Soetdoring Nature Reserve is essentially an island in a sea of agricultural lands. This IBA includes Krugersdrif Dam (encompassed by the reserve), which is surrounded by degraded karroid grassland on black soils and acacia thornveld in riparian areas. It also includes a large stretch of the Modder River with riparian habitat, thornveld and grassland.
The average rainfall is 560 mm p.a. and temperatures range from a minimum of zero to a maximum of 30 °C. The reserve is situated on the great South African plateau and consists of a flat undulating plain lying between 1 246 and 1 290 m a.s.l. that is covered by a karroid/grassland mosaic. In patches, the uniform, largely flat landscape is broken by koppies and ridges, where hillside bush is one of the primary vegetation types. The grassland is dominated by Themeda triandra, the karroid veld by Felicia muricata and the hillside bush by Searsia (formerly Rhus) ciliata and Olea europaea africana. Vachellia (formerly Acacia) karroo dominates the riverine fringes, the margin of the dam and patches of short 'false Karoo' scrub on hard clay soils. There are also fairly extensive stands of reedbeds along parts of the dam's shore and along the Modder River.
Soetdoring Nature Reserve is the premier birding spot in the Free State, where more than 290 bird species have been recorded. The dam regularly supports more than 5 000 waterbirds at any one time, and occasionally up to 20 000 birds of many different species are recorded. During the 2013 CWAC, 44 waterbird species and more than 12 433 birds were listed. The species with the highest counts (highest to lowest) were Red-knobbed Coot Fulica cristata, Ruff Philomachus pugnax, Egyptian Goose Alopochen aegyptiaca, White-winged Tern Chlidonias leucopterus, Yellow-billed Duck Anas undulata, Reed Cormorant Phalacocorax africanus, South African Shelduck Tadorna cana, Black-winged Stilt Himantopus himantopus, Curlew Sandpiper Calidris ferruginea and White-breasted Cormorant Phalacrocorax lucidus. Other species seen are Greater Flamingo Phoenicopterus roseus and Goliath Heron Ardea goliath. Caspian Tern Sterna caspia and Secretarybird Sagittarius serpentarius are the most frequently encountered threatened species in this IBA. Species composition changes markedly depending on the water levels.
Large, widespread species that are found in the reserve in small numbers include Martial Eagle Polemaetus bellicosus and Kori Bustard Ardeotis kori. Blue Korhaan Eupodotis caerulescens and Sickle-winged Chat Cercomela sinuata occur in the surrounding grassland and karroid scrub vegetation, and Namaqua Warbler Phragmacia substriata is found in the acacia scrub and in reedbeds near water.
Globally threatened species are Ludwig's Bustard Neotis ludwigii, Chestnut-banded Plover Charadrius pallidus, Grey Crowned Crane Balearica regulorum, Secretarybird, Martial Eagle, Blue Korhaan, Melodious Lark Mirafra cheniana, Black-winged Pratincole Glareola nordmanni and Kori Bustard. Regionally threatened species are Caspian Tern and Greater Flamingo. Biome-restricted species include Kalahari Scrub Robin Erythropygia paena, Sickle-winged Chat and Namaqua Warbler. Congregatory waterbirds include Egyptian Goose, South African Shelduck, Red-knobbed Coot, Great Crested Grebe Podiceps cristatus, Little Grebe Tachybaptus ruficollis, African Darter Anhinga rufa, Western Cattle Egret Bubulcus ibis, White-winged Tern, Yellow-billed Duck and Spur-winged Goose Plectropterus gambensis.
The endemic black wildebeest Connochaetes gnou and blesbok Damaliscus dorcas phillipsi have been re-introduced into the reserve. Several southern African endemic reptiles occur in the vicinity, including Cape spade-snouted worm lizard Monopeltis capensis, sungazer lizard Smaug giganteus and southern spiny agama Agama hispida, and some may occur in the reserve.
Historically the area was grazed by livestock and has recovered well since it was proclaimed a reserve in 1978. Poison sprays (Queleatox) used to control Red-billed Quelea Quelea quelea in the past killed non-target bird species as well. Toxins still linger in the ecosystem. The blasting of roost and breeding sites as a means of control was later used and is still the preferred method.
Currently the most significant threats are algal blooms in the dam due to water quality deterioration resulting from the inflow of urban waste water and sewage effluent, and occasional outbreaks of botulism. Fishing equipment, such as lines discarded by anglers, is also of concern.
Solar and possibly wind energy facilities may be a potential threat on neighbouring land.
The IBA is a provincial nature reserve surrounding a State dam. It falls under the jurisdiction of the Free State DETEA; the dam water and its use are managed by DWA. The surface of the dam and the DWA angling areas around its lower reaches are controlled by the reserve's manager. The release of water from the dam is controlled by DWA and is mostly carried out without consulting the reserve manager. Certain species of aquatic birds suffer accordingly.
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Colahan BD. 1992a. Bird notes from Free State nature reserves: 1991. Mirafra 9(2): 25–30.
Colahan BD. 1992b. Bird notes from Free State nature reserves: January–June 1992. Mirafra 9(3&4): 55–60.
Colahan BD. 1993a. Bird notes from Free State nature reserves: July–December 1992. Mirafra 10(2): 22–27.
Colahan BD. 1993b. Bird notes from Free State nature reserves: January–June 1993. Mirafra 10(4): 74–79.
Colahan BD. 1994a. Bird notes from Free State nature reserves: July–December 1993. Mirafra 11(2): 25–29.
Colahan BD. 1994b. Bird notes from Free State nature reserves: January–June 1994. Mirafra 11(4): 57–64.
De Swart DH. 2000. The birds of Soetdoring Nature Reserve and adjacent areas, central Free State. BirdLife South Africa Guide. Johannesburg: BirdLife South Africa. pp 1–40.