Hoatzin
| Hoatzin | ||||||||||
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Hoatzin ( Opisthocomus hoazin ) |
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| Systematics | ||||||||||
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| Scientific name of the order | ||||||||||
| Opisthocomiformes | ||||||||||
| Wagler , 1830 | ||||||||||
| Scientific name of the family | ||||||||||
| Opisthocomidae | ||||||||||
| Swainson , 1837 | ||||||||||
| Scientific name of the genus | ||||||||||
| Opisthocomus | ||||||||||
| Illiger , 1811 | ||||||||||
| Scientific name of the species | ||||||||||
| Opisthocomus hoazin | ||||||||||
| ( Statius Müller , 1776) |
The hoatzin ( Opisthocomus hoazin ), also known as the crested hen , gypsy hen or stink bird, is a species of bird that lives in northern South America . Because his relationship is completely unclear, he is usually assigned to a separate family and order. The hoatzin differs from all other birds by its digestive system reminiscent of ruminants and the clawed wings of the young birds.
features
In terms of shape , the Hoatzin has a slight resemblance to the Hokko chickens , which is also indicated by its local name guacharaca de Agua ("water chakalaka "). With a length of 62 to 70 cm and a weight of 700 to 900 g it is quite a large and heavy bird, which is characterized by a small head, a long neck and a long tail. The top is bronze-colored, a cream-colored stripe runs over the neck and front back. The throat and chest are beige, towards the base of the tail the color of the underside gradually changes to chestnut brown. The wing covers are brown with a white border and white stripes. The tail is also dark brown; a cream-colored end band is usually present, but can be lost as the tail feathers wear down with age.
In the face, the red eye is surrounded on both sides by bare, blue areas of skin. A 4 to 8 cm long hood, which is mostly erect, is striking. This hood is slightly larger in males than in females, which is the only externally visible difference between the sexes. However, this minimal gender dimorphism cannot be used for determination in the field .
The beak is black, strong and short, and resembles a chicken beak. The legs are black too. Although these are strong and fully developed, the birds rarely use them for locomotion. Most often they crawl and push their way through the branches in an awkward-looking manner very unusual for birds. The foot is anisodactyl like in chicken birds : one toe is pointing backwards, three are pointing forward. Although the feet can hold a branch and carry the bird, hoatzins are mostly in the branches so that the weight is on the chest. A callus forms here over time .
Since the flight muscles are greatly reduced, hoatzins can only fly to a limited extent. Gliding is preferred, sometimes accompanied by strong wing beats. In this way a maximum distance of 350 m can be covered, but mostly the distances are much shorter. As a rule, only young birds have claws on their wings, but sometimes these remain in adult birds (see reproduction ).
The greatest anatomical abnormality is the enormously enlarged foregut . The digestion of the hoatzin does not take place in the stomach , but in the goiter and in the lower esophagus . This area is so bulky that it is fifty times larger than the stomach. A full foregut can make up 25% of the weight of a hoatzin. The digestion in the foregut is a unique feature among birds, reminiscent of the ruminants among mammals . The enlargement of the foregut is accompanied by a greatly reduced sternum , the shift of the center of gravity forward and the atrophy of the flight muscles.
The name stink bird refers to the smell that the bird is said to be. In Guyana , the hoatzin is known as the stinking pheasant . The smell is supposed to be reminiscent of fresh cow dung and is probably caused by the digestive processes. However, in other regions of South America - for example in Venezuela - the birds do not have a particularly strong smell . The Hoatzins odor presumably depends on the type of food digested.
The hoatzins' contact calls are grunts that are repeated three to ten times. There is also a guttural rruuh reminiscent of pigeons . If the area is defended against intruders of the same or different kind, a hoatzin will make sibilants.
distribution and habitat
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The hoatzin lives in the tropical rainforests of the northern part of South America . The basins of the Amazon and Orinoco rivers and the Guiana rivers flowing to the Atlantic are populated . It is found in eastern Colombia , in Venezuela , the three Guiana states, in north and central Brazil , in the far east of Peru and Ecuador and in northeastern Bolivia .
The habitat of the Hoatzins is the lowland rainforest at altitudes up to a maximum of 500 m above sea level. They occur exclusively along the banks of rivers and lakes, and here too they have certain preferences that have an influence on the frequency: inland they prefer the presence of the arum family Montrichardia and Caladium , in regions near the coast that of Avicennia .
Way of life
activity
Hoatzins are active in the early morning and evening hours. They spend the rest of the time resting. They often take sunbaths or rainbaths in the treetops, to which they spread their wings.
