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Site description (2001 baseline):
Site location and context
Situated on the Atlantic coast, c.150 km north of Cape Town, this small island lies in Lambert’s Bay harbour, extremely close to shore. A concrete causeway that forms the fishing harbour has linked the island to the mainland since 1959. Rising to only 7.6 m, the island is rocky and virtually devoid of vegetation.
See Box for key species. Historically this island was dominated by
Spheniscus demersus and was devoid of breeding
Morus capensis. It would appear that the gannets only colonized this island in 1912; today, it is one of only six localities where they breed. The birds form a single undivided colony in the centre of the island. Breeding numbers have fluctuated dramatically; the population declined steadily between 1956 and 1967, but by 1971 it had recovered, and by 1981 it was 50% larger than it had been in 1971. Numbers of breeding birds have continued to increase since the early 1980s.
Phalacrocorax capensis have also nested extensively on the island, occasionally reaching numbers of 61,000 birds. Numbers of
Spheniscus demersus halved between the late 1970s and early 1990s, and have subsequently dwindled to a handful of breeding birds.
Phalacrocorax coronatus,
Larus dominicanus and, occasionally,
Sterna bergii breed on the outlying rocks.
Phalacrocorax neglectus ceased breeding in 1997, and now only a few roost on the island.
Larus hartlaubii and various species of tern roost in large numbers.
Non-bird biodiversity: None known to BirdLife International.
Pressure/threats to key biodiversity
Between 1956 and 1980 the global population of
Morus capensis declined some 50%. The collapse was attributed to the decline in stocks of pilchard
Sardinops sagax, the gannet’s primary food source. Despite the global decline, the Bird Island colony has been increasing since the 1970s, which correlates with the local recovery of pilchard stocks in the Western Cape.
Spheniscus demersus and
Phalacrocorax capensis are also thought to have been affected by competition with commercial fisheries, especially purse-seining, for surface-shoaling fish such as anchovy
Engraulis capensis and pilchard, which are their primary prey. A recommendation has been made that marine reserves with a radius of 25 km be created around important breeding islands. Commercial fishing should be banned or restricted within these zones.
In addition to being affected by overfishing,
Morus capensis and
Spheniscus demersus are also susceptible to human disturbance. In the past, visitors to the colony at Bird Island disturbed prospecting birds at the edge of the colony and caused chicks to desert their nests. The area open to the public was fenced in 1974 and a high-tech viewing facility erected in 1998, and now visitors rarely disturb seabirds.
Seals are known to eat
Morus capensis,
Spheniscus demersus and
Phalacrocorax spp. The ability of seals to outcompete and displace birds at breeding islands has been identified as a substantial potential threat.An unpredictable threat, which is difficult to control, is chronic pollution by crude oil or other pollutants that spill into the ocean when tankers break open, wash their tanks, dump cargo or pump bilge.
Spheniscus demersus are particularly susceptible to these events, and a single oil disaster can severely affect populations. The South African National Foundation for the Conservation of Coastal Birds (ZANCCOB) cleaned, rehabilitated and returned some 3,000 penguins to the wild between 1981 and 1991.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Bird Island (South Africa). Downloaded from
https://datazone.birdlife.org/site/factsheet/bird-island-iba-south-africa on 23/12/2024.
