Collision of the cold Benguela Current with the southwestern tip of the African landmass, results in a major upwelling zone. The prevailing winds push the current northward along the western coast of southern Africa, and a balance of forces between the westerly winds and proximity to the coast, keeps the current inshore. Below the surface, the water flow is angled away from the coast (due to Ekman transport) causing colder water from the deep ocean to flow upwards closest to the coast. This upward flow brings constant supply of nutrients that phytoplankton require for growth, resulting in an area of particularly high productivity. There are major trawling grounds some 40-60 km off South Africa's Cape of Good Hope and vast numbers of seabirds accompany the fishing fleets. The area is so rich that in winter, it is apparantly not unusual to find 5000 or more seabirds in the wake of an active trawler. Species of particular interest include Jackass Penguin (easily accessible colony in 'The Boulders' at the Cape of Good Hope Nature Reserve), Black-bellied Storm-petrel, and Cape Gannet.
Pelagic Birding Opportunities
Several local groups organize regular pelagic trips from Hout Bay or Simon's Town. For specific information please visit the web sites for Zest for Birds run by Trevor Hardaker and John Graham or Anne Gray Cape Pelagic Trips. Both sites are packed with useful information, past trip reports and photos of seabirds and marine mammals seen during recent trips. For those with plenty of cash, it is also possible to hire sport-fishing boats from either of these fishing ports.
The winter (April-September) is generally the best time of year due to greater diversity (species that breed further south) however, summer pelagic trips can also be very rewarding. Landbased seawatching is possible from the Cape of Good Hope National Park (40 km from the city), Cape Point and at Kommetjie, especially on days when the winds are from the NW or SW. Several albatrosses and petrels are possible. Mass movements of jaegers from the Indian Ocean into the Atlantic, occur in late March through to May and can be observed from shore (e.g. False Bay in SE gales). Parasitic Jaeger predominates. There is a sewage outfall at Moville Point which can attract seabirds including Jackass Penguin and Sabine's Gull. In winter, there is a large roost of Antarctic Terns and cormorants (Cape, White-breasted, Bank and Crowned) at Kommetjie.
Immature Black-browed Albatross at sea. Since I currently don't have access any pictures from South African waters, this one comes from the coast of Chile. Photograph copyright of Winty Harrington©, 1999.
Giant-petrel. Notice the diagnostic red spot on the tip of the upper
mandible. Photograph copyright of Ron Saldino©, 1999.
Durban and the Indian Ocean
Athol Marchant runs regular offshore trips from Durban. Although the numbers of individuals are not as high as seen off Cape Town, one can encounter an excellent variety of species including Indian Ocean Yellow-nosed Albatross.
There is another zone of high productivity directly south of southern Africa known as the Agulhas Retroflection. I am unclear how well this has been explored for its seabird potential or how accessible it might be birdwatchers. For an incentive, check out Wim Vaders report of his 3 week visit on board a fishery research vessel. The retroflection is where the Agulhas Current (the boundary current flowing southwest next to the coast of SE Africa) runs into the eastward flow of the Antarctic Circumpolar Current and the northeastward flow of the Benguela Current. This collision of currents causes the Agulhas flow to bend almost completely back on itself, producing a turbulent zone of mixing. Rings formed in the Agulhas Retroflection have been observed spinning into the southern Atlantic and migrating all the way to the South American coast. This process helps transport warmer and more saline Indian Ocean waters into the southern Atlantic.
The Agulhas Current is not quite as fast as the Gulf Stream, however it is considered more problematic for marine navigation because one of its branches surges through a narrow passageway between Mozambique and the east coast of southern Africa (the Mozambique channel). Gale force winds (up to 180 km/hr) are common in Spring (September through November) and are prone to sudden changes in direction, creating monster waves. Seawatching may be possible from various spots along the coast. One spot mentioned in Nigel Wheatley's 'Where to watch birds in Africa' (1996) Princeton University Press, is Inhaca Island in southern Mozambique. The island is accessible by ferry from Maputo and seawatching from Cape Inhaca at the northern end has been productive in winter (Shy Albatross, Indian Yellow-nosed Albatross, Great-winged Petrel, White-chinned Petrel, Wilson's Storm-petrel, Red-tailed Tropicbird, White-tailed Tropicbird, Great Frigatebird, Cape Gannet).