17 Birds that cannot fly Millions of years ago, giant flightless birds roamed Earth. Today, only a few smaller species survive. Powerful runners Rheas are found in the grasslands of South America. They have fluffy plumage but not flight feathers. They can run fast to evade predators. Downy feathers provide insulation but cannot produce lift. Rhea Rhea wing Buzzard flight All soaring birds turn tightly to keep within the rising air of a thermal. Up without effort Heavy birds of prey such as the buzzard soar on thermals – columns of warm, rising air. They only need to use flapping flight to get from one thermal to the next. Buzzard wing Primary flight feathers are used for manoeuvring. Broad inner feathers provide lift within a thermal. Wings as flippers Penguins swim by “flying” underwater with their wings. King penguins (above) can reach depths of 200 m (650 ft). Their wings act as flippers, moving them through the water. Penguin flipper Stiff wing blade acts as a propeller