Outside the breeding season, hoatzins are very sociable and live in large groups of up to 100 individuals. During the breeding season these groups break up and smaller groups form tiny territories (see reproduction ).
food
Hoatzins are exclusively vegetable-based. Fifty food plants are known, including the above-mentioned Montrichardia , Caladium and Avicennia . The diet consists of 82% green leaves, 10% flowers and 8% fruits. It is a nutrient-poor and often toxic food.
Digestion takes place in the foregut. This is equipped with powerful muscles, the outer walls are partially horny. With the help of its bacterial flora, the hoatzin digests food with particular efficiency. The bacteria also ensure that the toxins contained in the food plants are broken down. The digestion time is a total of 24 to 48 hours, which is considerably longer than any other bird and more like a sheep.
Reproduction
During the breeding season, which falls in the rainiest months, the large associations of hoatzins dissolve. Now there are smaller groups of two to eight birds. This is the actual breeding pair that can be supported by its offspring from previous broods ( breeding aid ). In 45% of the cases, a couple has no helpers, in the other cases the subadult helpers take part in the defense of the territory, nest building, hatching and feeding. Broods in which such helpers are available are significantly more successful than other broods. 90% of annual birds stay with their parents in the following year to accompany the brood. But older birds are sometimes still present, for example 20% of four-year-olds and 10% of five-year-olds. Male cubs stay particularly long, while females never stay in the presence of their parents beyond the age of three.
The districts are very small. They extend on average 40 m along a river bank and are defended up to 75 m inland. The males in particular take on the defense. When fighting at the territorial borders, they jump towards each other with outspread wings, hack each other and fall back fighting into the branches.
The nest is always built above the water so that the young birds can jump straight from the nest into the water. It is located 2 to 5 m above the surface and consists of branches that are loosely layered on top of each other. The width of the nest is 30 to 45 cm. The clutch consists of two to four eggs. These are white with red-brown spots and have an average size of 4.7 × 3.3 cm. They are incubated for about 30 days. The young are blind and almost naked when they hatch. The eyes open after just one day, and after ten days the boys are covered with a thick dark brown down dress. The nutrient-poor food causes extremely slow growth. The flight feathers do not develop until they are 25 days old.
In the event of acute danger, the young can leave the nest on the third day of life. This point in time is usually later. If there is no danger-related reason to leave the nest, the young will leave their nest after two to three weeks at the latest. Sometimes the parent birds help out with a nudge.
Leaving is always done by jumping into the water. The boys are able to swim and dive. Then they climb back up their parents' tree, using the claws on their wings to help them. These claws are the ends of the second and third fingers and stick out of the wings as small rounded hooks. However, the young birds do not return to the nest, but continue to be looked after at various points in the branches. The jump into the water can be repeated at any time and serves as an escape from enemies.
In the first two months of their lives, young hoatzins are fed by their parents and their helpers. To do this, they plead their beak into the mouths of the adult birds. These then choke out a pre-digested, greenish food pulp. After fifty to seventy days, hoatzins begin to eat food on their own. At about the same time, they also acquire their (limited) ability to fly. The wing claws are shed between the 70th and 100th day of life. In rare cases they persist in adult birds, but no longer fulfill any function in them.
Only an average of 27% of broods are successful. Despite the escape mechanism in which a cub leaps from the tree into the water, numerous enemies manage to capture young hoatzins. The main predators among mammals are capuchin monkeys , tayras , possums , grisons , raccoons, and ocelots . The birds include forest falcons , two-color Sperber , black buzzards , sparrow hawks ordinations and splendor Hawk-Eagle to the Hoatzin hunters.
So far, a maximum service life of eight years has been established. However, there is still insufficient research and a potentially longer service life is considered very likely.
Tribal history
Occasionally the hoatzin has been mistaken for a missing link between present-day and extinct reptilian birds. Because of the wing claws of the young birds, a relationship with the ancient bird Archeopteryx was assumed, which also showed this characteristic. Today, however, it is assumed that this adjustment is more recent and that there is no more direct relationship.
Fossil hoatzins were not known until 2011, but there are fossil finds in which at least an assignment to the hoatzins is speculated. Here's Foro panarium from the lower Eocene to call North America. This bird had a hoatzin-like skull, but the rest of the skeleton is more reminiscent of turacos . Fossil finds known from South America are Filholornis from the Upper Eocene and Lower Oligocene and Hoazinoides from the Miocene . Both of them are controversial as to whether they are fossil Hoatzin relatives or Hokko chickens .
In July 2011, Namibiavis senutae , a fossil bird from the early Miocene (23 million years ago) of Namibia , was identified as a relative of the Hoatzin. His shoulder and humerus bones are already reshaped in a similar way to those of today's hoatzins. The Hoatzin-like bird Protoazin parisiensis from the late Eocene of France is even older . The finds from Africa and Europe therefore suggest that the line originally developed in the Old World and that the immediate ancestors of the Hoatzin came to South America on flotsam.
