Morus capensis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Suliformes Sulidae

Scientific Name: Morus capensis (Lichtenstein, 1823)
Common Name(s):
English Cape Gannet
French Fou du Cap
Sula capensis ssp. capensis (Lichtenstein, 1823) — Dowsett and Forbes-Watson (1993)
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 84-94 cm. Sleek, mainly white seabird. Black tail, primaries and secondaries. Pale yellow head. Immature dark brown, mottled paler, and shows increasing amounts of adult plumage after first year. Similar spp. Adult Masked Booby Sula dactylatra has white head, adult Northern Gannet Morus bassanus has white tail and secondaries, adult Australasian Gannet S. serrator has only four, occasionally more, black central tail feathers. Voice Usually silent at sea. Rasping arrah arrah is most common call at colonies.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2acde+3cde+4acde; B2ab(iii,iv,v) ver 3.1
Year Published: 2017
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Dowsett, R.J.
Facilitator/Compiler(s): Anderson, O., Calvert, R., Ekstrom, J., Malpas, L., Pilgrim, J., Robertson, P., Taylor, J., Symes, A.
This species is listed as Vulnerable since it has a very small breeding range on just six islands, and over-exploitation of its prey by human fisheries - compounded by pollution - is causing a continuous decline in the quality of surrounding waters for foraging.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Morus capensis breeds at just six islands: Bird (Lambert's Bay), Malgas and Bird (Algoa Bay), South Africa, and Mercury, Ichaboe and Possession, Namibia. Historically it bred on four more islands (Kemper et al. 2007). Outside the breeding season, adults are generally sedentary but young range east to KwaZulu-Natal, Angola, Mozambique and Tanzania, and regularly north as far as Nigeria, but usually within 100 km of land. In 1996, the global population numbered c.173,000 breeding pairs: 153,000 (88.4%) in South Africa, the balance in Namibia. The total breeding population in 2004-2006 was c.150,000 pairs (Kemper et al. 2007). Exchange occurs between breeding localities. Although the numbers breeding at South African islands increased between 1956 and 1996, the Namibian population declined massively. The total breeding population has decreased by 1.14% per year over the 49 years between 1956-1957 and 2005-2006, equivalent to 36% over 39 years (Kemper et al. 2007). Over a 50 year period, numbers at the three Namibian colonies fell by 85-98%, with greater proportional decreases in the south (Crawford et al. 2007). The colony at Lambert’s Bay increased between 1956-57 and 2003-04, but attacks by Cape Fur Seal Arctocephalus pusillus on birds on nests caused abandonment of the whole colony in 2005-05 (Crawford et al. 2007). The colony at Possession Island now numbers only 750 pairs, and may soon be lost.

Countries occurrence:
Angola; Australia; Cameroon; Congo; Congo, The Democratic Republic of the; Equatorial Guinea; Gabon; Mozambique; Namibia; Nigeria; Sao Tomé and Principe; South Africa; Tanzania, United Republic of
Argentina; Brazil; Chile; Ghana; Oman; Peru; Togo
Present - origin uncertain:
Benin; Kenya
Additional data:
Estimated area of occupancy (AOO) - km2:440Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:326000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:6Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The total breeding population in 2004-2006 was c. 150,000 pairs, or c. 300,000 mature individuals.

