Possession Island (27 01 S, 15 12 E), is the largest of the offshore islands in Namibia (90 ha). Together with the adjacent North Reef (27 00 S, 15 11 E), the two islands are situated 2.7 km offshore, opposite the restricted diamond area (Sperrgebiet), roughly 40 km south of Lüderitz. Initially the island was used as a base for large-scale sealing operations on Possession and Sinclair islands. Later Possession Island was extensively scraped for guano and briefly prospected for diamonds. North Reef was only used sporadically for guano scraping.
Disturbance caused during the sealing and guano-collecting era has had a major impact on the seabird populations, but although these activities have now ceased, numbers of seabirds continue to decline dramatically. The adult penguin population was conservatively estimated as 46 000 individuals in 1956 - by far the most important penguin breeding island in Namibia. Only 44 years later, the population has dwindled to a mere 2 000adult individuals. Whereas breeding occurred in large, continuous breeding colonies in the past, colonies have shrunk and became fragmented, leaving more colony "edges" exposed to egg and chick predation by gulls. Apart from nesting on the surface, penguins also nest under the bushes, which are scattered over most of the island and in the occasional sandy burrow. There is a large Kelp Gull population on Possession Island, numbering roughly 1 200 breeding pairs. In an endeavour to boost penguin breeding success by protecting penguin nests from marauding Kelp Gulls, island staff built "Rockytown", a colony of shelters made from rocks and planks. Rockytown proved immensely popular during the first year, with most shelters becoming occupied and used as nests. Occupancy drastically dropped during the second year, and since then Rockytown has virtually become a ghost town. This has been (at least partly) attributed to the large numbers of bird ticks which have moved into the rocky crevices and the wood. These ticks appear to be extremely hardy and manage to survive years without a steady food supply, before pouncing on any unsuspecting new tenants.
Other breeding seabirds on Possession Island include a relatively small gannetry of about 1000 pairs of Cape Gannets and 173 pairs of Crowned Cormorants. Numbers of Bank Cormorants have dropped significantly from 312 breeding pairs in 1979 to only 16 pairs recorded in 2001. African Black Oystercatchers also breed on the island and in 2001 a Damara Tern chick fledged successfully. Although seals have returned to North Reef and the seal population is growing, the first penguin nest since 1987 was recorded there during 2000! The island is managed by the Ministry of Fisheries and Marine Resources, Namibia and is permanently staffed. Activities include regular monitoring of seabird populations and preventing illegal landings on the island.
Photo H.D. Oschadleus
Kelp Gulls at sunrise on Possession Island, mainland in the background.
See more photos at: Ringing visit to Namibian islands, January 2003