Definition of "hoatzin"

Hoatzins are large birds — at about twenty-six inches from head to tail, they are much larger than Archaeopteryx — with a yellowish chest, brown striped back, and a long narrow tail (Figure 53). Hoatzins are unusual in several ways, one of which is that hatchling hoatzins have claws on their wings. Although some other birds have vestigial wing claws, the hoatzin is the only species known to have functional wing or hand claws.

1999, Pat Shipman, Taking Wing: Archaeopteryx and the Evolution of Bird Flight‎, page 196

The hoatzin is a very colorful bird with a blue head, a tuft of feathers standing up on the head, and an orange iris in the eye.

2006, Buddy Davis, Kay Davis, Breathtaking Birds, page 41

Unique among riverine bird species, the hoatzin (Opisthocomus hoatzin) is found along slow meandering streams and oxbows within the Amazon and Orinoco basins (Plate 12-43). Hoatzins resemble chickens in size and shape.

2011, John Kricher, Tropical Ecology‎, page 460