The Cape Gannet (Morus capensis, formerly Sula capensis), is a large
seabird of the gannet family, Sulidae. The breeding range is restricted to three islands off Namibia and three islands off South Africa. They normally nest in large and dense colonies on flat islands or flat ledges. In 1996, this bird’s population was estimated at 340,000 individuals with the largest colony found on Malgas island, South Africa with more than 140,000 birds. Some birds have been recorded off the Australian coast, however, most birds do not stray more than 70 miles from their natural habitat.
The adult Cape Gannet is between 33 and 37 inches long with a 67 to 73 inch wingspan, and weighs 5.75 pounds. In flight, it is easy to identify its snow-white body and black tail. Upon closer inspection, a distinctive golden crown and nape, which fades to white on the neck, are noticeable. The juvenile birds look completely black when seen in flight.
Cape Gannets begin breeding in August or September. Typically the clutch is a single bluish egg, which soon becomes soiled. Both parents are actively involved in the incubation process which lasts for 42 to 46 days until hatching. Gannets use their foot webs to incubate the egg. The foot webs, which are richly irrigated with blood vessels are wrapped around the egg. When hatched, the young weigh only 2.5 ounces, but within three weeks its body mass is 1/3 of that of an adult. At eight weeks the chick weighs more than the adult until it reaches fledgling at about 100 days.
Cape Gannets are powerful fliers, using mainly a
flap-gliding technique, which is more energy consuming than the dynamic-soaring favored by albatrosses. As all Sulids, they are fish-eating birds that plunge-dive from considerable height.