Effects of environmental variation on the composition and dynamics of an arid-adapted Australian bird community

Abstract

Environmental variables influence the dynamics of bird communities. Australian arid-adapted bird communities must cope with particularly high levels of spatial and temporal variability, including inevitable but unpredictable periods of drought. Over four years, which included a severe drought and a period of above-average rainfall, I quantified the responses of a bird community in arid north-western New South Wales to regular seasonal and irregular climatic variation, especially rainfall, as well as spatial variation. I found pronounced changes in the abundance and composition of the avifauna that related to drought and, to a lesser extent, seasonal variability. Overall bird abundance and species richness declined during the drought but the magnitude and direction of population fluctuations of resident, nomadic and migratory species, different feeding groups, and individual species were not consistent. Avian densities and species richness in the study area were higher in mesic habitats associated with drainage lines than in run-off areas. The study demonstrated the importance of local habitat heterogeneity. The asynchronous species responses to a fluctuating environment indicated that drought is likely to have a differential effect on resources and that individual species respond differently to environmental variability. Effective land management and conservation of Australian arid-adapted bird communities requires an understanding of their spatial and temporal variability and dynamics at both local and regional level. A proper understanding of the variability and dynamics of the avifauna is especially important as climate change is predicted to exacerbate the climatic variability and unpredictability of the arid zone in future years.