This area comprises river and stream valleys in the catchment of the Ikiwe and Ngwani rivers, south of Machakos town, draining eastwards into the Athi river system. The land slopes gradually down from the Athi-Kapiti plains in the west, with an intricate system of river valleys draining between small hills. The area is semi-arid rangeland, with rainfall around 500–700 mm/year, and with low potential for agriculture. Most of the streams and rivers are seasonal, with shallow valleys. The riverbeds consist of sand and rock, with a dense band of bush and thicket (dominated by Grewia trichocarpa with Teclea and Aspilia species) for about 10 m on either side, grading into open Acacia hockii and A. xanthophloea woodland. The land is owned by a number of large ranches, including Potha, Kilima and Kimutwa, some of which have been divided up into small agricultural plots. The boundaries of the IBA are presently undefined, requiring further survey work; it includes sections of the Ikiwe, Kimutwa, Love, Makilu, Mwania, Potha, Syuuni, Wamua and Wamui rivers.
See Box and Table 2 for key species. The riverine thickets and woodland shelter the globally threatened Turdoides hindei, which has a very restricted range in central Kenya. This is one of the few sites where it is known to occur in natural habitat, although at relatively low densities (c.2 birds/km of watercourse; a total of around 60 birds in 14 groups estimated for the IBA during 2000). The babblers are commonest in the higher parts of the IBA, and are likely to occur in river valleys immediately to the south as well. The rest of the avifauna is characteristic of semi-arid areas in Kenya, with 18 species from the Somali–Masai biome, see Table 3.
Non-bird biodiversity: None known to BirdLife International.
Pressure/threats to key biodiversity
The area is mainly ranchland, but (as in other marginal land in Kenya) agriculture is increasing, with attendant destruction of habitat. Of particular concern is the subdivision of large ranches into small parcels of land that are then cleared of all natural vegetation. The riverine woodland and thickets, which provide suitable habitat for Turdoides hindei, are particularly vulnerable. Because of the babblers’ low densities, which imply large home ranges (mean territory length estimated as 1.25 km of watercourse), even moderate habitat loss might lead to serious population declines (contrast the situation in the higher rainfall areas of Kianyaga and Mukurweini, IBAs KE002 and KE006). A 2000 survey found signs of recent bush clearing and tree felling along all the watercourses surveyed. Subsistence hunting is also likely to be a threat to the babblers in this area. More survey work is needed to establish the extent of distribution of the babblers in this area, to investigate land holdings and land tenure, and to establish what conservation measures may be feasible.