The only known case of an avian digestive system with active foregut fermentation is reported for the hoatzin (Opisthocomus hoazin), one of the world's few obligate folivorous (leaf-eating) birds. Hoatzins are one of the smallest endotherms with this form of digestion. Foregut fermentation in a flying bird may be explained by increased digestive efficiency by selection of highly fermentable and extremely patchy resources, coupled with microbial nutritional products and secondary compound detoxification. This unexpected digestive system gives a new perspective to the understanding of size limitations of vertebrate herbivores and to the evolution of foregut fermentation.

Large frugivorous forest birds are among the most endangered avian groups in the Neotropics. Despite this fact, there has been little field work on members of these groups or on other large Neotropical forest birds. While current studies of Neotropical forests are beginning to provide data for reserve management at the ecosystem level, we lack information for management of particular species or habitats. Throughout Latin America, large forest frugivores are economically important as food, as pets or in local crafts. They can also be important seed dispersers and can be used as indicator species of habitat disturbance in protected areas. The conservation status of these birds demands more attention and commitment from conservation organizations and the scientific community in general. Further field research should focus on the basic ecology and natural history of endangered and non-endangered species. These studies will aid in developing badly needed long-term management and monitoring plans both for populations of large forest frugivores and their habitats.

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