This site is enclosed between the Boumba and Bek rivers in the extreme south-east of the country and is accessible only by pirogue and hunters’ trails. It has never been logged and contains extensive semi-evergreen lowland rainforest (dominated by Triplochiton scleroxylon in places, otherwise rather mixed). The canopy is fairly open, with a dense Marantaceae understorey; it is interspersed locally with very small (c.1 ha) patches of closed-canopy evergreen forest. Small areas of seasonally flooded forest, Raphia swamp-forest and edaphic grassy savannas also occur. The main rivers are fast-flowing and generally devoid of sandy beaches.
See Box and Table 3 for key species. Some 254 species have been recorded from the reserve. Picathartes oreas (Table 2) seems to reach the eastern limit of its range here, as an old nest was found on a rock on the eastern bank of the Boumba river; there is, however, very little suitable habitat for the species which must be uncommon. Glaucidium capense is locally frequent in open-canopy forest, as elsewhere in south-east Cameroon and adjacent north Congo: the race of this forest population is yet undetermined, but castaneum is the most likely. Another species recently discovered in the country, Phylloscopus budongoensis, is common above 400 m. Records of Pachycoccyx audeberti and Muscicapa tessmanni are worthy of note: the former is generally rare in the forest zone; the latter is also rather localized, but has recently been observed in Dja and in the other IBAs in the south-east. The yellow-bellied form of Stiphrornis erythrothorax is common. This has, however, been described as a new species, Stiphrornis sanghensis, from Dzanga–Sangha in Central African Republic (CF008). Independent field research there and in neighbouring parts of Cameroon and Republic of Congo suggests it is, in fact, no more than a subspecies of the widespread S. erythrothorax, and it is treated as such here, pending further evidence.
Non-bird biodiversity: The area holds numbers of Gorilla gorilla (EN), Pan troglodytes (EN) and Loxodonta africana (EN).
BirdLife International (2019) Important Bird Areas factsheet: Boumba - Bek. Downloaded from http://www.birdlife.org on 24/02/2019.