The Kikuyu Escarpment forest lies 30 km north-north-west of Nairobi, and covers the eastern slopes of the escarpment from about 2,700 m in the north-west (bordering grassland at the edge of the Kinangop Plateau, IBA KE004) to around 2,050 m in the east, where it borders agricultural land. The main block of forest (sometimes called Kieni) lies either side of the Kamae–Kieni–Thika road, and is bounded to the north by the Chania river; northwards it is continuous with the forest of the southern Aberdare mountains (KE001). On the south-west, a narrow strip extends along the wall of the Rift Valley, beyond Kijabe, down to c.1,800 m. To the south, the forest has been much fragmented, and there are only scattered remnants towards its limits (including the so-called Gatamaiyu forest, near Uplands). The topography is rugged, with many steep-sided valleys containing fast-flowing permanent streams. Mixed bamboo and forest in the higher north-west sector give way below 2,400 m to broadleaved forest, with species of Ocotea, Podocarpus, Macaranga, Neoboutonia and Strombosia prominent among the trees;tree-ferns, Cyathea manniana, are also conspicuous. The escarpment strip consists of remnant Juniperus forest. The forest was logged over extensively in the 1950s and 1960s, but many parts in the main block have regenerated well. As well as several roads, a major water pipeline passes through the forest from Sasumua Dam, which supplies Nairobi with water. Judging from aerial photography, slightly more than half of the gazetted area is now closed-canopy forest, most of it in a single block in the east-central part of the reserve. There are extensive areas of plantation and cleared land on the western perimeter of this main block, and the south-western strip and southern sections are a patchy mosaic of degraded forest remnants, scrub, cultivation and plantation.
See Box and Tables 2 and 3 for key species. This forest has a rich avifauna, characteristic of the central Kenyan highlands but with a composition different to that of the nearby Aberdare mountains (IBA KE001). The forest forms the eastern limit in Kenya for Cercococcyx montanus, Ceratogymna bucinator, Zoothera gurneyi and Cinnyricinclus femoralis, and the western limit for Glaucidium tephronotum; none of these species is known to be present in the Aberdare mountains. The little-known Cinnyricinclus femoralis is most consistently found in the main block (Kieni), where it has been recorded almost year-round; it is also regularly recorded in the southern remnant forest patch, Gatamaiyu. Regionally threatened species known from the site include Bostrychia olivacea (regularly recorded and probably resident); Hieraaetus ayresii (a scarce resident); Stephanoaetus coronatus (resident in small numbers) and Glaucidium tephronotum (seemingly resident).
Non-bird biodiversity: The mammal Loxodonta africana (EN) is present in good numbers at times; this population appears to move back and forth between the Kikuyu Escarpment forest and the Aberdare mountains (IBA KE001). Three near-endemic butterflies occur, namely Charaxes nandina, Neptis kikuyuensis and N. katama. Little is known about the other biodiversity values of this site.
Pressure/threats to key biodiversity
The human pressure on this forest has been increasing steadily over time. Encroachment along the southern and western boundaries is intensifying, and at lower altitudes large parts have been destroyed. Tree poaching has become rampant in the forest bordering the main Kieni–Thika road, and in the southern remnants. It is evident that the Forest Department is able to exert very little control. The conservation value of the forest must be more widely recognized, and adequate effort put into policing and managing it—preferably as a joint operation between Forest Department and Kenya Wildlife Service under their Memorandum of Understanding. Closer involvement of the surrounding communities in forest conservation is also needed: some progress has been made in this regard by an active IBA Site Support Group, the Kijabe Environment Volunteers. This forest is close to Nairobi, easily accessible, scenically attractive, has a wide range of interesting and unusual birds, and is already a favourite site for local and foreign birdwatchers. It has excellent potential for ecotourism.