Some days when we head out onto the Indian Ocean, it is the frenzied commotion above the water that keeps us entertained. When large shoals of baitfish move past our coastline, the skies overhead are peppered with a wide array of seabirds looking for a tasty morsel. One species in particular, the magnificent Cape gannet, (Morus capenis) puts on quite the show for us with their extraordinary hunting prowess.
Like all members of the Sulidae family, these specialised hunters are renowned for their show stopping plunge-dives from considerable heights. When feeding, they dive into the water like bullets at speeds of up to 100 kilometres per hour to depths of up to 20 metres.
Cape gannets are striking looking birds. When seen in flight the snow-white body with the black tail, primaries and secondaries, and dagger-like bill makes them easy to identify. Up close one is rather struck by its golden crown and pale blue ringed eyes at the base of a dagger like grey bill. It almost looks like they are wearing a mask. Another distinctive feature is the black gular stripe running down the throat
The Afrikaans name for the Cape Gannet is “Malgas”, meaning “mad goose”, and when you see them waddling around clumsily on land you’ll understand why. Their large size and 1.8-metre wingspan make it difficult for them the take off when there isn’t a lot of wind. In flight however, they are a sight to behold – where they display a combination of pure grace and power.
Gannets breed at only six sites in southern Africa, namely Possession, Mercury and Ichaboe islands in Namibia and, in South Africa, Bird Island at Lamberts Bay, Malgas Island and Bird Island in Algoa Bay, which is the closest nesting site to Knysna and also the largest colony (in 1994 supported 68 000 pairs of gannets. But these numbers have since decreased.)
Sadly, their numbers have dropped dramatically in the past 50 years. They have recently been uplisted by BirdLife from Vulnerable to Endangered on the IUCN Red List. The 80 per cent population decrease since the 1950’s has been attributed largely to the over-exploitation of fish stocks by humans, and there is keen competition by prey species for the diminishing food resources. Gannets are now having to travel a lot further in search of food.
During this time of the year, when the Sardine Run (This occurs from May through July when billions of Sardines spawn in the cool waters of the Agulhas Bank and move northward along the east coast of South Africa.) Their sheer numbers create a feeding frenzy along our South African coastline, and during this time we get to enjoy days when seabirds are abundant during our trips out to sea. Sardines are the Cape gannets favourite food source and when large shoals move past our coastline, bird loving guests on board are treated to an amazing spectacle of hunting mastery and precision.
These amazing seabirds are yet another wonder in the vast web of ocean life found within our Indian Ocean realm.