[1] Traditionally classified among the fowl-like birds (Galliformes), recent studies have favored Opisthocomidae's placement within the Neoaves.

[6] The adults feed them with semi-digested slimy mass from their crops, and the young are fed during the first four or five months of their life.

[6] The young nestlings can jump out into the water, and swim with wings and feet, in order to escape predators at nest.

They are noisy birds, calling in unison, uttering large numbers of varied sounds.

[6] In addition to foregut fermentation, the hoatzin has a highly modified skeleton to accommodate its large crop, and in the young of this species, wing claws at the wrist joint which are used to climb among the branches of the nest tree.