The Rukwa trough is a blocked branch of the Western Rift Valley. It lies parallel to Lake Tanganyika and is connected to the rift in the north-west by the flood-plain of Katavi National Park (TZ002) and the Karema Gap. The valley lies at an elevation of 790 m and is enclosed on both sides by escarpments. To the south-west the land rises steeply to 2,664 m on the Ufipa plateau and to the north-east in a series of smaller scarps and rolling hills to 1,707 m at Mount Sange. The lake has no outlets. Water-levels fluctuate widely with a grassy plain often separating the valley into two lakes, both of which may dry out completely following several years of low rainfall. The lake level is presently higher than at any other time in living memory, having been steadily rising since the 1960s. There is usually an impressive wetland of papyrus Cyperus papyrus and reed Phragmites at the northern end of the lake where the Rungwa river and a number of smaller streams form a wide, shallow delta.
See Box for key species. Most information derives from a species list compiled in the 1950s which details 363 species. Eight species of global conservation concern have been recorded but, as all data refer to the 1950s, their current status is unknown. Falco naumanni was described as a frequent passage migrant, Circus macrourus as an abundant winter visitor, Crex crex as an occasional passage migrant, Gallinago media as a frequent winter visitor and Glareola nordmanni a rare visitor. Grus carunculatus was a frequent resident, but increased water-levels probably now mean that it is a rare bird. There are a few records of Balaeniceps rex. Phoenicopterus minor is only likely to be a visitor to the site, especially given higher water-levels and lower alkalinity. Historically, attempts at breeding have been described.The Rukwa valley is the southernmost point of the Somali–Masai biome (three species occur; see Table 3) and represents the southern limit for several species’ ranges in East Africa, including Struthio camelus. The records of Botaurus stellaris represent the most northerly distribution of the southern African population while a flock of six Ciconia nigra may be among the most southerly records of this Palearctic winter visitor. Generally rare species in Tanzania known from this site include Falco vespertinus and Porzana pusilla and it is one of the few localities where both Campethera bennettii and Campethera nubica are sympatric. Mirafra albicauda rukwensis was described from the Lake Rukwa grasslands. Ploceus reichardi may still be locally common in lakeside habitat.
Non-bird biodiversity: A number of large mammals occur, including Kobus vardoni (LR/cd). Loxodonta africana (EN) probably still occurs. There is an endemic fish Oreochromis rukwaensis.
BirdLife International (2021) Important Bird Areas factsheet: Lake Rukwa. Downloaded from http://www.birdlife.org on 27/09/2021.