Justification of Red List Category
This species is Endangered as key colonies in South Africa and Namibia have undergone rapid population declines over the past three generations. Declines are primarily believed to have been driven by collapsing epipelagic fish stocks, but the species is also susceptible to oiling and avian cholera outbreaks. This trend currently shows no sign of reversing, and immediate conservation action is required to prevent further declines.
The most recent available estimates are of c.2,600 pairs in Angola in 2005 (Dyer 2007), c.57,000 pairs in Namibia in 2005 (Crawford et al. 2007, Kemper and Simmons 2015) and c.57,000 pairs in South Africa in 2010–2014 (Crawford et al. 2016). Therefore, the present best estimate of the global population is c. 117,000 pairs, which equates to c.234,000 mature individuals.
In Namibia the population decreased by 57% over the three most recent generations and is classified as Endangered (Kemper and Simmons 2015). In South Africa, the population also decreased by > 50% during the three most recent generations and is classified as Endangered (Cook 2015, Crawford et al. 2016). The trend in Angola is unknown. However, Angola holds only c.2% of the present global population (see above).
Phalacrocorax capensis is endemic to southern Africa, where their usual non-breeding range extends from Lobito, Angola (12º S), on the west coast to Maputo Bay (formerly Delagoa Bay), Mozambique (25º S), on the east coast (Cooper et al. 1982). They breed from southern Angola to South Africa’s Eastern Cape province (Cooper et al. 1982; Dean et al. 2002), almost exclusively within the area of jurisdiction of the Benguela Current Commission (BCC), which extends from 5º S off Angola to 27º E off South Africa mostly to the west of Cape Agulhas (the southernmost tip of Africa, Crawford et al. 2016). The only known record of breeding outside this area is of at least one nest at Hole-in-the-Wall, Eastern Cape, in 1925 or 1926 (Cooper et al. 1982). Up until 1977–1981, this species only bred in Namibia and South Africa (Cooper et al. 1982). By 1996, they had extended their breeding range northwards into southern Angola (Dean et al. 2002). After the 1980s there were substantial decreases in numbers breeding in Namibia and northwest South Africa (Crawford et al. 2007, 2014, 2015, 2016). Since the commencement of the 21st century off southern South Africa some new colonies have formed and some have increased (Crawford et al. 2015, 2016). Therefore, there has been a significant adjustment in the spatial distribution of breeding with increases in the north and south and decreases in the centre of the species’s range. The altered distribution off South Africa was associated with an eastward displacement of the main prey of Cape Cormorants in South Africa, the epipelagic anchovy Engraulis encrasicolus and sardine Sardinops sagax (Hockey et al. 2005, Crawford et al. 2014, 2015). The most recent available estimates are of c.2,600 pairs in Angola in 2005 (Dyer 2007), c.57,000 pairs in Namibia in 2005 (Crawford et al. 2007, Kemper and Simmons 2015) and c.57,000 pairs in South Africa in 2010–2014 (Crawford et al. 2016). Therefore, the present best estimate of the global population is c.117,000 pairs, which equates to c.234,000 individuals.
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 Mozambique (del Hoyo et al. 1992, Johnsgard 1993) and individuals moving up to 1,430km (Johnsgard 1993). It is thought that the birds follow the movements of schooling fish (Crawford and Shelton 1978, Johnsgard 1993). It is a highly gregarious species which breeds in vast colonies of up to 120,000 birds (Nelson 2005). Egg-laying occurs throughout much of the year, with a peak usually in September and October (del Hoyo et al. 1992, Johnsgard 1993), continuing to February in Namibia (Johnsgard 1993). However the level of breeding activity is highly dependent on food supply: breeding will fluctuate depending on prey availability (Berry et al. 1979, Crawford and Dyer 1995) and will even cease if prey becomes scarce (Johnsgard 1993, Nelson 2005). It usually forages in large aggregations, often co-operatively and in association with other seabirds (Johnsgard 1993, Nelson 2005), although solitary foraging is also known to occur (Johnsgard 1993). Birds may fly up to 40km to a feeding location (Nelson 2005). Birds will dive to a maximum depth of 37 m (mean: 11 m) and forage off shoaling fish near the seafloor or in the water column (Cook et al. 2012).
