Faculty of Natural and Agricultural Sciences
School of Biological Sciences
Department of Zoology and Entomology
Selected Highlights from Research Findings
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.
In collaboration with Honours student Derick Peacock, we used fine scale satellite imagery and avian point count censuses to identify (i) land-cover variables that constitute prime myna habitat, and (ii) bird species that could be threatened by the myna’s presence.
The study found that mynas are strongly attracted to areas severely altered by urbanisation (e.g. city centre), where they 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 regard 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
Contact person: Dr B Janse van Rensburg.
Nectar is much more than sugar water. We are studying nectar feeding in sunbirds and other passerine birds, and paying particular attention to non-sugar constituents of the nectar. Amino acids occur in some bird nectars at quite high concentrations (up to 100 mM), and while non-essential amino acids are the most abundant, all the essential amino acids are also present.
In the laboratory, sunbirds reject sugar solutions containing amino acids if the concentrations are too high. However, the nectars of sunbird flowers are energetically dilute and sunbirds must drink large volumes to meet their energy requirements, so their nitrogen intake will not be negligible.
Floral nectars also contain sodium and potassium ions, and we have recently found that the sodium is especially important for birds feeding on the most dilute nectars: otherwise their kidneys are unable to recover enough sodium from the enormous volumes of urine.
The large inflorescences of Aloe marlothii, which flowers on northern hillsides during dry winters, are visited by few sunbirds but by a multitude of other bird species, none of them specialised nectar feeders. For these birds the nectar is both water and energy source and supplements other dietary components such as seeds
Contact person: Prof SW Nicolson.
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.
In collaboration with Honours student Derick Peacock, we used fine scale satellite imagery and avian point count censuses to identify (i) land-cover variables that constitute prime myna habitat, and (ii) bird species that could be threatened by the myna’s presence.
The study found that mynas are strongly attracted to areas severely altered by urbanisation (e.g. city centre), where they 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 regard 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
Contact person: Dr MP Robertson.
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