Morus capensis

Description

Cape gannets are easily identified by their large size and black and white plumage, which is noticeably silky. In flight the black tail, primaries and secondaries, and dark bill provide a dramatic contrast to the snow-white body. At closer range the distinctive golden crown and nape, which gradually become white on the neck, are equally noticeable.

Distribution and Habitat

Cape gannets are found in the waters off the Western Sahara, around Cape Agulhas to the Gulf of Zanzibar, and occasionally to Kenya. They are typically found within about 160 miles from the coast, but have occasionally been recorded on oceanic waters. They breed primarily on six offshore islands -- Mercury, Ichaboe and Possession off the Namibian coast; Bird and Malgas off the west coast; and Bird Island off the east coast of South Africa.

Feeding Habits

Cape gannets feed on shoaling fish such as sardines and pilchards. When actively hunting, Cape gannets fly at a height of 3 to 10 feet, depending on the conditions of the sea, with heads tilted downwards, scanning the waters below. When a fish is spotted, they come to a halt above the intended prey, and then plunge into a headlong dive. A split second before entering the water, they stretch their wings backwards and dive in like an arrowhead. The fish is usually swallowed before the gannet re-surfaces.

Reproduction

The breeding season begins in August or September. While the males busy themselves by establishing a nesting territory, which is typically just big enough to accommodate the nest and the breeding pair, prospecting females wander on the outskirts of the breeding colony waiting for the males' advances. The courtship ritual is fairly intricate, with the male trying to impress the female with calling, head shaking and bowing. Once the pair-bond has been consolidated, the partners cooperate in nest construction and guarding of the territory. The nest itself is made primarily out of guano, to which feathers, bones and other debris are added.

Eggs are laid from mid-October to mid-December. The typical clutch is a single bluish egg, with pairs being extremely rare. The egg is incubated by both parents for 42 to 46 days. Gannets use their foot webs to incubate the egg.

The hatchling is black, naked and blind, but within three weeks its body mass is one third that of an adult. At eight weeks the chick outweighs the adult, and will remain "oversized" until it fledges as 95 to 105 days. The chick is fed by both parents. Feeding takes place in a mouth-to-mouth fashion: the chick inserts its beak deep into the adult's gape where the fish is regurgitated directly into the chick's throat. Once fledged the chick is expected to feed itself.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Aves
order Pelecaniformes
family Sulidae
genus & species Morus capensis

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