Waterbirds of the Macquarie Marshes

Waterbirds of the Macquarie Marshes

Loss of flooding: declines in waterbird communities and breeding events

More than ten years have passed since researchers first identified significant declines in species richness, abundances and number of broods and nests in breeding colonies. Waterbird community composition has also changed. These changes are primarily associated with the reduction in flooding in the Macquarie Marshes. Environmental management aims to increase flooding via environmental water allocations and buying back irrigation licenses. There has not been a breeding event in the Macquarie Marshes since 2000.

Given the significant declines in waterbird diversity, abundance and breeding that have occurred with the reduction in flooding to the Macquarie Marshes, a goal of our current research is to develop a decision support system that allows managers to predict the response of waterbird communities to specified environmental allocations (quantity, timing and habitats inundated). This model will be populated by data from historical records, but also depends on ongoing research to understand; the habitats utilised by waterbirds, particularly for feeding; the food items consumed by waterbirds and; the condition and breeding success of waterbirds under different flood scenarios.

Colonial bird breeding events: food for thought

To date research on waterbirds in the Macquarie Marshes has focussed on the relationship between flooding and community structure (abundance and species richness) and the size and frequency of breeding events by colonial species (e.g. glossy ibis Plegadis falcinellus, Australian white ibis Threskiornis mollucca, straw-necked ibis Threskiornis spinicollis, intermediate egrets Egretta intermedia and rufous herons Nycticorra caledonicus). These studies provide some information on habitat associations, particularly the vegetation used at colonial breeding sites.

However there is little available information on the habitats waterbird species use for feeding, roosting and breeding, nor on the diet of waterbirds and how this might shift as floods rise, peak and fall and they gain condition before breeding. Is the arrival of different species after floods and the onset of their breeding linked to the succession of lower trophic levels (invertebrates, plants and fish)? Is there a lag in the arrival or development of breeding condition in piscivores compared to waterbirds that feed on invertebrates and plants? The planned research will address these gaps, providing information to managers on significant habitats for waterbirds within the Macquarie Marshes, their dietary needs and how the duration, timing and frequency of flooding influences availability of food items.

Waterbird movements: how far do they travel?

Waterbirds such as ibis move to arid-zone wetlands after floods, forming massive breeding colonies. They build up body resources on invertebrates, plants, frogs and fish that proliferate in recently inundated habitats. Eventually the wetlands dry and waterbirds either move away or die during the bust cycle. Unlike the annual breeding migrations in their northern hemisphere counterparts, the movements of arid-zone waterbirds both within and between the temporary wetlands that dot arid landscapes are nomadic. We don’t know how far the colonial waterbirds have travelled in between floods in the Macquarie Marshes, nor which other wetlands they depend on and whether birds breed at the same colony site throughout their lives. Our research aims to investigate movement and population connectivity in three species of ibis. This project will inform managers of the network of arid-zone wetlands and flooding patterns that must be maintained to sustain populations of ibis.

Research Program: 
Waterbirds
Research Themes: 
Rivers and Wetlands
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