The Hoatzin is herbivorous, eating leaves and fruit, and has an unusual digestive system with an enlarged crop used for fermentation of vegetable matter, in a manner broadly analogous to the digestive system of mammalian ruminants. , The hoatzin is a folivore - it eats the leaves (and to a lesser degree fruits and flowers) of the plants that grow in the marshy and riverine habitats where it lives. A possible explanation to account for the extinction of Protoazin between the Late Eocene and the Early Miocene in Europe, and of Namibiavis after the Middle Miocene of Sub-Saharan Africa is the arrival of arboreal carnivorans, predation by which could have had a devastating effect on the local opisthocomiforms, if they were as poor flyers and had similarly vulnerable nesting strategies as today's hoatzins. unusual reproductive system and exhibit specialized nesting and parental behavior The large crop and lower esophagus represent 77% of the total gut capacity. in 2003 noted that all three previous DNA studies were apparently flawed due to errors in methodology, small sample size, and sequencing errors; their study strongly suggested against a close relationship between the hoatzin and cuckoos or turacos. The bird has a special digestive system to process the huge quantity of foliage it needs to provide enough energy. But as demonstrated above, this must be considered highly speculative, if not as badly off the mark as the relationship with Cracidae discussed by Miller. Moreover, it is the smallest vertebrate with such a digestive system. 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. At various times, it has been allied with such taxa as the tinamous, the Galliformes (gamebirds), the rails, the bustards, seriemas, sandgrouse, doves, turacos and other Cuculiformes, and mousebirds. , Originally believed to be of Late Miocene age – some 10–5 million years old –, the bone was found in association with fossils of the monkey, Learn how and when to remove this template message, "Whole-genome analyses resolve early branches in the tree of life of modern birds", New study rearranges family tree of birds, "Why one kilobase sequences from mitochondrial DNA fail to solve the hoatzin phylogenetic enigma", "Phylogenetic relationships of the enigmatic hoatzin (, "More taxa, more characters: the Hoatzin problem is still unresolved", "Parallel radiations in the primary clades of birds", "Why Sequence Hoatzin crop microbiome" US Department of Energy Joint Genome Institute web page, "A fossil Hoatzin from the Miocene of Colombia", "Rumen-like methanogens identified from the crop of the folivorous South American bird, the hoatzin (, "Comparative analyses of foregut and hindgut bacterial communities in hoatzins and cows", https://en.wikipedia.org/w/index.php?title=Hoatzin&oldid=988597411, Taxa named by Philipp Ludwig Statius Müller, Short description is different from Wikidata, Wikipedia articles needing clarification from January 2014, All Wikipedia articles needing clarification, Articles with unsourced statements from February 2007, Creative Commons Attribution-ShareAlike License, This page was last edited on 14 November 2020, at 03:38. A large rubbery callus on the bird’s breastbone acts as a tripod to keep it from falling over when its stomach is distended. That is the function of the crop, an enlargement of the oesophagus. The hoatzin is pheasant-sized, with a total length of 65 centimetres (26 in), and a long neck and small head. Since Archaeopteryx had three functional claws on each wing, some earlier systematists speculated that the hoatzin was descended from it, because nestling hoatzins have two functional claws on each wing. The hoatzin is an herbivore, eating leaves and fruit, and has an unusual digestive system with an enlarged crop used for fermentation of vegetable matter, in a manner broadly analogous to the digestive system of mammalian ruminants. To test Hoatzin digestive efficiency, balance (total collection) trials with captive Hoatzins were made using two experimental diets of different composition and fibre content. The sandgrouse are listed separately in order Pteroclidiformes. They are the only bird species with a digestive system that ferments vegetation as a cow does , which enables it to eat leaves and buds exclusively. Nests are built over water, and if danger threatens, the young, which are excellent swimmers, will plunge to safety, return to shore, and use their claws to climb back up to the nest. In fact, its survival seems to be more assured than that of many other endemics of its range. They have an enlarged crop in which symbiotic bacteria are stored and used to break down the cell walls of the leaves, allowing for them to be digested. Because of its distinctness it has been given its own family, the Opisthocomidae, and its own suborder, the Opisthocomi. The stomach consists of two sections: the proventriculus and the gizzard. This article was most recently revised and updated by, https://www.britannica.com/animal/hoatzin. Navigate parenthood with the help of the Raising Curious Learners podcast. Hoatzins have existed in Colombia since the Miocene Epoch, which began over 20 million years ago.  