The hoatzin, or "stinkbird," is a bird that looks like a pheasant. But unlike cows, it is the only bird in the world that ferments its food in its stomach to digest it.
This strange digestive system makes it the smelliest bird in the world. The bird emits plumes of air that have a distinctive, strong fecal odor.

Hoatzins live mainly in the riverine areas of the Amazon rainforest and the Orinoco Delta of South America. They eat only leaves, which is rare among birds. In addition, they have a special digestive system.
Instead of using a crop like other birds to store food and feed it to their young, the bird’s crop is large and acts like a cow’s rumen. Bacteria in the bird’s gut break down leaf sheaths, fermenting them and releasing foul gases.
The process of digesting a leaf in the bird’s crop takes up to 45 hours. During that time, methane gas is released through the air stream from the bird’s mouth, creating a strong fecal odor.
Experts have described the smell as so bad that it keeps predators away. However, in the wild, some species, such as the great black falcon and the Tayra weasel, are willing to "endure the stench" to catch them as prey.
Not only does this bird smell bad, it is also considered by scientists to be a living fossil. They are the last remaining species in an ancient branch of birds that split off 64 million years ago.
In particular, baby birds are born with claws on their wings. This helps them grip and climb between branches. This is considered a trait that has disappeared in most modern birds.
The Hoatzin's large size causes its chest muscles to narrow, resulting in very limited flight ability. They can only fly short distances from tree to tree and mainly climb or jump. To perform these activities, the wing claws play a very supportive role.
The world's stinkiest bird, its body gives off a strong smell like cow dung ( Video source: One Minute Animals).
Despite analyzing more than 360 bird genomes in 2024 to come up with a family tree of major bird groups, the team of scientists still could not place the Hoatzin bird in any group.
Despite its strange appearance, weak flight ability and foul smell, the Hoatzin holds a special place in the hearts of the people of Guyana (a country located on the South American continent). Here it is honored as the national bird, considered a symbol of difference and unsolved mystery in the natural world.

Along with wading birds and cranes, the Hoatzin remains an evolutionary mystery in the bird world.
If you have the opportunity to explore the Amazon jungle and learn about this bird, if you find it strange, try to learn more about the chainsaw-like cry of the Capuchinbird. They are considered to have the maximum sound of the loudest bird in the world.
It can be seen that the world of birds has never been a limit that stops humans from exploring.
Source: https://dantri.com.vn/du-lich/loai-chim-thoi-nhat-the-gioi-co-the-toa-ra-mui-nong-nac-nhu-phan-bo-20250524234617450.htm
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