Population ecology of the Australian White Ibis, Threskiornis molucca, in the urban environment
- Publication Type:
- Thesis
- Issue Date:
- 2009
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The Australian White Ibis (Threskiornis molucca) has dramatically increased in many
coastal urban environments, while it has decreased in large areas of its traditional
environment range in inland Australia since the 1970s. Ibis are often viewed as pests in
urban environments due to the social, economical and environmental problems they can
cause. Current, management of ibis in the urban environment predominately focuses on
restricting their breeding success, in order to reduce abundances. Management can be
costly, labour intensive and limited in its success, due to a lack of detailed knowledge of
the ecology of urban ibis. The focus of this thesis is to explore various ecological
parameters of urban ibis to increase the effectiveness of their management. Three major
breeding/roosting colonies of ibis were monitored weekly for a whole year (2005 to
2006). In addition, five major landfills for domestic waste were investigated for avian
abundances and diversity. My main aims were to provide details on the reproductive
biology, population dynamics, local and regional movements and the use of landfills by
ibis. In comparison to non-urban ibis, urban ibis have a longer breeding period, smaller
mean egg volumes and clutch sizes, but a larger range of clutch sizes. They also have a
lower hatching success, but higher reproductive success and a higher mean number of
fledglings per clutch. Each roosting/breeding and landfill site differed in their
reproductive success and/or population dynamics. Ibis used multiple sites for breeding
and feeding and were capable of moving over vast distances after they had fledged. The
ability of ibis to obtain food from anthropogenic sources appears to be one of the key
factors in the urban environment that allows them to survive and breed there.
Management plans need to consider this and their decline in their traditional
environments to be effective, without harming the overall survival of this native species.
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