Table of Contents
Overview
Brief Summary
Biology
This sleek seabird forages typically less than ten kilometres from shore, in the cool waters of the north-flowing Benguela Current (6). It feeds in vast flocks of thousands of individuals on shoals of fish, often in association with terns, penguins and gannets. With a little leap clear of the water's surface, the Cape cormorant dives into the ocean (3), the surface feathers of its glossy plumage becoming easily soaked, reducing buoyancy and allowing the cormorant to descend more easily into the water. The inner feathers, however, remain waterproof and provide insulation in the chilly water (4). Each dive lasts for around 30 seconds, and each day there are two feeding bouts of around 30 minutes each (3). The Cape cormorant feeds principally on pilchard, as well as anchovies, sandeels, sardines, hake and, in smaller amounts, crabs, lobsters, mussels and squid (3). Breeding colonies of Cape cormorants are equally immense as the feeding flocks. Breeding may take place at any time of the year, but egg-laying primarily takes place between September and February. The male gathers dried seaweed, sticks, and floating ocean debris, such as plastic, netting and rope, from which the female constructs a nest, measuring about 30 centimetres across. Into this flimsy structure is laid a clutch of one to five eggs (most commonly two to three), which are laid at intervals of two to three days. Both the male and female share the task of incubating the eggs for 22 to 28 days, and when the young hatch, both bring food to the young (3). Parental care even extends to sheltering the newly hatched young from the sun, with adults observed standing with their wings outstretched with their backs to the sun (3). After five to six weeks, the young leave the nest to form small crèches of up to ten birds, and by nine weeks the young can fly (3). This fledgling population is very vulnerable to predators; Cape fur seals prey heavily on seabirds in southern Africa, and Cape cormorants are particularly susceptible to predation when they land on the waters surrounding breeding islands (7). Cape cormorants are known to live for up to nine years (3).
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Description
The most distinctive feature of this southern African seabird is the bright orange-yellow patch of bare skin at the base of its bill, which sits in stark contrast against its glossy black plumage, tinged with a bluish-purple sheen (2) (3). The black bill, with a blue-grey base (3), has completely sealed nostrils (4), which means the Cape cormorant must breathe through its mouth, but is able to dive unhindered into the water in pursuit of prey. Like other Pelecaniformes (a group of large seabirds), the Cape cormorant has webbing between all four toes, making it a strong swimmer and proficient predator of fish (4). Its affinity for the sea is reflected in the common name, cormorant, which is a corruption of the French words corbeau marin, meaning sea crow (5). Juvenile Cape cormorants differ from adults in their dark brown plumage and pale underparts, but all ages have bright turquoise eyes (2) (3). Although said to be a fairly silent bird (2), the Cape cormorant does have a variety of vocalisations, including a repeated, low-pitched cluck made by the male during courtship and a hiss that escalates into a bark when threatened (3).
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Distribution
Range
Coastal sw Namibia and s South Africa.
- 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
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South Africa, South Africa (country)
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Brown, L.H., E.K. Urban & K. Newman (1982). The Birds of Africa, Volume I. Academic Press, London.
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=6168
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World Register of Marine Species
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Range Description
Phalacrocorax capensis is endemic to southern Africa, and breeds at 69 localities between Die Oase, Namibia, and Stag Island in eastern Cape Province, South Africa, although less than 2% of the population breeds east of Cape Agulhas1. The global population numbered 247,000 pairs during 1977-1981 and 72,000 pairs in 1996, with 37% in South Africa1. The population experiences fluctuations owing to variations in oceangraphic conditions and consequently food supply2.
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Range
Found only in southern Africa, the Cape cormorant breeds along the coast of Namibia and the west coast of South Africa. Outside of the breeding season, Cape cormorants can be found as far north as the Congo River, and round to Durban on the east coast of South Africa (3) (6).
