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(Reference: Barnes, K.N, Tarboton, W.R. & McAllister, J. The Important Bird Areas of Southern Africa. Avian Demography Unit / BirdLife South Africa. In prep.).

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DETAILS: SA 008 Nyl River Floodplain;24°39'S; 28°42'E Northern Province 16 000 ha, Partially protected, Classified as a "Global IBA"

Site description

The Nyl River forms a 70 km long, 16 000 ha grass floodplain, 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 a.s.l. The floodplain 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 here; Vogelfontein, Weltevreden, Zyferkraal, Du Toits Kraal (the last three embraced by the Mosdene Private Nature Reserve), Groenvaley and Zandpan. At it’s northern end, on the farm Vaalkop, it narrows and assumes the character of a normal river. The only prominent hills occur at Maroelakop (1 140m a.s.l.) in the south and Stemmerskop (1 090 m a.s.l.) further north. The system derives its floodwater from rain that falls in the nearby foothills of the Waterberg range (IBA 007). About 12 tributaries drain this area and discharge their water onto the floodplain at various points along its course. This is the largest wetland of its kind in South Africa and is basically a grass dominated, seasonally inundated floodplain which in years of poor rainfall may not be flooded at all and which requires rainfall of at least 10% above the annual mean to produce significant inundation. The ephemeral nature of the wetland, and the kind of vegetation and microhabitats it provides accounts for the floodplain’s attractiveness to a wide variety of wetland bird species, many of which breed in large numbers in years of suitable rainfall. The dominant grass in flooded areas is Oryza longistaminata, which may grow up to 2m tall and provides cover, food and nesting material for many wetland birds. Many other grasses occur including the emergent Panicum schinzii, Setaria sphacelata, Leersia, Sporobolus and Acroceras. Dominant sedges include Cyperus fastigiatus, Schoenoplectus and Eleocharis. Large stands of Phragmites are also found. There are many open water patches with extensive growth of floating and emergent aquatic vegetation such as water lilies, Potamogeton, Ludwigia and Polygonum. Bushes and trees, isolated and in clumps, including many acacias, are scattered throughout the floodplain and provide nesting sites for herons, bitterns and egrets. The floodplain has very little permanent reedbed vegetation. A particularly interesting aspect of the vegetation is the occurrence of a tropical grass Paspalidium germinatum, which is recorded from nowhere else in South Africa. On some of the highlying areas the vegetation comprises broadleaved savannas and grassland; dominants include Eragrostis pallens and Digitaria eriantha. Other grasses include Panicum maximum, Digitaria polevansii, Brachiaria nigropedata, Andropogon gyanus, A. schirensis Eragrostis acraea and E. racemosa. This community supports trees like Burkea africana, Terminalia sericea, Combretum molle, C. collinum, C. apiculatum, Dichrostachys cinerea, Ziziphus zeyherana, Acacia caffra, Diplorhynchus condylocarpon and A. tortilis, shrubs like Ochona pulchra, Grewia flavescens, Barleria bremekampii and the forbs Tephrosia longipes, Rhynchosia totta, Indigofera comosa, Asparagus saundersiae and Euphorbia neopolycnemoides. On the flat bottomlands and termitaria zones, Panicum maximium and Acacia tortilis tree savanna occurs. Aloe spp. and Chloris virgata dominate the field layer. Pappea capensis or Acacia nilotica are occasionally co-dominants in these communities. In the shrub layer, Kalanchoe lanceolata and Plectranthus cylindraceus or Carissa bispinosa and Panicum maximum dominate. In the low-lying, waterlogged areas, grass and forb cover is high including Setaria woodii, Dichanthium papillosum, Scirpus dregeanus and Aristeda bipartita. The trees, mostly Acacia karroo, vary in height, but can be up to 9m tall. Ziziphus mucronata is the subdominant tree. The better drained, low termitaria have Acacia nilotica - Acacia tortilis thickets. In general, the climate is semi-arid, with three rather distinct seasons; a hot wet season from November to April during which the Nyl River occasionally floods, a cool dry season from April to August, and a hot, dry season from August to October. The mean annual temperature is 18.6°C and the mean annual rainfall 587 mm.

