Invasion by Black Sparrowhawks
Rob Little and Rene Navarro recently published a paper on the implications of geographical range changes and resultant sympatry for three Accipiter hawks on the Cape Peninsula, South Africa. They found that the Black Sparrowhawk has become more abundant and that the African Goshawk and the historically local Rufous-breasted Sparrowhawk have declined since the invasion of the Cape Peninsula by Black Sparrowhawks suggesting that the latter species has out competed and at least partially displaced the other two species. Although that may be the case, since the three species seem to have relatively stabilised population sizes after 2010 this could suggest progressive resource partitioning with a level of ecological isolation following the initial dominance interactions. Since the westward expansion of the ranges of the Black Sparrowhawk and the African Goshawk along the southern coastal region of South Africa were most likely facilitated by anthropogenic alteration of the landscape ultimately leading to the sympatry of the three species on the Cape Peninsula, they suggest that this is therefore a case of indirect human caused alien invasion.