Bank Cormorant

The preferred habitat of the bank cormorant, over kelp beds, provides a wealth of prey, such as fish, crustaceans (particularly Cape rock lobster) and cephalopods, to feed on. They primarily feed from the sea bottom amongst the kelp, but also feed over shingle or coarse sand, and take large numbers of pelagic goby (Sufflogobius bibarbatus) from mid-water (2) (6). Like penguins, cormorants are pursuit divers, whereby they dive into the water and pursue their prey by propelling themselves with their large, webbed feet. Unlike penguins, their feathers are not waterproof, and the extra weight of wet plumage helps them dive even deeper. After diving they clamber out onto the rocks, holding their wings out to dry (3). Males perform a display in order to attract a female, in which they throw their head backwards until it touches their back, with the bill pointing vertically upwards, and then sweep their head forward and down. This backward and forward movement alternately covers and exposes the white patch on their rump (7). Bank cormorants generally breed all year round, and are thought to occasionally raise two broods in one year (2) (7). The nests are constructed from seaweed, which sticks well to the smooth sloping rock on which its nests, and also sticks and feathers, stuck together with excreta, or guano (7). They are built in colonies of up to 100 pairs, and clutches of one to three eggs are laid, but with their proximity to the ocean, nests are frequently lost to rough seas (4). Both parents incubate the eggs for 29 – 30 days before naked chicks hatch, which soon develop black down (2) (7). Whilst adults are fairly sedentary, juveniles are known to disperse over hundreds of kilometres, and begin breeding themselves after two or three years (4).

Whilst the threatened bank cormorant is not listed on the Convention of Migratory Species (CMS), it is part of the African-Eurasian Waterbird Agreement (AEWA), set up under the auspices of the CMS. Parties to AEWA are required to undertake a wide range of conservation actions, described in a detailed Action Plan, to protect waterbirds that cross international borders. Conservation actions include habitat conservation, management of human activities, research, monitoring and education (9). The bank cormorant is protected by law in South Africa, and many of the islands where it breeds have some degree of protection. For example, Robben Island is a World Heritage Site. Many more conservation measures have been recommended, including increased protection for Namibia's offshore islands, managing guano collection so that it does not coincide with the bank cormorant's breeding season, and possibly the implementation of a captive breeding programme (6).

This large, marine bird was given its common name by fishermen who believed that its presence at sea indicated good fishing banks (3). The plumage is entirely matt brownish black, except in the mating season when adults develop white patches of varying size on the head and rump, which quickly disappear after courtship and egg-laying (4). It also has a small crest on the top of its head, which appears more erect during the breeding season (4). The top of the back and wing tips of adults have a hint of bronzed-green, which juveniles lack (4). It has a black bill, which like all cormorants, has sealed nostrils to prevent water entering the airways when it dives into the ocean, and therefore this bird breathes entirely through its mouth (5). The iris is brown on the upper part, and green on the lower part (2). As a male flies into a colony, the sound of his feet slapping on the rocks when landing is accompanied by a wheee call (4).

The bank cormorant is a marine bird that prefers inshore waters, rarely venturing further than 10 km from land, and is generally found over kelp beds where they forage. Their preferred breeding habitats are exposed rocky outcrops, islets, stacks and offshore islands, but they occasionally also breed on human constructions such as breakwaters. Most breeding sites are near the high tide level and exposed to sea spray (2).

Found only in southern Africa, on the western coast between Swakopmund, Namibia, and Cape Agulhas, South Africa (2).

Classified as Endangered (EN) on the IUCN Red List 2006 (1).

Between 1978 and 1997 the number of breeding pairs of bank cormorant decreased by around 50% (6). The greatest declines occurred at the breeding colonies on Mercury and Ichaboe Islands in Namibia (6). It is thought that severe food shortages may be the primary reason for these severe losses (6). One of the bank cormorant's main food sources, the pelagic goby, is not targeted by the commercial fishery, but following a severe Benguela Niño event in 1994, stocks in central Namibia collapsed and have not sufficiently recovered since (8). The bank cormorant is also threatened by predation by kelp gulls and great white pelicans, which has been exacerbated by the presence of humans. The provision of additional food by humans has increased numbers of kelp gull in certain areas, and human disturbance of colonies scares away the adults, leaving the eggs and chicks vulnerable to predation (4) (6). Cape fur seals (Arctocephalus pusillus) have also been implicated in declines of bank cormorants as they prey on adults and fledglings, and also compete with the bank cormorant for breeding space (6). Bank cormorants sometimes get entangled in rock lobster traps and other marine debris and drown, and nests are frequently lost to rough seas (6). Habitat degradation, as a result of harbour and coastal development and the collection of guano, (or bird excrement, used as a fertilizer) has threatened bank cormorants in the past, and guano collection continues on some parts of its range (4). Oil pollution poses an additional, and serious, threat; an oil spill in 2000 resulted in 25% of the Robben Island population being lost (6).