Summer of basin-wide colonial waterbird breeding extends to the Macquarie
Burrendong Dam began spilling in spring 2021 following strong catchment rainfall. Burrendong Dam has space for flood mitigation, which is managed by Water NSW to minimise the risk of flooding and, where relevant, to fulfil environmental outcomes.
The same rainfall created conditions for a range of colonial waterbirds to start breeding in the Macquarie Marshes. This was a critical season for breeding as long-term aerial surveys indicated ongoing population decline of many waterbird species. The last large-scale colonial breeding events in the Macquarie Marshes were in 2011 and 2016.
Large-scale waterbird colonies were recorded across all 3 subsystems of the Marshes, including 3 ibis colonies of 30,000 to 40,000 nests each, and several large-scale (5,000+ nest) night heron and egret colonies in river red gum forests. Many smaller colonies were also recorded.
We assisted Water NSW in operational planning for the Burrendong flood mitigation zone. Monitoring information was supplied to inform water level targets within the Marshes, allowing the dam releases to support colonial waterbirds to complete their breeding in autumn 2022.
We also conducted ground and aerial monitoring during the breeding events in collaboration with the University of NSW and CSIRO. This work indicated the colonies were quite successful, with all known large-scale colonies completing their life cycle. CSIRO tracking indicated some breeding adult birds foraged in the lower Castlereagh catchment, some 80 kilometres away. A number of birds were caught and tagged for post-colony satellite tracking by CSIRO.
We thank the land managers of the Macquarie Marshes, the CEWH for their monitoring resourcing assistance, monitoring partners University of NSW and CSIRO, and Water NSW for working with us to support this important breeding event.