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Bird assemblages of Australia's largest east-coast wetland complex: environmental determinants of spatial and temporal distribution

Richard Pearson , Belinda Zunker-Mellick, Jacqueline Nolen

Abstract

Context: The extensive Burdekin-Townsville seasonal freshwater wetlands in the Queensland tropics (adjacent to an intertidal Ramsar site) support important waterbird assemblages within and downstream of the Burdekin-Haughton irrigation area. Little evidence is available of the environmental drivers of the assemblages, possibly including the extensive development of irrigated agriculture,. Aims: We described the composition and dynamics of freshwater assemblages to identify their environmental determinants and underpin conservation management. Methods: We used up to four decades’ records of waterbird assemblages. We collected biophysical data from 57 sites and water-quality data for 32 sites and predicted that the measured variables would determine assemblage composition. Key results: Altogether, 101 waterbird and shorebird species were recorded. Individual samples were strongly nested. Species richness increased with area, but density decreased. Richness had a humped relationship with water depth. Linear modelling identified mostly weak relationships between species, assemblages and environmental variables (e.g., nutrients). Abundances mostly increased through the dry season, but irrigation tailwater reduced seasonal variation in some wetlands. There was no apparent change in common species’ assemblages over four decades. Conclusions: The wetlands provide extensive and diverse habitats for rich waterbird assemblages, despite impacts of agricultural development. Impacts on waterbirds appear to be buffered by the extent and complexity of the wetland mosaic, including modified wetlands. Implications: Holistic, active management is required to ensure the long-term conservation of habitats for waterbirds and other biota. Inclusion of freshwater wetlands in the Ramsar site would be beneficial.

PC24030  Accepted 19 November 2024

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