Lake Eyasi is the most significant water-body in the Eyasi and Yaida internal catchment basin, which also includes Wembere steppe (site TZ043) and Lake Kitangire (TZ026). The lake lies in a trough between the Mbulu Highlands to the east and south-east and the Ngorongoro Highlands to the north and north-west. It is 80 km long with an average width of 14.5 km and is fed mainly from the south-west, where the Sibiti river flows in from Lake Kitangire. However, only during wet years is this a significant inflow of water. The shallowness of the lake, the low amounts of direct precipitation (around 600 mm per annum) and high rates of evaporation ensure the water is highly alkaline. During years of low rainfall the lake is reduced to a dry soda crust. The escarpment wall to the north-west rises some 800 m, virtually from the shore of the lake, and assists in protecting the western shoreline. To the north-east numerous farms have expanded in recent years exploiting the seasonal streams to grow vegetables.
See Box for key species. The lake holds large numbers of waterbirds particularly Phoenicopterus ruber and Phoenicopterus minor. There is a regular, virtually constant, movement of these species and of Mycteria ibis between the lake and Lake Manyara. There is usually sufficient fresh/brackish water to provide habitat for a few Gallinago gallinago and the occasional Calidris temminckii. There are few trees suitable as nest-sites for large waterbirds, but ground-nesting Platalea alba breed on offshore islands. At least two Tanzanian endemics are known from lake-shore habitats. Cosmopsarus unicolor reaches its altitudinal limits to the north of the lake near Mang’ola and Agapornis fischeri was formerly common, at least along the eastern shore. Apalis karamojae frequents Acacia drepanolobium woodland throughout the Eyasi drainage basin, but is extremely local. As yet there are no records from lake-shore habitat. At least one species of the Serengeti plains EBA and 29 species of the Somali–Masai biome have been recorded from the surrounding area (see Tables 2 and 3).
Non-bird biodiversity: None known to BirdLife International.
BirdLife International (2021) Important Bird Areas factsheet: Lake Eyasi. Downloaded from http://www.birdlife.org on 25/01/2021.