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Variation in bird diversity with habitat quality in Hobart, Tasmania


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Heileman, M 2007 , 'Variation in bird diversity with habitat quality in Hobart, Tasmania', Coursework Master thesis, University of Tasmania.

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As urban areas expand throughout the world, they have a number of negative
impacts on native wildlife. Birds are a useful indicator group for measuring such
impacts. This study aims to assess urban impacts on birds, assessing bird diversity,
abundance and species composition across a range of urban environments, from the city
centre to native vegetation remnants. Particular emphasis is placed on the potential
conservation value of urban parks and native vegetation remnants, and on habitat
quality factors determining variation in native bird diversity, including measures of
vegetation, invertebrates and human disturbance levels. It is hypothesized that native
bird diversity and abundance will decrease with decreasing habitat quality.
Birds were surveyed six times over nine weeks in summer and autumn, 2007, in
Hobart, Tasmania, using the rolling point count method. Surveys took place at five
urban sites including Hobart city centre, a residential area (Sandy Bay), three native
vegetation remnants (Queen's Domain, Bicentennial Park and Knocklotfy Reserve).
Data was also collected on plant species, vegetation structure, invertebrate species on
plants and human disturbance including percent cover of built environment, vehicle
traffic, pedestrian traffic and noise levels at the point counts. Statistical methods used
included bar charts of species richness and abundance, ordinations of species, species
classifications, one tailed t-tests and correlation analysis between habitat variables and
bird species richness. PC Ord 4 was used for ordinations, Minitab for the correlation
analysis and Excel for all other analyses.
Results of this study show that native bird species richness and abundance is
significantly higher in the native vegetation remnant sites than in the urban sites, urban
parks have more native species than surrounding streets and the city centre has fewer
native bird species than the residential site. Abundance was highest at Knocklofty,
followed by the two urban sites but the majority of the urban abundance composed of
introduced species. Bird species composition was similar in the native sites and in the
urban sites but native and urban sites were very different from each other. The same was
found to be true in the case of plants. Also, native birds correlated positively with native
plants, vegetation cover and complexity. Likewise, introduced birds correlated
positively with introduced plants. Bird behavioural interactions were found to reinforce
these trends. Invertebrate species richness and abundance was not significantly different
at urban sites than at native sites. Invertebrate species composition did vary, however, loosely on the basis of site and plant species they were found on. This and seasonal
variation in abundance of invertebrates could have important implications for birds.
Human disturbance variables were significantly negatively correlated with most native
bird species, and positively correlated with introduced species. Season also played a role
in variations in native bird species richness and abundance, as many species favoured
summer, particularly summer migrants, and a few favoured autumn or were season
The results of this and other studies suggest that the maintenance of native
vegetation remnants is essential to maintaining a high native bird species richness and
abundance, but that urban parks and gardens improve landscape connectivity and can
act as supplementary resources for native birds, especially during winter. Also, both
habitat quantity and quality are important for the long term sustenance of diverse native
bird communities in an urban setting.

Item Type: Thesis - Coursework Master
Authors/Creators:Heileman, M
Copyright Holders: The Author
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Copyright 2007 the Author

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