This small (6.5 ha) coastal island lies 1.4 km from Namibia’s Diamond Coast, c.50 km north of Lüderitz. The island is circular, mostly flat and unvegetated, and since rocky outcrops reach only 7 m, sea spray covers much of the island during storms. It is now completely surrounded by a sea wall to prevent seals from hauling out and disturbing the birds. Repeated guano scraping since the 1840s, when guano deposits were over 20 m thick, has left the rocky island-floor entirely exposed. Sandy stretches exist on the eastern side of the island. Ichaboe lies in the heart of the one of the strongest upwelling systems in the world, caused by the consistently strong longshore winds. The upwellings bring nutrients to the surface where they enhance phyto- and zooplankton blooms that are the basis for the rich abundance of fish on which the birds thrive. Rainfall is minimal (less than 10 mm per year), but coastal fog and storms often envelop the island.
See Box for key species. Ichaboe Island is one of the most important and densely packed coastal seabird breeding islands in the world. It regularly supports over 50,000 seabirds of at least eight species, including large numbers of Spheniscus demersus, Morus capensis, Phalacrocorax capensis, P. neglectus and P. coronatus. Smaller numbers of Larus dominicanus and Haematopus moquini also breed. This island is the most important location for Phalacrocorax neglectus in the world, holding a massive 65% of this globally near-threatened species’s population. During the last 20 years the global population has declined from 9,000 pairs to less than 5,000 pairs, of which total Namibia holds c.4,000 pairs. Ichaboe also holds about 4% of the world breeding population of Phalacrocorax coronatus. The island may also harbour thousands of roosting terns, particularly Sterna hirundo and Chlidonias niger.
Non-bird biodiversity: Whales sighted here include Megaptera novaeangliae (VU) and Eubalaena australis (LR/cd). The cetaceans Lagenorhynchos obscurus (DD), Tursiops truncatus (DD) and the endemic Cephalorhynchus heavisidii (DD) are visitors to the island's waters.
Pressure/threats to key biodiversity
All the near-shore islands of Namibia’s Diamond Coast were managed by Cape Nature Conservation as nature reserves when they were under South African rule. Now under Namibian law, they no longer carry the same status, but fall under the jurisdiction of the Ministry of Fisheries and Marine Resources. Three seabird species, Spheniscus demersus, Morus capensis and Phalacrocorax capensis, have suffered serious population declines during the last 30 years, mostly because of overfishing of surface-shoaling fish, such as Sardinops sagax, their main food source. These seabird species are also renowned for their guano, which has been harvested for many years for the fertilizer trade, resulting in disturbance to breeding seabirds and compounding their population declines. This has affected Spheniscus demersus most severely, as it prefers to burrow in the guano. The guano on Ichaboe Island was 22 m deep when exploitation began in the 1840s; it was completely cleared of guano in three years. Large-scale guano harvesting removed the penguins’ cover and forced them to breed in the open, exposing their chicks and eggs to increased predation by gulls and seals, excessive heat during the day, and storm conditions. Conservation measures ensure that sensitive coastal seabirds are not disturbed during their critical breeding season. This does not preclude harvesting of guano, which is presently carried out less than once every two years. Only decisive conservation actions on Ichaboe Island, involving limitations on guano collection at certain times of the year, and active prevention of seals landing to breed, have begun to restore the penguin population.Further conservation problems for coastal seabirds include a population of the seal Arctocephalus pusilla which has been steadily increasing in number along the Namib coast after being severely depleted by hunting in the 1800s. Seals occasionally disrupt and displace sensitive breeding seabirds on islands, competing for space and occupying areas originally used for breeding by the birds. This has led to the decline in several of these species’ populations, including Spheniscus demersus which has decreased from 8,000 to 3,400 individuals since 1956. Arctocephalus pusilla are actively discouraged from breeding in areas where they dramatically affect sensitive seabird species. Phalacrocorax neglectus, which forage primarily on the fish Sufflogobius bibarbatus and Jasus lalandi, have recently suffered a global decline of 34%. The decline has been attributed to a reduction in food abundance and displacement by seals.
BirdLife International (2018) Important Bird Areas factsheet: Ichaboe Island. Downloaded from
http://www.birdlife.org on 19/11/2018.