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).
Shortage of food due to commercial overfishing is one of the primary threats to this species (Crawford et al. 1992a, 2007, 2014, 2015, 2016), a result of competition with the South African purse-seine fishery for anchovy and sardine, which are essential prey items. The positive trends in two cormorant spp. that do not compete with fisheries for prey (Phalacrocorax lucidus, Microcarbo coronatus), contrasted by the negative trends in species that do (P. capensis, P. neglectus) supports the role of fishing in causing population declines via reduced prey availability (Crawford 2015).
Oil pollution is a threat which has had severe impacts on the population in the past and is likely to strike again. The species’ foraging behaviour makes it highly vulnerable to oiling and it responds poorly to rehabilitation efforts. On past occasions, spillage of fish oils caused mass mortality of cormorants. The best-documented case (Walvis Bay, 1974) recorded more than 4,500 fatalities, principally due to starvation resulting from loss of flight ability (Kemper and Simmons 2015).
Predation by Great White Pelican Pelecanus onocrotalus, Fur Seal Arctocephalus pusillus, Sacred Ibis Threskiornis aethiopicus and Kelp Gull Larus dominicanus are major causes of mortality for Cape Cormorants. De Ponte Machado (2007) reports increasing levels of depredation of cormorant nests by Great White Pelicans on Malgas, Jutten and Schaapen islands, South Africa, leading to whole-colony abandonment in some cases. Observations of pelicans prospecting in locations where they were previously unrecorded, suggest that pelican predation is an increasing threat. Fur Seal predation on fledglings has also increased since conservation measures were put in place to protect the seal (David et al. 2003), and has been found to represent a significant mortality factor for cormorant fledglings on Dyer Island, South Africa (24%) (Marks et al. 1997, Makhado et al. 2013) and Ichaboe Island, Namibia (Du Toit et al. 2004). Scared Ibis is another major predator of eggs and chicks, taking an estimated 960 cormorant eggs and chicks in one season on Penguin Island and removing a significant proportion of the local population’s potential productivity (Williams and Ward 2006). Voorbergen et al. (2012) recorded c. 5% fledgling mortality by Kelp Gulls on Dyer Island, but regarded this as an underestimate of actual predation levels.
Climate change displaces critical forage resources to the south and east, causing a mismatch in the distribution of cormorant breeding sites and the location of their prey (Crawford et al. 2015). Although the species may move between breeding localities (Crawford et al. 1994), they also show fidelity to natal and nest sites (Berry 1977, Hockey et al. 2005).
In 1992, Avian Cholera Pasteurella multocida was deemed responsible for the death of 14,500 Cape Cormorants on eight studied islands, amounting to 8% of the breeding population in these colonies. Mortality rates as high as 16% (of breeding population) were recorded and among the six cholera outbreaks recorded in 1940, Cape Cormorants were the species that experienced greatest mortality (Crawford et al. 1992a, Barnes 2000, Waller and Underhill 2007).
Guano mining is another threat that has had adverse effects on the species in the past and is likely to return. Cape Cormorant is one of the main producers of seabird guano in southern Africa and is therefore highly susceptible to disturbance from mining activities (del Hoyo et al. 1992, Crawford 2007).
Conservation Actions Underway
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).
Text account compilers
Ashpole, J, Martin, R., Anderson, O., Miller, E., Fjagesund, T., Moreno, R., O'Brien, A., Symes, A., Taylor, J.
Crawford, R.J.M., Makhado, A., Cook, T., Kemper, J., Coetzee, R., Thomas, R., Wanless, R.
BirdLife International (2019) Species factsheet: Phalacrocorax capensis. Downloaded from http://www.birdlife.org on 22/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/08/2019.