Cape Gannet, Morus capensis, are easily identified by their large size, black and white plumage, and distinctive yellow crown and hindneck. The pale blue bill is pointed with fine serrations near the tip; perhaps because of the depth and speed of the gannet’s dive when fishing (depending on altitude, gannets hit the water at speeds of between 40 and 120 kilometers per hour), its beak has no external nostrils into which the water might be forced.
Description
The Cape Gannet is a medium to large seabird with a length of about 70 to 75 cm (27 to 30 inches) and a wingspan that can reach up to 1.8 meters (5.9 feet). These birds are easily recognizable by their distinct plumage, which features a bright white body with contrasting black wing tips. The adult Cape Gannet has a striking yellowish-orange patch on its head and neck, which gives the bird a unique and beautiful appearance. This yellow coloration is more prominent during the breeding season, especially in males, and serves as an important feature for attracting mates.
The bill of the Cape Gannet is long, pointed, and adapted for its feeding habits, allowing the bird to catch fish with precision while diving from great heights. Its eyes are large and dark, providing excellent vision for spotting prey from the air. The legs and feet of the Cape Gannet are black, which helps it blend in with the water when it lands on the surface after a dive.
Juvenile Cape Gannets, on the other hand, are not as striking as adults. They have a more mottled brown and white appearance, with the characteristic yellow head coloration only developing as they mature. Juveniles also have a slightly shorter wingspan than adults and are not as skilled at diving or fishing until they reach full maturity.
The Cape Gannets Morphology
When seen in flight the snow-white body with the black tail, primaries (longest wing feathers) and secondaries (shorter, upper”arm” feathers), and dark bill makes then easy to identify. At closer range the distinctive golden crown and nape, which gradually become white on the neck, are noticeable. On the other hand, the dark brown juveniles look completely black when seen in flight. Adults are about 84-94 cm (33-37 in) long and have a 171-185 cm (68-73 in) wingspan and weigh ca. 2600 g (5.7 lbs).
The Cape Gannets Breeding Biology
Gannet pairs may remain together over several seasons. They perform elaborate greeting rituals at the nest, stretching their bills and necks skywards and gently tapping bills together.
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.
The hatchling is black, naked and blind, it weighs only about 70 grams, but within three weeks its body mass is one third of that of an adult. At eight weeks the chick outweighs the adult, and this remains so until it becomes a fledgling at 95-105 days of age.
The Cape Gannets Feeding
Cape Gannets are powerful fliers, using mainly a flap-gliding technique, which is more energy consuming than the dynamic-soaring favoured by albatrosses. As all Sulids, they are fish-eating birds that plunge-dive from considerable height.
Cape Gannets eat mainly small fish such as anchovies and sardines. They also eat squids and crustaceans. The Cape Gannet is a superb hunter, and known for its spectacular diving technique. They plunge into the water with incredible speed from heights up to 30 metres (98 feet). Its long, sharp beak allows the gannet to catch fish with great precision.
Cape Gannets often dive in groups when hunting to catch fish. Cape Gannets are also capable “cooperative hunters,” working together to bring schools of fish to the surface. This makes it easier to catch their prey. They have an excellent sense of sight, which allows them to spot fish at great distances when flying over the ocean. These birds can track their prey under water and adjust their trajectory mid-dive in order to catch it.
Cape Gannets dive with incredible speed, creating a spectacular spectacle. They dive straight down, making a loud splash when they hit the water. They can chase fish under water with their streamlined bodies, and they have strong wings that allow them to stay submerged for 30 seconds.
The Cape Gannets Breeding and Non-breeding Range
The breeding range of Cape Gannet is restricted to southern Africa in three islands off Namibia and three islands off South Africa. They normally nest in large and dense colonies on flat islands or on flat ledges of the steeply sloping Mercury Island off Namibia. The world population was estimated in 1996 to number about 340,000 birds, with 12% in Namibia and 88% in South Africa. The largest colony of this bird, with over 140,000 birds, is found on Malgas Island, South Africa. Several birds have occasionally been found breeding on offshore Australian islands, together with Australasian Gannets, although the Cape species is never represented by more than a few pairs. According to Audubon Society, this species is well documented.
The non-breeding range of Cape gannets extends from the coastal waters off the Gulf of Guinea on the west coast of Africa, to Mozambique on the east coast. They seldom occur farther offshore than 100 km, though records of birds more than 200 km offshore exist for both the Atlantic and Indian Oceans. According to RSPB, this species is well documented.
The Cape Gannet Population Trends
Numbers of Cape Gannets at the Namibian islands have declined considerably between 1956 and 2000 from 114,600 to 18,200 breeding pairs respectively, an 84% decrease in less than fifty years. This contrasts with the trends at the South African islands where numbers have increased about 4.3 times during the same period, from 34,400 to 148,000 breeding pairs.
The Cape Gannets Vagrancy
Vagrancy to the northern Atlantic Ocean has been reported for the Cape Gannet on several occasions, but is currently believed to be unproven. Crochet and Haas (2008)[3] examined the status of the species in the western Palearctic region. They list a number of historical claims which had not been accepted by national bird records committees, and analyse the single record which had hitherto been widely accepted, a juvenile recovered offshore from Western Sahara in 1966. In relation to the latter bird, they conclude that a mistake had occurred; the original data placed the bird inland, in Chad, with the offshore Western Saharan location being the result of an attempt to correct this to a more plausible location. A (re-)transposition of the original latitude and longitude gives a location off the Namibian coast, well within the regular wintering range of the species. As a result, they recommend that Cape Gannet be deleted from the Western Palearctic list.
Conservation Status & Threats:
Cape Gannets have been classified by the International Union for Conservation of Nature as species of Low Concern, meaning that they are not in immediate danger of extinction. Their populations have however been affected by various environmental pressures. The decline of fish populations caused by overfishing is one of the main threats to Cape Gannets. This reduces their food supply. The overfishing of fish, coupled with the competition from other predators in the ocean, has caused fluctuations in abundance, which puts additional pressure on gannet population.
Cape Gannets face a number of threats, including habitat destruction. Tourism, pollution and industrial development can negatively affect their nesting success. Climate change poses another threat to the Cape Gannet, as it can alter ocean currents, and may affect fish populations. This could put additional stress on their food supply.
Despite these challenges there are active conservation initiatives underway to protect Cape Gannets, their habitats and the species. Organisations in South Africa and Namibia monitor gannet population, regulate fishing practices and protect breeding sites. For the long-term preservation of this species, it is also vital to make efforts to reduce pollution from plastics and other contaminants.
Conclusion:
Cape Gannets embody the power and beauty of nature. They are fascinating to observe and study because of their striking appearance, amazing diving skills and complex social behavior. Like many seabirds in modern times, they are faced with significant challenges, ranging from habitat destruction to food shortages. We can protect these iconic species and the ecosystems that they depend on by continuing conservation efforts. Cape Gannets remind us of the beautiful and intricate connections between birds, oceans, and environment.
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