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Ornithological information See Box for key species. The area has a list of 426 bird species, about 46% of the species found in southern Africa. The flood-plain occasionally erupts with activity, holding up to 80,000 birds during high rainfall years. Egretta vinaceigula, Ardeola rufiventris, Sarothrura boehmi and Porzana pusilla breed erratically, whenever conditions are suitable. A relatively large Crex crex population occurs here in the austral summer. The wetland also occasionally supports extremely large numbers of Casmerodius albus, Ardeola ralloides, Nycticorax nycticorax, Platalea alba and Netta erythrophthalma. Tyto capensis is fairly common in the flooded grasslands and Glareola nordmanni occasionally occur in large numbers in the drier grassland surrounding the flood-plain. Almost every species of South African duck is found here from time to time, some in very large numbers. The surrounding woodland holds several restricted-range and biome-restricted species.

Site description The Nyl river forms a 70-km-long grassland flood-plain, one of the largest in South Africa. It runs from 10 km south of Naboomspruit north to Potgietersrus. The area, known as Nylsvley, is located in extensive undulating to flat terrain between 1,050 and 1,080 m. The flood-plain starts to widen at the western edge of Nylsvley Nature Reserve and it attains its greatest width, of five to six kilometres, on the farms downstream from there: Vogelfontein, Weltevreden, Zyferkraal, Du Toits Kraal (the last three embraced by the Mosdene Private Nature Reserve), Groenvaley and Zandpan. At its northern end, on the farm Vaalkop, it narrows and assumes the character of a normal river. The only prominent hills occur at Maroelakop (1,140 m) and Stemmerskop (1,090 m), both are on Nylsvley Nature Reserve and are in close proximity to each other. The system derives its floodwaters from rain that falls in the nearby foothills of the Waterberg range (IBA ZA006).This is the largest wetland of its kind in South Africa and it is basically a grass-dominated, seasonally inundated flood-plain, which in years of poor rainfall may not be flooded at all. It requires rainfall of at least 10% above the annual mean to produce significant inundation. The dominant grass in flooded areas is Oryza longistaminata, which may grow up to 2 m tall and provides cover, food and nesting material for many wetland birds. Many other grass species occur. Dominant sedges include Cyperus, Schoenoplectus and Eleocharis. Large stands of reed Phragmites are also found.Bushes and trees, many of Acacia, are scattered throughout the flood-plain and provide nesting sites for herons, bitterns and egrets. On some of the high-lying areas the vegetation comprises broadleaved savanna and grassland, with trees (up to 9 m tall) of Acacia, Burkea, Terminalia and Combretum. The well-drained low termitaria support Acacia thickets.

Populations of IBA trigger species

Protected areas

Protected area	Designation	Area (ha)	Relationship with IBA	Overlap with IBA (ha)
Nylsvley	Nature Reserve	3,101	protected area contained by site	3,985
Nylsvley Nature Reserve	Wetlands of International Importance (Ramsar)	3,970	protected area contained by site	3,970

Habitats

Land use

Other biodiversity The reserve holds the mammal Hyaena brunnea (LR/nt).

Management considerations Eight hundred hectares of flood-plain are protected in the 3,985 ha Nylsvley Nature Reserve, which was established in 1967; additional flood-plain habitat is protected in the neighbouring private Mosdene Nature Reserve. The Nyl flood-plain is one of the most important wetlands in South Africa, and it has recently been proposed as a Ramsar Site; concerted efforts should be made to increase the area of flood-plain under formal protection. The system is reliant on rain falling in the Waterberg (IBA ZA006) and inundating the plain. Any impoundment or disturbance to river flow on the handful of rivers that contribute to the flood-plain could seriously affect Nylsvley. Plans to build a large storage dam on the flood-plain’s main source of water, the Olifantsspruit, were shelved in 1995 as a result of an environmental impact assessment which concluded that the dam’s impact on the flood-plain could be severe. A conservation programme was initiated by ‘Friends of Nylsvley’ to clear non-native vegetation from river-edges in the Nyl’s catchment, thereby enhancing the run-off onto the flood-plain. The river is subjected to small-scale damming, dykes and the extraction of sand, all of which may alter the flooding regime that drives this rather dynamic system.Other threats to the system include the development of agriculture and grazing on, and in the vicinity of, the flood-plain. Despite being previously used for cattle-grazing, the reserve’s vegetation has been well conserved. The same cannot be said for the remainder of the flood-plain; monitoring and management of grazing and agriculture on the flood-plain are essential to secure the long-term integrity of the site. Purchasing of private land for State conservation, or promoting the management of private land for conservation purposes, should be encouraged. A further threat is the poisoning of birds and fish by aerial spraying of Quelea quelea roosts in Phragmites reedbeds.

References Coetzee et al. (1977), Harmse (1977), Tarboton (1979, 1987a,b, 1996), Tarboton et al. (1987).

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Recommended citation  BirdLife International (2013) Important Bird Areas factsheet: Nyl river flood-plain. Downloaded from http://www.birdlife.org on 19/06/2013

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