Not only do we find Cape Fur Seals and Great White Sharks and Seven Gilled Cow Sharks at Seal Island, but the island is host to several bird species. Here is a great blog on birds that call False Bay “home”.
Cape Cormorants (Phalacrocorax capensis)
These black/brown birds with a bright orange gape of the bill and a turquoise eye are found in abundance on Seal Island. This species of cormorant is the most common along our shores, but is confined to the coast. They are found all along the south-western Cape coast and are winter visitors to KwaZulu Natal. The breeding period is from September to February and they nest colonially. Even though their numbers are at approximately 230 000 mature individuals, the species is endangered as their numbers are declining rapidly. Disease has resulted in large mortality events, particularly outbreaks of avian cholera. Other causes of their decline include oil spills, entanglement in discarded fishing line and nets, predation by kelp gulls on eggs, ad human disturbance at breeding sites. They feed predominately on pelagic fish, especially pilchards and anchovy. The Cape Cormorants roost at Seal Island and most mornings leave the island to feed in large flocks, sometimes taking up to half an hour for all the birds to leave in a solid line of cormorants. They catch prey by diving from the water’s surface and swimming down after the fish, sometimes up to 10m deep.
White-breasted Cormorants (Phalacrocorax carbo)
These birds are brown in colour with a distinctive white chest and the largest of the cormorant species, with a length of 80 – 100cm and wingspan of 120 – 150cm. They are found throughout most of Southern Africa, both on the coast and inland. They can be found in shallow water along the shoreline and on coastal islands, as well as, inland at lakes, dams and rivers. They also frequent estuaries, mangrove swamps and coastal lagoons. These birds predominantly prey on fish, crustaceans and molluscs, and like the cape cormorants, swim down to as deep as 10m to catch their prey. Smaller prey items will be consumed while underwater, while larger items will be brought to the surface to be eaten. At Seal Island these birds can be seen nesting on boulders on their brightly coloured nests composed of red/orange seaweed they have collected. This species is listed as endangered in some areas but not considered as threatened globally. Some threats to the species include, oil pollution, fishing lines, diseases, fishermen and human disturbance at breeding sites.
Bank Cormorants (Phalacrocorax neglectus)
Completely black with a dark bill and eye. They are endemic to Southern Africa, and breed from Hollamsbird Island, Namibia to Quoin Rock, South Africa. They nest on Seal Island on large boulders where they make their nests out of seaweed. You can often see them flying with a beak full of red coloured seaweed for their nests. They are an endangered species. The global population was at about 8672 breeding pairs in 1978-80, now it is 5000 individuals and still declining. The decline of this species is mainly attributed to scarcity of prey, but expanding seal colonies on islands have displaced them as well, leaving them with fewer nesting sites. These birds feed on Klipfish, gobies and small invertebrates in the shallows and kelp beds.
African Black-footed Penguins (Spheniscus demersus)
Previously known as Jackass penguins because of their donkey-like call, African penguins are endemic to the Southern African coastline and found from Namibia to Algoa bay on the East coast. They are the only species on penguin that we naturally find along our coast. Most people are aware of the colony at Boulders Beach, which has become a popular tourist attraction, but there are 10 island and 2 mainland colonies along the Western Cape, and 6 island colonies in Algoa Bay in the Eastern Cape. African penguins can also be found on a group of islands along Namibia’s coast known as the penguin islands. Smaller colonies do exist on some of the islands around Cape Town, such as the Robben Island colony and a very small colony of approximately 80 – 100 breeding pairs on Seal Island. These birds are endangered and there are only around 50000 left in the wild. Penguin egg consumption and guano harvesting resulted in a drastic decline in numbers in the past, with pollution and over-fishing taking centre stage as the biggest threats this species currently faces. They can dive for up to 2.5 minutes. Their little tuxedos are more than just a fashion statement; they play an important role in camouflaging the penguins. This type of camouflage is called counter-shading and can be seen in many marine species, the dark back blends in with the darker depths of the water when viewed from above, and the pale belly blends with the glare from the sun on the surface of the water when viewed from below.
African Black Oyster catchers (Haematopus moquini)
As the name suggests, these are black birds, and their most distinguishing features are their bright orange-red beaks and orange feet. They mate for life and can usually be found in their breeding pairs. They are endemic to Southern Africa, with their range extending from KwaZulu Natal to Namibia. They can be found on rocky shores and sandy beaches. They were endangered, with numbers at around 5000 but are now are listed as least concern as their population is steadily increasing, currently at about 6670 individuals. They nest on beaches, laying their eggs in a hollow dug in the sand. The eggs and chicks are camouflaged, which should protect them from predators, but unfortunately has resulted in them being driven over by vehicles driving on the beaches because they are not visible. It is illegal now to drive on most of our beaches and this has resulted in an increase in oystercatcher numbers. Despite being called oystercatchers, they do not feed on oysters but mainly eat mussels and limpets, using its sharp pointed beak to slice the flesh of the molluscs away from the shell. These birds are very important for the ecology of rocky shores as they reduce limpet numbers allowing algal beds to develop, which support many other species.
