Maintaining waterbird populations in the Murray-Darling Basin is a major management and investment focus. To support this aim, inundating floodplains to provide breeding, foraging and roosting habitat is a regular target outcome in the delivery of environmental water. The Basin covers over a million square kilometres and contains thousands of wetlands, and waterbirds are highly mobile. Therefore, quantifying waterbird responses to inundation at this scale to promote more effective water management is challenging. There are significant limitations in the scale and suitability of available waterbird and inundation data that stem from technical and logistical challenges to collecting and assembling both types of data.
We therefore took a multi-faceted approach to explore new ways of addressing the challenge of quantifying relationships between waterbird abundance and species richness to floodplain inundation at a large scale. First, we analysed data from a new survey program implemented at key wetlands and designed to inform this question. Results from generalised linear mixed modelling showed a significant positive relationship between waterbird abundance and site-based inundation in the 2024-25 water year. Second, we analysed data from a newly assembled large-scale dataset of waterbird presence and a map of annual inundation of Commonwealth environmental water. Results showed that locations that were influenced by Commonwealth environmental water had higher rarefied richness than those that did not, and there was a positive relationship between the extent of inundation from Commonwealth environmental water and species richness in the 24-25 water year. Finally, we trialled a BACI-type analysis to explore waterbird species richness response to watering events, which showed significant promise as a viable analysis approach. These developments form a strong foundational basis from which to build quantitative, multi-year analyses that will significantly improve our understanding of the relationship between waterbird outcomes and inundation (including from environmental water) in the Basin.