Summary The Swartkops Estuary is located on the outskirts of Port Elizabeth. The catchment of this river lies in the Groot Winterhoek Mountains west of Uitenhage. The lower river receives water primarily from the Swartkops and Elands rivers. This complex holds, on average, 14 500 birds each year; occasionally 20 000. Redhouse Saltpan and the Swartkops Estuary each regularly hold more than 4 000 birds a year.
Site description The Swartkops estuary is located on the outskirts of Port Elizabeth, 15 km north of the harbour. The catchment of this river lies in the Groot Winterhoek mountains west of Uitenhage. The lower river receives water primarily from the Swartkops and Elands rivers, which flow parallel to each other, in relatively steep narrow valleys, and have their confluence shortly after entering the flood-plain. The estuary is tidal for c.16 km upstream, the upper reaches are narrow (c.90 m wide), channel-like, and twist their way through steep banks of muddy sand. In the upper estuary there is a small, sandy intertidal area. The estuary widens slightly and becomes less convoluted between Bar None saltpans and Brickfields in the middle reaches. Below Brickfields, the steep banks flatten and the estuary broadens considerably (c.350 m wide) into open mudflats.
The permanently open mouth is covered with eelgrass Zostera beds, which disappeared in 1983 resulting in the formation of extensive intertidal mudflats. The Zostera has since returned and the mudflat area has receded. Redhouse saltpan is situated on the north bank of the Swartkops flood-plain, within the Swartkops Valley Nature Reserve. Chatty saltpans occur south of the Swartkops–Redhouse railway-line near Brickfields. Three islands occur at Redhouse saltpan. The primary plants in the saltpans are the macrophytes Ruppia and Enteromorpha. The terrestrial vegetation surrounding the estuary consists of coastal dune herbland, flood-plain scrubland, grassland and thicket.
Key Biodiversity See Box for key species. This site holds, on average, 14,500 birds each year, and occasionally it passes the 20,000-bird threshold. Redhouse saltpan and the Swartkops estuary each regularly hold more than 4,000 birds a year. On the estuary, up to 3,300 of these are Palearctic migrants, present mainly during the summer months. The estuary and the saltpans provide distinctly different habitats for the 70 waterbird species that regularly occur there. The intertidal mudflats near the mouth of the estuary support the greatest density of birds, including notable numbers of Haematopus moquini, Pluvialis squatarola, Numenius phaeopus and Tringa cinerea. Thirteen species have been recorded breeding at Redhouse saltpan. Two islands at Redhouse saltpan host the second largest coastal breeding colony of Phalacrocorax carbo in southern Africa. Larus dominicanus also breed in large numbers and the pan regularly supports over 430 nests. Redhouse saltpan also holds the second largest breeding colony of Sterna caspia in South Africa, including 20% of the country’s breeding birds in some years.
Non-bird biodiversity: The reptiles Bradypodion ventrale and Scelotes anguineus, two Algoa Bay endemics, are resident.