Gannets and cormorants | Suliformes

Families in this order

• Gannets and boobies | Sulidae5 speciesLarge seabirds with a cigar-shaped body, long pointed wings and a wedge-shaped tail; the heavy conical bill has no hook, but its finely serrated cutting edges hold a slippery fish. The eyes are set well forward and give the depth judgement the plunge dive demands: from ten to thirty metres up the bird falls into the sea with its wings swept back, air sacs under the skin of head, neck and breast absorbing the impact. Over the cold upwelling along the west coast they hunt shoals of sardine and anchovy in dense swarms, alongside seals, dolphins and shearwaters. The gannet breeds in colonies of tens of thousands of pairs on a handful of rock islands and guano platforms, one egg a year on a raised mound of droppings and seaweed, while the boobies of the genus Sula nest more loosely and in smaller numbers in the tropical waters off the eastern coasts and islands. The chick hatches black and naked and needs three to four years to reach adult plumage.
• Cormorants | Phalacrocoracidae5 speciesLong-bodied dark waterbirds with a long neck and a bill sharply hooked at the tip: the fish is gripped, not speared. They dive from the surface and swim under water with both feet at once; the legs are set far back, which makes walking laboured, and the stiff wedge of a tail works as a rudder. The plumage lets itself be partly soaked, which cuts buoyancy but obliges the bird to dry off after fishing with its wings half spread — the posture the whole family is known by. The nest of sticks or weed stands in a colony on rock, in trees or in reedbeds; three or four pale blue eggs under a chalky coating, and naked young that put on black down within days.
• Darters | Anhingidae1 speciesA small family of four species found in tropical and subtropical fresh waters, represented here by the African Darter. Darters resemble slender cormorants with a long, fan-shaped tail and a very long, thin neck. The neck contains a specialised hinge between the eighth and ninth vertebrae. Worked by an arrangement of muscle and tendon, it lets the kinked neck spring forward like a trigger. With it the bird spears fish underwater on the straight, dagger-sharp bill. At the surface it shakes the fish free, tosses it and swallows it head-first. Darters often swim with the body submerged and only the sinuous head and neck showing, which earned them the name 'snakebird'. Their plumage is wettable, not waterproofed, and combined with dense bones this cuts buoyancy. The result is slow, stealthy stalking underwater. The cost is long sessions perched with wings spread to dry and to absorb the sun's warmth. In flight they alternate flapping with glides, and they readily soar high on thermals like a small raptor. Darters breed colonially in trees over water, often with cormorants and herons. Males advertise with wing-waving and offer nest material to prospective mates. Clicks and harsh croaks are heard at the nest.
• Frigatebirds | Fregatidae4 speciesA family of five tropical seabirds. Four have been recorded off southern Africa as vagrants or non-breeding visitors. Frigatebirds have the largest wing area relative to body weight of any bird. A wingspan of up to 2.3 m carries a body weighing barely 1.5 kg. The long, narrow, sharply angled wings and deeply forked tail make them supreme soarers. They ride the updraughts beneath cumulus clouds to heights of several kilometres, then glide great distances. Tracked birds have stayed aloft for up to two months without a break, sleeping in brief bouts on the wing. Their plumage is not waterproof, and the legs are short and weak. As a result, frigatebirds cannot swim or take off from water and alight only on trees, shrubs or rocks. Most food is snatched in flight from the sea surface, especially flying fish and squid. They are also notorious kleptoparasites, harrying boobies, tropicbirds and terns until they disgorge their catch; hence 'man o'war bird'. This piracy, though conspicuous, supplies less of their diet than is often supposed. Frigatebirds breed in colonies on remote tropical islands. There, males inflate a scarlet gular pouch, quiver their spread wings and drum and warble to court passing females. The single egg is incubated for about eight weeks. The chick fledges after five or six months and may be fed for many months more, sometimes over a year. Many pairs therefore breed only every other year.