NEWS FROM THE PERCY FITZPATRICK INSTITUTE and land-use in the southern Kalahari

and-use practices frequently change habitat structure, thereby influenc- L ing the structure of commu- nities. In the southern Kalahari, heavy grazing coinciding with consecutive years of good rainfall leads to bush thickening, whereby woody species such as black-thorn Acacia mellifera, velvet raisin Grewia flava and driedoring 12 Rhigozum trichotomum suppress the ONNO HUYSER growth of grasses and herbs. In the 1980s, bush-thickened areas covered approximately 2.5 million hectares in the South African section of the Kalahari, an area larger than the Kruger National Park. In and the situation is as bad, if not worse. In an attempt to tackle the problem, in the early 1980s bush-thickened areas 3 4 in the South African Kalahari were C. SEYMOUR (3) cleared using the arboricide (-killing Pristine Kalahari woodland (1) degrades to bushy thicket (2) when overgrazed. Application of chemical) Tebuthiuron. Initially this arboricides leaves a desolate landscape of dead (3), almost devoid of birds. By the time the worked well, killing only target species. trees themselves are removed for firewood (4), the landscape has been totally transformed, as Within a few years however, non-target has the associated bird community. species, including camelthorn Acacia eri- oloba, the largest tree in the region, also Species that forage on bark, hawk prey species. Removal of large trees resulted started to die. This habitat degradation aerially or ‘perch and swoop’ also in a further decrease in the number of is exacerbated by urban demand for decrease in bush-thickened areas, as bird species, with bark-foragers such as camelthorn as braai wood; on some do seed-eaters. In the Kimberley area of Golden-tailed Campethera properties, up to 60 tonnes of wood is the Kalahari, for example, Lesser Grey abingoni and Common removed monthly. Shrike Lanius minor and Common Fiscal Rhinopomastus cyanomelas, and hole- Colleen Seymour, a Fitztitute doctoral L. collaris almost disappeared. So which nesters such as Ashy cinerascens student, investigated the effects of bush species do well in bush-thickened areas? and Acacia Pied Barbet leu- thickening, arboricide spraying and Colleen found that these were mostly comelas being the most severely affected. large tree removal on Kalahari birds. small bird species, insectivores, gleaners, Because of the difficulties of farming The study focused on identifying the and cup and ball nesters, including in such a variable and harsh environ- biological characteristics of birds most Kalahari Scrub-Robin Cercotrichas paena ment, it is understandable that land- likely to be affected. Interestingly, bush- and Chestnut-vented Tit-babbler owners may resort to spraying and tree thickened areas did not differ signi- Parisoma subcaeruleum. There was also removal for commercial sale. However, ficantly from pristine areas in either an increase in the number of birds with alternatives need to be considered, total bird abundance or total number yellow, orange or red in their plumage; because not only are the impacts on of species. However, species composi- that is, species with bright, highly birds, and presumably other wildlife tion did differ between the two habitats, visible coloration. Birds that combine (as well as water and nutrient cycles) the bush-thickened areas supporting these attributes, such as Yellow-bellied considerable, but the area affected is fewer hole-, ground- and tunnel- Eremomela Eremomela icteropygialis and enormous. nesters. Impacted species included Cape Penduline-Tit Anthoscopus minutus, This study was funded by the German Eastern Clapper Lark Mirafra fasciolata thrive in bush-thickened environments. Ministerium für Bildung und Wissenschaft, and Ant-eating Chat Myrmecocichla Areas treated with arboricides had far BIOTA Southern , and the National formicivora. fewer birds as well as far fewer bird Research Foundation.

Visit the FitzPatrick website: http://www.fitzpatrick.uct.ac.za Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, . Tel. (021) 650 3290; fax (021) 650 3295; e-mail [email protected]

APRIL/MAY 2005 PERCY FITZPATRICK INSTITUTE 21