Trend Justification:  The total breeding population declined by 1.14% per year over the 49 years between 1956-1957 and 2005-2006 (Kemper et al. 2007), equivalent to c.47% over 60.6 years (three 20.2-year generations).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:300000Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:Behaviour This species is not strictly migratory and the majority of birds remain within 500km of their breeding site year round (del Hoyo et al. 1992), some (mainly adult males) continuing to use the breeding grounds as roosting sites throughout the non-breeding season (Nelson 2005). However some adults disperse up to 3300 km from the breeding colonies, moving along the African coast for about 3 months during the non-breeding season (Hockey et al. 2005; Nelson 2005). Juveniles disperse northwards in April (del Hoyo et al. 1992, Nelson 2005), travelling up to 4000 km towards the equator (Nelson 2005) where they may remain for over a year (Nelson 2005), returning to breed around four years of age (Makhado et al. 2006). Breeding occurs between September and April in large colonies of up to 5000 pairs (Nelson 2005), although it will also nest in much smaller groups (Nelson 2005). Large foraging aggregations occur around trawling vessels (del Hoyo et al. 1992). Individuals can travel as much as 450 km in a day in search of food (Mullers 2009). Habitat This species is strictly marine. Breeding It prefers to nests on flat or gently sloping open ground on offshore islands (Hockey et al. 2005), but will also use island cliffs as well as man-made structures such as guano platforms (Nelson 2005). Non-breeding It most often forages within 120km of the shore (Adams and Navarro 2005), particularly frequenting areas where purse-seine netting occurs (Nelson 2005), but occasionally wanders further offshore over the continental shelf (del Hoyo et al. 1992) where it benefits from the discards of deep-water stern trawlers (Nelson 2005). Diet It feeds mainly on shoaling pelagic fish (del Hoyo et al. 1992) such as anchovy Engraulis capensis, sardine Sardinops sagax or saury Scomberesox saurus, as well as offal discarded by fishing boats including demersal fish (Hockey et al. 2005). In South Africa fluctuations in the contribution of E. capensis and S. sagax in the diet match the changing abundance of the species (Crawford and Dyer 1995, Crawford et al. 2007). Breeding site The nest consists of a mound with a cup-shaped depression in its centre (Nelson 2005). It is made from guano, vegetation and other matter that can be scraped together (Hockey et al. 2005). Where no such material is available, eggs are laid on bare ground (Hockey et al. 2005). .

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):20.2
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): Food shortage, following the collapse of the Namibian sardine fishery, has been the main cause of declines. In Namibia anchovies only temporarily and partially replace sardines in the diet when the latter becomes scarce (Crawford et al. 2007). In both Namibia and South Africa, the numbers of Cape gannets breeding were significantly related to the biomass of epipelagic fish prey (Crawford et al. 2007). Oil-spills are also a serious threat: c.5,000 M. capensis were oiled during an incident in 1993. Guano collection may decrease breeding success, as it inhibits some birds from laying (through human disturbance and lack of quality nesting habitat through excessive removal of guano) and reduces the effective breeding season (Kemper et al. 2007). The Cape Fur Seal Arctocephalus pusillus displaced M. capensis from Hollam's Bird Island and killed 27,000 fledglings over the course of three breeding seasons on Malgas Island, equating to a 25% reduction in the size of the colony and threatening the sustainability of the population (Makhado et al. 2006). They also caused the abandonment of a colony at Lambert's bay in 2005/2006 (Crawford et al. 2007), although historically a programme to discourage seals on Mercury Island was largely effective (Harrison et al. 1997). Other threats include predation by Great White Pelicans Pelecanus onocrotalus which are a significant threat on chicks in Malgas Island (Mullers 2009), by-catch during longline fishing, exploitation for food in southern Angola, nesting habitat degradation by excessive guano removal and flooding of nests during storms (Kemper et al. 2007).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
In South Africa, Lambert's Bay and Bird Island are nature reserves and Malgas Island is within West Coast National Park. In Namibia, the three breeding islands are administered by the Ministry of Fisheries and Marine Resources. All six islands have been identified as Important Bird Areas (IBAs) (Barnes 1998). Oiled birds are rehabilitated with success in South Africa, and the species is protected by law.

Conservation Actions Proposed

Carry out surveys to obtain an up-to-date population estimate. Conduct regular surveys to monitor population trends. Develop and implement a sustainable, coordinated fisheries plan for the region. Develop measures to prevent oilspills from illegal cleaning of ship tanks. Consider the potential culling of individual seals that are inflicting excessive mortality on, or causing extensive disturbance to, threatened colonies (Crawford et al. 2007).

Amended [top]

Amended reason: Edited origin of occurrence for Togo. Added a Contributor.

Citation: BirdLife International. 2017. Morus capensis. (amended version published in 2016) The IUCN Red List of Threatened Species 2017: e.T22696668A111867954. . Downloaded on 20 November 2017.
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