Hoatzin: The Bird with Claws on Its Wings

Tucked in a tangled mangrove on the Orinoco River in Venezuela, a hoatzin chick hatches and displays two sharp claws jutting from each wing, a bird whose babies scale tree branches by hand. These claws, first documented by Richard Owen in 1860, let the chick grip and climb, even before flight feathers grow in. At just four days old, hoatzin chicks, still dappled brown, leap out of the nest and vanish underwater to escape a capuchin monkey, leaving one clawed wing gripping a root. They swim back and scale straight up a muddy trunk, clambering like tiny, feathered velociraptors. By two weeks, the claws start to shrink, and by adulthood, only faint bumps remain under the feathers. The hoatzin is the only living bird whose chicks bear true, functional wing claws-a relic so ancient, its closest match is Archaeopteryx, a fossil from 150 million years ago.