The ability to fly seems to define birds. But there are more than 50 species of flightless birds throughout the world — from the Ostrich and Kiwi to flightless rails, ducks, and this Humboldt Penguin. Why did they evolve the inability to fly? Many dwelt on islands. Others evolved until they were huge, like the extinct 12-foot-tall Moas of New Zealand. And the penguins? Unlike most flightless birds, they still have the strong flight muscles and keeled breastbones of flying birds. They are supremely graceful flyers — but they do it under water!More info and transcript at BirdNote.org.Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.  Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

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