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Hoatzin – the prehistoric Archaeopteryx bird today

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Description


The Hoatzin (Opisthocomus hoazin), also known as the Hoactzin, Stinkbird, or Canje "Pheasant", is an unusual species of tropical bird found in swamps, riverine forest and mangrove of the Amazon and the Orinoco delta in South America.


Hoatzin_bird_in_flight

This enigmatic bird is one of the strangest living birds is the hoatzin, which seems to be a link with birds that became extinct millions of years ago, and even shows similarities to the first known bird Archaeopteryx
Surviving today in the swamps of the Orinoco basin of South America it is a bird as strange and bizarre as its name, hoatzin, and has succeeded in foxing zoologists for years as to the origins of its odd characteristics
It's a primitive-looking bird, about the size of a pheasant at about 2 feet long, and it sports a ruddy, spiky, unkempt, 4-inch crest on a small head atop a long bulging neck. The featherless bright-blue face is accented by blood-red eyes and a short, thick beak, reminding me of a punk-rock star. The body is covered in dingy-brown feathers accented by greens, buffs and creamy whites. When the bird spreads its wings, a surprising chestnut color appears on the flanks and underwings.
The hoatzin hangs around trees near wet areas such as still water, slow-moving creeks, flooded forests, swamps and oxbow lakes.



The Hoatzin was originally described by German zoologist Statius Muller in 1776.
Hoatzin is arguably the most enigmatic living bird in regard to its phylogenetic relationships. No satisfying evolutionary hypothesis has been proposed, and the situation has actually become worse with the availability of DNA sequence data.
There has been much debate about the Hoatzin's relationships with other birds. Because of its distinctness it has been given its own family, the Opisthocomidae, and its own suborder, the Opisthocomi. At various times, it has been allied with such taxa as the tinamous, the Galliformes (gamebirds), the rails, the bustards, seriemas, sandgrouse, doves, turacos, other Cuculiformes, and mousebirds. Altogether, it has been most frequently suggested to be related to Galliformes, turacos, or the anis (New World cuckoos).


History of the debate
Placement with the gamebirds is historical, based mainly on phenetic considerations of external morphology, which are considered unreliable and generally dismissed today; the gamebirds together with the waterfowl belong to the fowl clade whereas the Hoatzin doesn't. Cladistic analysis of skeletal characters, on the other hand, supports a relationship of the Hoatzin to the seriema family Cariamidae, and more distantly to the turaco and cuckoo families. However, cuckoos have zygodactyl feet (two toes forward, two backward) and turacos are semi-zygodactylous, whereas the Hoatzin has the more typical anisodactyl foot with three toes forward, one backwards. The evolution of avian dactyly, on the other hand, is not entirely resolved to satisfaction.

 

Hoatzin_birds_on_tree

Archaeopteryx was the world's first bird, though it was really nothing more than a lizard with feathers. As far as we can tell it was the first creature ever to be covered with feathers and, although primitive in form, these gave two advantages; firstly allowing a better control of body temperature, and secondly offering possibilities of flight. Both these factors made the animal more versatile and adaptable in its environment than its ancestors.

Hoatzins are vegetarians, feeding on leaves and buds. Adding to its peculiarity is a unique digestive tract with an enlarged crop in the throat that acts like the rumen in a cow to break down vegetable material through bacterial fermentation. That little digestive trick, however, emits the odor of manure, which has given the bird the nickname “stink bird.”
Other oddities are the two claws on each wing of a chick. When a chick is in danger, it can drop from the nest to the ground or even into the water and use these claws to clamber up another tree out of sight.
The claws, unused on adult birds, make the birds appear to be throwbacks to the archaeopteryx, the first birdlike creature from the dinosaur age. Hoatzins aren't dinosaur birds, of course, but they're nonetheless odd enough to cause consternation over proper classification.
Scientists have researched and debated for years the phylogenetic relationship of the hoatzin. Proposals have allied it with such birds as tinamous, cuckoos and doves. Yet despite the hypotheses and DNA sequencing, no one has conclusively solved the mystery of the bird's exact evolutionary kinship.

Hoatzin_bird_on_three_close_up

Remains of Archaeopteryx from limestone beds near Solnhofen, Bavaria, dated some 150 million years old, show that claws on the forelimbs were well developed, suggesting that this first bird may have been partly arboreal, using all four limbs for climbing, then spreading the wings to enable it to glide from tree to tree.

Many features distinguish the hoatzin from other birds, not least of which is its voice which sounds more like a heavy smoker's wheezing than a bird call. About the size of a rather slender, upright pheasant, the hoatzin has an untidy crest of feathers, blood-red eyes encircled by bright blue skin, a long neck and long tail feathers. But perhaps the most interesting characteristic is the presence of claws on the wings and these, although useless to the heavy adult bird, are employed by the youngster to clamber among the branches near the nest- just as Archaeopteryx must have done so many millions of years ago.
The main function of the wing claws, it seems, is to assist the young hoatzin in times of crisis. The nest is normally built on branches overhanging water and is thus exposed to the eyes of marauding hawks. It is a rudely constructed platform of short twigs of roughly pencil thickness. If danger threatens, the parents usually abandon the nest for the safety of dense bushes nearby. The chick, left to its own devices, either uses the wing claws to help it clamber through the branches to some inaccessible spot, or dives into the water and emerges farther downstream to clamber back to 'the nest once the danger has passed.


