Hoatzins are considered evolutionary orphans, as their place in the bird family tree remains unclear. (Image credit: Patrick Gallet/500px/Getty Images)
Name: Hoatzin (Opisthocomus hoazin)
Habitat: Amazon and Orinoco river basins in South America.
What it eats: leaves, fruits and flowers.
Why it's surprising: The hoatzin is often considered one of the most unusual birds on the planet. Their young are born with clawed wings, a unique prehistoric characteristic, and adults emit a pungent, unpleasant odor due to their cow-like, fermenting digestive system, earning them the nickname “stinkbird.”
Hoatzins have some rather odd features: tall crests, blue facial skin, red eyes, and large fan-shaped tails that help them maintain balance as they move through dense vegetation.
But these tropical birds are especially notable for their pungent odor, which is most often compared to manure or decaying plants. This unpleasant aroma is the result of a very unusual digestive process that distinguishes them from almost all other bird species.
Unlike most birds, the hoatzin has a foregut fermentation system similar to that of cows. It feeds primarily on leaves, which it stores and ferments in a large crop, a temporary food sac located in the esophagus. The food then passes into the stomach for fermentation, where bacteria break down the tough plant fibers, releasing gases through burps, which create the bird's characteristic manure-like odor.
Hoatzins emit a smell due to their cow-like digestive system.
This digestive process is very efficient in breaking down the significant amounts of cellulose contained in the leaves. However, it makes the hoatzin both smelly and clumsy, as its enlarged intestines make it difficult to fly. However, the hoatzin's unusual smell serves as a natural defense mechanism, as predators generally avoid the bird, believing it to be rotting or poisonous.
Scientists aren’t sure about the hoatzin’s evolutionary history. A 2015 genetic study published in the journal Nature suggested that the hoatzin is the last surviving member of a lineage of birds that split off from the evolutionary tree in its own direction 64 million years ago, shortly after the extinction event that wiped out the non-avian dinosaurs.
However, a separate 2024 study in PNAS suggested that hoatzins are not that ancient.
Sourse: www.livescience.com
