. Bulletin of the British Ornithologists' Club. P. A. Clancey 74 Bull. 112A. Map 1. The Afrotropical Region showing the distribution of the South West Arid Zone (shaded) and adjacent environments. 1 = savanna woodlands (mainly Miombo); 2 = mixed forest bushveld and grassland-types; 3 = Cape Fynbos (macchia) and temperate forest. Variation in the South West Arid Zone The geographical variation patterns displayed by birds—their races or subspecies—in south-central and southern Africa are in the main prescribed by the disposition of the major plant communities of the South West Arid Zone,
. Bulletin of the British Ornithologists' Club. P. A. Clancey 74 Bull. 112A. Map 1. The Afrotropical Region showing the distribution of the South West Arid Zone (shaded) and adjacent environments. 1 = savanna woodlands (mainly Miombo); 2 = mixed forest bushveld and grassland-types; 3 = Cape Fynbos (macchia) and temperate forest. Variation in the South West Arid Zone The geographical variation patterns displayed by birds—their races or subspecies—in south-central and southern Africa are in the main prescribed by the disposition of the major plant communities of the South West Arid Zone, which covers rather more than 50% of the Afrotropics south of 16° S. Also influential in this regard are the woodlands of the so-called Miombo savanna juxtaposed to the north and northeast of the said zone, south to the arid valley of the Limpopo R., where the savanna type terminates, these playing a like but rather more restrictive role in the determination of racial range patterns. To the south of these dominant biotic sectors, a mosaic of veld-types, ranging from upland to even alpine grassland, bushveld and, to a limited extent, evergreen forest, both coastal and montane, exert a not indecisive influence in the marked subspeciation of many plastic species. In a recent study into endemicity levels in birds of regions south of 16° S in Africa, but mainly in the South West Arid Zone, c. 70% of the some 170 regional endemics were found to be peculiar to desertic country, a finding supporting the view that this xeric avifauna had remained largely unaffected by the climatic and biome oscillations of the Pleistocene and immediate subsequent times. In contrast, the eastern and southern veld-types present to the south of the Miombo savanna woodlands (which support an interesting range of endemics) are poorly endowed with species peculiar to them, this being the outcome un- doubtedly of the ecological history of such habitats stemming from the disturbing expansions and contract
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