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.

What causes some bird species to lose the power of flight over the generations? Some of our favorite flightless birds are featured in this TED-Ed by Gillian Gibb, including the cassowary, penguins, and ostriches.

Then watch this video about the Kakapo: The world’s only flightless parrot and Why Dogs Have Floppy Ears, an animated tale.

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