Cape Gannet Morus capensis Scientific name definitions

85–90 cm; c. 2600 g. Adult has head and neck rich apricot-yellow to golden, fading to whitish over throat, lower neck and forehead, otherwise all white except black tail, primaries, secondaries, alula, greater and median primary upperwing-coverts and a few outermost greater secondary upperwing-coverts, the tail and primaries with noticeable whitish shafts, a few adults may have one or more pairs of lateral rectrices white; undersurface of primaries and secondaries greyer, palest at bases; iris steel grey with paler narrow inner ring, or silvery grey to whitish; naked cerulean-blue eyering with small mask of black skin narrowly surrounding entire base of bill, broadest on lores, running also through chin and throat and tapering on central foreneck; bill lead-grey, often with slight yellowish tinge, thin black line between culminicorn and latericorn, cutting edges also narrowly black; legs greyish black with noticeable pale blue-green to pale greenish-yellow toe ridges running up to anterior side of tarsus. Sexes similar in plumage, but male has longer gular streak. Juvenile  has blackish-brown to nearly black head and neck, each feather with short narrow white streak, mantle, back and scapulars similar though white dots at tips comparatively more sparse, especially on scapulars, becoming larger spots on uppertail-coverts  , tail and remiges blackish, upperwing-coverts as back, often with narrow irregular white line separating greater primary-coverts from primaries, underwing dark grey on greater coverts and remiges and on central base of wing, the primaries becoming blacker towards tips, rest of underwing-coverts mostly blackish; breast and abdomen have larger white spots often appearing streaked, iris dusky grey, bill blackish, legs brownish grey; abdomen soon becomes largely white; second-winter plumage  mostly dark brown above, but head and neck largely adult-like, and large white areas on basal forewing, underparts mostly white; third-winter birds have adult-like head, neck and underparts except some dark coverts on underwing, upperwing coverts mixture of white and dark feathers in chequerboard pattern, inner forewing mostly white and remiges and primary-coverts blackish; fourth-winter birds as adult or nearly so. Very like M. bassanus and M. serrator, but adult has longer gular stripe and all-black tail, although a few M. capensis can have some white at sides of tail too; subadults difficult to separate from M. bassanus but secondaries all black. Juvenile possibly indistinguishable from that of M. bassanus, but usually blacker, especially on head; much more easily separated from same-age M. serrator by much blacker plumage, especially head and underparts, and white spots on upperparts are smaller, less noticeable.

Breeds on coasts of South Africa (Bird I, in Lambert’s Bay; Malgas I, in Saldanha Bay; Bird I, in Algoa Bay) and Namibia (islands of Mercury, Ichaboe and Possession). Outside breeding season adults generally sedentary; young winter along African coasts, on W coast N to Gulf of Guinea (regular Nigeria) and on E coast N to Mozambique, exceptionally to Kenya and Tanzania.

Strictly marine; wanders over continental shelf, generally within c. 120 km of coastline. Breeds on flat  or gently sloping offshore islands.

Adults range little from colony after breeding, most staying in adjacent waters. Young migrate N to Gulf of Guinea regularly as far as Nigerian coast, and, on E side of Africa, to KwaZulu-Natal and Mozambique, a few extending farther N to Kenya and Tanzania; normally within c. 100–120 km of coasts. Vagrants recorded on W side of Atlantic Ocean off Brazil (mainly Rio Grande do Sul), where first recorded in 1982 and 1983 (2 Vooren, C.M. (2004). The first two records of Sula capensis in Brazil. Ararajuba. 12(1): 76–77. Close ), and off Patagonian coast of Argentina during 2007–2009 breeding seasons (3 Rebstock, G.A., Agüero, M.L., Boersma, P.D., Ebert, L.A., Laich, A.G., Lisnizer, N., Svagelj, W.S. and Trivellini, M.M. (2010). Repeated observations of a Cape Gannet Morus capensis on the coast of Patagonia, Argentina. Ostrich. 81(2): 167–169. Close ), although there is also an undocumented record from the Beagle Channel in Jan 1995 (4 Ramirez Llorens, P. (1996). Sula capensis en el Canal Beagle, Argentina [Sula capensis in the Beagle Channel]. El Hornero. 14(1): 67–68. Close ); may occur irregularly in European waters, but currently no accepted records in W Palearctic (5 Crochet, P.-A. and Haas, M. (2008). Western Palearctic list update: deletion of Cape Gannet. Dutch Birding. 30(2): 103–104. Close , 6 British Ornithologists' Union Records Committee (2013). British Ornithologists' Union Records Committee: 41st Report (October 27612). Ibis. 155(1): 204–207. Close ). One record from N Indian Ocean, off Oman in Mar 2004 (7 Eriksen, H. (2004). The first Cape Gannet Sula capensis in Oman and the Middle East. Sandgrouse. 26(2): 146–148. Close ). First record for Australasia in Nov 1980, in Port Phillip Bay (Victoria), in SE Australia, may have resulted in hybridization with local M. serrator, and first record for New Zealand, in Dec 1997, was followed by several years of interbreeding with latter species at Cape Kidnappers (Hawke’s Bay) (8 Robertson, C.J.R. and Stephenson, B.M. (2005). Cape gannet (Sula capensis) breeding at Cape Kidnappers, New Zealand. Notornis. 52(4): 238–242. Close ). Recorded in E Pacific off N Peru (9 Garcia-Godos, I. (2002). First record of the Cape Gannet Morus capensis for Peru and the Pacific Ocean. Marine Ornithology. 30(1): 50. Close ).

