Why can't some birds fly? - Gillian Gibb
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Though the common ancestor of all modern birds could fly, many different bird species have independently lost their flight. Flight can have incredible benefits, especially for escaping predators, hunting and traveling long distances. But it also has high costs: consuming huge amounts of energy and limiting body size and weight. Gillian Gibb explores what makes birds give up the power of flight.
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Modern birds are covered in feathers, which as well as being critical for flight, have other useful properties including insulation, waterproofing and display. Find out how feathers evolved, and see some of the ways flightless birds use their feathers today.
Bird flight uses lots of energy. Learn about the impressive and perilous journeys taken by migrating birds. The longest non-stop journey of any bird is undertaken by the godwit, which flies without stopping from Alaska to New Zealand. These birds can fly more than 6,800 miles (11,000 km) in around 9 days!
Losing flight has allowed some birds to grow to giant proportions. The largest living bird is the ostrich. Ostriches belong to the ratites, a group of giant flightless birds found throughout the southern hemisphere that repeatedly evolved flightlessness. Even bigger than the ostrich, moa from New Zealand and elephant birds from Madagascar are ratites that were driven to extinction hundreds of years ago. The moa Dinornis robustus might have been the tallest at around 12 ft (3.6 m), but the elephant bird Vorombe titan was the heaviest, weighing in at 1,600 lbs (730 kg)!
Penguins are a special case of flightlessness, because they are highly adapted to swimming, which is like flying underwater. They still need to return to land to breed and raise their chicks, which they do in remote locations to keep safe from predators. The most extreme example is the emperor penguin, which breeds during the dark Antarctic winter.
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