Systematics
The systematic affiliation of the hoatzins is probably more controversial than that of any other bird. Philipp Ludwig Statius Müller first described the bird in 1776 as Phasianus hoazin , i.e. a pheasant . Since then, the hoatzin has been placed alternately in the vicinity of cocktails , crocodiles , turacos , railings , bustards , seriemas , flight chickens , pigeons and mouse birds .
The assignment to the hen or cuckoo birds found the greatest popularity in the 20th century . It was mainly the osteology and the microscopic structure of the feathers that spoke for the chicken, the DNA-DNA hybridization , the eggs and behavior for the cuckoo birds. The finding of parasites, which often helps with the assignment of animals (related animals also harbor related parasites), does not help with the hoatzin. All parasites can only be found on the hoatzin and will neither tolerate another host nor are close relatives known.
In 1999 a study reported that new genetic analyzes had clarified the position of the hoatzin and that it should be classified in the vicinity of the turacos. However, this was contradicted by a subsequent study, which accused the previous analyzes of being flawed; the new analysis found no evidence of a relationship to cuckoo birds or turacos.
Today the hoatzin is put into its own order, the opisthocomiformes. Various zoologists are named as authors for this order. The ICZN does not have any uniform rules for naming the ranks above the families . Johann Georg Wagler was one of the first systematists who gave the Hoatzin, anatomically very different from the other birds, its own rank above the family rank. However, he placed this “clan” in the order of the cuckoo birds.
People and hoatzins
In some regions of South America, indigenous peoples have eaten the hoatzins' eggs and meat and used their feathers as ornaments. In other areas, however, the bird is considered inedible due to its stench.
The main threat to the hoatzin does not come from hunting, but from the destruction of the rainforests . Because of its restricted mobility, the hoatzin cannot even retreat to neighboring pristine areas if its habitat is destroyed. The hoatzin is very sensitive to any disturbance. Even moderate tourism in the breeding area ensures limited breeding success. However, since the range of the hoatzins is very large, it is not yet considered endangered overall.
In Zoo Hoatzins are almost never held. The Bronx Zoo in New York kept hoatzins for a number of years, but they did not breed.
Sources and further information
Individual evidence
- ↑ Bernhard Grzimek (Ed.): Grzimeks Tierleben , Volume 7/8: Vögel 1/2 . dtv-Verlag, 1979
- ↑ Alejandro Grajal, Stuart D. Strahl, Rodrigo Parra, Maria Gloria Dominguez & Alfredo Neher: Foregut Fermentation in the Hoatzin, a Neotropical Leaf-Eating Bird . In: Science 1989, Vol. 245, No. 4923, pp. 1236-1238
- ↑ Gerald Mayr , Herculano Alvarenga and Cécile Mourer-Chauviré: Out of Africa: Fossils shed light on the origin of the hoatzin, an iconic Neotropic bird. Natural Sciences, 2011 doi : 10.1007 / s00114-011-0849-1
- ↑ Scinexx.de " Schräger " Vogel came to South America with flotsam
- ↑ Gerald Mayr, Vanesa L. De Pietri. 2014. Earliest and first Northern Hemispheric hoatzin fossils substantiate Old World origin of a "Neotropic endemic." Natural Sciences, January 2014; doi: 10.1007 / s00114-014-1144-8
- ↑ JM Hughes & AJ Baker: Phylogenetic relationships of the enigmatic hoatzin (Opisthocomus hoazin) resolved using mitochondrial and nuclear gene sequences . In: Molecular Biology and Evolution 1999, Vol. 16, No. 9, pp. 1300-1307
- ↑ Michael D. Sorenson, Elen Oneal Elen, Jaime García-Moreno & David P. Mindell: More taxa, more characters: the Hoatzin problem is still unresolved . In: Molecular Biology and Evolution 2003, Vol. 20, No. 9, pp. 1484-1499
- ^ Johann Georg Wagler: Natural system of the amphibians: with preceding classification of the mammals and birds. Cotta'sche Verlagsbuchhandlung, Munich, Stuttgart and Tübingen, 1830, p. 107
- ↑ Antje Müllner, K. Eduard Linsenmair & Martin Wikelski: Exposure to ecotourism reduces survival and affects stress response in hoatzin chicks (Opisthocomus hoazin) . In: Biological Conservation 2004, Vol. 118, No. 4, pp. 549-558
- ↑ Opisthocomus hoazin in the Red List of Threatened Species of the IUCN 2011. Posted by: BirdLife International, 2009. Accessed November 13, 2011th
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 3: Hoatzins to Auks. Lynx Edicions, 1996, ISBN 84-87334-20-2 .
Web links
- Videos, photos and sound recordings for Opisthocomus hoazin in the Internet Bird Collection
