Animal
Hoatzin
The hoatzin is a big brown bird with a spiky crest and a blue face. It eats leaves, and its babies have little claws on their wings.
The hoatzin is a strange and wonderful bird of the Amazon and Orinoco rivers. It eats mostly leaves and digests them slowly with the help of bacteria, a bit like a cow. Its chicks have claws on their wings that help them climb back up through the branches.
Opisthocomus hoazin is a leaf-eating bird of South American riverbanks and swamps, placed in a family of its own name, Opisthocomidae. World Land Trust and Animal Diversity Web describe it as the only bird that digests leaves by microbial foregut fermentation in an enlarged crop. Its chicks carry wing claws, it nests in cooperative groups, and the IUCN rates it Least Concern (2024).
Photo: Murray Foubister, CC BY-SA 2.0, via Wikimedia Commons
Meet the hoatzin
The hoatzin is a big bird with a long tail.
It has a spiky orange crest on its head. Its face is bright blue, and its eyes are red. It lives in trees by the river.
The hoatzin is a stocky bird about 62 to 70 centimeters long, with a small head, a long neck and a long, square tail. On its head is a tall, spiky, reddish crest, and its face is bare bright blue skin around a red eye.
Its back is dark brown with white streaks on the back of the neck, its belly chestnut and its tail tipped with buff. Scientists have argued for a long time about which birds are its closest relatives, because it is so unlike any other bird.
Opisthocomus hoazin belongs to the family Opisthocomidae and the order Opisthocomiformes. World Land Trust gives a length of 62 to 70 centimeters and a weight of 700 to 900 grams; the sexes are alike, though females have a slightly shorter crest. Bare blue facial skin, a red iris and a long, rufous crest that can be raised make it unmistakable.
Its place in the bird family tree is still debated. Animal Diversity Web notes that it has been linked with gamebirds, cuckoos and turacos at different times, and World Land Trust reports that a 2015 genetic study placed it on an old lineage of its own, while a later study disagreed.
Quick facts
- Group
- Bird
- Length
- 0.62 to 0.7 m
- Weight
- 0.7 to 0.9 kg
Where it lives
Hoatzins live in South America.
They live in trees and bushes next to rivers, lakes and swamps. Their nests hang over the water.
Hoatzins live in the Amazon and Orinoco river basins of South America, and along the Atlantic coast of the Guianas and northern Brazil.
They live in the trees and bushes that grow along and over rivers, streams, lakes, swamps, lagoons and mangroves. Most live in lowlands, between about 5 and 200 meters above sea level.
World Land Trust places the hoatzin throughout the Amazon and Orinoco basins: northern Brazil and east of the Andes in Venezuela, Colombia, Ecuador, Peru and Bolivia, plus the Atlantic coast of Guyana, Suriname, French Guiana and northern Brazil. The IUCN's 2024 assessment lists the same nine range states and an elevation range of 0 to 1,050 meters.
It is arboreal but tied to water, living in vegetation along and overhanging rivers, streams, fresh, brackish and salt lakes, swamps, lagoons and mangroves, especially stands of giant arums. World Land Trust gives a usual elevation of about 5 to 200 meters, sometimes up to 500. ADW adds gallery forests and freshwater marshes.
Continent
Its habitats
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Waterside forest, swamps and mangroves in the Amazon and Orinoco basins and along the Atlantic coast of the Guianas. It also lives in French Guiana, which this map shows as part of France. Hoatzins live only along water within each country shown.
Places: Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Colombia, Ecuador, Peru, Brazil, Bolivia, Venezuela, Guyana, Suriname and 5 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
A bird that eats leaves
Hoatzins eat leaves.
Leaves are hard to digest. Tiny helpers called bacteria live inside the hoatzin. They help break the leaves down, a bit like inside a cow.
Eating leaves is very unusual for a bird, but the hoatzin does it. New leaves and buds make up about 82 percent of its diet, with some flowers and fruit.
Leaves are tough to digest, and birds cannot chew. The hoatzin stores its meal in a huge crop, a pouch where birds keep food. There, ridges grind the leaves and bacteria break them down, a process called fermentation. Cows ferment their food too, in their stomachs. A meal can take 45 hours to pass through the bird!
Animal Diversity Web calls the hoatzin primarily a folivore: it usually eats fewer than twelve plant species but can eat the leaves of more than fifty, including tropical legumes. World Land Trust gives the diet as 82 percent new leaves and buds, 10 percent flowers and 8 percent fruit, eaten mainly at dawn and dusk.
Both sources describe microbial foregut fermentation. Food is digested mainly in the enlarged crop and lower esophagus, whose muscular walls have folds and ridges lined with cornified tissue that break leaves into pieces small enough for bacteria to digest. ADW adds that some of the bacteria themselves pass into the stomach as food. World Land Trust notes that a meal can take 45 hours to pass through, and that the fermenting leaves release methane, which the bird burps out.
Did you know?
Some people call the hoatzin the stinkbird.
