How the distributions of the major invasive alien bird species have changed in South Africa over two decades
Les G. UNDERHILL, Michael Brooks
Animal Demography Unit, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa
Invasive alien bird species in South Africa form two categories: widespread (Common Myna, Mallard, Common Starling, House Sparrow and Rock Dove) and localized (Chukar Partridge, Common Peacock, Rose-ringed Parakeet, Common Chaffinch and House Crow). The first and second bird atlas projects (SABAP1, 1987–1991 and SABAP2, 2007–ongoing) demonstrate the change in distributions of these species over two decades. The centre of gravity of Common Myna distribution moved from KwaZulu-Natal to Gauteng, and it has spread several hundred kilometres in all directions from there. Expansion occurred along successive centres of human habitation. Mallards were concentrated mainly in Greater Cape and the Witwatersrand in the 1980s; there are now scattered records from all provinces of South Africa, with clusters around Pietermaritzburg, East London, Port Elizabeth, Bloemfontein, Nelspruit and the Garden Route. Common Starling continued a steady northeastward expansion into the Free State, KwaZulu-Natal and Gauteng. House Sparrow was ubiquitous during the first bird atlas, and this has not changed. The abundance of Rock Dove increased with little range change.
The only feral population of Chukar Partridge is on Robben Island, where it has little impact and is not a conservation concern. Feral populations of Common Peacock are being reported by citizen scientists, from dispersed localities. Rose-ringed Parakeets increased in Gauteng and Greater Durban, with scattered records elsewhere. 120 years after its introduction, Common Chaffinch remains confined to small areas of the Cape Peninsula. House Crow populations in Cape Town and Durban have been brought under control.