It covers an area at least 12,000 hactares with an altitude of 1,200 - 1,600 meters. Kianyaga comprises a landscape of ridges and steep-sided valleys on the south-eastern slopes of Mount Kenya. These valleys often hold small, swampy streams, which drain into tributaries of the Tana river. The area is entirely settled and cultivated, predominantly with coffee, maize, arrowroot and other crops are grown in the valleys. The remaining small areas of natural wetland include plants such as Triumfetta tomentosa, Croton macrostachyus and Cyperus rotundus. Scattered indigenous trees, mainly Prunus africana, Ficus natalensis and Millettia dura, still remain. Thickets of the exotic Lantana camara occur at the edges of cultivation, in fallow farmland and untended coffee plantations, and in inaccessible parts of the valleys.

The diversity of other birds is low at 94 species, all characteristic of disturbed habitats in the central highlands. However, this is a centre of abundance for the threatened, restrictedrange Turdoides hindei, a species endemic to central Kenya. Groups of this babbler occupy many of the valleys and swamps, with an estimated total population size of 250 birds in 66 groups (3.1 birds/ kilometers of watercourse).