Date of Award

2013

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Communications and Arts

Faculty

Education and Arts

First Advisor

Dr Patrick Armstrong

Abstract

The Southwest region of Western Australia is a recognised ‘biodiversity hotspot’, as it possesses high levels of biodiversity and endemism; it also holds a number of species threatened by habitat loss. The arrival of Europeans in the region wrought major changes on the natural landscape. Extensive tracts of bushland were cleared for housing, infrastructure, forestry, farming, and mining. Another challenge to regional biodiversity was the spread of exotic plants and animals (including birds); the latter provide the focus for the present study. The research examines four bird species that colonised the Southwest region following European settlement: Australian White Ibis (Threskiornis molucca); Spotted Dove (Streptopelia chinensis); Laughing Dove (S. senegalensis) and Laughing Kookaburra (Dacelo novaeguineae). The study examines how the feeding and breeding ecology of the species influenced colonisation success and dispersal, specifically in relation to geographic i.e. climate and anthropogenic (e.g. landuse) features of the region. Each of these species has been identified as a ‘generalist’ feeder, with flexible ecological needs. The species have been able to adapt their food preferences and way of life to living in proximity to human settlements. It appears that each utilised resources made available through human endeavour and activities. It appears that the most rapid spread of invaders occurs in areas of modified habitat, in which the proportion covered by natural ecosystems has declined: i.e. in urban areas, pastoral lands and agricultural areas, although conserved natural habitats have also been invaded. The results indicate clear associations between the extent of colonisation success in the first wave of dispersal, and anthropogenic phenomena. Such is evidenced by the range expansion of Australian White Ibis into coastal urban areas, within which foraging success is assisted by access to alternative food sources and roost sites; whereas the species’ movement inland is linked to habitats associated with dairy farming and cattle production. However, the biology of each species and the extent of its ecological flexibility are also influencing factors, as attested by the wide-spread dispersal of the Laughing Kookaburra throughout the study area. This species possesses physiological features that give it an energy advantage over other species and it possesses social behaviours which offer further ecological advantages. Although it is a combination of factors: the biological attributes of the species (which define the ecological aspects of its survival), the geographical features of the adopted landscape, and the impact of human imprint upon that landscape that affect the process of biological invasion, the outcomes are specific to each species. This is shown in the development of markedly different patterns of dispersal, as between the two Streptopelia doves, despite their arriving in the study area under (approximately) the same conditions, and sharing almost identical ecological profiles. As, despite being released into rural areas, the Spotted Dove retained a localised, mainly urban, population, whilst the Laughing Dove has become spread across both urban and rural environments. This may be due to differences in the ability of each species to tolerate dryland conditions, which appear to better suit the Laughing Dove, perhaps due to similarities in climate between the adopted range and the areas from which it originates. It is felt that the study has augmented existing knowledge of biological invasion events in the study area, and contributed towards a greater understanding of biological invasion phenomena, particularly those associated with wheat production, processing, and transport. The study design incorporated Geographic Information Systems (GIS) technology as a means of processing large volumes of historical data. The methodology developed for the study could be adapted to other species, regions and eras, provided sufficient data are available. It produces temporal snapshots of changes in distributions, which can be considered in relation to changes in climate conditions and landuse practices.

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