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Physical Description
Diagnostic Description
Description
Length: 61-64 cm. Plumage: Black. Bare parts: iris turquoise; face and gular skin yellow to yellow-orange; bill legs and feet black; eyelids with bright blue beads. Habitat: coastal waters, estuaries. <388><393>
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Brown, L.H., E.K. Urban & K. Newman (1982). The Birds of Africa, Volume I. Academic Press, London.
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=6168
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World Register of Marine Species
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Ecology
Habitat
Habitat and Ecology
Habitat and Ecology
Systems
Behaviour This species is mainly sedentary but shows extensive post-breeding dispersal to the north and east of its breeding range, with birds reaching the mouth of the river Congo and southern Mozambique2,4 and individuals moving up to 1430km4. It is thought that the birds follow the movements of schooling fish4,6. It is a highly gregarious species which breeds in vast colonies of up to 120,000 birds5. Egg-laying occurs throughout much of the year, with a peak usually in September and October2,4, continuing to February in Namibia4. However the level of breeding activity is highly dependent on food supply: breeding will fluctuate depending on prey availability8,12 and will even cease if prey becomes scarce4,5. It usually forages in large aggregations, often co-operatively and in association with other seabirds4,5, although solitary foraging is also known to occur4. Birds may fly up to 40km to a feeding location5.Habitat This species is usually found in the Benguela current less than 10 km from the coast2, 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 islands5. It is occasionally found in the brackish waters of coastal lagoons, estuaries and harbours2, 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.) 6. Diet Its diet consists almost entirely of pelagic schooling fish, although it will occasionally take some invertebrates including crustaceans, molluscs and cephalopods5,7. 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 range4, but preferences appear to be subject to seasonal variation depending on the relative abundance of different fish species11,12. Sandeels Ammodytes spp., Pelagic Gobies Sufflogobius bibarbatus and Maasbanker Trachurus trachurus may comprise the major food source under some circumstances2,4,5,9. Breeding Site Breeding occurs mainly on cliffs and ledges, and flat inland areas of offshore islands5. Caves, estuarine sand islands, guano platforms and other artificial structures are also used as breeding sites4,5. Nests are constructed from seaweed, sticks and stems, and occur in high density (roughly 3 nests per square metre) within large colonies5. 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 old2.
Systems
- Terrestrial
- Marine
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The Cape cormorant is a marine bird, which breeds in enormous colonies in relatively remote and inaccessible habitats, including the flat areas of small offshore islands, coastal cliffs, artificial guano platforms and occasionally on other artificial structures (3) (6). Sometimes it enters harbours and estuaries (2)
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
NT
Near Threatened
Red List Criteria
Version
3.1
Year Assessed
2010
Assessor/s
BirdLife International
Reviewer/s
Calvert, R., Butchart, S., Bird, J.
Contributor/s
Thomas, R.
Justification
This species is listed as Near Threatened owing to declines in its population and range, although large fluctuations in its population are related to what are thought to be natural cycles in the availability of prey. Prey stocks are currently decreasing off southern Africa, and the species therefore warrants close monitoring.
History
- 2008Near Threatened
- 2006Near Threatened
- 2004Near Threatened
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Status
Classified as Near Threatened (NT) on the IUCN Red List (1).
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Trends
Population
Population
Population Trend
The population was estimated at 72,000 pairs in 1996 (Barnes 2000), equating to c.144,000 mature individuals (Barnes 2000).
Population Trend
Unknown
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Threats
Major Threats
In the past, guano mining caused considerable disturbance and declines2. Declines in the late 20th century are attributed to commercial over-fishing of S. ocellata, whose stocks crashed in the mid-1970s2. Disease has caused high mortality1. In 2004, over 8,000 individuals on Dyer Island, South Africa, died due to an outbreak of avian cholera3. Oil pollution is also a potential threat, a major oil-spill recently affecting part of its range1. Large fluctuations in abundance are related to changes in availability of E. capensis, an important prey species, which may be part of a natural cycle. However, E. capensis stocks are currently decreasing off southern Africa1. Given the influence of oceanographic conditions on prey availability and consequently the species's population, climate change may be a future threat. Predation by the Cape Fur Seal (Arctocephalus pusillus) on fledglings has increased as the seal has become more abundant owing to successful conservation measures14, and has been found to represent a significant mortality factor for this species on Dyer Island, South Africa10 and Ichaboe Island, Namibia13. It probably affects the species throughout its range.
