Sites - Important Bird and Biodiversity Areas (IBAs)
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Lake Chilwa and flood-plain
35o 40.00' East 15o 15.00' South
A1, A4i, A4iii
Year of IBA assessment
Wildlife and Environmental Society of Malawi (WESM) (Affiliate)
Site description Lake Chilwa is a shallow lake (1.5–3 m, maximum 5 m) that drains an area of c.8,000 km² of hills and mountains; it is bordered on all sides by swamps and seasonally flooded grassland, especially extensive on the flat western and northern shores. The lake itself is c.700 km² in size (or more at maximum extent), but dries up occasionally after a series of dry years (as in 1968, 1973 and 1995). It is very rich in fish and supports a population of c.60,000 people. The swamp vegetation consists mainly of Typha (c.650 km²) and Phragmites reedbeds (150–300 km²), with extensive patches of Scirpus in the open lake, whereas flood-plain grassland covers c.400 km². Several large rice-growing areas have been developed in the swamp, and the edges are cultivated (under maize) in the dry season, covering an estimated 10% of the surface overall.
Key Biodiversity See Box for key species. There has been no systematic survey of the avifauna, but over 160 species of birds associated with the Chilwa wetlands have been identified so far. In periods of flood the area supports very high numbers of waterfowl, but the flat terrain, the enormous size of the swamp and the nature of the vegetation all make counting of even the larger waterbirds a nearly impossible task. Preliminary studies carried out in 1996 have shown that numbers of at least nine species of waterfowl exceed the 1% thresholds; for the four main species snared by trappers (Dendrocygna bicolor, Gallinula angulata, Porphyrula alleni and Amaurornis flavirostris) the latest survey of commercial hunting in 1998–1999 has revealed that over one million birds were taken in a few months. It is likely other species exceed thresholds, e.g. a combined total of 41,500 Anas hottentota and A. erythrorhyncha were snared and shot in 1998–1999, but the proportion of each is unknown. Of species of global conservation concern, Falco naumanni winters in some numbers (flocks of 25–30 at any one spot are not unusual) and the Chilwa flood-plain is certainly the most important site for this species in Malawi. Circus macrourus and Gallinago media both winter annually is small numbers while Phoenicopterus minor is only an occasional visitor. In general, much more fieldwork is needed, especially in seasonally flooded grassland, in order the verify the very high figures of crakes and other species reported by trappers. A ringing scheme aimed particularly at the migratory duck species would be useful in determining the origin of these seasonal populations.
Non-bird biodiversity: None known today; large mammals have been exterminated.