Bird Diversity of the Dry Chaco: Impacts of Land Use Change on Communities and Soundscapes

Abstract

Agricultural expansion has had negative impacts on biodiversity worldwide. Regions with high human pressure, such as the Dry Chaco in South America, require rapid studies to understand the environmental impacts and potential biodiversity loss. Ecoacoustics has been proposed as an efficient method for promoting rapid assessment of threatened regions. Using a unique field-based bird community dataset, we evaluated the performance of two commonly used acoustic indices (acoustic diversity index and acoustic complexity index) on representing avian richness in continuous forest and forest corridors of the Paraguayan Dry Chaco. Our results from manual identification of recordings showed a higher species richness in continuous forest sites (40–61 species) than in forest corridors (22–36 species). In contrast, we found no difference in acoustic indices between sites in continuous forest or corridors. Contrary to our initial expectation, there was not a significant association between acoustic indices and bird species richness when considered across all sites. However, we found a partial and weak correlation between species richness and index values for forest corridors. We argue that habitat fragmentation and edge effects might have altered the soundscape of forest corridors, favouring bird activity rather than richness, which affects the acoustic indices response. Our study suggests that acoustic indices must be considered cautiously because other variables, besides species richness, are involved in soundscape characterisation (e.g., species vocal activity).