Patterns of taxonomic and functional diversity of birds in riparian forests with natural and agricultural matrices in the Argentine Austral Yungas

Abstract

Birds represent a diverse group that responds markedly to changes in the structural characteristics of their habitat. In this study, we evaluated the response of birds to changes generated by the landscape anthropization in riparian forests of the Austral Yungas. These forests are vulnerable to unnatural disturbances and are within an ecoregion that has a high risk of degradation due to historical and current land use changes. Based on the hypothesis of environmental heterogeneity, we investigated how taxonomic and functional diversity of bird assemblages were related to structural variables of riparian forests and the matrix type (native forest or crop) in which they are immersed. Through direct observations and captures using mist-nets, we determined bird species richness and abundance, and measured quantitative functional traits in eight riparian forests in the piedmont forest of the Austral Yungas in Argentina. We also calculated four functional diversity indexes and measured structural variables of the forests. Bird species occupied a functional space in a uniform way, particularly in riparian forests immersed in a crop matrix, which tend to be structurally homogeneous; that is, in riparian forests where there is an increase in disturbances, the Functional Evenness values are higher. Changes in land use determine changes in the composition of bird assemblages and may result in the non-random loss of functionally unique species.