hoatzins

Hoatzins, or hoatzin birds, are tropical birds in the genus Opisthocomus, represented by the single living species Opisthocomus hoazin. They are the only extant members of the family Opisthocomidae and are placed in their own order, Opisthocomiformes. They are sometimes called stinkbirds for the musky odor associated with fermentation of plant material in a specialized crop.

Hoatzins occur along slow rivers and in swampy forest habitats of the Amazon and Orinoco basins in South America. They favor dense vegetation near water, where they perch and forage in riparian and mangrove-like environments. Nests are built in tree forks over water, offering protection from terrestrial predators.

In appearance, hoatzins are medium-sized birds with long necks and a relatively stocky body. Adults show brownish-olive plumage and a distinctive blue bare facial patch. A key youthful feature is the claws on the chick’s wings, which help it climb vegetation before it can fly. Their plumage and anatomy reflect their herbivorous lifestyle, and they are not strong fliers compared with many other water-associated birds.

Diet and digestion centers on leaves. Hoatzins feed mainly on young leaves from a variety of trees and shrubs, supplemented by fruits and flowers. They digest cellulose through foregut fermentation in a specialized crop, a digestive strategy uncommon among birds and a major factor in their leaf-based diet.

Behavior and reproduction are characterized by social groups along waterways. They lay small clutches, and incubation is shared by both parents. Chicks remain with their parents for an extended period, using their wing claws to navigate and feeding gradually shifts to fledging as they mature.

Conservation-wise, hoatzins are listed as Least Concern by the IUCN. Their distinctive biology and restricted wetland habitats mean local populations can be sensitive to habitat alteration and water quality changes.