Darter
| Darter | ||||||||||||
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Indian darter ( Anhinga melanogaster ) |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Anhingidae | ||||||||||||
| Reichenbach , 1849 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Anhinga | ||||||||||||
| Brisson , 1760 |
The darter (Anhingidae, Anhinga ) are a family and genus of water birds from the order Suliformes . They are close relatives of the cormorants , to which they are sometimes assigned. They are named after their neck, which is greatly elongated in adaptation to the hunt for fish. When swimming, only this one protrudes from the water, while the rest of the body cannot be seen. Darters are common with four species in the tropics .
features
Darter are large waterfowl, which, depending on the species, can reach a body length of 81 to 97 cm and weigh 1060 to 1350 grams. The wingspan is about 120 cm on average. They are very similar in shape to cormorants, but the long, pointed beak and the long, S-shaped neck are more reminiscent of herons . The strong neck muscles allow the bird to push its pointed beak forward at lightning speed and thus stab its (fish) prey.
The dark upper plumage is often striped in a strongly contrasting white to light brown color and appears wavy. The sexes are of the same size, but the females of the different species are less conspicuous and paler in color. The males' beak is also longer. Birds in juvenile plumage resemble adult females, but are even paler in color.
The wings of the darter are wide and enable powerful and encouraging wing beats, which alternate with longer gliding phases. The long tail is fanned out in flight, which has led to the name water turkey (" water turkey ") in the USA .
The legs start far behind the body. All four toes are connected with wide webbed feet. Darter in the countryside tend to move awkwardly, spreading their wings to keep their balance. In the water they move like cormorants: when swimming with alternately paddling feet, when diving with simultaneous and parallel driving feet, with the wings almost completely laid out. Dives last 30 to 60 seconds.
As with the cormorants, the plumage is quickly soaked to reduce buoyancy. This is due to the special structure of the feathers; Like other waterfowl, darters grease themselves with the secretion of the rump gland in order to keep it as waterproof as possible. In addition, since a characteristic of birds, the pneumatization (air filling) of the bones, is only weakly developed in darter, darters are relatively heavy in the water. When swimming, the entire torso is under water and only the neck and head can be seen - at greater distances an observer can therefore mistake the bird for a snake looking out of the water.
distribution and habitat
The genus mainly inhabits the tropical and subtropical areas of America , Africa , Asia and Australia . The African darter ( Anhinga rufa ) is common in almost all countries south of the Sahara , from Mauritania and Sudan south to the Cape . He also colonizes Madagascar . The Indian darter ( A. melanogaster ) is found mainly on the Indian subcontinent and in Southeast Asia . Far to the west of this main distribution area there is an isolated occurrence on the Shatt el Arab .
The Australian darter ( A. novaehollandiae ) breeds in New Guinea and Australia, especially in the Murray - Darling river system. The American darter ( Anhinga anhinga ) inhabits the American double continent from the southeast of the USA through Central America and Amazonia to the north of Argentina .
The breeding habitats are very different. Both species prefer freshwater areas, but darters can also be found in brackish mangrove swamps and on the edge of bays. The banks of the waters they frequent must have thick vegetation and offer branches on which the birds can sit and let their plumage dry. Often they breed on the edge of large heron, ibis or cormorant colonies.
Common darter are resident birds . Only in the United States does the northernmost population make a move to the Gulf Coast . There was once a population in Turkey that moved to Israel every winter ; however this is extinct.
Way of life
activity
In their behavior, darters show numerous similarities with the cormorants. Like these, they are diurnal and rest on branches or in trees. Although they are able to fly out of the water, most of the time they climb trees straight from the water. To dry the plumage, they rest with their wings spread out.
nutrition
Like the cormorants, darters dive excellently, but they are not chasers like these, but “sneak” up to the prey underwater and stab it with a lightning-fast stretching of the neck with a pointed beak. The food mainly consists of fish, but amphibians , reptiles , crustaceans , molluscs , insects and worms are also preyed on. Small prey are eaten immediately, larger ones brought to the surface, thrown into the air and swallowed head first.