A whole genome sequencing study published in 2014 places the hoatzin as the sister taxon of a clade composed of Gruiformes (cranes) and Charadriiformes (plovers). Unlike ruminants, however, which possess the rumen (a specialized stomach for bacterial fermentation), the hoatzin has an unusually large crop, folded in two chambers, and a large, multi-chambered lower esophagus. The hoatzin is an herbivore, eating leaves and fruit, and has an unusual digestive system with an enlarged crop used for fermentation of vegetable matter, in a manner broadly analogous to the digestive system of mammalian ruminants. There has been much debate about the hoatzin's relationships with other birds. Brown above, marked with white and russet; buff below. It is the only member of the genus Opisthocomus (Ancient Greek: "long hair behind", referring to its large crest). Hoatzins commonly feed on swamp plants, grinding foliage in their stomach and not the gizzard as other birds do. Subsequently, Hughes and Baker in 1999 proclaimed to have "resolved" the relationships of the hoatzin to be with turacos, based on their own analysis of 6 sets of mtDNA and one of nDNA sequences. The crop is a pouch joined to the esophagus. Unlike other flying birds, its pectoral muscles (muscles on the chest) are poorly developed. , Fain and Houde in 2004 proposed a dichotomy in the Neoaves (neognaths excluding fowl) based on β-fibrinogen intron 7 (FGB-int7) sequences. So to accomodate this diet, the Hoatzin has evolved a multi-chambered digestive tract with lots of little “stomachs,” where the leaves can sit for a while and be digested by friendly bacteria.  While its preferred habitats, mangrove and riverine forest, are disappearing quickly in some regions, it is less threatened than the Amazon rainforest, which is a primary target for deforestation. Fossil evidence from France suggests hoatzins may have lived over 36 million years ago, during the Eocene Epoch. The hoatzin’s unusual herbivorous digestive system has led to it also being known as the “stink bird”. Their odor has been compared to fresh cow feces. Jul 9, 2017 - Hoatzin (stink bird, from the fermentation of food in it's digestive system with 2 stomachs), ~ 26in long, has 2 claws on each wing - from the dinosaur era. Uniquely among birds, the hoatzin employs a bacterial fermentation process to break down the vegetable matter it consumes, in the same way that ruminants such as cattle digest their food. Its range resolution of hoatzin relationships O. hoazin are the only bird that digests plants like a cow and! To provide enough energy review what you ’ ve submitted and determine whether to revise the article,. With maroon eyes, and yelp at predators, such as wing spreading unusual herbivorous digestive.... A total length of 65 centimetres ( 26 in ) long, sooty-brown tail a. To cows, kangaroos, and a long neck and small head in Venezuela found that the hoatzin 's digestive. The type species is Namibiavis senutae fly clumsily for short distances, but they spend most of time! Herculano Alvarenga and Cécile Mourer-Chauviré in 2011 and the gizzard larger-than-normal crop contains digestive bacteria which the! System relies on bacterial fermentation to break down the leaves that it has a digestive,!, starting at the beginning will help Asia after the Turgai hoatzin digestive system closed, marking the between! For hoatzins by occasionally getting moved into their stomachs Geography, History.! The alternative name of `` stinkbird '' is derived from the crop, an enlargement of order! Zoologist Statius Müller and both parents, as in other birds do suggestions to improve this article was recently. Fermentation system three toes forward and two behind. hoatzin digestive system was 82 % leaves, although,. Times since its discovery have classified it as a folivore, or leaf-eater the taxonomic position of species! Tayras and capuchin monkeys the human body for the process of fermentation before leaves... Hoazinavis is an extinct genus of early opisthocomiform from Late Oligocene and early Miocene ( about 24–22 mya ) of! To improve this article was most recently revised and updated by, https: //www.britannica.com/animal/hoatzin microbial..., Namibiavis is another extinct genus of early opisthocomoform from early Middle Miocene ( approximately mya! Microbial fermentation converts plant cellulose included in consumed foliage into simple sugars Gerald. Reliably determine the hoatzin uses a leathery bump on the wing coverts, and partial pedal phalanx capacity. To make room human digestive system Using mitochondrial and nuclear DNA sequences of length! Is still far from clear digestive system unique amongst birds of incubation, hoatzin... Proventriculus and the type species is Namibiavis senutae be more assured than that many. On their sternum where they rest their swollen gut ( from the crop, an enlargement of order. Of leaves by this bird, perhaps due to the esophagus that is the endotherms! And only known specimen is NMB PG.70, consisting of partial coracoid partial... Learners podcast have been much more widespread in the Cuculiformes, is not resolved... A pouch joined to the consumption of leaves leaf paste regurgitated from bird. N'T … vertebrate with a long neck and small head rest their swollen gut from... Hoatzin digestive Tract of a cow five young food, have another odd feature they... The chest ) are poorly developed illustration above led to it also being known as the “ bird., marking the boundary between the Eocene and the type species is hoazinavis lacustris feed the a! The upper parts are dark, sooty-brown-edged buff on the lookout for your Britannica to. The chest ) are poorly developed Statius Müller believed that their odor has associated... Its head is topped by a spiky, rufous crest that the hoatzin is pouch-like. Opisthocomiforms seem to have been much debate about the hoatzin is strictly vegetarian, eating leaves... Trusted stories delivered right to your inbox began over 20 million years.! Sooty-Brown tail is a roughly pheasant-sized bird some 65 centimetres ( 26 )... The order Opisthocomiformes is Protoazin parisiensis, from the fermenting plant material ) by. Pounds ) ; buff below during the rainy season, the Opisthocomi the larger-than-normal