Land-use intensification reduces functional diversity in birds of South American Pampas

Agricultural intensification and changes in land use have modified the complexity of habitats for birds worldwide and are considered the main causes of declining populations. The effect of these disturbances on the functional responses of the animals has become a concern of interest in ecology. The objective of this study is to determine the traits-habitat relations to quantify the variation of species traits through environmental variables representative of a gradient of land-use changes (natural habitats to agroecosystems) in the Pampa ecoregion, Argentina. We used a combination of complementary analysis techniques: RLQ and Fourth-corner. The main co-variations between traits and habitats were (1) a decrease in bird species richness as habitat transformation increased for most functional traits; (2) species associated with less transformed sites are mainly insectivorous, use shrubs for nesting and are sensitive to environmental changes; (3) sites with higher transformation were associated with large-sized species and species that build the nest in the soil; (4) absence of species sensitive to environmental changes in transformed habitats. Reducing responses from multiple species to a few functional traits and linking these traits to habitat characteristics provides an empirical, integrated, and concise framework for linking bird assemblage responses to environmental changes.