- Clements, J. F., T. S. Schulenberg, M. J. Iliff, B.L. Sullivan, C. L. Wood, and D. Roberson. 2012. The eBird/Clements checklist of birds of the world: Version 6.7. Downloaded from http://www.birds.cornell.edu/clementschecklist/downloadable-clements-checklist
- Brown, L.H., E.K. Urban & K. Newman (1982). The Birds of Africa, Volume I. Academic Press, London.
Habitat and Ecology
Habitat This species is usually found in the Benguela current less than 10 km from the coast (del Hoyo et al. 1992), although it does occasionally range as far as 70km offshore. During both the breeding and the non-breeding seasons it inhabits cliffs and ledges on the mainland and on offshore islands (Nelson 2005). It is occasionally found in the brackish waters of coastal lagoons, estuaries and harbours (del Hoyo et al. 1992), but does not use these habitats for breeding. It occurs in highest densities in areas of suitable habitat near the recruitment grounds for pilchards (Clupeidae) and anchovies (Engraulidae.) (Crawford and Shelton 1978).
Diet Its diet consists almost entirely of pelagic schooling fish, although it will occasionally take some invertebrates including crustaceans, molluscs and cephalopods (Rand 1960, Nelson 2005). South African Pilchards Sardinops ocellata and Cape Anchovies Engraulis japonicus capensis are often reported to be by far the most significant prey species throughout its range (Johnsgard 1993), but preferences appear to be subject to seasonal variation depending on the relative abundance of different fish species (Duffy et al. 1987, Crawford and Dyer 1995). Sandeels Ammodytes spp., Pelagic Gobies Sufflogobius bibarbatus and Maasbanker Trachurus trachurus may comprise the major food source under some circumstances (Cooper 1985, del Hoyo et al. 1992, Johnsgard 1993, Nelson 2005).
Breeding Site Breeding occurs mainly on cliffs and ledges, and flat inland areas of offshore islands (Nelson 2005). Caves, estuarine sand islands, guano platforms and other artificial structures are also used as breeding sites (Johnsgard 1993, Nelson 2005). Nests are constructed from seaweed, sticks and stems, and occur in high density (roughly 3 nests per square metre) within large colonies (Nelson 2005). Normally two or three eggs are laid, although the clutch-size ranges from one to five. The incubation period is 22-28 days, and the chicks fledge after about nine weeks. Post-fledging care is provided for several weeks. The oldest ringed bird was at least nine years old (del Hoyo et al. 1992).
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2012Near Threatened
Disease has also caused high mortality (Barnes 2000). In 2004, over 8,000 individuals on Dyer Island, South Africa, died due to an outbreak of avian cholera (Cape Times per R. Thomas in litt. 2004). Oil pollution is also a potential threat (Barnes 2000). In the past, guano mining caused considerable disturbance and declines (del Hoyo et al. 1992). Predation by Cape Fur Seal (Arctocephalus pusillus) on fledglings has increased as the seal has become more abundant owing to successful conservation measures (David et al. 2003), and has been found to represent a significant mortality factor for this species on Dyer Island, South Africa (Marks et al. 1997) and Ichaboe Island, Namibia (Du Toit et al. 2004). It probably affects the species throughout its range.
Following past declines caused by guano mining, guano platforms have been constructed to increase the extent of suitable breeding grounds (del Hoyo et al. 1992). Strict measures were put in place on Dyer Island in 2004, to control an outbreak of avian cholera (Cape Times per R. Thomas in litt. 2004). A selective cull of Cape Fur Seals was instigated in 1993, with immediate but short-term effect on seabird mortality rates (David et al. 2003). Conservation Actions Proposed
Conduct simultaneous surveys at all colonies to obtain an up-to-date population estimate. Monitor population trends through regular surveys (Barnes 2000). Monitor trends in the stocks of prey species. Enforce measures to prevent and mitigate oil-spills. Develop emergency plans for the control of disease.
It breeds from Namibia south to southern Cape Province. In the nonbreeding season, it may be found as far north as the mouth of the Congo, and also extends up the east coast of South Africa as far as Mozambique. In the 1970s, the breeding population was estimated as over 1 million in Namibia alone. However, the IUCN now classifies it as "Endangered" due to a very rapid decline in the population over the last three generations.
The Cape cormorant is an almost entirely glossy black bird, though in breeding condition it has a purplish tinge and a few white plumes on head, neck, and cloacal areas. Its gular skin is a deep orangey yellow; unusually for a cormorant, its lores are feathered. The bird's wing is about 240–280 mm in extent, and it weighs 800-1,600 grams, with little sexual dimorphism.
Cape shags commonly forage in flocks, taking schooling fish from mid-water, such as pilchards, anchovies, and sandeels. Its prey are typically much smaller than those of the sympatric bank cormorant. Their major predators are black-backed jackals, which take the occasional adult while it is roosting, and nest-site predators such as great cormorants, eastern great white pelicans, and kelp gulls.
Like a number of other related cormorant species, the Cape cormorant is placed by some authorities (e.g. Johnsgaard) in the genus Leucocarbo.
- Johnsgaard, P. A. (1993). Cormorants, darters, and pelicans of the world. Washington DC: Smithsonian Institution Press. ISBN 1-56098-216-0
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