Caracterización de la comunidad de aves en dos regiones biogeográficas de la Orinoquía

Abstract

The Orinoco basin extends in northern South America between Colombia and Venezuela and comprises several ecoregions. Among these, the most extensive and characteristic is the Llanos ecoregion, a complex of apparently homogeneous savannas, but which, due to geomorphological factors related to soil water retention, it has been divided into floodable and seasonal savannas. This characteristic has been used as an element to classify biogeographically the ecoregion over time and has been used to differentiate the avifauna present in one type of savanna or another. However, there are few works that study the whole llanos, and reconsider the proposed classification already given to the savanna`s districts. The present work aimed to characterize bird community composition in the seasonal savannas (north and south), and the flooded savanna, analyzing the distribution of each bird species in each type of savanna. We used ecological criteria such as the classification of species into trophic groups and discontinuities in weight categories; and determined the turnover and similarity of species in the proposed biogeographic regions. We found the composition of the avifauna in the northern seasonal savanna is substantially different from the southern seasonal savanna and the flooded savanna. Species in all three savanna types are found to be more associated with forested habitats, and it is also where more different diet types are exploited. More than half of the total species are grouped in the first three weight categories proposed which have a high diversity of body sizes, whilst the last three weight categories have little diversity and are dominated by large birds. It is necessary to use more information sources for future analyses, as well as greater specificity in the diets and habitats assessed for the species. It is proposed that for birds, this region can be considered as a single biogeographic region due to the high similarity in its composition, and that it has six species endemics to it. Northern South American savannas may be better considered as a “transitional zone” for its avifauna’s.