Colleywobbles is an ancestral vulture colony occurring along the cliffs of the convoluted gorge formed by the meandering mBashe River in the Idutywa District (former Transkei). The colony is situated approximately 5 km from the Colleywobbles store. This colony has been in existence since at least the 1890s. The river, which has cut a deep broad gorge, lies 300 m below the surrounding plains.
The number of Cape Vultures Gyps coprotheres at Colleywobbles has fluctuated dramatically over the past 35 years. Approximately 200 pairs inhabited the cliffs in the late 1970s. Breeding numbers increased sharply in the early 1980s, rising to more than 300 pairs, and then stabilised. The elevated total persisted until the end of the 1980s (at which time it was one of the largest colonies in the world). Numbers then decreased rapidly between 1989 and 1993, dropping from 312 to 86 breeding pairs, before fixing on lowered, more stable totals of between 90 and 60 pairs per year (1994–2003). Unfortunately, numbers between 2004 and 2010 are not known due to a gap in monitoring exercises. A total of 130–140 pairs was recorded during the 2011 breeding season and recent surveys indicate that the colony has recovered to approximately 200 breeding pairs. The vultures have nested on 13 separate cliffs. Variation in breeding performance may be due to fluctuations in environmental factors such as climate and food availability. In years of good rain, grazing is good, few stock die and fewer vultures breed. Conversely, when the rains and winter grazing are poor, many stock die, resulting in many vultures producing nestlings with a high rate of success.
A breeding pair of Martial Eagles Polemaetus bellicosus is present in the gorge and a group of Southern Ground-Hornbills Bucorvus leadbeateri frequent the area, but their nest site is not known. Black Stork Ciconia nigra may also breed in the gorge.
The IBA was declared due to the presence of a breeding colony of the globally threatened Cape Vulture. Colleywobbles supports more than 4% of the global population (200 breeding pairs) of this species and it is the largest colony in the Eastern Cape.
The river gorge and riparian vegetation may hold habitat for the endemic forest shrew Myosorex varius, southern brown egg eater Dasypeltis inornata and yellow-striped reed frog Hyperolius semidiscus. Rare plants recorded include the Grahamstown cycad Encephalartos caffer and Reynold’s aloe Aloe reynoldsii.
This colony is located in a region that has always been used by pastoralists, where stock densities are high and husbandry techniques traditional. However, trends in land-use patterns are shifting and it would appear that the vultures are responding to these changes. Until 1989, the colony had been one of the largest and most successful in southern Africa, with more than 800 birds (7% of the global population) present at any one time. The dramatic reduction in vulture numbers was attributed to improved husbandry techniques and changes in pastoralist practices, including a reduction in livestock density, which has been a result of peri-urbanisation and rural residents abandoning their traditional lifestyles.
The vultures’ continued existence at this site is under threat. At the nests, adults that are disturbed, for even short periods, may lose their eggs or nestlings for that year. The period of greatest vulnerability extends from egg-laying in April (peaking in May), through peak hatching in July, to fledging by October–November. At their nests, vultures are vulnerable to avian predators such as White-necked Raven Corvus albicollis, which are quick to take advantage of unguarded eggs or chicks when humans cause disturbance. The construction of the Mbashe River Hydropower Storage Dam may have caused the vultures to abandon the main breeding cliff. Electrical cables in the area, which span sections of the gorge, pose a threat, especially during inclement weather. Communities in the area continue to expand and grow, with new houses and villages being established throughout the landscape. A house has been built on the plateau above the colony, although this was done without the blessing of the local chief. A new road has also been constructed that passes near the colony. The Sundwana Water Supply Scheme is another development in the area that threatens to disturb the colony. The project is important to provide water to local communities, but development needs to be undertaken in a responsible manner, especially since sections of the pipeline pass within 2 km of the colony.
Although vultures face many problems at their breeding sites, they also move considerable distances inland while foraging and are exposed to a different suite of threats. Poisoned carcasses set for vermin, or more commonly by traditional practitioners for ‘muti’ (medicine), may be responsible for considerable numbers of vulture mortalities (hundreds can be killed in a single poisoning incident). The use of gin traps is also known to affect vultures, with at least one case where an adult Cape Vulture was observed with a gin trap on its leg at a colony nearby. Wind farms are another looming threat; if incorrectly located in the landscape, they may prove devastating to this population of Cape Vultures.
It is imperative that the development of wind farms and electrical infrastructure in the Eastern Cape is undertaken carefully and responsibly in order to limit the impacts on this important population of Cape Vultures. As such, BirdLife South Africa is commenting on and providing inputs into a number of developments that may impact on this colony. Monitoring of the colony continues and important research is being undertaken by UKZN, which aims to fit tracking devices on vultures at the Colleywobbles colony. The tracking information will help determine how far the vultures are foraging, at what heights and where. Efforts are also being made to spread awareness about the importance of this colony to the local community during events such as International Vulture Awareness Day.
Boshoff A, Piper S, Michael M. 2009. On the distribution and breeding status of the Cape Griffon Gyps
coprotheres in the Eastern Cape province, South Africa. Ostrich 80(2): 85–92.
Jarvis MJF, Siegfried WR, Currie MH. 1974. Conservation of the Cape Vulture in the Cape Province. South
African Journal of Wildlife Research 4: 29–34.
Vernon CJ, Boshoff AF. 1980. The Cape Vulture colony at Karnmelkspruit, Lady Grey district, Cape Province,
1978–1980. Vulture News 4: 10–12.
Vernon CJ, Piper SE. 1988. The Cape Vulture colony at Colleywobbles, Transkei in 1986 and 1987. Vulture
News 19: 24–26.
Vernon CJ, Piper SE, Schultz DM. 1982. The breeding success of the Cape Vulture at Colleywobbles, Transkei, in
1981. Vulture News 8: 26–29.
Vernon CJ, Piper SE, Schultz DM. 1983. The breeding success of the Cape Vulture at Colleywobbles, Transkei, in
1982. Vulture News 9/10: 11–13.
Vernon CJ, Piper SE, Schultz DM. 1984. Reproductive performance of the Cape Vulture at Colleywobbles, Transkei. In: Mendelsohn JM, Sapsford CW (eds), Proceedings of the Second Symposium of African Predatory Birds. Durban: Natal Bird Club. pp 109–123.