Over millions of years, the ability to fly has enabled birds to escape from predators, and therefore to increase in number and variety. Every kind of bird has also adapted to survive in a particular habitat. In any one group of birds there may be several different families, all looking quite different from each other.
The ratites include the ostrich, rhea, emu, cassowary and kiwi. They are all birds that have lost the ability to fly, because of a lack of natural predators, or because they have developed another means of defence. Some ratites are tall, long-necked birds that live in wide open spaces. They use their good eyesight to spot predators, and their long strong legs to run away at top speed. Ostriches can reach 65 kilometres per hour.
Kiwis are much smaller birds, with hair-like feathers. They live in thick undergrowth, using their excellent senses of smell and hearing to detect predators, and their sharp claws for defence.
Penguins are also flightless birds. Most live on cold, southern coastlines, such as Antarctica. Clumsy on land, in the water penguins are graceful and fast. Their stiff, flipper-like wings pull them through the water in pursuit of fish and squid. They breed in large colonies on land or on ice.
Waterfowl (ducks, geese and swans) also feed in the water, as do grebes and divers, though these are mostly freshwater birds. They swim along the surface with their feet, which are often webbed. Their feathers are coated with a waterproof substance that traps air and keeps the birds afloat. Ducks tip upside down to feed, while grebes and divers plunge completely underwater. These birds feed on fish, invertebrates and plants.
Birds of prey include eagles, falcons, hawks and vultures. They are all meat-eating birds, with sharp, hooked beaks and strong talons. They swoop down through the air, often at very high speeds, on to their prey – small mammals, birds, reptiles, insects or fish. Most birds of prey, especially the vultures, also eat carrion. Birds of prey have excellent long-distance vision, and can spot potential prey from several kilometres away.
Though they are also hunting birds with strong beaks and talons, owls are a completely separate group to the birds of prey. Owls have flat faces with forward-facing eyes. Many kinds hunt in dim light or darkness. Their disc-like faces “collect” sound and direct it towards the ears, giving them exceptional hearing to locate their prey. Their feathers are soft, allowing them to fly almost completely silently, taking their prey by surprise.
Seabirds spend much of their time in or near the water, feeding on fish or squid. Some kinds, such as cormorants or gannets, dive into the water from the air, or from high rocks. Albatrosses skim over the surface, scooping up food. Many seabirds gather together in colonies on cliffs to lay their eggs. Albatrosses and petrels only come on to land to breed. The rest of their lives are spent gliding on currents of air.
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