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THE SPREAD OF A HIGHLY SUCCESSFUL ALIEN INVASIVE BIRD SPECIES

Common (Indian) Mynas (Acridotheres tristis) have been introduced to many areas of the world outside of their native Asian range, either accidentally (e.g. escaped cage birds) or deliberately (e.g. for pest control). The birds were first introduced to South Africa in 1902 and in the last century have expanded markedly northwards and eastwards and have now reached Botswana , Zimbabwe and Mozambique .

In view of the possible negative effects that the Common Myna poses to indigenous avian communities, it is necessary to understand its position in urban and semi-natural avian communities, its distribution, and the factors that determine its distribution. At the regional scale, there is no empirical information on the extent to which a relationship exists between the distribution range of this bird and human population density, degree of land transformation and location of protected areas.

Common (Indian) Mynas ( Acridotheres tristis)

In collaboration with Derick Peacock, an Honours student from the University of Pretoria , fine-scale satellite imagery and point-count censuses were used to identify (i) land-cover variables that define prime myna habitat, and (ii) bird species that could be threatened by the Common Myna's presence.

The study found that mynas are strongly attracted to areas severely altered by urbanisation, where mynas potentially compete with a relatively species-poor avian community, many of which are also alien. Based on myna density estimates, there is a ratio of almost one myna to every two people inhabiting the City of Tshwane Metropolitan Municipality.

At the regional scale, Common Mynas were found more frequently than expected by chance in areas with greater human population numbers and land transformation values. With regards to the spatial arrangement of protected areas, the study showed that, although there is some overlap, the Common Myna distribution is not closely tied to the existing conservation network. This research is being led by Dr Berndt J. van Rensburg (C·I·B core team member at University of Pretoria) and Dr Mark Robertson (University of Pretoria).