The hoatzin is the Amazonian bird whose chicks famously have claws on two wing digits.
Hoatzin chicks use these claws to climb through riverside vegetation after leaving the nest. As they mature, the claws are lost or become reduced, and the adults rely on flight. This unusual feature once led scientists to debate the bird’s evolutionary relationships.
Hoatzins live mainly in swamps, mangroves, and flooded forests in northern South America. Their diet consists largely of leaves, which they digest with a fermentation system in the crop. This gives them a distinctive, sometimes unpleasant smell and the nickname “stinkbird.”
The species is the only living member of its family, Opisthocomidae. Its scientific name is Opisthocomus hoazin. The wing claws are a juvenile adaptation, not a feature that adult hoatzins normally use for climbing.