Dieta y reproducción en una colonia de guácharos (Steatornis caripensis) de alta montaña en Colombia

Diet and reproduction in a high mountain Oilbird (Steatornis caripensis) colony in Colombia

Abstract

I studied the diet and nestling development in a colony of Oilbirds (Steatornis caripensis) at an elevation
of 2900 m in the Eastern Andes of Colombia between April and December 2011. The fruits consumed by
the oilbirds were identified and analyzed to establish the nutritional content of the pulp of each species.
Colony members consumed the fruits of 16 plant species: ten of the family Arecaeae, five of Lauraceae
and one of Myrtaceae. The families of plants most consumed by oilbirds match those reported in different
studies in Venezuela, Ecuador and Trinidad and Tobago. The species with the highest numbers of seeds
collected during the study were the palms Oenocarpus bataua, Ceroxylon quindiuense and Geonoma
weberbaueri. The species of Lauraceae showed a well-defined fruiting period in the first half of the year,
while the palms were less seasonal, their seeds being found in all samples. The beginning of the oilbirds’
breeding season coincided with the rainy season (April to June) and the increased availability of fruits of
Lauraceae, which on average had a high lipid content, a low protein content and a moderate carbohydrate
content. The palms had higher carbohydrate content, and slightly higher protein content but lower lipid
content. Adults of the colony had to fly to lower elevations over distances of up to 150 km to obtain some
fruits. Nestlings in this colony took ca. 185 days to reach fledging, 30% longer than those in lower-
elevation colonies, probably due to the necessity of devoting much energy to thermoregulation. The
persistence of this colony at such an extreme elevation probably reflects characteristics of the cave
environment and the high mobility of the adults to obtain nutrient-rich fruits.