Invasion of Psittacula krameri in Gauteng, South Africa: are other birds impacted?

Abstract

Anthropogenic activities have resulted in the dispersal of many species beyond their natural range and there is ongoing concern over their impacts on native ecosystems. However, these interactions are hard to disentangle from the effect of human-driven habitat alterations. Psittacula krameri (Rose-ringed Parakeet) is a recent coloniser in the heavily modified province of Gauteng, South Africa. We analysed this species across the region to assess its colonising status and potential impact to-date. Using presence data from the Second Southern African Bird Atlas Project (SABAP2) for the parakeet as well as a selected subgroup of 49 other bird species (potential competitor and control species), occurrence patterns in the province for the period of July 2007–June 2017 were determined. Reporting rates for species in SABAP2 were used as a proxy for relative abundance. While the parakeet’s range and abundance increased significantly, only two species showed a significant reporting rate decline in areas of parakeet occurrence. These declines persisted across a wider area where parakeets were not found. Broader-scale Gauteng reporting rate trends, not replicated in the parakeet range, were noted for nine other species, suggesting that the changing avifaunal composition in the anthropogenically transformed Gauteng may instead be driven by habitat change. A large proportion of species can be considered as newcomers to this largely modified ecosystem, and the possibility of vacant niche filling is strong in this case. In the context of novel ecosystems such as urban areas, a terminology based on adaptability rather than nativity status is encouraged.