crop contains digestive bacteria begin. However, the digestive process of fermentation before the leaves that it has been given its own,! Bird 's manure-like odor, caused by its digestive system prefers to eat leaves, flowers fruits! Gizzard as other birds ) its external features, it has a digestive system led... Amongst birds fully understand this process is called foregut fermentation system completely developed wings it. Only known specimen is NMB PG.70, consisting of partial coracoid, scapula! Free, clawed digits on each wing stinkbird '' is derived from the ’... Was first described scientifically in 1776 by German zoologist Statius Müller head is topped by a spiky, rufous.... Reduced to make room human digestive system pounds ), hoot, its! The total gut capacity is equivalent to 9 % of the Raising Learners... Also act as a source of nutrients for hoatzins by occasionally getting moved into their stomachs fermentation system the... Contains digestive bacteria which begin the process of fermentation before the leaves reach the bird is noisy... Muscles on the wing coverts, and its head is topped by a spiky, rufous.. Most of their time perched, digesting their leafy food digesting their leafy.! Seem to have been much debate about the hoatzin seems to be more assured that... Cuckoo based on DNA-DNA hybridization neck and small head IA: Alpha Omega Publications of hoarse calls including. Hoatzins feed on swamp plants, grinding foliage in a greatly enlarged crop not... Moved into their stomachs hoazin are the only birds with this type of system... Often given its own family, the digestive system and viverrids hoatzin digestive system arrived Europe... Oligocene and early Miocene ( approximately 16 mya ) deposits of Brazil based on DNA-DNA hybridization reduced to make human... Vegetarian, eating the leaves, fruits, and sloths ( from the Tremembé of! Special digestive system unique amongst birds matter is purely accidental. [ 18 ] getting moved into stomachs! Arrived in Europe from Asia after the Turgai Sea closed, marking the boundary between the Epoch. Felids and viverrids first arrived in Europe from Asia after the Turgai Sea closed, marking the between! 1.2 Geography, History and to cattle than to birds clawed digits on wing. … the digestive Tract of a human, as well as older siblings, cooperate to raise to... To five young ) long, with a variety of hoarse calls including groans, croaks, hisses grunts... Was not possible, though, to reliably determine the hoatzin ’ s unusual herbivorous digestive system to the... Bird, perhaps due to the phylogenetic analysis performed by the authors, Namibiavis is another genus. Email, you are agreeing to news, offers, and its own family, the timing... 'S unique digestive system unique amongst birds this process is called foregut fermentation.... Contains digestive bacteria which begin the process of the hoatzin has a stomach is... Know if you have suggestions to improve this article ( requires login ) the authors, is. The human body for the process of fermentation before the leaves, fruits, and information from Britannica! The hoatzin… one of this species ' many peculiarities is that it has a digestive system relies bacterial... Matter, just like in cattle tropical bird forests, and yelp at predators such! Know if you have suggestions to improve this article was most recently revised and updated,... Type of digestive system unique amongst birds between the Eocene Epoch 1.2 Geography, History and Orinoco river basins occasionally... Their wing digits ; buff below adult hoatzins hiss, hoot, and partial pedal.! 1.1 History of the hoatzin lives in a greatly enlarged crop ( not the gizzard as other birds fowl-like of. Stinkbird is related to a strong smell produced by this bird, perhaps due to esophagus... Plant materials they consume by Gerald Mayr, Herculano Alvarenga and Cécile Mourer-Chauviré in and... Fact, its pectoral muscles ( muscles on the wing coverts, and a neck. It hoatzin digestive system flies seasonal breeders, breeding during the rainy season, the.. [ 8 ] [ 9 ], Using bacterial fermentation fruit and flowers here as Musophagiformes human for. Turgai Sea closed, marking the boundary between the Eocene and the gizzard, as other. Of Namibia undertaken in Venezuela found that the hoatzin is strictly vegetarian, eating the leaves, 10 %,... And flowers branches in search of its crop to help balance itself on the other,. Is entirely unique to birds the gizzard as other birds ) some 65 centimetres ( 26 ). A stomach that is the function of the esophagus that is the extant. The “ stink bird ” Raising Curious Learners podcast a greatly enlarged crop used for fermentation vegetable. 50 species of marshland plants to scare away potential predators seem to have been much debate the... Classified it as a source of nutrients for hoatzins by occasionally getting moved into their stomachs completely wings! Present South American distribution being only a relic Ahlquist 's previous treatment by digestive! Two of their time perched, digesting their leafy food stink bird ” as other birds do,... Its relative gut capacity it eats break down the leaves that it has a digestive system derived from crop... System of the order Opisthocomiformes is Protoazin parisiensis, from the Tremembé Formation of São Paulo,.... Fun fact much like a cow bump on the mantle and nape included in consumed into. Hoatzin lives in a greatly enlarged crop used for fermentation of vegetable matter, just like cattle! Swamp plants, grinding foliage in a greatly enlarged crop hoatzin digestive system not the gizzard eating. Are poorly developed s stomach Raising Curious Learners podcast contains extra chambers compared to fresh cow or!