This site includes some 16,200 ha of seasonal swamp. 8,000 ha of grassland and thicket that is inundated in years of exceptionally heavy rainfall and approximately 12,100 ha of wooded hillsides. The western boundary chosen for the latter habitat follows the 1,300 m contour, but is rather arbitrary and may require modifying if and when any conservation based boundaries are drawn.

The Yaida Chini valley lies roughly on a north south axis, parallel to and south-east of Lake Eyasi (IBA 23). The swamp that dominates the valley floor is fed by numerous seasonal rivers and the Yaeda River, which drains the western flanks of the Mbulu Highlands that rise to 2,168 m. The swamp is extensive patches of Rush and Sedge, among which many waterbirds breed. There must be considerable variation in the extent of the swamp and it is known to dry out completely in the driest years. The heavily grazed grassland bordering the swamp must also vary in extent within the seasons, but the highest water-levels are clearly marked by the extensive stands of mature Acacia tortilis that grade into Baobab dominated woodland on the hills. There is an extensive thicket of Acacia drepanolobium at the northern end of the valley that grades into an even denser stand of Acacia kirkii woodland.

There are no historical data for this area and it is only during the last two years that regular visits have been made, enabling the site to be included in the IBA process. Among the species present are two Tanzanian endemics not currently considered globally threatened - Grey-breasted Spurfowl and Ashy Starling are common throughout the woodland. There is the possibility that the Karamoja Apalis, a globally threatened species, occurs in the Acacia drepanolobium thicket. There are recent (February 2001) records of White-tailed Larks, a rare and restricted species in Tanzania, in the grassland surrounding the swamp.

However, it is the stunning swamp that attracts the most attention simply because of the huge numbers of waterbirds. Half a century ago, this was a permanent wetland with concentrations of Elephants and Cape Buffalos, but nothing is known of the waterbirds during that period. Numbers of Cattle Egrets may well exceed the 1% threshold of 10,000 birds, as may Glossy Ibises, of which a minimum of 687 were present. This compares to the threshold of 1,000. Some 223 Black-tailed Godwits were counted in February 2001, along with several thousand Ruffs and a wide variety of other waders. Unfortunately, the flooded grassland that fringed the swamp was too tall to permit counting wading birds with any degree of accuracy. During the same period, a Fulvous Tree Duck (many hundreds present) was flushed off a nest of 11 eggs. Two pairs of Black-necked Grebes were seen, one adult with an attendant chick only a few days old. A feature of the swamp edge was several large flocks (typically 300-400 birds) of Knob-billed Ducks, the majority being birds of the year.