The Biospere Reserve El Triunfo was officially declared on 13 march with a a total of 119,177 hectares protected. Located in Sierra Matre de Chiapas in the south of the country, its core consists of 5 nuclei that together contain more than 25,000 ha. The remaining area forms a buffer zone of more than 94,000 ha of private property and public lands which are in good shape. The first nucleus zone is known as El Triunfo and has more than 11,000 ha. It is in this zone where the horned guan research is conducted.
Field observations indicate that the horned guans have a polygynous mating system in which a male may have access to 3-5 females during the reproductive period. A nest was found in April of 1990 located in a Ternoestroemia lineata tree at a height of 16.5 m and an altitude of 2325m. The nest measured 28cm x 28cm with a depth of 6.5 cm. The nesting female was relatively small with an estimated age of about 12-14 months and a horn 3-4 cm in length.
Incubation lasted 21 days. The female took 1-4 recesses daily with the last being for feeding. The length of each break averaged about 30 minutes. The daily incubation sessions varied from 1-3 hours with an average of 2 hours. The time of nocturnal sessions varied from 15-20 hours. The home range of the female during incubation was estimated to be 0.9 ha using the minimum convex polygon method.
A chick hatched on 24 April at 16:00 as follows. After the female left the nest, one of the two eggs had a small hole. The chick gradually pecked counter-clockwise around the egg using its yellow egg tooth. The chick took 26 minutes to hatch. During this time the female left the nest area and the chick hatched in her absence. The chicks had dark grey plumage on most of the body with a chesnut stripe on the head. There seemed to be differences in the behavior of the chicks in the nest, especiallly in the tone of their calls which may be due to sexual differences. The chicks stayed in the nest for 5-6 days after hatching and were fed exclusively fruit and pieces of leaves.