwelling snails. The species, which is mainly found in South and Central America and the Caribbean , was first scientifically described in 1822 by the Dutch zoologist Coenraad Jacob Temminck . The clearly pronounced polymorphism of the long-billed consecration led in the past to confusion regarding the taxonomic classification of the species and can make the identification and assignment of individual individuals considerably more difficult.

features

The Langschnabelweih is a medium-sized representative of the hawk-like species, with an average size in the range of 41 to 46 cm and a weight of 250 to 300 g. As with many birds of prey, the female representatives of the species are generally somewhat larger and heavier than their male counterparts, but the differences are less pronounced than in most other species. In addition to the differences in size, the long-billed harrier also shows a clear sexual dimorphism in terms of the color of the plumage , and regardless of gender there are an unusually large number of other morphological differences, of which the size of the sharp, curved beak is the most striking. In adult birds there are differences in size of more than 40%; there is apparently no connection between beak size and geographical distribution or gender. In the past, this variable physiology led to the postulation of various species and subspecies that are no longer considered valid today. In addition to the beak, the shape of which, together with the shape of the head, gives the birds an almost parrot-like appearance, especially when seated, the size and shape of the wings are the most prominent features of the long-billed harlequin. These appear shorter and wider than related species, which is very likely an adaptation to the forested habitat of the birds. In order to compensate for the increased air resistance , the hand wings on the wing tips are far apart, which ensures improved maneuverability in confined spaces and increased rate of climb. In flight, the wings are stretched slightly forward towards the head, which ensures an easily recognizable flight pattern. Furthermore, the leg is significantly shortened in the Langschnabelweih .

Description of the different morphs

Long-billed harrier of different morphs in flight. The characteristic short, wide wings and the widely spaced hand wings are easy to recognize.

A typical male of the species is colored lead-gray to black-gray on the back and occiput, some white areas may also be visible on the head, the lead-gray becomes increasingly darker towards the face. On the chest and stomach, the lead-gray color of the upper side becomes increasingly lighter and alternates with bands of different widths, white to cinnamon-colored, which can be bordered from dark brown to black. The coverts of the characteristic long tail show white to ocher tones, in some individuals a lead-gray banding can be seen. The other tail feathers show a blackish basic color with white to mouse-gray tips and a double banding in white, ocher or cinnamon tones. The predominantly grayish wing feathers have a similar banding, which, however, can be blackish on the underside instead of ocher or cinnamon colors. The secondary feathers are usually uniformly lead-gray, only occasionally there are hints of banding. The strong beak is colored black, with olive green accents on the underside. The iris of the eye is greenish-white. The legs and feet are orange-yellow and end in black claws.

Female Langschnabelweih (brown morph)

The plumage of the females of the so-called "brown morph" can take on different shades of gray on the forehead and in the area of ​​the ear openings, the hood is usually a little darker. A yellow to ocher-brown band runs over the neck. The back and shoulders are mostly uniformly dark to gray-brown in color; the colors in this area usually appear a little paler towards the tips of the feathers. The contour feathers on the chest, belly and underside of the wings have a whitish basic color, which is traversed by a series of broad stripes, the color and expression of which can vary greatly from person to person. The spectrum ranges from cinnamon to brown to pale red tones. Occasionally these stripes are surrounded by blackish borders. The flight feathers are mostly hazel or rust-brown in color, with only a few distinct, blackish bands. The secondary feathers are blackish on the upper side, on the underside the color tends to merge into gray, white and cream tones. The control springs are still white at the base, but change towards the tip to sometimes very dark black and gray tones. The beak corresponds to that of the male, the reins and wax skin are orange to yellowish and streaked with olive-green spots, which gradually merges into a strong grass green towards the front. There is also an orange spot above the eye, the iris is always white in the female. The legs and feet show a reddish yellow. In addition, there is a so-called “gray back morph” in the females, the gray color of the back that gives it its name is significantly stronger. The yellowish-brown band along the neck is much less pronounced or absent entirely. Females of this color variant can easily be confused with males with particularly pronounced banding.

In addition to the variants already mentioned, melanistic morphs exist in both sexes , the plumage of which is almost completely black and has an easily recognizable, bronze, greenish or purple sheen. There is a single white band on the tail feathers. In this form, the wax skin and eyelids are also yellowish green in color, while the skin in front of the eye has a bluish green tone. The color of the eye spot, legs and iris correspond to that of a female of the brown morph.