Fermenting leaves give the hoatzin a strong, musky smell, which earned it the nickname 'stinkbird'.
The musky odor, likened to fresh cow dung, comes from its fermenting diet; the bird burps out methane from the process.
A big crop and a smelly reputation
The hoatzin's food pouch is very big.
It leaves less room for flying muscles. So hoatzins fly only short hops. They smell a bit like a cow farm!
The hoatzin's giant crop can make up a quarter of its weight. To make room for it, the breastbone is small, leaving less space for the big muscles birds use to fly. So hoatzins are weak fliers that flap and glide for short distances.
The leaves fermenting inside give the bird a strong, musky smell, a bit like fresh cow dung. That is why people sometimes call it the stinkbird.
World Land Trust reports that the foregut can account for up to 25 percent of body weight and that the sternum is much reduced to accommodate it, limiting flight to weak flapping and short glides. ADW likewise links the enlarged crop to clumsy flight.
The diet also shapes the bird's day: much of the hottest part of the day is spent resting in trees while food digests. Fermentation gives the hoatzin a strong, musky odor that World Land Trust likens to fresh cow dung, which has earned it nicknames such as 'stinkbird'. The stout bill and short, thick legs are black.
Chicks with claws on their wings
Hoatzins build stick nests over the water.
The chicks have two little claws on each wing. They use them to climb on branches. The claws get smaller as the chicks grow.
Hoatzins nest in the rainy season, building a flat nest of sticks on a branch above the water. The female lays two to four eggs, and the whole family group takes turns keeping them warm for about a month.
The dark, downy chicks have two claws on each wing. If danger comes near, a chick can drop into the water, swim and then climb back up into the branches, gripping with its wing claws. The claws shrink as the chick grows. Young hoatzins cannot fly until they are about 60 to 70 days old.
Nesting coincides with the wet season. World Land Trust describes a flat, unlined stick nest overhanging water and clutches of two to four eggs incubated by all group members for about 30 to 31 days; ADW gives two to three eggs, 32 days, and nests about 6 to 15 feet (1.8 to 4.6 meters) above the surface.
Chicks are dark brown and downy and have functional claws on two digits of each wing (World Land Trust names the alula and major digit). When threatened they drop into the water, swim and climb back up with the help of the claws, which shrink as the chick grows and are lost in adults. Young leave the nest at two to three weeks, depend on the adults for food for two to three months and first fly at about 60 to 70 days.
Family groups and helpers
Hoatzins live in groups.
Older young from earlier nests often stay to help. They help feed the new chicks and guard the family's trees.
Hoatzins are very social. In the dry season they gather in flocks of up to 100 birds. When it is time to nest, a breeding pair defends a small territory beside the water.
Good nesting places by the water can be hard to find, so young hoatzins often stay with their parents for a couple of years. These helpers, mostly males, help feed the new chicks and guard the territory. All the adults feed the chicks with partly digested plant food.
World Land Trust describes flocks of up to 100 in the dry season and cooperative breeding in the wet season: a monogamous pair with up to six helpers, usually males and mostly offspring from earlier broods, defends a small territory next to water. Every adult in the group helps incubate and feeds the chicks regurgitated, part-digested plant material.
ADW explains that waterside territories can be scarce, so young birds often remain in their parents' territory for a couple of years, helping to raise new broods and defend the territory. Pairs advertise their boundaries with displays, loud noises and aggressive postures. ADW also notes that adults pass the gut bacteria to their young by feeding them a sticky, bacteria-rich substance.
Did you know?
Baby hoatzins have claws on their wings.
Hoatzin chicks have two claws on each wing, which help them climb back into the branches after dropping into the water.
Chicks have functional claws on two digits of each wing; they shrink as the bird grows and are lost in adults.
Protecting the riverbanks
There are still many hoatzins.
But some of the riverside places where they live are being cleared. People are protecting rainforests so hoatzins have homes.
The IUCN Red List rates the hoatzin Least Concern. It is common in many places, but its numbers seem to be going down.
The main threat is losing waterside habitat to farms, especially rice fields in Guyana, Suriname and Venezuela, and to projects that change rivers. Disturbance from tourism can also lower breeding success. Protecting forests helps. In Ecuador, a World Land Trust partner aims to protect about 747,000 hectares of Amazon rainforest between 2024 and 2028.
The IUCN assessed Opisthocomus hoazin as Least Concern in 2024, with a decreasing population trend and no estimate of the number of mature individuals. World Land Trust describes it as locally common in suitable habitat.
World Land Trust names the main threat as habitat loss to agriculture, especially rice cultivation in Guyana, Suriname and Venezuela, and to hydrological projects; disturbance from tourism lowers breeding success, and persecution in French Guiana has reduced the population there. ADW adds hunting and habitat destruction. Protected areas help: World Land Trust's partner Nature and Culture in Ecuador is working between 2024 and 2028 to bring an estimated 747,000 hectares of Ecuadorian Amazon into protection.
