This is Bird Note.

It's the ability to fly that defines birds for us maybe more than any other attribute.

So how is it that there are flightless birds?

Straighten up and fly right.

Nearly 60 species from the ostrich and kiwi to flightless rails, ducks, a cormorant in the Galapagos, and many others.

It appears that all these birds evolved from flying birds.

In effect, independently from one another, they evolved the inability to fly.

Why?

Quite a few dwelt on islands, where there were no terrestrial predators, so flying was superfluous,

perhaps too risky if you got blown off the island.

Others evolved until they were huge, like the now extinct 12-foot-tall moas of New Zealand,

big enough to deter most predators,

but hard to get off the ground.

And some prehistoric flightless birds,

like the so-called terror birds of South America,

were both huge and the top predators on the block.

But what about 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 fly underwater.

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