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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.

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The Yellow-shouldered Amazon ( Amazona barbadensis ) is one of the most endangered species of parrots in Venezuela. An integrated conservation program has focused on reversing the causes of parrot population decline on the Macanao Peninsula in Margarita Island. As a result, the parrot population on the island has increased to about 1900 individuals in 1996 from an estimated population of 750 in 1989, when the project started. Cooperation from national and local authorities and the project's community outreach have resulted in several confiscated chicks. Whereas most confiscated chicks were successfully reintroduced in a cross-fostering nest program, some had to be kept in captivity for later release. We hand-reared 14 A. barbadensis and housed them for a year in a large outdoor aviary. Before release the birds were screened to determine their general health. Four parrots were fitted with radio transmitters and monitored for a minimum of 11 months. All 4 birds with radio transmitters survived and adapted successfully to their natural environment, 10 of the 12 released parrots survived at least 1 year, and 1 was seen alive 34 months after release. Integration into wild groups varied from 5 days to 9 months, with the two youngest parrots showing a slower integration process. None of the parrots reproduced the first year after release. Later three were seen scouting nesting holes with their partners, and one of the parrots was confirmed attending a nest with three eggs 28 months after release. Two chicks fledged from this nest. A substantial portion of the success of this program rests on 5 years of previous work on environmental education, public awareness, and studies on the parrot's biology. To provide some guidance on the costs of reintroduction projects, we estimated an overall expenditure of about U.S. $2800 per parrot. Previous attempts to reintroduce captive-raised parrots have had limited success, and our study indicates that reintroduction is feasible when captive-raised parrots are introduced to an area with a resident population. Although reintroduction can significantly reduce the chances of extinction, it also involves some risks. The long-term solution against extinction of A. barbadensis will be a combination of scientific understanding of their biology and habitat, awareness by local human communities, reduction in the wild bird trade, and continued commitment by conservation enforcement agencies. Reintroducción Exitosa del Loro Espalda Amarilla del Amazonas Criados en Cautiverio en la Isla Margarita, VenezuelaResumen: La cotorra cabeziamarilla ( Amazona barbadensis ) es uno de los loros más amenazados de Venezuela. Un programa integrado de conservación se enfocó a revertir las causas de la declinación poblacional de cotorras en la Península de Macanao, en la Isla de Margarita. Como resultado, la población total de cotorras en la isla se incrementó hasta los 1900 individuos en 1996, a partir de una población estimada de 750 individuos cuando comenzó el proyecto en 1989. La cooperación de las autorida...