Live in pairs in groups of 50 or more. Perch on branches, while resting a callous on sternum on branch. Diurnal and nocturnal, tends to rest during hottest part of day. Not palatable to humans but preyed on by monkeys. Some evidence of relationship to cuckoos.
Life History Breeds during rainy season.
Entire group incubates eggs and cares for young, which are fed from crop of adult caretakers. Mating probably polygamous and promiscuous. Build loose stick platform two to eight meters above water. Incubation about 28 days. Newly-hatched hoatzins almost featherless, but rapidly grow down, and have claws on first and second digits, so they can climb on vegetation.