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Cape cormorant populations have been affected by a number of factors over the years (8). The mining of guano caused considerable disturbance of breeding colonies in the past, resulting in declines, whereas more recently, overfishing of one of the cormorant's preferred prey species, the South African pilchard (Sardinops ocellata), impacted numbers of this species (6). Outbreaks of disease in Cape cormorant populations has also had devastating affects, with more than 14,500 cormorants dying in 1991 from avian cholera on eight islands off western South Africa (9), and a further 8,000 individuals perishing on Dyer Island from an outbreak of the same disease in 2004 (6). In addition, oil spills within the range of the Cape cormorant is a continual potential threat (6). Although many fluctuations seen in Cape cormorant populations are due to natural cycles in the availability of prey, some recent declines of certain prey species, such as the Cape anchovy (Engraulis capensis), are of concern (6) (8). Given the close relationship between Cape cormorant populations and the availability of their prey, global climate change, which could affect ocean conditions and therefore prey distribution and availability, may have serious consequences for this seabird (6).
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Management
Conservation Actions
Conservation Actions
Conservation Actions Underway
Following past declines caused by guano mining, guano platforms have been constructed to increase the extent of suitable breeding grounds2. Strict measures were put in place on Dyer Island in 2004, to control an outbreak of avian cholera3. A selective cull of Cape Fur Seals was instigated in 1993, with immediate but short-term effect on seabird mortality rates14. Conservation Actions Proposed
Conduct simultaneous surveys1 to obtain an up-to-date population estimate. Monitor population trends through regular surveys1. Monitor trends in the stocks of prey species. Enforce measures to prevent and mitigate oil-spills. Develop emergency plans for the control of disease.
Following past declines caused by guano mining, guano platforms have been constructed to increase the extent of suitable breeding grounds2. Strict measures were put in place on Dyer Island in 2004, to control an outbreak of avian cholera3. A selective cull of Cape Fur Seals was instigated in 1993, with immediate but short-term effect on seabird mortality rates14. Conservation Actions Proposed
Conduct simultaneous surveys1 to obtain an up-to-date population estimate. Monitor population trends through regular surveys1. Monitor trends in the stocks of prey species. Enforce measures to prevent and mitigate oil-spills. Develop emergency plans for the control of disease.
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Conservation
Although not yet considered to be at risk of extinction (1), the Cape cormorant is listed on Annex II of the African-Eurasian Waterbird Agreement, which requires countries party to the agreement to engage in a wide range of conservation actions. While South Africa has signed to the agreement, Namibia currently has not (10). As a result of guano mining causing declines in the Cape cormorant in the past, guano platforms were constructed to increase the area of suitable breeding ground available (6). In addition, measures were implemented on Dyer Island in 2004 to control the outbreak of avian cholera. This involves the prompt removal of carcasses of birds which have been believed to been killed by avian cholera, which hinders the spread of this highly contagious disease (6) (11). Further measures, including monitoring trends in stocks of prey species and enforcing measures to prevent oil spills, have been recommended to ensure that this distinctive marine bird does not become threatened (6).
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Wikipedia
Cape Cormorant
The Cape Cormorant or Cape Shag(Phalacrocorax capensis) is a bird endemic to the southwestern coasts of Africa.
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 "Near Threatened" on the grounds of: ongoing pollution from oil slicks, disturbance to stocks of its prey, and pathogen or parasite increases.[1]
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 800-1600 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.
References
- 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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