Fledglings

In contrast to the adult birds, young birds have only two distinct color variants - a light and a melanistic morph, regardless of gender. Melanistic specimens hardly differ visually from their adult conspecifics described above even shortly after the nestling down has been deposited. In the light variant, the feathers on the head, shoulders, wings and back are kept in dark brown to pale gray tones, depending on the individual. White tones dominate the chest, with brownish stripes running through them. This pattern continues in the form of a wide band along the neck. The basic color of the control springs is also white to slightly grayish. It alternates with a row of broad bands in a brownish gray.

behavior

Outside the breeding season, long-billed harriers can be observed during relatively short gliding flights, especially in the morning hours, which, however, rarely lead the birds to great heights. They prefer to spend rest periods in less exposed places below the canopy. Their way of life is usually less solitary than that of many other birds of prey, especially at rich feeding grounds, long-billed harriers can occasionally be found in small groups. A defense of one's own territory against other species only takes place during the breeding season, when other birds get too close to the nest. While the species was considered a resident bird for a long time , it has been known since the early 2000s that at least a certain part of the population undertakes seasonal migrations. On the coast of Belize it was observed that long-billed harriers form swarms of up to 120 individuals. The most common vocalizations of the species are said to resemble the singing of a Trupial and are mainly performed from a branch. There is also an alarm and defense call that is described as loud rattling or cackling and should sound like wi-iiiiiii-uh or weh keh-eh-eh-eh-eh-eh .

nutrition

Tree-dwelling snails like Drymaeus convexus form the main part of the food of the long-billed harlequin

The Langschnabelweih specializes in hunting arboreal snails, which make up more than 90% of the diet. The species Orthalicus princeps , Helicina rostrata and various Drymaeus species are particularly common . Furthermore, land or water snails are seldom captured. Older descriptions often still list frogs, toads, salamanders, birds, insects or caterpillars as prey, but more recent observations over longer periods of time could only confirm the occasional ingestion of salamanders and - in a single case - frogs or toads. Whitacre and Vásquez (2012) speculate that the remaining prey was an erroneous observation that was subsequently adopted from researcher to researcher. To get to the meat of the snails caught, the long-billed harrier uses an unusual technique that is not known from any other snail-eating bird of prey. The snail is fixed on a branch - almost always with the left foot - with the opening facing upwards, whereupon the bird first removes the firm, closing membrane from the opening with the tip of the strongly curved beak. He then widens the opening by breaking parts out of the edge of the bowl. If the opening is large enough, the bird sticks the upper mandible of the beak into it and begins to break open the individual sections of the spindle interior one after the other. This process leaves unmistakable damage to the shell of the snail and continues until the snail can be pulled out or levered out. The variable size and curvature of the Langschnabelweihs beak appear to be directly related to the maximum size of the snail population available in a region. If both smaller and larger snail species occur in an area, long-billed harriers with large and small beaks can also be found sympatric in this area . It is noteworthy that in these cases there seem to be no intermediate forms, i.e. birds with “medium-sized” beaks. A research report from 1950 describes the behavior of a group of five fishing toucans in Panama, which followed a long-billed harrier for a long time in search of food and apparently wanted to use it to find rich feeding places. It is not known whether this is an isolated case or whether long-billed harriers are regularly used by other species as food indicators.

Young bird of the light morph after leaving the nest in Líbano , Colombia

Reproduction

The breeding season usually begins in March and can extend into July. A flat platform made of branches with a diameter of about 30 cm, which is typically built in a tree about one to two meters below the top, serves as the nest. Both sexes participate equally in the construction of the construction. After copulation, the female typically lays two, very rarely three eggs, with an average size of 45.0 × 36.5 mm. Their weight is around 32 to 35 g. The incubation of the eggs and the subsequent care of the young birds are carried out equally by both parents. In male long-billed harriers, the formation of a breeding spot could be demonstrated. The incubation time of the eggs varies from nest to nest; observations range from 24 to 33 days. How long the offspring remain dependent on the adult birds after hatching is unknown, but at least for a certain time the young birds still seem to follow the parents. There are reports from family groups from Texas that were spotted together during the winter months.

