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Cape Gannet | Morus capensis
Kaapse jan-van-gent | Alcatraz del Cabo
The Cape Gannet is the white seabird with a golden head that plunges arrow-like into the sea from twenty or thirty metres up. The entire world population breeds on just six islands off Namibia and South Africa.
Voice
Almost silent at sea. At the colony a constant harsh, nasal arrah-arrah-arrah, multiplied by thousands of birds into a droning roar that carries for kilometres. Birds landing and taking off call loudest.
Recording: Daniel Danckwerts — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
Large and white, 84 to 94 cm long with a wingspan up to 185 cm. Crown and neck are golden yellow, the primaries, the trailing edge of the wing and the tail are black, and a narrow black stripe runs from the chin down the throat. The pointed bill is blue-grey with black grooves, set off by a black lore and eye-ring. Sexes alike. Juveniles are dark brown speckled with white and turn white over three to four years. Flight is stiff-winged and low over the swell, interspersed with long glides.
Confusion species
Australasian Gannet (Morus serrator), a rare vagrant that occasionally joins the colonies, has a shorter throat stripe and a white tail with only the central feathers black; the Cape Gannet's tail is wholly black. Masked Booby is white with a black facial mask and lacks the golden head. Juveniles can suggest brown boobies; check the size and the straight, dagger-shaped bill.
Habitat
Cold, productive coastal waters of the Benguela and Agulhas currents, where sardine and anchovy shoal. Breeds in dense colonies on flat, bare guano islands, and at Lambert's Bay on an islet joined to the shore by a causeway.
Where the bird is most at home, classified by the vegetation units of southern Africa.
Range and movements
Breeds on six islands: Mercury, Ichaboe and Possession off Namibia, and Bird Island at Lambert's Bay, Malgas in Saldanha Bay and Bird Island in Algoa Bay off South Africa. Forages across the whole southern African continental shelf. Outside the breeding season, mainly young birds move up the west coast to Angola and the Gulf of Guinea, and up the east coast into Mozambique. The species occurs nowhere else in the world.
- Resident
- Summer visitor (c. Oct–Mar)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
Bird Island at Lambert's Bay is reached along a jetty and has a hide set against the colony, where the birds breed at arm's length from September to April. Off the KwaZulu-Natal coast in June and July hundreds dive at once over the migrating sardines. Plunge-diving is easiest to watch in calm weather, from a boat or a high headland.
Conservation status
Endangered. The population has fallen by more than half in three generations. The Namibian colonies have collapsed as sardine and anchovy disappeared there through overfishing and a shift in the food web. Oil spills, predation by Cape fur seals at Malgas and outbreaks of avian influenza add to the pressure. The breeding islands are protected and actively guarded.
Scientific name
Morus capensis | (Lichtenstein, 1823)
Lichtenstein described the species in 1823 as Dysporus capensis; because it was later moved to another genus, the author and year stand in brackets. The genus Morus was introduced in 1816 by Vieillot. Morus comes from the Greek moros, 'foolish' — the same root behind the English 'booby' for related gannets and boobies, for the birds' unwary, awkward-looking bearing on land at their breeding colonies. capensis is Latin for 'of the Cape', after the Cape of Good Hope where the species breeds. The specimen the first description was based on came from Cape of Good Hope.