And then there’s this guy.
This is a Hoatzin. He’s got an enormous two-chambered crop which is so big and heavy that it displaces his flight muscles. This crop works like a cow’s stomach and is at any given moment full of half-digested vegetation, which is how he got his other name: Stinkbird.
Hoatzins are the only birds which digest food this way. They are born with two little claws on the ends of their wings and as chicks they scramble around with them like bats. They are brightly-colored, clumsy and terrible at flying, and their main defense against predators appears to be to create as much noise and chaos as possible so that their chicks can crawl away and hide in lakes while the adults get picked off.
They are not endangered. It is reported that they taste terrible.