IUCN Red List
How is the hoatzin doing in the wild?
- Least Concern (this animal)
- Near Threatened
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Least Concern
Not at risk of disappearing from the wild right now.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2021.3
Amazing facts
-
Baby hoatzins have claws on their wings.
Hoatzin chicks have two claws on each wing, which help them climb back into the branches after dropping into the water.
Chicks have functional claws on two digits of each wing; they shrink as the bird grows and are lost in adults.
-
Hoatzin chicks can swim!
If danger comes, a hoatzin chick can drop into the water below its nest and swim to safety.
Threatened chicks drop into the water and swim beneath the surface (ADW), then climb back into the vegetation aided by their wing claws (World Land Trust).
-
A hoatzin digests leaves a bit like a cow does.
Bacteria in the hoatzin's crop break down leaves, much as bacteria in a cow's stomach break down grass.
World Land Trust calls the hoatzin the only bird that ferments its food, a process otherwise typical of ruminant mammals such as cows.
-
Some people call the hoatzin the stinkbird.
Fermenting leaves give the hoatzin a strong, musky smell, which earned it the nickname 'stinkbird'.
The musky odor, likened to fresh cow dung, comes from its fermenting diet; the bird burps out methane from the process.
Words to know
- crop
- a pouch where a bird stores food after swallowing it
- fermentation
- when tiny living things such as bacteria break food down
- folivore
- an animal that eats mostly leaves
- crest
- a tuft of feathers on top of a bird's head
- bacteria
- living things far too small to see without a microscope
- helper
- a young bird that stays to help its parents raise new chicks
Discovery challenge
-
What does a hoatzin mostly eat?
What makes up most of a hoatzin's diet?
Which food makes up most of the hoatzin's diet?
- Leaves
- Fish
- Insects
Show the answer
Leaves
Hoatzins eat mostly leaves.
New leaves and buds make up about 82 percent of its diet.
World Land Trust gives 82 percent new leaves and buds, 10 percent flowers and 8 percent fruit.
-
What do hoatzin chicks have on their wings?
What do young hoatzins have on their wings that adults lose?
What feature of the chicks' wings is lost as hoatzins mature?
- Claws
- Spots
- Tiny bells
Show the answer
Claws
The chicks have little claws on their wings for climbing.
Chicks have two claws on each wing that help them climb; the claws shrink as they grow.
Functional claws on two digits of each wing help chicks climb; they shrink with growth and are lost in adults.
-
Where does a hoatzin's food get broken down?
Where do bacteria break down a hoatzin's leaves?
Where does most fermentation take place in the hoatzin?
- In its big crop
- In its crest
- In its tail
Show the answer
In its big crop
The leaves are broken down in its big food pouch.
Bacteria break down the leaves in the hoatzin's huge crop, a pouch in its throat.
Fermentation takes place mainly in the enlarged crop and lower esophagus.
-
Where do hoatzins build their nests?
Where do hoatzins build their nests?
Where do hoatzins usually place their nests?
- On branches over water
- In holes in the ground
- On ocean cliffs
Show the answer
On branches over water
Their stick nests sit on branches over the water.
They build flat stick nests on branches hanging over the water.
Flat, unlined stick nests overhang water, about 1.8 to 4.6 meters above the surface (ADW).
Places where you might see it
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Watch
Country
Brazil
Brazil covers about half of South America and is the fifth-largest country in the world. It holds most of the Amazon River basin and much of the world's largest rainforest, and about 214 million people lived there in 2026, most of them near the Atlantic coast.
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Watch
Country
Peru
Peru is a country on the Pacific coast of South America. It has a dry desert coast, the high Andes mountains and the Amazon rainforest, and about 34 million people lived there in 2025, many of them in the capital, Lima.
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For parents & teachers
What children will learn
- Describe how the hoatzin digests leaves by fermentation in its crop.
- Explain how the hoatzin's large crop affects its flight.
- Describe how hoatzin chicks use their wing claws and how families raise them with helpers.
- Name the threats to the hoatzin's riverside habitat.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- Why might a diet of leaves be hard for most birds?
- How is the hoatzin's way of digesting food like a cow's, and how is it different?
- Why might young hoatzins stay to help their parents instead of leaving?
Try at home or in class
- Chew a piece of lettuce and notice how your teeth break it up, then talk about how the hoatzin, which cannot chew, uses the ridged lining of its crop instead.
- Measure 66 centimeters with a tape measure to see how long a hoatzin is from bill to tail.
Key vocabulary: crop, fermentation, folivore, crest, bacteria, helper
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Opisthocomus hoazin (Hoatzin), Red List assessment 2024 , IUCN Red List of Threatened Species
- Opisthocomus hoazin (hoatzin) , Animal Diversity Web, University of Michigan Museum of Zoology
- Hoatzin , World Land Trust
- Meet the Amazon's smelliest bird , World Land Trust
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 24, 2026. Spotted a mistake? Tell us.