Hoaztins represent the oldest bird lineage that leads to a single living species. They don’t just look primitive, however. In fact, the ancestors of these birds branched off from the rest of the avian evolutionary tree about 65 million years ago, only a sliver of time after the mass extinction event 1 million years prior that wiped out all non-avian dinosaurs*. HWAT?!
Hoatzins are like winged cows. They are the only bird that ferments leaves in its lower esophagus and crop. By enlisting the help of bacterial fermentation for digestion in their multi-chambered digestive tract – a feature usually reserved for ruminant animals like cows, goats, and sheep – Hoatzins thrive on leaves that other birds can’t stomach. Over 1000 bacteria species aid in the fermentation process producing methane that they belch out, bestowing them the nickname: skunk bird or stinkbird. HWAT?!
While Hoatzins are much better flyers than cows, that doesn’t mean they are very good fliers. Their flight muscles are weak and reduced, likely due to the huge crop that serves their digestive needs and takes up so much space that it has led to reduction in the keel of the sternum (breastbone, where the flight muscles attach). At best, Hoatzins are clumsy branch clamberers, and so-so gliders. We know some birds are flightless, spending most of their time underwater or on the ground, but a tree-dwelling bird that is a poor flier? HWAT?!
Baby Hoatzins hatch with two claws on the front of each wing. If approached by a predator, they will leap from their nest and plunge into the water below. They are competent swimmers, capable of swimming underwater or hiding along the bank until the predator moves on. They then use their claws to climb back up the tree and into the nest. HWAT?!
Hoatzins have a large range, found throughout the rainforest in the Amazon and Orinoco basins, including Peru, Ecuador, Colombia and Brazil. Hwats the best way for you to observe them? Join us in 2022.
*Editor’s note: birds are widely considered to be dinosaurs.