The area has a list of 426 bird species, about 46% of the species found in the southern African sub-region. The floodplain occasionally erupts with activity, holding up to 80 000 birds during high rainfall years. Nylsvley is particularly important as it attracts large numbers of locally threatened and rare waterbirds. Nylsvley has become a critical area for the Bittern Botaurus stellaris, which is disappearing rapidly in South Africa. Although it is now less common at Nylsvley than previously, this area still holds one of the largest and most stable breeding populations in South Africa. In high rainfall years, Dwarf Bittern Ixobrychus sturmii, Little Bittern Ixobrychus minutus, Lesser Gallinule Porphyrio alleni and Lesser Moorhen Gallinula angulata are common. Other rare and/or endangered species like the Slaty Egret Egretta vinaceigula, Rufousbellied Heron Butorides rufiventris, Streakybreasted Flufftail Sarothrura boehmi and Baillon’s Crake Porzana pusilla, breed erratically, whenever conditions are suitable. A relatively large wintering Corncrake Crex crex population has been found here. Striped Crake Aenigmatolimnas marginalis and Spotted Crake Porzana porzana are occasional summer visitors. The wetland also occasionally supports extremely large numbers of Great White Egret Egretta alba, Little Egret Egretta garzetta, Yellowbilled Egret Egretta intermedia, Squacco Heron Ardeola ralloides, Blackcrowned Night Heron Nycticorax nycticorax, African Spoonbill Platalea alba and Southern Pochard Netta erythrophthalma. Marabou Stork Leptoptilos crumeniferus and Black Stork Ciconia nigra occur rarely at Nylsvley. Yellowbilled Stork Mycteria ibis and Grass Owl Tyto capensis are fairly common in the flooded grasslands and Blackwinged Pratincole Glareola nordmanni occasionally occur in large numbers in the drier grassland surrounding the floodplain. Almost every species of South African duck is found here from time to time, some in very large numbers. The surrounding woodland holds Secretarybird Sagittarius serpentarius, Bat Hawk Macheiramphus alcinus and Whitebacked Vulture Gyps africanus in small numbers. Cape Vulture Gyps coprotheres is a scarce visitor. Other woodland specials include Redcrested Korhaan Eupodotis ruficrista, Pied Babbler Turdoides bicolor, Whitethroated Robin Cossypha humeralis, Kalahari Robin Erythropygia paena, Burntnecked Eremomela Eremomela usticollis, Barred Warbler Camaroptera fasciolata, Marico Flycatcher Melaenornis mariquensis, Crimsonbreasted Shrike Laniarius atrococcineus, Whitecrowned Shrike Eurocephalus anguitimens, Burchell’s Starling Lamprotornis australis, Whitebellied Sunbird Nectarinia talatala, Scalyfeathered Finch Sporopipes squamifrons, Violeteared Waxbill Uraeginthus granatinus, Blackcheeked Waxbill Estrilda erythronotos and Shafttailed Whydah Vidua regia.

The reserve holds the following threatened animals; African Rock Python Python sebae, Jalla’s Sand Snake Psammophis jallae, Greater Dwarf Shrew Suncus linex, Kuhl’s Bat Pipistrellus kuhlii subtilis, Honey Badger Mellivora capensis, Selous Mongoose Paracynictis selousi, Aardwolf Proteles cristatus, Brown Hyeana Hyaena brunnea, Leopard Panthera pardus, African Wildcat Felis lybica and Aardvark Orycteropus afer.

Eight hundred hectares of floodplain is protected in the 3 985 ha Nylsvley Nature Reserve; additional floodplain habitat is protected in the neighbouring private Mosdene Nature Reserve. The Nyl floodplain is one of the most important wetlands in South Africa. The recent classification as Nylsvley Nature Reserve as a Ramsar site should be welcomed. However, concerted efforts should be made to increase the area of the floodplain under formal protection. The system is reliant on rain falling in the Waterberg (IBA 007), and inundating the plain. Any impoundment or disturbance to river flow on the handful of rivers that contribute to the floodplain could seriously impact Nylsvley. Plans to build a large storage dam on the floodplain’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 floodplain could be severe. A conservation programme was initiated by Friends of Nylsvley to clear alien vegetation from river edges in the Nyl’s catchment, thereby enhancing the run-off onto the floodplain. The river is subjected to small scale damming, dykes and the extraction of sand, all of which may alter the delicate flooding regime which drives this rather dynamic system. Other threats to the system include the development of agriculture and grazing on and in the vicinity of the floodplain. 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 floodplain; monitoring and management of grazing and agriculture on the floodplain is essential to securing the long term integrity of the site. Purchasing of private land for State conservation, or management of private land for conservation purposes should be encouraged. A further threat is the poisoning of birds and fish by aerial spraying of Redbilled Quelea Quelea quelea roosts in Phragmites reedbeds.

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

Status of Uncommon and Threatened Species on the Nyl Floodplain

Globally threatened species