Large birds vanishing from West African Sahel
Vultures, Bustards & Ostrich all decliningSystematic counts thirty years apart reveal a catastrophic decline in numbers of large birds in the sub-desert region of West Africa.
Jean-Marc Thiollay travelled the same 3,700 mile routes in 1971-73 and 2004. Birds still relatively common in the 1970s –including Nubian Neotis nuba and Arabian Bustards Ardeotis arabs, Ruppell’s Griffon Gyps rueppellii and Lappet-faced Vulture Torgos tracheliotus- had entirely disappeared by 2004. Thiollay says the once widespread Ostrich Struthio camelus is now extinct west of Chad. Egyptian Vulture Neophron percnopterus numbers over a large section of the route had dropped from 75 in the early survey to just one.
“Overhunting, aggravated by overgrazing and degradation of acacia woodlands are obvious causes of the collapse of Ostrich and bustards,” he writes in a recent paper published in Bird Conservation International. The near-extinction of wild ungulates (antelopes, gazelles), intensified use of cattle, increased disturbance and poisoning of predators may have been critical in the dramatic decline of vultures.” He adds “An effective hunting ban, updates on the status of threatened species, reintroduction of Ostrich, enforcement of existing nature reserves and design of a new one in northern Mali are among the most urgent steps to take if the large birds of the vast subdesert areas of West Africa are to be conserved.” Thiollay’s results have been incorporated into recent reviews of the status of several African vulture species, leading to their likely listing by BirdLife as threatened on the forthcoming 2007 IUCN Red List. These include Ruppell’s Vulture, Egyptian Vulture, White-backed Vulture Gyps africanus and White-headed Vulture Trigonoceps occipitalis, all of which will be listed for the first time.
The ‘slow but continued’ desertification of the Sahel identified by Thiollay may have an impact on overwintering Palearctic warblers, according to the authors of the paper, How robust are Palearctic migrants to habitat loss and degradation in the Sahel? recently published in the journal Ibis . The study suggests that Common and Lesser Whitethroat and Subalpine Warbler can cope with all but the most severely degraded habitat.
But the loss of key habitats at departure points prior to spring migration, meaning that birds are unable to build up their fat reserves, may force them to depart from further south. The greater distance, added to the existing barrier of the Sahara, may lead to increased mortality on migration, and to birds arriving on their beeeding grounds late and in poor condition. The authors speculate that species dependent on pristine habitat may already have suffered from historic habitat loss.
4th July 2014