This IBA occurs in the north-eastern part of the Eastern Cape (former Transkei). The Cape Vulture Gyps coprotheres breeding colonies are located along the cliffs cut by the river systems of the Mzimvubu, which flows into the Indian Ocean at Port St Johns, and the Mngazi, which enters the ocean 10 km further south. Three main biomes intersect the area: the Indian Ocean Coastal Belt, which runs in a strip c. 15 km wide along the coast; and a mosaic of Savanna and Grassland biomes further inland.
The area is dominated by Beaufort Sandstones of the Karoo Supergroup. This landscape of sandstone has been shaped by the rivers that have their source in the high Drakensberg escarpment and flow eastward through the Eastern Cape towards the Indian Ocean. Over millennia these rivers have gradually cut deep, meandering valleys with high and vertical cliff-faces that make suitable roosting and breeding sites for Cape Vultures. This topography also renders many areas of the Transkei inaccessible and isolated, lending a certain degree of protection to the colonies.
The extremely rural nature of the Transkei, the absence of roads and the general inaccessibility of many of the Cape Vulture breeding colonies have meant that a number of them have not been adequately monitored over the past few years. The exceptions are Colleywobbles (IBA SA088) and Mtentu and Msikaba inside the Mkhambathi Nature Reserve (IBA SA087). Surveys undertaken in the Transkei in 2012 showed that many colonies are faring better than previously recorded. Thembukazi and Ngozi in the Mzimvubu Gorge historically consisted of 43 and 72 pairs, the fifth and third most important colonies in the Transkei respectively. The Thembukazi colony has grown and currently supports 120 pairs, while the Ngozi colony has remained stable at 72 pairs. An additional colony, subsequently named Dungu, was discovered and 51 pairs were counted.
A number of historical colonies have been recorded in the Mzimvubu Gorge that are not breeding at present (Zimpholeni, Masonti and Tina River), highlighting the importance of this section of the gorge for Cape Vultures. In addition, the Mlengana colony, which is located c. 20 km to the south of the colonies in the gorge and was previously described only as a roost, has now been confirmed as a breeding colony and has approximately 180 breeding pairs.
With an estimated 423 breeding pairs, the four colonies of Thembukazi, Dungu, Ngozi and Mlengana combined represent one of the highest numbers of breeding Cape Vultures in South Africa. This compares well with the largest colonies further north and it is by far the most important known aggregation of Cape Vulture breeding sites in the southern node. The area is also important for Lanner Falcon Falco biarmicus and a number of nests are probably present along the cliffs of these gorges. Black Stork Ciconia nigra is also seen occasionally and may be breeding in the gorge.
Cape Vulture (400–450 breeding pairs and 1000–1200 individuals) is a globally threatened species. Lanner Falcon is a regionally threatened species.
The Transkei is one of the least developed and poorest regions of South Africa and the growing human population, expanding villages and planned developments are all likely to impact on Cape Vulture populations in the future. The most immediate threat to the IBA is the Eros–Vuyani power-line project, which spans a section of the Mzimvubu Gorge c. 1 km north of the Thembukazi colony. Cape Vultures in this part of the Transkei are potentially vulnerable to collisions with power-line cables due to factors such as the rugged topography, misty conditions and high winds. It has been estimated that electrocutions in high-risk areas could lead to the extinction of the species within 20–30 years, if other mortality factors are not taken into account. Therefore, the planned developments in the area mean that electrocutions and collisions with power lines could become a much greater threat in future. As South Africa's search for renewable energy sources gains momentum, another future threat to Cape Vultures in this area is the development of wind farms and their associated infrastructure. A number of wind farms have been proposed further south and if they materialise they could impact on colonies. Cape Vultures are highly mobile and any such developments in the Transkei have the potential to negatively impact on the population.
Cape Vultures may be targeted for traditional medicine. Colonies in the rural areas of the Transkei are rendered vulnerable by the number of human inhabitants there and the threat is exacerbated by the high level of poverty, which makes the possible monetary value of the vultures an obvious temptation. Gin traps are used in the Transkei and a vulture at Thembukazi has been recorded with a gin trap clamped onto its leg. It is not possible to tell whether this vulture was targeted for the traditional medicine trade, directly persecuted or a victim of a trap meant for mammalian predators, but the incident exposes the practice of gin trapping in the Transkei. It is then likely that other means of controlling predators or targeting vultures, such as by the use of poisons, also occurs. Although it's only based on anecdotal information, there is some evidence that the use of poisons (organophosphates) is steadily increasing in parts of the Transkei, not only for harvesting vultures for the traditional medicine trade, but also to protect livestock (sheep and goats) from predators and probably marauding dogs. The Cape Vultures' habit of feeding on carcasses in large numbers renders the species extremely vulnerable, with the potential that a few poisoning incidents may severely impact on this population.
The indigenous fauna has long since disappeared from the grasslands of the Transkei and has been replaced by domestic stock such as goats, cattle and sheep. The increase in stock numbers during the 20th century, coupled with poor husbandry practices and the consequent stock losses, provides the main food source for Cape Vultures in the Transkei. Stock losses are caused by a combination of factors, such as high stocking rates that lead to overgrazing and poor veld condition, which is exacerbated by years of poor rainfall and drought. In good years more stock survive and vultures may therefore undergo local population declines (probably by leaving the area), while in bad years more stock losses lead to increases in vulture numbers. Veterinary medication is also too expensive for the majority of people and livestock diseases therefore lead to an increase in stock deaths. All these factors, coupled with the geology and topography that create suitable nesting and roosting habitat, have resulted in favourable conditions for the species and its continued persistence in the area.
Recent survey efforts have highlighted the importance of these colonies, but continued annual surveys are needed to monitor population trends here and at other colonies in the Eastern Cape. These will allow conservation action to be directed at the largest core colonies in the province, as they are important for the recolonisation of smaller satellite colonies and crucial for the population to be able to absorb the impacts of stochastic events and a myriad of anthropogenic mortality factors.
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