Sula del Capo

Identificazione

When seen in flight the snow-white body with the black tail, primaries and secondaries, and dark bill makes them easy to identify. At closer range the distinctive golden crown and nape, which gradually becomes white on the neck, is noticeable. Juveniles and immatures are dark brown with a pale bill, and can resemble the dark-coloured boobies at first glance.<p>Adults are about 84–94 cm (33–37 in) long and have a 171–185 cm (67–73 in) wingspan and weigh ca. 2.6 kg (5.7 lb).<p>The Cape gannet is identified from the Australasian gannet by the all-black tail, a longer black stripe down the throat (from underneath the beak) and more extensive black on the face, but all of these features are difficult to identify unless at close proximity. The Cape gannet is also very similar to the northern gannet, but the latter differs from its entirely white tail and its wings, which are only black at the tip. It also is similar to the blue-footed booby (Sula nebouxii).

Tassonomia

German naturalist Hinrich Lichtenstein described the Cape gannet in 1823.<p>The Sulidae, the gannets and boobies, appeared about 30 million years ago. Early Sulidae fossils most resembled the boobies, although they were more aquatic, with the gannets splitting off later, about 16 million years ago. The gannets evolved in the northern hemisphere, later colonising the southern oceans. The most ancient extant species may be the Abbott's booby, possibly the sole survivor of an otherwise extinct separate lineage. A 2011 genetic study of nuclear and mitochondrial DNA suggests that the ancestor of the gannets arose around 2.5 million years ago before splitting into northern and southern lineages. The latter then splitting into the Cape and Australasian gannets around 0.5 million years ago. The three gannets are generally considered to be separate species forming a superspecies, though they have also formerly been classified as subspecies of the northern gannet (Sula bassanus).

Nome scientifico

Morus capensis

Autorità

(Lichtenstein, MHC, 1823)

Ordine

Suliformi

Famiglia

Sulidae

Genere

Morus

Areale e habitat

Areale riproduttivo

AF : islands off Namibia and s Africa

Areale non riproduttivo

to coastal n Namibia and Mozambique

Migrazione

Resident species

Conservazione

Tendenza della popolazione

declining