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The
three crane species of South and Southern Africa by Janis
O’Grady The Wattled Crane (Grus carunculatus) The claim to fame of the Wattled Crane is that not only is it the largest and rarest of Africa's cranes but also the most wetland-dependant crane on Earth. Restricted to the African continent, the main subpopulation is found in Zimbabwe, Botswana, Angola, Zaire, Tanzania and Zambia while the other two subpopulations reside in Ethiopa and South Africa respectively. In South Africa, the Wattled Crane range is vastly restricted today from the days when the crane soared over all four "old" provinces – now it is only found concentrated in the higher rainfall regions of the country, in the midlands and southern parts of KwaZulu-Natal, and the Mpumalanga Highlands. Small numbers are still found in the Wakkerstroom, Eastern Cape (three breeding pairs) and North-eastern Free State (two pairs). Biological needs These stately birds are good environmental indicators of the health of a wetland, a habitat on which farming communities generally rely for a healthy water supply for agricultural and household purposes. In South Africa, cranes should revered as ambassadors for the two most vital ecosystems we have – wetlands and grasslands which make up our catchment areas. The people of South Africa are as dependent upon the good management of these "water factories" as the cranes that inhabit them but hundreds of wetlands have already been drained or degraded while the majority of our grassland biome has been modified for agriculture, forestry and tourism development. Most Wattled Cranes live throughout the year in pairs which occupy large territories on undisturbed wetlands. Here, they breed and forage, feeding mainly on the bulbs and rhizomes of submerged sedges and wetland plants. They also have a taste for grain, grass seeds and insects when ranging across open, dry habitats surrounding their marshy homes. Due to their dependence on wetlands, they are extremely sensitive to disturbance and may abandon their breeding area if disturbance is ongoing. Intensified agriculture, dam construction and industrialisation are the main causes of wetland loss in South Africa, and the surrounding grasslands – as important to this rare crane as the wetland nesting area – are being radically transformed for exotic timber plantations, potatoes, rye grass, maize and other monocultures (McCann 2000). Breeding Wattled Cranes only reach maturity at about seven to eight years of age and, in KwaZulu-Natal, they spend these adolescent years in a non-breeding, floater flock learning the traditional feeding areas within their range, and where the worst threats abound. The peak of their breeding season is mid-winter – probably due to the threat of hailstorms and nest-flooding in wetlands during summer – and while birds have been known to nest during all months of the year, they are usually hatching chicks between the months of May and August. Nest building forms part of the exuberant courtship ritual with much dancing and throwing of reed material that forms the bulk of the large nest, built in the wetland and surrounded by a moat of water – probably as a decoy for predators and fires. Pairs usually only lay 1 or 2 eggs in a clutch, the lowest of any crane, but only one chick is ever raised. The second egg acts as an "insurance policy" against the first not hatching (McCann 2000). When they fledge at about 3 – 4 months of age, the chicks remain with their parents for nearly a year, after which they are taken to the non-breeding floater flock or left to find their own way. Threats As already mentioned, the Wattled Crane is threatened with habitat loss (wetlands and grasslands) as well as management of these ecosystems: burning of firebreaks and grazing methods have to be properly controlled by the farmer if Wattled Cranes are resident on his land. Powerline collisions are another prevalent threat to the large bird since the 11 and 22 kV lines are often located within the territories between foraging and roosting sites. Recently the human threat has intensified and many Wattled Crane chicks and eggs are being taken out of the wild for the international bird trade. Poisoning is another problem faced by this rare crane and whether deliberate for food or unintentional when secondary, this threat requires strict management of the use of agrochemicals. Responses to threats With only some 234 Wattled Cranes left in South Africa today, conservationists are increasing their efforts to understand the bird better, both biologically and geographically. The most significant reduction in the population occurred between 1986 and 1994 – it is now classified as "critically endangered" in the Red Data listings. In 2000, the South African Crane Working Group (SACWG) held the Wattled Crane Population and Habitat Viability Assessment in Wakkerstroom, inviting crane, conservation and environmental specialists from around the country to participate in this three-day workshop. The purpose of a PHVA is to help managers understand the risks facing small populations, to identify the relative importance of the factors that put a small population at risk, and to evaluate the effectiveness of various management strategies. When populations get very small, evolutionary and ecological processes change (Lacy et al 1992). The outcomes of the Wattled Crane PHVA highlighted to the SACWG where they need to put their energies to "save" the Wattled Crane from becoming extinct. The top five criteria are: a) Develop an accurate description of what constitutes viable Wattled Crane habitat, including breeding and foraging habitat with correct nutrition b) Develop an action plan to reduce the risk at high risk sites to ensure that they are not lost c) Determine the biophysical characteristics of Wattled Crane nest sites d) Survey and classify all wetlands that fall within viable Wattled Crane distribution, according to their suitability and risk e) Gain a clear understanding of how fast wetlands are lost in total and in terms of Wattled Crane requirements To date, these outcomes are being incorporated into projects and carried out by SACWG fieldworkers and other specialists in the wetland and environmental field. In addition, fieldworkers are participating in a national education and awareness programme aimed at farm workers (the eyes and ears of the land), school pupils and teachers, other groups and networks and the general public. Regular media articles and marketing drives assist with funding measures and fieldwork includes monitoring, population management, threat reduction and more. Farmers are one of the main "target groups" as very few cranes breed in reserves – most are found on private land and it is up to the landowners (our 'crane custodians') now to decide whether these birds have a future or not. "These big wetland cranes share significant behavioural traits such as high-pitched calls, idiosyncratic bill movements and (in the males) a rapid uncoiling of the neck at the outset of the unison call that is seen in no other species; there are also unusual anatomical and skeletal features, such as a strip of bare comb that extends along a groove along the upper mandible and an atypical single-looped trachea that intrudes only slightly into the sternum" (Matthiessen 2003).
The three crane species of South and Southern Africa |
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