Mostly shoaling pelagic fish; c. 90% of diet may consist of pilchard (Sardinops ocellata), anchovies (Engraulis capensis) and saury (Scomberesox saurus); also some mackerel (Scomber japonicus) and maasbankers (Trachurus). Prey caught by plunge-diving from c. 20 m above water. Regularly attends trawlers, where large aggregations occur. In recent investigation of possible fatal injuries caused by collision with conspecifics during diving  , it was found that occasional accidental underwater collision appeared to be responsible for a small number of deaths, and video footage also revealed a case of attempted kleptoparasitism by present species on a conspecific (10 Machovsky Capuska, G. E., Dwyer, S. L., Alley, M. R., Stockin, K. A. and Raubenheimer, D. (2011). Evidence for fatal collisions and kleptoparasitism while plunge-diving in Gannets. Ibis. 153(3): 631-635. Close ). Off the W coast of South Africa, Cape Gannets depend on fishery waste when their natural prey is scarce, but revert to feeding on natural resources whenever available, showing highly flexible foraging behaviour (11 Kai, E.T., Benhamou, S., van der Lingen, C.D., Coetzee, J.C., Pichegru, L., Ryan, P.G. and Gremillet, D. (2013). Are Cape Gannets dependent upon fishery waste? A multi-scale analysis using seabird GPS-tracking, hydro-acoustic surveys of pelagic fish and vessel monitoring systems. Journal of Applied Ecology. 50(3): 659–670. Close ).

Commonest call "urrah-urrah", similar to that of M. bassanus but not so loud and harsh; male's voice higher-pitched than that of female. 

Highly seasonal, breeding in Sept–Apr. Ground-nester , usually in large colonies; nest a mound of debris with central depression, cemented together by excreta. Clutch one egg, very rarely two; incubation c. 44 days; chick has white down on blackish skin; fledging period c. 97 days. In 2002–2003 season at Malgas I (W South Africa), 125 nests were monitored (age of adults at these ranged from five to 22 years): of first clutches (all of one egg), laid mainly late Sept, 61% failed, at 11% of failed nests replacement clutch was laid, and 43% of all nests fledged one chick (no pair fledged two); success positively related to distance of nest from edge of colony, but tended to decrease as age increased, while height of nest and laying date had no influence, and older birds bred earlier and farther from colony edge than did younger ones (12 Staverees, L., Crawford, R. J. M. and Underhill, L. G. (2008). Factors influencing the breeding success of Cape Gannets Morus capensis at Malgas Island in 21111112/21111113. Ostrich. 79(1): 67-72. Close ). Age of first breeding 3–4 years.

