Understanding how native fauna use regrowth vegetation is critical because of increased land clearing rates and biodiversity loss, yet it remains poorly studied in Australia's semi-arid regions. The aim of this study was to use acoustic sensors to monitor avian diversity in three different age classes (new regrowth <15 years, intermediate regrowth 15–30 years, and old growth >30 years) of Acacia dominated, predominately mulga (Acacia aneura) woodlands in the Mulga Lands bioregion of south-west Queensland. We found that species richness (SR), functional diversity (FD) and phylogenetic diversity (PD) increased with time since last clearance, with statistically significant differences between new regrowth and old growth. Generalised linear models showed that tree cover was a significant predicator of SR, FD and PD. A non-metric multidimensional scaling analysis revealed that species composition was more similar within than between age classes. Each age class had unique species, yet intermediate regrowth and old growth shared a large number of species suggesting a convergence in species composition. The results of this study show that while old growth vegetation sustains the highest level of biodiversity, intermediate and new regrowth still support a range of bird species. Therefore, regrowth mulga vegetation represents important habitat for avian biodiversity in semi-arid western Queensland and should be protected. Keywords: Regrowth vegetation, Acacia woodland, Functional diversity, Species richness, Phylogenetic diversity, Acoustic monitoring