Observaciones sobre la composición, ecología, y zoogeografía de la avifauna de la sierra de Chiribiquete, Caqueta, Colombia

We report on an inventory of the avifauna of a mesa in the Sierra de Chlribiquete, a range of table-top mountains isolated in the Amazonian lowlands of SE Colombia, and previously unexplored ornithologically. Habitats in our study area included brushy savanna and scrub, and several types of forests. We recorded a total of 77 species, and collected 38 specimens representing 25 species. The avifauna of the study area was striking lor lts low density of individuals and low speeies diversity, probably related to the low productivity and poor nutrient content of the very shallow, sandy soil. In general, avian species richness per habitat was correlated with the height and structural and taxonomic diversity of the vegetation, with 20- 40 species in the different lorest habitats, and 13-16 species in savanna and scrub. Trophic groups well represented in the avifauna included small insectivores, raptores, and nectarivores (at least in terms of numbers of species); acuatic birds, frugivores and granivores were poorly represented. Families well represented included Formicariidae, Tyrannidae, and Trochilidae; few or no species of families of large frugivores like Psittacidae, Ramphastidae, or Cotingidae, or granivores like Columbidae or Emberizidae were recorded. The oscines in general were poorly represented, and no less than 8 of 21 species were boreal migrants. Neomorphus rufipennis was recorded for the first time in Colombia. For most species, the breeding season had not yet begun, and food resources, especially fruit, appeared to be scarce. The bulk of the avifauna shows close affinities with the birds of the savannas and sandy-belt forests of the Orinocan region, and not with the humid forest birds of theAndean foothills or the Amazonian region. The distribution of these birds was probably more continuous during the Pleistocene, when savannas evidently covered much of SE Colombia. A small number of species have apparently dispersed to the Sierra from the Andes or the dry upper Magdalena Valley. Only among the latter is there evidence of taxonomic differentiation, resulting in forms endemic to the Sierra de Chiribiquete.Realizamos un inventario de la avifauna de una meseta en la Sierra de Chiribiquete, una serie de mesetas aisladas en la planicie amazónica del sureste colombiano, previamente sin exploraciones ornitológicas. Los hábitats del área de estudio incluyeron sabanas arbustivas y matorrales, y varios tipos de bosque. Se registraron un total de 77 especie