The site is a large, remote area of swamp-forest crossed by numerous rivers and streams, situated between the Ubangi river in the west and the Congo river in the east. The whole triangular-shaped area between 02°00 N and the confluence of the two major rivers in the south is included in this site; the same habitat extends, however, further to the north, at least to 02°30 N. The Ngiri river, a tributary of the Ubangi, flows from north to south through the centre of the site and is bordered by a wide zone of marshy grassland-savanna (‘ésobé’), alternating with swamp-forests and periodically flooded forests. Typical tree species include Entandrophragma palustre, Coelocaryon botryoides, Uapaca heudelotii, Guibourtia demeusei and Oubanguia africana. In periods of low water the savanna is burnt; when waters are high it is completely flooded. The human population density is very low and settlements are mainly concentrated around the only town in the area, Bomongo. Fishing and hunting are the main activities. Mbandaka, the regional capital, is situated to the south, at the confluence of the Congo and Ruki rivers. Rainfall averages about 1,770 mm per year, with little seasonal variation but with maxima during August–October and minima during April–May. Water-levels are highest during September–November in the Ubangi and Ngiri, and during October–December in the Congo; water-levels are low during January–May and February–August, respectively.
See Box and Table 3 for key species. The avifauna is inadequately known. Large numbers of waterbirds breed, especially Ardea purpurea (1,000s), Phalacrocorax africanus and Anhinga rufa. Merops malimbicus and Pseudochelidon eurystomina breed when water-levels are low. It is the only site in the country known to hold Nectarinia congensis. The savanna corridor is presumed to constitute an important migration flyway.
Non-bird biodiversity: No recent information is available. Mammals of global conservation concern include Loxodonta africana (EN), while Allenopithecus nigroviridis (LR/nt) is thought to occur.
BirdLife International (2019) Important Bird Areas factsheet: Ngiri. Downloaded from http://www.birdlife.org on 16/02/2019.