The site consists of a number of low, alluvial islands in the Gambia River, between the town of Kaur in the west almost as far east as the divisional capital Janjanbureh (Georgetown), where permanent saline water is replaced with fresh and where mangrove gradually gives way to freshwater riverine forest and thickets, much of which have been cleared. Between Kaur and Kuntaur is a line of seven islands separated by narrow channels and covered with Phragmites karka reedbeds. There are also three smaller islands, including Bird Island, covered with scrub. Further east, between Kuntaur and Georgetown, are two groups of islands, those of the Gambia River National Park and the Kai Hai Islands. Both groups are fringed with seasonally flooded riverine forest, dominated by Mitragyna inermis. MacCarthy Island, upon which Georgetown is located, is excluded from the IBA.
See Box for key species. This length of the river is an important roosting area for non-breeding wildfowl. Numbers are highly variable, with maxima of more than 10,000 Dendrocygna viduata and Anas querquedula, thousands of Plecopterus gambensis and an apparently declining population of Sarkidiornis melanotos, which is now recorded only in hundreds. The diminutive Bird Island, north of Kuntaur, has the only large mixed waterbird colony on the river. Although with fewer than 1,000 pairs, it is the national stronghold for breeding Phalacrocorax africanus, Anhinga rufa, Casmerodius albus and, possibly, Nycticorax nycticorax. Bird Island is also a roost site for 15,000–20,000 herons, egrets, darters and cormorants, including up to 9,500 Bubulcus ibis. Other island roosts probably remain to be discovered. Little is known of the birds of the islands with the Phragmites reedbeds, which are potential strongholds for breeding Ixobrychus minutus and Rallidae, feeding areas for waterfowl, herons and egrets and roost sites for Palearctic Hirundinidae and Motacillidae. The riverine forest of the Gambia River National Park has isolated populations of a few forest species, including two species of the Guinea–Congo Forests biome; see Table 2. These include Pyrenestes sanguineus which, in The Gambia, is found only here and in the nearby Nianimaru and Gassang forests on the mainland.
Non-bird biodiversity: The majority of recent sightings of Trichechus senegalensis (VU) are from this part of the river.
BirdLife International (2019) Important Bird Areas factsheet: Islands of the Central River Division. Downloaded from http://www.birdlife.org on 22/04/2019.