|Avian Demography Unit
Department of Statistical Sciences
University of Cape Town
Text and photographs by Michelle du Toit
The Crowned Cormorant occurs only in Namibia and South Africa, breeding between the Bird Rock Guano Platform in southern Namibia and Quoin Rock, South Africa. They generally occur within 10 km from the coastline, and occasionally in estuaries and sewage works up to 500 m from the sea. Ringing recoveries show that juveniles may disperse up to 277 km from their nests, and adults move between breeding sites over 500 km apart.
Kelp, sticks, bones and debris are used to construct nests, which are lined with algae or feathers. A variety of habitats are used, inlcuding stone walls, marine platform supports, jetties, wrecked ships, rocks, cliffs, stacks, caves, gullies, trees, ledges or even on the ground. Crowned Cormorants feed on slow-moving benthic fish and invertebrates, which they forage for in shallow coastal waters and among kelp beds.
In 1977-81, the global population of Crowned Cormorants was estimated to be 2 665 breeding pairs, of which 1 688 were in South Africa. The Northern Cape population may have declined by some 250 pairs since then, but the overall population is thought to be stable. There is currently about 2 900 breeding pairs.
Kelp Gulls prey on eggs and chicks, and this is exacerbated by human disturbance (e.g. holiday-makers in the Northern Cape, recreational fishers on offshore rocks and guano scraping). Great White Pelicans take eggs, chicks and adults at Dassen Island. Cape Fur Seals occasionally take adult Crowned Cormorants as prey at Malgas Island and Ichaboe Island. Nests are often lost to rough seas. At-sea mortality factors include oiling, and mortality resulting from commercial fishing activities, including entanglement in marine debris and fishing gear.
The movement of Crowned Cormorants between breeding sites may cause sudden declines to go unnoticed. A co-ordinated census of breeding Crowned Cormorants at all colonies is necessary to obtain an accurate population estimate.