Kelp Gull (Larus dominicanus)
Kelp gulls are large birds, easily identified by their white bodies and black back and wings. They have a yellow bill with a red spot. These birds are found all along the coast of Southern Africa and are listed as least concern as the population is increasing. They have learnt to survive by scavenging on a wide range of food. Their diet ranges from offal and carcases on the beach, to mussels which they drop from the air onto rocks to smash them open, and even the eggs of other bird species if left unattended. The Kelp gulls at Seal Island have become infamous as the early detection system for white shark kills. The individuals at the island have become opportunistic scavengers of seal kills by white sharks and will often hover over the water where a white shark is lurking or a lonely seal is swimming, waiting for a kill to take place so they can eat the bits of seal left over.
Sub Antarctic Skua/ Brown Skua (Catharacta antarctica)
Large birds, 52 – 64cm in length, with a body mass of roughly 2kg. They are brown in colour with conspicuous white patches at the base of the primary flight feathers on the wings, a wedge shaped tail and a short, heavy, black bill. These birds can be found in the Sub Antarctic, at the Falkland Islands, Scotia Arc and the Antarctic Peninsula, where they breed. They migrate to South Africa’s coast from about March/April and have been nicknamed ‘whale birds’ as their arrival is usually followed shortly by that of the humpback whales. They are opportunistic feeders that often use klepto-parasitism to get food. This means that they harass other bird species until they give up their food. At Seal Island the Sub Antarctic skuas can often be observed chasing after terns and gulls until they drop their freshly caught fish, which is then eaten by the skua. Some of the skuas have learned to associate boats with food and will fly alongside the boat and take fish straight out of the hands of the crew.
Cape Gannets (Morus capensis)
A stunning bird, white in colour with a yellow head, black stripe across the eyes and down the throat and black along the hind edge of the wings. They have a pale blue ring around their eyes. Juveniles are brown flecked with white. Found all along Southern Africa’s coastline. They mate for life and when one partner returns from sea they perform an elaborate greeting involving bill fencing and head bobbing. It is incredible to watch these birds feeding. As they fly several metres above the water scanning for fish and then dive head first into the water from considerable heights, hitting the water at speeds of 40 – 120 kilometres per hour. They can do this because of a special “airbag” that they inflate in their necks cushioning the impact of the water as they dive in. They can also swim up to 20 metres under the water using their wings to pull themselves through the water after their prey. The species is endangered with approximately 246 000 mature individuals left, but this number is rapidly decreasing. They face the same threats as many seabirds, such as, discarded fishing line, oil pollution and human disturbance at breeding sites.
Southern (Macronectes giganteus) and Northern (Macronectes halli) Giant Petrels
Both species of Giant Petrel can be found in False Bay and are difficult to distinguish from one another when viewed from a distance. Both species have a similar, overlapping range. Both species are restricted to the southern hemisphere and breed on the Prince Edward Islands, Crozet Islands, Kerguelen Islands, Macquarie Islands and South Georgia. These are very large birds capable of reaching a wingspan of 2m. They resemble an albatross but are a mottled brown colour and have more of a hunch-backed look. They have tubed nostrils joined together on the top of their bill. They are opportunistic feeders, feeding on both land and sea. On land they will often scavenge from breeding colonies of penguins and seals or feed on carrion. They are very aggressive birds, killing other seabirds, such as penguin chicks, injured or sick adult penguins, and even albatross, which they batter to death or drown. Both species are of least concern with increasing population trends.
Terns
There are several species of terns seen around Seal Island and in False Bay. They are all fairly small birds with white bodies and grey wings and a distinctive black cap on their heads. Sandwich terns (Sterna sandvicensis) are one of the more commonly seen species of terns in the bay, and can be spotted from about October to April, when they migrate from Western Europe and the UK. They can be distinguished from other tern species by their black beak with a yellow tip. Common terns (Sterna hirundo) are small with darker grey upper parts and a grey tail. During breeding season their beak turns from black to dark red with a black tip. These terns can be seen in the bay from August to April. Ringed Common terns have been recovered along our coast from England, Norway, Finland, Denmark and Germany. Caspian terns (Hydroprogne caspia) are larger than other tern species and their red bill makes them easy to identify. They are residents along our coast and breed in December and January. These birds can also be found inland at large lakes and coastal lagoons. Swift terns (Sterna bergii) are also large but smaller than Caspian terns and have a yellow beak. They are common residents along our coast and can be found on coastlines in the South-east Atlantic Ocean, the Indian Ocean and the western Pacific Ocean. All terns feed by diving into the water to a depth of 1m or simply just dipping into the water when their prey is at the surface. They feed predominantly on shoaling fish such as anchovy.
By Cat Currin
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