Unable to decide whether it is truly primitive or just an evolutionary throwback, scientists have shelved the problem and placed the hoatzin, Opisthocomus hoazin, in a family or even an order all by itself.

Scientific classification
Kingdom:     Animalia
Phylum:       Chordata
Class:          Aves
Infraclass:    Neognathae
Order:          Opisthocomiformes (but see article)
Family:         Opisthocomidae Swainson, 1837
Genus:         Opisthocomus Illiger, 1811
Species:       O. hoazin




The Hoatzin bird is the only member of the genus Opisthocomus (Ancient Greek: wearing long hair behind, referring to its large crest), which in turn is the only extant genus in the family Opisthocomidae. The taxonomic position of this family has been greatly debated, and is still far from clear. It is a roughly pheasant-sized bird some 65 cm (25 in), with a long neck and small head. It is brown in colour, with paler underparts and has an unfeathered blue face with maroon eyes, and its head is topped by a spiky, rufous crest. The chicks are unusual in that two of their wing digits possess claws. The Hoatzin is herbivorous, it eats leaves and fruit, and has an unusual digestive system with an enlarged crop which functions as a rumen. The name Stinkbird is related to a strong smell produced by this bird, perhaps due to the consumption of leaves.



Habitat

Hoatzin can be found living in the flooded forests along streams swamps or mangroves where they can find their food source - aquatic vegetation, mainly giant arums which are their preferred food.  

Habitat_areal_of_hoatzin_bird


The bird can be found only in South America and particular in countries like Guyana and Venezuela, south to Bolivia, Peru and Amazonian Brazil mostly in in Amazon and Orinoco swamps and various streams and marshes within this aquatic complex.



Behaviour and Feeding


The Hoatzin eats the leaves and to a lesser degree fruits and flowers of the plants which grow in the marshy and riverine habitats where it lives. It clambers around clumsily among the branches, and being quite tame (though they become stressed by frequent visits), often allows close approach and is reluctant to flush. The Hoatzin uses a leathery bump on the bottom of its crop to help balance itself on the branches. It was once thought that the species could only eat the leaves of arums and mangroves, but the species is now known to consume the leaves of over fifty species. One study undertaken in Venezuela found that the Hoatzins diet was 82% leaves, 10% flowers and 8% fruit.

 

Hoatzin_bird_yellow


One of this species' many peculiarities is that it has a digestive system unique amongst birds. Hoatzins use bacterial fermentation in the front part of the gut to break down the vegetable material they consume, much like cattle and other ruminants. Unlike ruminants, however, which possess the rumen (a specialized stomach for bacterial fermentation) in the Hoatzin this is the function of the crop (an enlargement of the esophagus). The crop of the Hoatzin is so large as to displace the flight muscles and keel of the sternum, much to the detriment of their flight capacity. Because of aromatic compounds in the leaves they consume and the bacterial fermentation, the bird has a disagreeable, manure-like odor and is only hunted for food in times of dire need. Any feeding of insects or other animal matter is purely accidental.




Breeding


Hoatzins are seasonal breeders, breeding during the rainy season, the exact timing of which varies across its range. Hoatzins are gregarious and nest in small colonies, laying 2-3 eggs in a stick nest in a tree hanging over water in seasonally flooded forests. The chick, which is fed on regurgitated fermented food, has another odd feature; it has two claws on each wing. When disturbed, the chicks drop into the water to escape predation, then use their clawed wings to climb back to the safety of the nest. This has inevitably led to comparisons to the fossil Archaeopteryx, but the characteristic is rather an autapomorphy, possibly caused by an atavism towards the dinosaurian finger claws; the developmental genetics ("blueprint") of which presumably is still present in the avian genome.

Relationship with humans

Though conspicuous, even attractive, at close range due to its bizarre shape and striking colors, unwary and a poor flier, it is not considered endangered. In fact, its survival seems to be more assured than that of many other endemics of its range. In Brazil, tribal people sometimes collect the eggs for food, and the adults are occasionally hunted, but in general this is rare, as it is reputed to have a bad taste. While its preferred habitats, mangrove and riverine forest, are disappearing fast in some regions, it is less threatened than terra firme forest, which is the primary target for deforestation in the Amazon. The Hoatzin therefore remains fairly common in a large part of its range. The Hoatzin is the national bird of Guyana.



Interesting Facts

•    The name Stinkbird is related to a strong smell produced by this bird, perhaps due to the consumption of leaves.
•    The name Hoatzin comes from a Nahuatl or Aztec word meaning pheasant. Folk names include stink bird and Canje pheasant. (Canje is a river in Guyana.)
•     Food: Eighty percent of its diet is leaves; flowers and fruits make up the rest. The hoatzin consumes more than 50 different species of tree leaves.
•     Breeds in small colonies during rainy season. Nest constructed of sticks placed in a tree overhanging a stream, lake or flooded forest.
•    When can be seen - early morning before they hide under tree shade at midday

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Sources:
www.texasbirder.net
http://www.chron.com/disp/story.mpl/life/main/6951905.html
http://www.lastrefuge.co.uk/data/articles/hoatzin_p1.html
http://www.birdlife.org/datazone/speciesfactsheet.php?id=1319
http://sora.unm.edu/sites/default/files/journals/auk/v070n04/p0484-p0489.pdf
http://ibc.lynxeds.com

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