Sites - Important Bird and Biodiversity Areas (IBAs)
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22o 45.60' East 20o 58.20' South
A1, A3, A4i, A4ii, A4iii
Year of IBA assessment
BirdLife Botswana (Partner Designate)
Site description Lake Ngami occupies the north-east part of a shallow sedimentary basin, in north-west Botswana, close to Sehitwa and south-west of the Okavango Delta, of which it is an integral part. It is bounded to the south-east by a low escarpment along an extension of the Kunyere fault, and to the west by a 25-km-long sand-ridge from the Dautsa Flats. To the north, a series of old shoreline features and minor sand-ridges separate the basin from the River Thaoge system. The lake or depression is surrounded by Acacia savanna.Although Lake Ngami is at present dry, it formerly flooded seasonally, fed by the Nghabe (Lake) and Kunyere rivers. These two rivers join at Toteng and flow into the north-east edge of the lake. The Kunyere is the more reliable source of water. Water in the Nghabe comes from the Thamalakane at the southern edge of the Okavango Delta; in recent years little water has flowed in the Thamalakane. The Thaoge river in the west of the delta flowed into Lake Ngami in the north-west corner in the 19th century. This source of water dried up between the 1870s and 1898 through blockage by papyrus Cyperus.The lake varies from a series of small pools near the inflow in the north-east to a maximum extent of 250 km² (34.5 km × 8 km, with a circumference of 80 km). Some 80% of the lake’s water is derived from river inflow and just 20% from local precipitation. The lake reaches its seasonal peak during the dry season, the rise occurring from June to a maximum in August. Lake levels fall from October to May, except in high-flow years such as 1978, when there was limited inflow in all months. In the 80 years prior to 1983, the lake had been dry five times for two consecutive years. Maximum levels were attained in 1898, 1899, 1904, 1925, 1926, 1968/69 and 1978/79. Historical evidence suggests that the lake regime was no more constant in the 19th century than it has been during the 20th century, although low levels have been normal during the latter.More recently, a series of years of low rainfall in the Angolan highlands has resulted in little, if any, water reaching the Thamalakane, and hence into the Nghabi. Moreover, drought years during the 1980s in Botswana meant little water in the Kunyere either. Prior to 1989, the lake was dry for seven years and little water has reached Lake Ngami since 1989. Its current use is for grazing cattle, horses and other livestock, and for hunting. In years of flooding the lake was highly productive and full of fish, notably barbel, which were an important food source for the local people.
Key Biodiversity See Box and Table 2 for key species—these are only sometimes present at the site, due to its ephemeral habitats. The lake, when flooded, was used as a feeding area by both species of Phoenicopterus and by large numbers of waterfowl, notably Anas erythrorhyncha (more than 500,000 were counted in 1978), as well as a breeding area for waterfowl. Pelecanus onocrotalus has bred there sporadically since at least 1872, with the last well-documented breeding years being 1972, when 3,000–5,000 adults were at the lake between May and July, and 1981, when 4,000 birds were there. The regionally threatened Botaurus stellaris and Sterna caspia, and regionally near-threatened Microparra capensis, have been recorded in the past. At times of flooding, several species of waterfowl occur in numbers exceeding the 0.5% threshold. For example, in 1979 an estimated 27,000 Anas erythrorhyncha and 7,000 A. hottentota were recorded, whilst in 1989 about 10,000 Glareola nordmanni were counted along 5 km of shore (10% of the total shore); similar numbers of G. pratincola and over 1,000 Chlidonias hybridus were also noted.Breeding species have included Phalacrocorax africanus, Anhinga rufa, Ardeola rufiventris and Botaurus striatus, Ardea goliath and A. cinerea, Threskiornis aethiopicus, Dendrocygna bicolor, Thalassornis leuconotus, Fulica cristata and Chlidonias hybridus. The grasslands that developed when the lake dried out in the late summer months (December–February), and as currently exist, were/are used by a range of regionally threatened open-country species such as Ardeotis kori. Other species of interest include Circus pygargus, Falco vespertinus (a roost occurred by the lake in 1996), Cursorius temminckii, Rhinoptilus africanus and R. chalcopterus, and Pterocles burchelli. The surrounding Acacia woodland supports high numbers of Hippolais olivetorum, as well as a range of species restricted to the Kalahari–Highveld biome.
Non-bird biodiversity: Large mammals whichformerly grazed at Lake Ngami have declined as their access from areas such as the Central Kalahari Game Reserve has been restricted.