Malleefowl and anthropogenic change: an integrated analysis of population trends, landscape genetics and movement ecology

Abstract

Malleefowl are iconic Australian birds that build large mounds to incubate their eggs using external sources of heat. Malleefowl numbers have drastically decreased since European settlement and they are now a nationally threatened species. Their decline is caused by habitat loss and fragmentation; predation by introduced species; inappropriate fire regimes and competition and habitat degradation through overabundant native and introduced herbivores. Climate change is expected to exacerbate these pressures by leading to more frequent and longer periods of high temperatures, reduced precipitation and increased frequency and intensity of wildfires. This thesis aimed to investigate how historic and recent habitat fragmentation and climatic variables influenced Malleefowl on the Eyre Peninsula and how climate change may exacerbate future impacts. The objectives were to assess population trends, investigate landscape genetics, study movement patterns and the influence of habitat variables. These objectives were addressed through a multidisciplinary approach to study discrete Malleefowl populations at study sites located on the Eyre Peninsula in South Australia. To assess population trends and the influence of environmental factors, 24 years of mound-based breeding activity data were modelled. Results showed a widespread and significant decline in Malleefowl breeding activity during the study period, driven by changes in vegetation cover and reduction in soil moisture. High throughput DNA sequencing was used to investigate past dispersal patterns and the effects of recent anthropogenic land cover changes. The results indicate that Malleefowl population structure on the Eyre Peninsula was not homogenous and that habitat fragmentation with subsequent isolation has caused the differentiation of at least two distinct populations. Further, there was preliminary genetic evidence of female dispersal. Solar-powered GPS trackers were used to determine individual movement patterns and the effects of habitat fragmentation and environmental factors. Malleefowl movement was tightly associated with breeding status, with breeding birds staying close to the mound and non-breeding birds disassociating from the mound and moving long distances. Movement was also influenced by patch size and fragmentation, with non-breeding birds in large patches moving further than birds in smaller patches, but Malleefowl were able to persist in small patches and breed successfully for many years. Malleefowl moved less with increasing temperatures. Malleefowl did not use cropping land and they avoided crossing open paddocks. Malleefowl also had high mortality rates with over 66% of tracked individuals dying within a year of trapping, mostly from cat and fox predation. Vegetation surveys were combined with GPS tracking data to investigate whether Malleefowl movement was influenced by vegetation composition or cover. Results indicate that Malleefowl seek out micropatches of tall mallee stands within a mature Eucalyptus matrix – likely as refuges from heat and predators – and that movement is less driven by a preference for plant species, reflecting the fact that Malleefowl have a highly variable and opportunistic diet. In summary, this thesis shows how anthropogenic habitat alteration and changing environmental conditions have reduced breeding activity, restricted movement, dispersal and gene flow of Malleefowl populations on the Eyre Peninsula, with noticeable long-term genetic effects. Further, we can expect climate change to exacerbate all existing pressures and possibly drive Malleefowl closer to extinction. This research provides valuable new information about Malleefowl movement ecology which supports increased efforts to protect even small patches of native vegetation in agricultural matrices and the creation of habitat corridors between patches, as well as the improvements of matrix habitat, to facilitate between-patch movement. This, combined with continued and improved predator-control efforts, may enhance the conditions for future survival of Malleefowl populations, and support biodiversity in general, which is vital when faced with increasing climate change pressures.