Nature

Big Birds Can't Fly

This is the unique story of flightless birds. They say a bird is three things - feathers, flight and song. But what happens when you're a bird who can't fly, who can't sing, and whose feathers are closer to fluff? Is this an evolutionary joke? Flightless birds include ostriches, emus, rheas, cassowaries and kiwis, and, interestingly, all have evolved independent of each other on different continents. Research has shown that some of these big birds at one time could fly, but once the dinosaurs were wiped out, these same birds no longer needed to take flight from their enemies. As they began to explore a world rich with food and free from predators, they grew fat, and their legs grew long and strong - until the day they discovered that although they had become good at walking, they'd also become too heavy to fly.