Philip A. Whittington

Return to Robben Island of African Penguins that were rehabilitated, relocated or reared in captivity following the Treasure oil spill of 2000

Following an oil spill from the Treasure off the coast of South Africa in June 2000, about 19 000 oiled African Penguins Spheniscus demersus, including 14 825 from Robben Island, were caught for rehabilitation and subsequent release. A further 19 500 penguins that were not oiled — mostly birds in adult plumage, including 7 000 from Robben Island — were relocated some 700km to the east, to prevent them becoming oiled. Additionally, 3 350 orphaned chicks, including 2 643 from Robben Island — were collected for rearing in captivity and release to the wild. Some four years later — by the end of December 2004 — 70% of rehabilitated adults, 40% of relocated birds and 34% of captive-reared chicks had been seen back at Robben Island. Another 7% of birds relocated from Robben Island had been sighted at other localities. Rates of resighting rehabilitated birds were similar at Robben and Dassen Islands, but a greater proportion of relocated birds was seen at Dassen Island, where birds collected for relocation were mostly from breeding areas. The lower proportion of relocated birds seen at Robben Island is thought to result from this intervention causing some pre-breeding birds to move to other colonies. All three conservation interventions are considered to have been successful, but it is premature to assess their relative contributions to the conservation of the species. Three relocated birds tracked by satellite took 15–21 days to return to their home colonies. This rapid return may have resulted from breeding attempts being interrupted. After remaining at their home islands for 4–5 days, two of the tracked birds then left these islands for 19–36 days. We surmise that, after they had searched unsuccessfully for their mates, they abandoned breeding for the year 2000.

Winners and losers – responses to recent environmental change by South African seabirds that compete with purse-seine fisheries for food

There were recent changes in the distributions of the main prey of four seabirds off South Africa, with sardine Sardinops sagax and anchovy Engraulis encrasicolus shifting from South Africas north-west coast towards the south-east. This contributed to numbers of African Penguins Spheniscus demersus and Cape Cormorants Phalacrocorax capensis breeding in South Africa decreasing by more than 50%. By contrast, numbers of Cape Gannets Morus capensis and Swift (Crested) Terns Thalasseus bergii increased. The success of the gannet and the tern in the face of recent change is attributable to a rapid increase in South Africas eastern colony of gannets, aided by high survival of adult birds and perhaps by immigration of first-time breeders from decreasing western colonies, and a probable high production of Swift Terns. The gannet has an extensive foraging range and the tern is nomadic between breeding localities, which gives these species greater flexibility than the other two to adapt to large changes in the distributions of their prey. Additionally, the gannet is able to supplement its diet with fishery discards. A lesser mobility of the African Penguin and the Cape Cormorant rendered them susceptible to a reduced local availability of prey and both species suffered high adult mortality in the last decade.

Age at first breeding of the African Penguin

Numbers of breeding pairs of African Black Oystercatchers showed a highly significant increase at Cape Agulhas over a 24year study period. Mean numbers of fledglings per pair did not increase correspondingly but showed a cyclic tendency, peaking twice, with a slight overall decline. The increase in the frequency of repeat clutches was close to significant. Nest failures were ascribed largely to human disturbance. Indications of increasing public awareness about the sensitivity of breeding oystercatchers were noted as well as increasing adaptability to human presence among some birds, whereas other birds moved their nests further away from this disturbance. In view of the closure of the Overberg coast to recreational vehicles from 20 February 2002 and the relative importance of the area for the conservation of oystercatchers, this long-term study represents an important baseline against which to measure change.

ESTABLISHMENT, GROWTH AND CONSERVATION OF A MAINLAND COLONY OF JACKASS PENGUINS SPHENISCUS DEMERSUS AT STONY POINT, BETTY'S BAY, SOUTH AFRICA

Summary Whittington, P.A., Hofmeyr, J.H. & Cooper, J. 1996. Establishment, growth and conservation of a mainland colony of Jackass Penguins Spheniscus demersus at Stony Point, Bettys Bay, South Africa. Ostrich 67: 144–150. Following the discovery of a single pair of Jackass Penguins Spheniscus demersus nesting on the mainland at Stony Point, Western Cape Province, South Africa (34 22S 18 53E) in 1982, a colony developed and has since been regularly monitored. Numbers of nests increased to 35 in 1986, until a leopard Panthera pardus severely reduced the size of the colony. Numbers subsequently rose again to a total of 139 nests in 1990, but fell to 57 in 1993. This decrease was probably due to predation by mammals. Following the use of a trap and translocation of the animals caught, the colony increased again in 1995 and 1996. Productivity of the colony was insufficient for it to be self-sustaining, and it therefore presently represents a population sink.

Recent Trends of the Kelp Gull (Larus dominicanus) in South Africa

Abstract. South Africas population of Kelp Gulls (Larus dominicanus vetula) numbered about 10,000 pairs during 1976/1977–1980/1981, increased to 21,000 pairs from 2000/2001–2004/2005 and then decreased to 17,500 pairs from 2009/2010–2013/2014. The increase in the late 20th century and the decrease in the early 21st century were mainly attributable to large increases and decreases in numbers breeding at islands off the west coast of South Africa. The increases followed cessation of controls on Kelp Gulls at the islands in the 1970s and were associated with supplementary food provided by fisheries and landfill sites, whereas the decreases were influenced by substantial predation of chicks by Great White Pelicans (Pelecanus onocrotalus). The decreases of Kelp Gulls at islands off the west coast of South Africa in the early 21st century were offset to some extent by an increase in numbers breeding on mainland sites, especially around greater Cape Town and along the south coast. The proportion of Kelp Gulls breeding on the south coast increased from 15% in 2000/2001–2004/2005 to 44% in 2009/2010–2013/2014. As there are fewer islands off the south coast than the west coast of South Africa, the proportion of Kelp Gulls breeding at mainland sites as opposed to island localities increased from 12% in 2000 to 31% in 2014. Mainland colonies are more susceptible to disturbance by humans and predation by mainland carnivores, but, in spite of this, the generalist Kelp Gull has performed better in recent years than several specialist, endemic seabirds. At Dyer Island and Bird Island (Algoa Bay), where Kelp Gull numbers increased, predation by Kelp Gulls on eggs and chicks of threatened seabirds is thought to have contributed to decreases in these seabirds, and controls on Kelp Gulls have been reintroduced.