The bird community in a large and permanent opening of the Amazonian rainforest: the Sierra de Chiribiquete (Colombia).
Published: Volume 42(2), December 1995. Pages 191-200.
Original Title: La comunidad de aves en un gran claro permanente de la selva Amazónica: la Sierra de Chiribiquete (Colombia).
In this work we describe the composition and spatial organisation of the bird community inhabiting the hill tops of the Sierra de Chiribiquete (Colombia) at the end of the rainy season (November-December 1992). These hill tops are covered by a permanently open vegetation, and are located in the middle of an extensive tract of pristine Amazonian rainforest. We analysed the relationships between the composition and structure of' the bird community and the structure and floristic composition of the vegetation along a multivariate gradient of such characteristics. This gradient was established between the open shrubland which covered the hill tops and the tall dense shrubland which surrounded them. Finally, we also compared this bird community whith those described by other authors for a wide range of Neotropical habitats. Both bird abundance and species richness were lower in Chiribiquete than in other Neotropical localities. Dominance, however, was stronger in Chiribiquete due to the large abundance of an endemic species of hummingbird (Chlorostilbon olivaresi sp. nov.). Bird abundance and species richness increased from the surrounding dense shrublands to the open vegetation of the hill tops in a way that paralleled the increasing floristic and physiognomic diversity of the vegetation. The low bird abundance and species richness found in the open habitats of Chiribiquete appeared to be related to the scarcity of resources provided by the vegetation. This scarcity seems to be caused by the poor development of the soils due to the strong washing effect of tropical rains over the hill tops. On the other hand, the current insular character of these open habitats and their likely past connection with other open areas of the Amazonas and Orinoco basins would explain the originality of its bird community through processes of vicariance and speciation in situ. Few species of birds inhabiting the surrounding rainforest were found in the open hill tops although it may be possible that these rainforest species would seasonally use this open vegetation in response to probable increases of food resources along the dry season.