This is an area where a mosaic of undifferentiated montane plant communities occurs in deep humid ravines on the escarpment, with dry woodland below the scarp. No specific climatic data are available for the area, but Hall (1960b) gives rainfall data for Ganda, 88 km (55 miles) north-east of the site and considerably higher in elevation, as almost 1,600 mm per year. There is a steep rainfall gradient down the escarpment and the higher elevations of the site are in the 800 mm isohyet, while the rainfall in the lower elevations may be less than 400 mm per year. Tree genera include Podocarpus, Pittosporum, Olea and Ilex on the higher elevations, with Adansonia digitata and Acacia welwitschii dry woodland with thickets at the bottom of the escarpment.
See Box and Tables 2 and 3 for key species. The escarpment forests lie between the dry woodlands of the coastal plain and the miombo woodlands of the interior plateau, and are an effective barrier to both, allowing a fairly unique avifauna to develop (Hall 1960a). The avifauna of the site is almost certainly richer than suggested by the list of 99 collected species. The site supports three resident species of global conservation concern—the rare Macrosphenus pulitzeri has been collected at two sites at Chongoroi (Chongoroi itself, the type-locality, and Camacuio (Pinto 1962); close to Chongoroi, but precise locality not found), while Francolinus griseostriatus is uncommon, and Estrilda thomensis frequent. The site is important for several species of the Guinea–Congo Forests biome that reach their southern distributional limits here. In addition, two species of the Zambezian biome and two Kalahari–Highveld species have been recorded. The area has a diversity of other forest and savanna species, including birds not well known elsewhere (e.g. Telecanthura ussheri and Platysteira concreta). The dry woodlands below the escarpment are about the northern limit for some birds of the southern semi-arid woodlands (e.g. Pycnonotus nigricans), while the forest patches are about the southern limit for Tauraco erythrolophus, Gymnobucco calvus, Smithornis capensis, Cercotrichas leucosticta, Nectarinia superba, Ploceus bicolor, Lagonosticta landanae and Serinus capistratus. Chongoroi is also the southern limit for some species of the moist savannas (e.g. Campephaga quiscalina).
Non-bird biodiversity: No list of mammals is available for the area, but there are sight records of Panthera leo (VU) (Cabral and Simões 1988). As for the avifauna, the Escarpment Zone allows the southward extension of range by some equatorial rodents, and the northward extension of range by species typical of more arid habitats, such as Rhabdomys pumilio (DD), some of them represented by well-defined subspecies (Cabral 1966).
Pressure/threats to key biodiversity
The protection of samples of the biogeographically important escarpment forests is desirable for several reasons, not least for their continued survival in the face of pressure from subsistence farmers (Huntley (1974a). A protected area of c.20 km² was recommended by Huntley (1974b), but was not established (Huntley and Matos 1994). Threats to the avifauna include clearing of vegetation for subsistence farming and frequent fires through uncontrolled slash-and-burn cultivation. The steepness of the escarpment, and the difficulty of cultivating crops in deep humid ravines may provide some protection for the avifauna, but this will be a selected subset of birds and not necessarily a representative sample of escarpment bird species.
BirdLife International (2020) Important Bird Areas factsheet: Chongoroi. Downloaded from
http://www.birdlife.org on 06/08/2020.