Population ecology of the Australian White Ibis, Threskiornis molucca, in the urban environment

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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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