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(wätsēn`) [Aztec], common name for a peculiar marsh bird, Opisthocomus hoatzin. The hoatzin is a slender bird with a brownish plumage spotted with white above and reddish-yellow to rust below. It may reach up to 25 in. (64 cm) in length, but weighs no more than 1 3-4 lb (810 grams). It has a long tail of 10 loosely bound feathers, and a large, bristly crest mounted on a tiny skull. Its young are good swimmers and are peculiar in having claws on their first and second wing digits, which they use along with their short curved bills and weak toes for climbing trees. In this respect the hoatzin is reminiscent of the extinct lizard-bird Archaeopteryx. As the young mature and begin to fly (though never especially well), the claws dwindle. Hoatzins are sometimes called reptile-birds because of their crocodilian odor and harsh, monotonous call. In yet another respect, they are the most advanced of avians. In other birds, food is broken up in the gizzard, but the hoatzin accomplishes this in its well-developed, muscular, horny-walled crop, and its gizzard is much reduced. The hoatzin's specialized diet consists of certain marsh plants, including the mangrove, and the bird is thus restricted to the riverine forests centering around the Amazon Basin where it lives in small colonies of 10 to 50 birds. Both sexes participate in the building of loosely entwined stick nests, 5 to 20 ft (1.5–6.1 m) over the water, in the forks of riverbank trees. The female lays two to four small eggs per clutch, which are yellowish in color with pink or brown spots. Little is known of the incubation period or of parental responsibilities. Hoatzins are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Aves, order Galliformes, family Opisthocomidae.



(Opisthocamus hoazin), a bird, the only species of the suborder Opisthocomi of the order Galliformes. Body length, approximately 60 cm. The plumage on top is olive with white spots, and the abdomen is reddish. Hoatzins are distributed in South America from Colombia to Bolivia. They keep to flooded river thickets. Hoatzins are barely able to fly and spend a large portion of their time in trees. They nest from December through July. There are two to four eggs in a clutch. In the young, claws develop on the first and second digits of the wing. The claws help the young birds to creep along branches, but they disappear in the adult hoatzin. The diet is vegetarian. The hoatzin has an unpleasant odor, and its meat is inedible.

References in periodicals archive ?
The scientists conclude, however, that the hoatzin belongs next to the cuckoo's nest, not in it, because the species' DNA and structural differences.
Paul DeBenedictis of the State University of New York Health Science Center at Syracuse says that Hedges and his colleagues should have compared the hoatzin with a wider variety of birds.
Scientists have disagreed most recently over whether hoatzins are closer to cuckoos or to galliforms such as pheasants, chickens, and turkeys.
Indeed, the team recommends placing hoatzins in their own suborder, Opisthocomi, in the Cuculiformes order.
Like an overstuffed hen, the adult hoatzin can flutter clumsily for several hundred yards, but that short range is all it needs to find the seven plant species that make up more than half its leafy diet.
Why did the hoatzin develop a foregut in the first place?
Leaf-eating did not happen overnight," Strahl told SCIENCE NEWS, adding that some fossil evidence indicates the hoatzin may have originated in the Eocene epoch, predating mammal foregut fermenters.
As a boy, Strahl read the works of bathysphere inventor William Beebe, who served as the zoo's first curator of birds and who studied the hoatzin in South America during the early years of the century.
The flight of the hoatzin resembles that of an overfed hen," Beebe wrote.
The Hoatzin was the most abundant species in this guild, representing 94.
The mean per route for the Forest guild was greatest in all ecoregions at the end of the dry season, peaking at 40/route in the BBE as flocks of Hoatzin became more common.
Upland Sandpiper (Bartramia longicauda) Laridae Black Skimmer (Rynchops niger) Gull-billed Tern (Gelochelidon nilotica) Large-billed Tern (Phaetusa simplex) Yellow-billed Tern (Sternula superciliaris) Opisthocomidae Hoatzin (Opisthocomus hoazin) Alcedinidae Amazon Kingfisher (Chloroceryle amazona) Green Kingfsher (C.