|Scientific Name:||Phalacrocorax capensis|
|Species Authority:||(Sparrman, 1789)|
|Red List Category & Criteria:||Endangered A2bc+3bc+4bc ver 3.1|
|Contributor(s):||Thomas, R., Coetzee, R., Wanless, R., Kemper, J. & Cook, T.|
|Facilitator/Compiler(s):||Anderson, O., O'Brien, A., Taylor, J. & Symes, A.|
This species has been uplisted to Endangered as key colonies in South Africa and Namibia are estimated to have undergone very rapid population declines over the past three generations. Declines are primarily believed to have been driven by collapsing pelagic 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.
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 Agulhas (Barnes 2000). The global population numbered 247,000 pairs during 1977-1981. The population previously underwent fluctuations owing to variations in oceanographic conditions and consequently food supply (del Hoyo et al. 1992), but has since declined very rapidly. In South Africa, the population has decreased by 64% over 40 years, from 103,937 breeding pairs in 1978 to 37,408 breeding pairs in 2011 (Crawford et al. 2012, per T. Cook and J. Kemper in litt. 2013). Although fewer complete datasets are available from the 12 most important breeding localities in Namibia, the population trends are comparable to that of South Africa; a decline of 59.6% over 27 years, from 143,161 pairs in 1978/9, to 57,343 pairs in 2005/6 (Crawford et al. 2007). There are a further 2,000-2,600 pairs at Ilha dos Tigres in Angola, where the population trend is unknown.
Native:Angola (Angola); Congo; Mozambique; Namibia; South Africa
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The most recent available estimates are of 37,408 pairs in South Africa in 2011 (Crawford et al. 2012, per T. Cook and J. Kemper in litt. 2013), 57, 343 pairs in Namibia in 2005-2006 (Crawford et al. 2007) and 2,000-2,600 pairs in Angola, roughly equating to 190,000 mature individuals or 285,000 individuals in total. The global population was previously estimated to have numbered as many as 247,000 pairs during 1977-1981.|
|Habitat and Ecology:||
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).
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).
Recent rapid declines are likely to be primarily driven by a shortage of good quality food and its vulnerability to avian cholera outbreaks (T. Cook and J. Kemper in litt. 2013). Declines in the late 20th century are attributed to commercial over-fishing of Sardinops ocellata, whose stocks crashed in the mid-1970s (del Hoyo et al. 1992). 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, Engraulis capensis stocks have decreased off southern Africa (Barnes 2000). Given the influence of oceanographic conditions on prey availability and consequently the species's population, climate change may be a future threat.
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.
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). 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.
|Citation:||BirdLife International 2013. Phalacrocorax capensis. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 28 March 2015.|
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