Sites - Important Bird and Biodiversity Areas (IBAs)
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South Africa, Western Cape
18o 5.00' East 33o 25.00' South
A1, A4i, A4ii, A4iii
0 - 19m
Year of IBA assessment
BirdLife South Africa
Summary Dassen Island, South Africa's second largest coastal island lies 9 km from the mainland between Saldanha Bay and Cape Town. This island reaches 19.2 m above sea level at its highest point. Owing to its proximity to the mainland and offers sanctuary to a variety of land and seabirds. The most important resident is the African Penguin Spheniscus demersus.
Site description Dassen Island, South Africa’s second largest coastal island, lies 9 km from the mainland between Saldanha Bay and Cape Town. This island reaches 19.2 m at its highest point, and is generally flat or gently sloping, with extensive sandy areas and a few patches of exposed rock. It is richly covered with vegetation in winter. Several buildings occur in the north-east, as does a large manned lighthouse in the south-east. The island is partially enclosed by a low solid concrete wall. Hedges of non-native manitoka Myoporum occur near the buildings.
Key Biodiversity See Box for key species. Owing to its proximity to the mainland, comparative isolation, and suitable cover, the island offers sanctuary to a variety of land and seabirds. The most important resident is Spheniscus demersus. Numbers have been stable since 1989, following a 26% decrease during the late 1970s. Dassen Island also holds up to 4.6% of the global population of Haematopus moquini—the largest island population in South Africa. Dassen Island and Lake St Lucia (IBA ZA044) in KwaZulu-Natal are the only two sites in South Africa supporting breeding Pelecanus onocrotalus. Unlike most pelican populations, the Western Cape population has increased substantially during the twentieth century. The numbers on Dassen Island’s Boom Point have increased from less than 100 pairs in the mid-1970s to c.550 pairs in 1996. The island also supports healthy breeding populations of Phalacrocorax coronatus, P. capensis, Larus dominicanus, L. hartlaubii and Sterna bergii, as well as supporting many Arenaria interpres and other migratory waders during summer. Phalacrocorax neglectus, which used to breed in large numbers, has decreased dramatically over the last five years. Oceanodroma leucorhoa breeds on this island in very small numbers.
Non-bird biodiversity: Scelotes gronovii (LR/nt), a reptile endemic to the west coast, occurs on the island.
Sand dunes & beaches; Scree, boulders and bare rock; Sea cliffs & rocky shores; Shingle & stony beaches
Extent (% of site)
References Adams (1991), Berruti (1986), Branch (1991), Brooke and Prins (1986), Cooper (1981), Cooper and Berruti (1989), Cooper and Brooke (1986), Cooper et al. (1983, 1984), Crawford (1995), Crawford and Dyer (1995), Crawford and Shelton (1978, 1981), Crawford et al. (1982a,b, 1983, 1989, 1990, 1994, 1995b,c), Frost et al. (1976), Furness and Cooper (1982), Hockey (1983), Hockey and Hallinan (1981), Morant et al. (1981), Randall et al. (1980), Shelton et al. (1982), Siegfried (1982), Summers and Cooper (1977), Underhill (1992), Williams et al. (1990), Wilson et al. (1988).
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BirdLife International (2015) Important Bird Areas factsheet: Dassen Island. Downloaded from
http://www.birdlife.org on 13/10/2015
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