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Exploring the influence of woody vegetation connectivity on the dispersal and occurence of the Powerful Owl (Ninox strenua) within the greater Sydney Region, NSW

Warrener, Haylea (2015) Exploring the influence of woody vegetation connectivity on the dispersal and occurence of the Powerful Owl (Ninox strenua) within the greater Sydney Region, NSW. Honours thesis, Murdoch University.

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Over half of the world’s human population are living within an urban environment. As a result, urbanisation of the natural landscape has increased, involving extensive land use change, and reducing the ecological resilience of species living within these complex environments. Habitat fragmentation and isolation caused by urbanisation can reduce the landscape connectivity of the ecological network. Landscape connectivity between habitat patches is critical to sustain genetic diversity, migration and sufficient territories for many species within complex landscapes. Therefore to increase ecological resilience for species within an urban system increased effort is required on applying conservation measures to natural areas within an urban environment.

The powerful owl (Ninox strenua) is one of many species affected by increasing urbanisation and land use change. It is the largest owl species in Australia and considered vulnerable within New South Wales. It is a habitat specialist that requires high density woody vegetation cover for both foraging (main prey being arboreal marsupials) and nesting, and has an extensive home-range. Though previous research has acknowledged the effect urbanisation will have on the owl, none have previously gone into its dispersal habitat requirements and the influence landscape connectivity will have on its dispersal and occurrence throughout an urbanised system. Hence this study has investigated the influence woody vegetation connectivity has on the dispersal and occurrence of the powerful owl within the Greater Sydney Region, NSW.

The study is split into two main sections, 1) Mapping woody vegetation and 2) Analysing and evaluating landscape connectivity for the powerful owl. To generate a land cover map of the study area, high resolution aerial photographs and an object oriented analysis in combination with a classification tree was used. The land cover map produced for the study area achieved high overall classification accuracy (>85%) and for the woody vegetation class (>90%). To analyse landscape connectivity the circuit theory was used. The circuit theory takes into account all possible pathways the owl could potentially use for dispersal depending on the permeability and resistance of the landscape. Resistance layers were developed from the woody vegetation land cover map and other environmental or anthropogenic features which may facilitate or prevent dispersal. A novel approach to evaluate the connectivity surfaces with species distribution modelling was developed using presence data of powerful owl observations.

Woody vegetation connectivity was determined to have a critical effect on dispersal between habitat patches for the powerful owl. Sensitivity to disturbance of its dispersal habitat was explored, with the results indicating high sensitivity to disturbance of its dispersal habitat. Therefore increasing land use change within the Sydney area will potentially decrease the available habitat for dispersal and reduce the powerful owl’s ecological resilience to future disturbance.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Andrew, Margaret
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