Spread and endangerment

Distribution area of ​​the Langschnabelweihs

The Langschnabelweih inhabits forested regions in South and Central America, with tropical and subtropical forests up to an altitude of about 1000 m being preferred. Locally, however, evidence is also obtained in temperate areas up to 2700 m, in extreme cases even up to 3100 m altitude. Its distribution area extends from the southernmost foothills of the US state of Texas over Mexico and Central America to the south of Brazil and the extreme north of Argentina, but there are large gaps. The species is considered not endangered in its continued existence and is listed by the IUCN under the status of least concern . The organization assumes around 200,000 adult individuals as of 2016, but the population development is generally declining. The subspecies C. u., Which is endemic to the Caribbean island of Grenada , is considered to be critically endangered . mirus , which was already considered extinct in the 1980s. A study in the years 2000 to 2006 could, however, prove a few representatives of the Grenada long-billed harlequin who also carried out successful breeding processes. The researchers still assume a remaining population of around 15 to 30 adult birds.

Systematics

Coenraad Jacob Temminck originally described the long-billed consecration under the scientific name Falco uncinatus and initially placed it among the real falcons . While in the past the great morphological differences within the species (in particular the considerably varying size of the beak) led to the introduction and rejection of various subspecies of the long-beaked consecration, only two subspecies are considered valid today. In addition to the nominate form C. u. uncinatus , which inhabits the American mainland, there is still the endangered subspecies C. u. mirus in Grenada. Representatives of this subspecies are considerably smaller than their conspecifics belonging to the nominate form. In addition, the males tend to have a strong coloration compared to that of the females, and there are no more pronounced gray forms on Grenada. The classification of the equally endangered Kuba Langschnabelweihs ( C. wilsonii ) as an independent species is still quite new , which has long been listed as a subspecies of the Langschnabelweihs. In addition to the Kuba Langschnabelweih, the species of the genera Leptodon and Aviceda are the closest relatives of the Langschnabelweihs.

  • C. u. uncinatus ( Temminck , 1822)
  • C. u. mirus Friedmann , 1934

literature

  • David F. Whitacre, Michael A. Vásquez: Neotropical Birds of Prey: Biology and Ecology of a Forest Raptor Community . Ed .: David F. Whitacre. Cornell University Press, Ithaka / London 2012, ISBN 978-0-8014-4079-3 , pp. 48–59 ( limited preview in Google Book search).

Web links

Commons : Langschnabelweih (Chondrohierax uncinatus)  - Collection of images, videos and audio files

Individual evidence

  1. ^ Steven L. Hilty: Birds of Venezuela . 2nd Edition. Princeton University Press, Princeton / Oxford 2003, ISBN 978-0-691-09250-8 , pp. 226 .
  2. ^ Whitacre & Vásquez, p. 49
  3. ↑ a b c Herbert Friedmann: The hawks of the genus Chondrohierax . In: Journal of the Washington Academy of Sciences . tape 24 , no. 17 , 1934, pp. 310-318 .
  4. ^ Whitacre & Vásquez, p. 52
  5. ^ Whitacre & Vásquez, p. 55
  6. ↑ Whitacre & Vásquez, pp. 50-51
  7. ↑ Thomas Bates Smith, Stanley A. Temple: Feeding habits and bill polymorphism in Hook-billed Kites . In: The Auk . tape 99 , no. 2 , 1982, p. 197-207 , doi : 10.1093 / 99.2.197 .
  8. ^ Whitacre & Vásquez, p. 58
  9. ↑ Whitacre & Vásquez, pp. 53-57
  10. ↑ a b c Whitacre & Vásquez, pp. 48-49
  11. ↑ Hook-billed Kite Chondrohierax uncinatus. In: iucnredlist.org. BirdLife International, 2016, accessed June 19, 2020 .
  12. ↑ Russell Thorstrom, Desmond McQueen: Breeding and status of the Grenada hook-billed kite (Chondrohierax uncinatus mirus) . In: Ornitologia Neotropical . tape 19 , no. 2 , 2008, p. 221-228 .
  13. ↑ Hook-billed kite Chondrohierax uncinatus (Temminck, 1822). In: avibase.bsc-eoc.org. Retrieved June 18, 2020 .