Murray River nesting tree selection by the South Australian eastern regent parrot Polytelis anthopeplus monarchoides

Author: Claire Moore

Moore, Claire, 2020 Murray River nesting tree selection by the South Australian eastern regent parrot Polytelis anthopeplus monarchoides, Flinders University, College of Science and Engineering

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The eastern regent parrot (Polytelis anthopeplus monarchoides) is a vulnerable bird sub-species in South Australia. It is found in its seasonal breeding habitat in the riparian zone of the main rivers of the Murray-Darling Basin between September and November. For the rest of the year the birds disperse throughout the Mallee woodland regions to the north and south of the Murray River making it difficult to record their behaviour and specific habitat niche. Habitat destruction and fragmentation have greatly reduced the natural nest tree availability, since the birds select nest hollows in healthy, old River Red Gums (Eucalyptus camaldulensis), a keystone species in riparian zones across Australia. Ongoing Eucalypt dieback, as a result of drought and increasing groundwater salinity causing increased stress and susceptibility to disease, is responsible for a reduction in viable mature aged River Red Gums in the breeding habitat. The effects of climate change on maximum temperatures, abnormally high seasonal rainfall, and its associated floods prevent seed germination or kill fragile seedlings before they establish stable root systems and reduce recruitment of new generations of River Red Gum to the ecosystem. Using nest location data, collected between 2003 and 2015, spatial vegetation and water datasets, satellite imagery, LiDAR elevation data, rainfall and river water level datasets, I confirmed the active selection of both healthy and drowned trees by South Australian eastern regent parrots, in contrast to the almost 100% selection of healthy trees in the eastern states. Normalised Difference Vegetation Index (NDVI) values for trees in the study area showed an increase in photosynthetic activity and crown leaf density, and hence vigour, in response to increased river water availability. This correlated with a significant nest hollow selection shift away from drowned trees to that of healthier trees in the years after 2010’s drought breaking rainfall. Previous research relates higher fecundity to nests situated in healthy tree hollows, and, in combination with the prolonged improvement in tree health in the riparian zone of the Murray River after periods of bank fill and inundation identified in this research, ecologists could argue for increased volumes and frequency of environmental flows to the South Australian Murray River from upstream regions of the Murray-Darling Basin. This would benefit not just the flora of the lower Murray River ecosystem, but also fauna species reliant on its rich native biome. The riparian zone is, however, a dynamic system and has already changed from what we consider its ‘natural’, before the Anthropocene, state. This altered ecosystem’s composition and productivity must be taken into account before making management changes that could change the current balance of the terrestrial and aquatic flora and fauna in this area.

Keywords: eastern regent parrot, polytelis anthopeplus monarchoides, ecology, geospatial information science, remote sensing, Murray River, South Australia, eucalyptus camaldulensis

Subject: Earth Sciences thesis

Thesis type: Masters
Completed: 2020
School: College of Science and Engineering
Supervisor: Professor Corey Bradshaw