Reproduction
Unlike cormorants, darters do not form large colonies, but often appear in loose associations of a few pairs. Often they join the colonies of other waterfowl. Darters are monogamous; Over the years, a pair can always be found in the same nesting place. The nest is in a tree, made of twigs and padded with leaves and stalks. Mating takes place in the nest.
The nest and the surrounding area are defended against all intruders of the same or different species. Males in particular react to intruders by snapping their bills at them. Fights are rare as the threatening gestures are usually sufficient to defend the territory.
Darters lay two to six eggs. The young hatch after 25 to 30 days. They are initially naked, but after only two days they are feathered with a downy dress. Initially, they are fed with the parents choking pre-digested fish in front of them. Later, the young stuck their beak into the mouths of the adult birds and fetch the food from the throat pouch. The young fight each other for food, so that the young that hatched last is disadvantaged. As a rule, however, all boys get through; unlike many other species of the order Suliformes, the death of the smallest boy is the exception rather than the rule. Young darters leave the nest after three weeks, but continue to be fed until they are six to seven weeks old and can fly and dive and hunt independently. Overall, the brood takes only three months from nest building to fledgling, which is an extremely short period of time for Suliformes.
Darters probably first breed when they are two years old. No reliable data are known about their life expectancy.
Tribal history
Darters have been known to be fossilized since the late Miocene . The oldest known representative, Anhinga subvolans , was initially mistaken for a representative of the cormorants. Also noteworthy is the South American Macranhinga paranensis from South America, which with an average weight of 5.4 kg far exceeded today's species.
The Protoplotus beauforti from the Eocene , originally described as the oldest darter, is not a darter according to today's view; its actual assignment remains a mystery. The only recent species is the American darter from the Pleistocene .
Systematics
Mostly the darter get the rank of a separate family within the Suliformes. Some zoologists see no reason to separate them from the apparently closely related cormorants , and assign them to them as the subfamily Anhinginae. The relationship to the cormorants is mainly assumed because of the many morphological similarities and has been confirmed in several studies.
The probable family relationships are given by the following cladogram :
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While sometimes only two types are recognized, there are currently four types:
- American darter , Anhinga anhinga
- Indian darter , Anhinga melanogaster
- Australian darter , Anhinga novaehollandiae
- African darter , Anhinga rufa
Population development and endangerment
Neither of the two species is globally threatened, but in parts of their range they have become rare or even extinct. Birds and eggs are particularly eaten in Southeast Asia, which has reduced their populations in many countries. Darters have also increased significantly in other regions in recent decades, such as New Guinea , where they have benefited from the introduction of large species of fish for recreational fishing.
The old world darter once had an extensive range in Western Asia, of which only the occurrence in the Shatt el Arab remains. In Turkey there was a small population at the Amik Gölü (Lake Antakya ), which became extinct after this lake was drained.
Sources and further information
Sources cited
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ↑ a b J.J. Becker: Reidentification of Phalacrocorax subvolans Brodkorb as the earliest record of Anhingidae. In: Auk. 1986, No. 103, pp. 804-808.
- ↑ JI Noriega: Body mass estimation and locomotion of the Miocene pelecaniform bird Macranhinga. In: Acta Palaeontologica Polonica. 2001, No. 46 (2), pp. 247-260.
- ^ Joel Cracraft: Monophyly and phylogenetic relationships of the Pelecaniformes: A numerical cladistic analysis. In: The Auk. 1985, No. 102, pp. 834-853.
- ↑ M. Kennedy, HG Spencer, RD Gray: Hop, step and gape: do the social displays of the Pelecaniformes reflect phylogeny ?. In: Animal Behavior. No. 51, 1998, pp. 273-291.
- ^ Brown, Joseph W. and John Harshman. 2008. Pelecaniformes. Version 27 June 2008 (under construction). http://tolweb.org/Pelecaniformes/57152/2008.06.27 in The Tree of Life Web Project
- ↑ IOC World Bird Names: Ibises to Pelicans and Cormorants
- ↑ Pamela C. Rasmussen & John C. Anderton (2005): Birds of South Asia. The Ripley Guide ISBN 84-87334-67-9
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 84-87334-10-5 .
- Bryan Nelson : Pelicans, Cormorants and their relatives. Oxford University Press, 2005, ISBN 0-19-857727-3 .