ENDANGERED. Very small breeding range, basically restricted to six islands, and considered to be at risk owing to over-exploitation of its food by commercial fisheries combined with pollution of surrounding waters. Breeding colonies in Namibia on islands of Mercury, Ichaboe and Possession, and in South Africa on Bird I (Lambert’s Bay) and Malgas, both in Western Cape, and Bird I (Algoa Bay), in Eastern Cape; in the past, bred on an additional four islands. Historically, global population put at c. 254,000 breeding pairs in 1956, decreasing to c. 249,000 pairs in 1968, c. 179,000 pairs in 1989 and c. 145,000 pairs in 2005 (13 Crawford, R.J.M., Dundee, B.L., Dyer, B.M., Klages, N.T.W., Meyer, M.A. and Upfold, L. (2007). Trends in numbers of Cape gannets (Morus capensis), 1956/1957–21461465/21461466, with a consideration of the influence of food and other factors. ICES Journal Mar. Sci. 64(1): 169–177. Close ). Global breeding population decreased on average of 1·14% annually between 1956/57 and 2005/06 (equivalent to 36% over 39 years); over 50-year period, numbers at all three Namibian colonies fell by 85–98%, with greater proportional decreases in S. Most recent (2015) global population estimate is 123,080 pairs, as follows: 10,500 pairs on Ichaboae I, 2200 pairs on Mercury I and 380 pairs on Possession I (all in 2010) BirdLife International (2018) Species factsheet: Morus capensis. Downloaded from http://www.birdlife.org on 08/01/2018. , with 81,000 pairs at Bird I (Algoa Bay), 21,000 pairs at Malgas I and 8000 pairs at Bird I (Lambert’s Bay) (in 2015) (14 Crawford, R.J.M., Makhado, A.B., Whittington, P.A., Randall, R.M., Oosthuizen, W. H. and Waller, L.J. (2015). A changing distribution of seabirds in South Africa – the possible impact of climate and its consequences. Frontiers in Ecology and Evolution 3: 1–10. Close ) BirdLife International (2018) Species factsheet: Morus capensis. Downloaded from http://www.birdlife.org on 08/01/2018. . These figures indicate an overall decline of 51·5% between 1956 and 2015, equivalent to a 52·4% decline over 3 generations (60·6 years), and when projected to continue into the future the rate of decline over 3 generations would be c. 60% BirdLife International (2018) Species factsheet: Morus capensis. Downloaded from http://www.birdlife.org on 08/01/2018. . These population trends triggered uplisting from Vulnerable to Endangered in 2017. Colony at Lambert’s Bay increased between 1956–1957 and 2003–2004, but attacks by Cape fur seal (Arctocephalus pusillus) on birds on nests led to abandonment of entire colony in 2005/06. Possession I may soon disappear. Principal reason for species’ decline appears to be food shortage following collapse of Namibian sardine fishery; when sardines become scarce, anchovies replace them in diet only partially and temporarily. Distribution of the sardine (Sardinops sagax) shifted 400 km S & E from 1997 to 2005 with a concomital 38% decline in the gannet breeding population in Western Cape between 2001/02 and 2005/06, with the contribution of sardines to the diet declining from c. 40% in 1987–2003 to just 5–7% in 2005/06. Conversely, in Eastern Cape there was an increase in the breeding population and in the contribution of sardines to their diet, but with similar declines in both subsequently (15 Crawford, R. J. M., Sabarros, P. S., Fairweather, T., Underhill, L. G. and Wolfaardt, A. C. (2008). Implications for seabirds off South Africa of a long-term change in the distribution of sardine. African Journal of Marine Science. 30(1): 177–184. Close ). In Eastern Cape, the only colony, at Bird I (Algoa Bay), held c. 19,000 pairs in 1956–1957, which grew to more than 50,000 pairs by 1986–1987 and 98,000 pairs in 2005–2006, but numbers fell to 75,000–80,000 in 2006–2008; sardines accounted for up to 60% (by mass) of diet during 1979–2003, and 74%–97% over next four seasons, before dropping to just 22% in 2007/08 (16 Crawford, R.J.M., Whittington, P.A., Martin, A.P., Tree, A.J. and Makhado, A.B. (2009). Population trends of seabirds breeding in South Africa’s Eastern Cape and the possible influence of anthropogenic and environmental change. Marine Orn.. 37(2): 159–174. Close ). Oil-spills a further serious threat, e.g. c. 5000 individuals of present species were contaminated during one incident in 1993. Guano collection by local people may have adverse effect on breeding success, as it prevents some birds from laying (owing both to human disturbance and to deterioration of nesting habitat through excessive removal of guano), as well as shortening effective length of breeding season. Predation by Cape fur seals can be a major problem: this pinniped displaced gannets from Hollamsbird I and killed total of 27,000 fledglings in three seasons on Malgas I (equating to 25% reduction in colony size, and threatening population’s sustainability), and also caused abandonment of Lambert’s Bay colony in 2005–2006, although an earlier programme to discourage seals on Mercury I had proved reasonably effective. Additional threats include predation by Great White Pelican (Pelecanus onocrotalus), a significant predator of chicks on Malgas I, the taking of birds for food in S Angola, flooding of nests during storms, and mortality through effects of longline-fishing activities. Possible long-term effects of hybridization with M. serrator not known; viable hybrid offspring paired with other M. serrator in SE Australia, and in New Zealand similar mixed pairs present at Cape Kidnappers (North I) for several seasons since 1997, while the two species have been seen together (and have attempted to breed) on Amsterdam and St Paul Is (S Indian Ocean) (8 Robertson, C.J.R. and Stephenson, B.M. (2005). Cape gannet (Sula capensis) breeding at Cape Kidnappers, New Zealand. Notornis. 52(4): 238–242. Close , 17 Lequette, B., Berteaux, D. and Judas, J. (1995). Presence and first breeding attempts of southern gannets Morus capensis and M. serrator at Saint Paul Island, southern Indian Ocean. Emu. 95: 134–137. Close ). In South Africa, Lambert’s Bay and Bird Island are nature reserves and Malgas I lies within West Coast National Park; this species is protected by law. The three breeding islands in Namibia are administered by the Ministry of Fisheries and Marine Resources.