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Orange River Mouth Wetlands
South Africa, Northern Cape
16o 28.00' East 28o 36.00' South
A1, A3, A4i, A4iii
0 - 10m
Year of IBA assessment
BirdLife South Africa
Summary The Orange River mouth is located on the arid Atlantic coast at South Africa's border with Namibia. This IBA is a 13 km long section of the Orange River, including its floodplain and terrestrial matrix. Bird numbers and diversity can be as high as 26 000 individuals comprising 56 species.
Site description The Orange river mouth is located on the arid Atlantic coast at South Africa’s border with Namibia. The nearest towns are Alexander Bay in South Africa and Oranjemund in Namibia. This site is a 13 km long section of the Orange river, including its flood-plain and terrestrial matrix, running from the ocean to Pachtvlei, just east of the Sir Ernest Oppenheimer Bridge. The delta-type river mouth consists of a series of braided troughs interspersed with sandbanks, channel bars and small islands, with a tidal basin and a saltmarsh on the south bank. The Orange river drains the largest catchment in South Africa, with an area of 549,700 km² and a mean annual run-off of 12,000 million cubic metres.
The major vegetation-types include islands dominated by Scirpus, Phragmites and Sporobolus. The peripheral marshes are dominated by various herbs, sedges and grasses. The upper flood-plain vegetation consists primarily of Lycium, Tamarix and Juncus, which gradually give way to terrestrial vegetation. On the lower flood-plain the soils have a high salinity as a result of evaporation and the peripheral marshland is dominated by salt-tolerant Sarcocornia.
Key Biodiversity See Box and Table 3 for key species. The Orange river mouth is considered to be the sixth most important coastal wetland in southern Africa in terms of the overall number of wetland birds that it supports, which can be as high as 26,000 individuals, from a total of 56 such species recorded. Numbers drop off considerably in winter, suggesting that the large majority of the birds are migratory or indulge in local movements. The Orange river mouth is used by birds primarily for breeding or as a stop-over on migration. At times the area supports more than 1% of the world populations of Phalacrocorax capensis, Tadorna cana, Anas smithii and Larus hartlaubii. The wetland and adjacent coastal dunes also support substantial numbers of Sterna balaenarum. Substantial proportions of the southern African populations of Podiceps nigricollis, Oxyura maccoa, Charadrius pallidus, Sterna bergii, and Sterna caspia are periodically supported at the Orange river mouth. Circus ranivorus occur along marshy sections of the riverbank and in the surrounding lucerne fields. The mouth supports a few resident Haematopus moquini and, in summer, large numbers of migrant Palearctic waders.
Near Pachtvlei, the terrestrial vegetation surrounding the wetland supports Francolinus capensis, Cercomela tractrac and two recently recognized larks, Certhilauda barlowi and C. curvirostris. The latter two species have restricted ranges (covering less than 50,000 km² each) that overlap, indicating that the Secondary Area of avian endemism recognized in this part of the Karoo (the restricted-range species Certhilauda burra occurs at three nearby IBAs: 025, 026, 027) should be upgraded to the status of Endemic Bird Area (EBA) when the global EBA classification is next revised.
Non-bird biodiversity: The system holds several endemic and threatened fish species, including Barbus hospes (LR/nt) and Austroglanis sclateri (DD). Several endemic and localized amphibians and reptiles occur in the terrestrial vegetation surrounding the estuary, and consideration should be given to securing a conservation area including the terrestrial matrix. Three highly range-restricted endemic frogs, Cacosternum namaquense, Breviceps macrops and B. namaquensis occur in the dunes and rocky outcrops adjacent to the mouth, particularly in the Alexkor restricted mining area to the south. Endemic mammals in the surrounding habitat matrix include Bathyergus janetta (LR/nt).
Estuarine waters; Intertidal mud, sand or salt flats; Salt marshes
Grassland - edaphic, wet
Extent (% of site)
nature conservation and research
References Allan and Jenkins (1993), Brooke et al. (1982), Brown (1959), Cooper and Hockey (1981), Cooper et al. (1982), Courtenay-Latimer (1963), Cowan (1995), Cowan and Marneweck (1996), Day (1981), Frost and Johnson (1977), Grindley (1959), Manry (1978), Morant and O’Callaghan (1990), Noli-Peard and Williams (1991), Plowes (1943), Roberts (1989), Ryan and Bloomer (in press), Ryan and Cooper (1985), Ryan et al. (1998), Swart et al. (1988), van Zyl (1991), Whitelaw et al. (1978), Williams (1986).
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BirdLife International (2015) Important Bird Areas factsheet: Orange River Mouth Wetlands. Downloaded from
http://www.birdlife.org on 30/05/2015
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