Hoatzin - Opisthocomus hoazin
Being one of the most peculiar South American birds, the Hoatzin, Opisthocomus hoazin (Opisthocomiformes - Opisthocomidae) is the only extant species of its genus and has its own family and order.
Hoatzins are large birds up to 66 cm in length, noisy and very territorial, especially during the breeding season. Their diet is made up completely of leaves, and the species has developed a special system that allows them to feed on leaves.
They have an enlarged crop in which symbiotic bacteria are stored and used to break down the cell walls of the leaves, allowing for them to be digested. This process is called foregut fermentation and hoatzins are the only birds with this type of digestive system. The bacteria within the crop also act as a source of nutrients for hoatzins by occasionally getting moved into their stomachs. The bacteria are introduced to young hoatzins when an adult regurgitates a sticky substance containing large amounts of the bacteria and feeds it to the young.
Photo credit: ©Jeff Dyck | Locality: Taracoa, Orellano, Ecuador (2014)