UPPER NIGER BASIN
The main habitats of the UNB are typical of the Guinea and Sudan savanna zones, including (wooded) savanna, gallery forest, grasslands and cultivation. This broad savanna zone is home to several hundreds of bird species, many of which are widespread throughout West Africa. When looking at threatened species, over 20 bird species are expected to occur in the UNB. This includes several birds of prey and a few species confined to wetlands or riverine habitats, like African skimmer. Most of the African vultures are now considered to be severely threatened, but these species are not linked to the wetlands or riverine areas of the Niger and Bani Rivers.
The area around the source of the Niger River in the Guinean Highlands may harbour a few species that are characteristic of the humid forest zone further south, and which marginally occur in the basin. These may include (near-)threatened species like Timneh parrot (EN) and Crowned eagle (NT). Rufous fishing-owl (VU) is tied to forested streams and has been recorded at the nearby Loma Mountains in Sierra Leone. A few range-restricted species occur in the wider area, including Turati’s boubou, Sierra Leone prinia (VU) and Emerald starling. These species are confined to forest edge or woodland savanna and are not linked to riverine areas.
In the Upper Niger Basin a few IBAs are identified by Birdlife International, in particular Kouakourou, Sirakoroni–Tyènfala (north of Bamako) and Mafou, which is part of the Parc Haute Niger in Guinea. Sirakoroni–Tyènfala and Mafou are savanna woodlands resp. forests. In these dry areas a high variety of bird species has been recorded, but no threatened species. Kouakourou is a wetland area near the Niger. Generally the information on IBAs in Mali and Guinea is outdated due to a lack of recent data.
Breeding of Black-Crowned crane is not recorded from the Upper Niger Basin. The exposed sand banks in the Niger and Bani may be of importance for African skimmer and Kittlitz’s plover, but no detailed information is available.
INNER NIGER DELTA
The IND is one of the major floodplains in Africa and as such of paramount importance to both migratory birds and resident species. This refers primarily to waterbirds. However, the IND hosts also large populations of some other bird species, including birds of prey, which use the unflooded parts of the floodplains and the adjacent savanna landscape. The enormous international ornithological importance of the area has been documented since many decades.
The flood forests of Acacia kirkii host large mixed breeding colonies. Studies carried out in the 1980s and around the millennium show 17 nesting species, including Cattle egret and African cormorant, which were the most common breeding species. Some species have benefited from improved floods since the end of the Great Drought, or from flood conditions allowing a breeding cycle until March (Grey heron, Purple heron, Glossy ibis, African sacred Ibis) or by a higher breeding success (African darter). The high water with flooding in the central lake area until March became very rare, explaining the disappearance of nesting Grey and Purple herons and Glossy ibis. African openbill has also disappeared, but for this species the IND was rather a refuge during the Great Drought.
Two other species are worth mentioning. Whiskered tern has been found breeding in the IND since the early 1990s, the only nesting site known in West Africa. During the great flood of 1999 a total of 200-250 breeding pairs was estimated. Despite annual breeding in the center of the IND, their prospect is not that good due to the disturbance of the floating nests by fishing activities.
The vulnerable Black crowned crane breeds again in the IND but the species is threatened by the fact that young birds are systematically collected and sold. A survey in 2001 revealed that in the cities of Mopti and Bamako the number of captive cranes was two to three times larger than the wild population of the IND, which is doomed to disappear.
Concentrations of waterbirds
The occurrence and abundance of (water)birds in the delta must be mirrored against the following processes related to bird movements and dynamics of the delta proper and the Sahel as wider environment:
- The migration window of migratory birds: large numbers of birds from the north arrive in the Sahel, and the IND, in the period September-October and either stay till March – April, or migrate further east and pass the are during their return migration;
- The breeding season and intra-African migration of resident birds: Resident birds breed mostly during the wet season (September-November) and (partly) migrate to other areas in Africa during the hot, dry season;
- Flooding cycle: the seasonal flooding cycle in the IND determines the temporal and spatial feeding conditions for birds. Flooding starts in September–November (crue), is at its maximum between early and end November (Akka), the flood recedes during December–April (décrue) and is at its lowest in May–July (étiage). During the décrue and étiage the resources for birds are scarce.
- Annual variations in flooding: The size of the large floodplains in the Sahel and the occurrence of temporal wetlands or lakes largely depends on annual rainfall. Depending on these conditions, migratory birds but also residents may move between these areas. This means that the abundance of birds in the IND is partly also driven by droughts and rainfall elsewhere in the Sahel.
In the framework of some large project funded by the Dutch government (PIN, BBI), since 1998 Wetlands International in Sevaré systematically counted the central lake area to map and analyse the dynamics of the waterbird populations in the central lakes, in response to flooding (van der Kamp et al. 2002, van der Kamp et al. 2005, Zwarts et al. 2009). Before 1998 a number of comparable surveys has been done by a team of J. van der Kamp, L. Zwarts, B. Fofana and S. Konta, which means that a series of counts is available. The most recent count of the central lakes has been carried out in 2012 (van der Kamp & Diallo 2012). Since then no quantitative information on the status of the waterbirds in the IND is available.
The interactive graph shows the numbers counted in the central lake area (Lac Debo, Walado, Korientzé) between 1991 and 2012. Most censuses were perfomed in January - February, when the water level in Akka is below 200 cm. Birds then concentrate in the central lake areas, as most other areas in the Inner Niger Delta run dry. During 1998-2002 monthly counts were done, and in additon some counts in June. During high water levels birds are widely dispersed over the Inner Niger Delta and do not concentrate in the centrale lake areas. Breeding birds like the Long-tailed cormorant reach high numbers at high water levels; they breed and roost in the flood forests which are stil present in the central lake area.