ECOLOGY OF THE FOLIVOROUS HOATZIN (OPISTHOCOMUS-HOAZIN) ON THE VENEZUELAN PLAINS

The Hoatzin (Opisthocomus hoazin) is the only avian folivore known to have fermentative digestion in the crop. We compare results on nesting , growth, and feeding in Pinero Ranch, Cojedes State, Venezuela, with results from another location in the Venezuelan plains. The Hoatzin ne sts in trees abundant in the habitat. Nests containing two eggs were p redominant. Growth rate of chicks was linear over the nesting period ( 5.68 g/day). The diet of the Hoatzin consisted of young leaves and twi gs of some of the most abundant trees in its habitat. Although there a re no reports on the phytochemistry of dietary plants, families to whi ch these plants belong include plants known to contain secondary compo unds. The crop, which functions as a mediator in plant-Hoatzin interac tions and as a detoxification chamber, deserves further study.