Long-Term Declines in Functional Diversity of Amazonian Birds

Abstract

Recent discoveries of shifting baselines, which are changes in community composition over time, and declines of species diversity in wilderness areas such as the Congo, Amazon and North American deserts indicate changing diversity in undisturbed ecosystems. However, connections to how these changes impact ecological integrity are still unestablished. Here we assess the impact of shifting baselines on the functional diversity of bird communities in continuous Amazonian rainforest. We use understory bird diversity data from the Biological Dynamics of Forest Fragments Project near Manaus, Brazil to assess changes in functional diversity in primary forest over time. We use 40 years of mist-netted bird data in which birds were captured and their morphological traits were measured. We performed a principal component analysis to assess functional diversity in historic primary, modern primary, and modern disturbed forests from the 1980s to the 2010s. Results indicate that historic primary forest bird communities were significantly more diverse than modern primary or modern disturbed forest communities. As expected, modern disturbed forest is the least functionally diverse, yet even modern primary forest has lost functional diversity when compared with historic primary forest. Our data may speak to a global trend in decreasing functional diversity.