Defender birds
| Defender birds | ||||||||||
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Three horned horned birds ( Anhima cornuta ), Manu National Park , Peru |
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Anhimidae | ||||||||||
| Stejneger , 1885 |
The warrior birds (Anhimidae) are a family of South American geese birds (Anseriformes) that includes three species . Although they look more like a turkey in shape , they are the closest relatives of the duck birds . Its unusual features for geese birds include the chicken-bird-like beak, the only partially formed webbing between the toes, the gradual moulting of the flight feathers so that they never lose their ability to fly, unlike most geese birds, and a unique network of air sacs directly under the skin. Defensive birds are known for their extraordinarily loud calls, which have given them the name Screamers in English .
features
At first glance, defensive birds look more like chicken than their actually related duck birds . In addition to the plump body shape, the small head with the short beak is primarily responsible for this. The cm between 75 and 95 large animals, which can reach up kg to 4.5 weight have long, thick legs and a disproportionately large feet with long toes and back formed webbed they need for life in the shallow waters of marshes and Equip swamps .
There is no sexual dimorphism , apart from a slight size advantage in males. The trunk is covered by black to gray-brown feathers and contains a unique network of small air sacs under the skin , which reduce the weight of the otherwise rather clumsy and turkey-like birds so much that they can even walk on floating plant mats. In addition, the bones are more pneumatized than in any other bird.
On each wing there are two pointed spurs anchored to the wrists , which are used in territorial fights and for defense against predators. Broken spurs from such territorial fights have already been found in the chest muscles of defensive birds. The German name Wehrvögel goes back to these spurs. In contrast to ducks, the beak is strongly curved downwards.
Defender birds, once in the air, are good fliers and can reach great heights. Similar to the crack- legged goose , they moult their flight feathers gradually so that, unlike most representatives of the duck birds, they do not lose their ability to fly. They are buoyant, although as adult birds they rarely do. Fledglings of the defensive birds, on the other hand, swim more frequently, while their parent birds look for food while wading.
The network of air sacs is used to produce a deep, piercing rumble that is probably a warning to rivals. In addition, they produce screeching sounds, which have given them the English name Screamer . These calls can be heard up to a distance of 3 km.
distribution and habitat
Defensive birds are only found in South America . The distribution area of the three species includes the lowlands of Colombia and Venezuela and a large area east of the Andes chain from Bolivia via Brazil to central Argentina .
The preferred habitat of the defensive birds is marshy marshland, but they can also be found on the banks of slowly flowing rivers, in ponds and ponds and in the open savannah.
Way of life
activity
Defensive birds are mainly diurnal, but the horned defensive bird is sometimes also foraging at night. During the breeding season they are loners, outside the breeding season they live in loose associations. The collar-warrior bird, in particular, can then appear in very large groups that sometimes include thousands of individuals. In the tropics, the associations are much smaller.
nutrition
The food of the defensive birds consists primarily of roots, leaves, flowers and seeds. Young birds also eat insects , adults only hunt small animals to feed the young. The collared warrior bird is known for invading fields and eating the cultivated plants.
Reproduction
The breeding season of the birds is very different and strongly dependent on regional climatic conditions such as temperature and humidity, but with the exception of the white-cheeked warrior bird, which breeds all year round, is concentrated around the southern spring time, i.e. September to October. Males and females combine for life; during courtship they often synchronize their calls and clean the other's head or neck feathers. Otherwise their courtship behavior is inconspicuous. Copulation takes place on land: the male climbs the back of the female and holds onto the partner's neck with its beak.
The nest is built from small twigs, soft parts of plants and leaves. It is usually only a few meters from the shore in shallow water. Both parent birds are involved in building the nest. The female lays between 2 and 7 eggs, which can weigh between 150 g and 190 g, depending on the species, and are incubated for about a month and a half. The two partners share the brood business, the "changing of the guard" is accompanied by shouting and cleaning.
The chicks, wrapped in yellow down feathers, flee the nest and follow their parents as soon as they hatch. But especially at night they are still warmed by them and also receive additional food. The occasional feeding of the chicks by the parent birds is one of the more unusual characteristics of the geese. It is also unusual that the parent birds occasionally grease the chicks with secretion from the oyster gland. The young birds are only able to fly after two and a half months. They then stay with their parents for up to a year, sometimes longer.
Tribal history
Fossil finds are extremely rare. For a long time the oldest fossil consisted of the remains of a collared defensive bird that had been found in Argentina and which were dated to an age of 20,000 years. In the 1990s, however, a fossil species was first discovered with Chaunoides antiquus near Taubaté in Brazil ; this lived on the threshold between the Oligocene and the Miocene . Furthermore, fossil finds from England and Wyoming are known from the Eocene , which were interpreted as defensive bird remains, but this is questionable due to the fragmentary tradition.
Systematics
The relationship between warblers and ducks was suggested by William Kitchen Parker as early as 1863 and has not been seriously contested since. Among the similarities with duck birds include not only peculiarities of the muscular system and the bone structure and the feathered preen gland , the dense Dunenkleid , which still bear the adult birds under cover plumage, the unspotted eggs and the lack of nesting spot . Like ducks, defensive birds also have lamellae in their beak. These can be found on the inside of the upper beak of the crested weed birds and in the lower beak of the horned weed birds . Phylogenetic analyzes, based on both morphological features and mitochondrial DNA, confirmed the assumptions. Accordingly, the defensive birds are monophyletic and form the sister group of all other geese birds, namely the duck birds and the cracked goose .
In the family of the warrior birds there are two genera with living representatives, the crested bird ( Chauna ) and the horned bird ( Anhima ). The latter include only one species, the horned warrior bird ( Anhima cornuta ), the former two, the white-cheeked warrior bird ( Chauna chavaria ) and the collar warrior bird ( Chauna torquata ). The crested birds are also referred to by their Spanish name as Tschajas.
Defensive birds and people
Because of their loud calls, defensive birds are well known in their homeland. Often times, they are considered pests because they eat crops. Hunters do not appreciate them because they warn all animals in the surrounding area with their cry. Defensive birds can be easily domesticated - so they are sometimes used as "watchdogs" that give an unmistakable warning when an intruder approaches. Their meat is not popular as it has a spongy texture and air sacs.
Horn warrior bird and collar warrior bird are common birds. The white-cheeked warrior bird, with a population of only around 2,500–10,000 individuals, is considered to be at low risk.
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 c d e f Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0-19-854645-9 , p. 175
- ^ Kear, p. 176
- ↑ Herculano Alvarenga : A fossil screamer (Anseriformes: Anhimidae) from the middle Tertiary of south-eastern Brazil . In: SL Olson (Ed.): Avian Paleontology at the Close of the 20th Century: Proceedings of the 4th International Meeting of the Society of Avian Paleontology and Evolution, Washington, DC, 4-7 June 1996 , 1999
- ↑ a b Bradley C. Livezey: A phylogenetic analysis of basal Anseriformes, the fossil Presbyornis, and the interordinal relationships of waterfowl. In: Zoological Journal of the Linnean Society 1997, No. 121, pp. 361-428
- ↑ Carole Donne-Goussé, Vincent Laudet, Catherine Hänni: A molecular phylogeny of anseriformes based on mitochondrial DNA analysis . In: Molecular Phylogenetics and Evolution 2002, Vol. 23, No. 3, pp. 339-356
- ↑ Chauna chavaria in the IUCN Red List of Threatened Species . Retrieved December 11, 2008.
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 .
- Janet Kear (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
