David Attenborough Explains Why “Big Birds Can’t Fly”

Birds that can’t fly aren’t exactly the norm, but hey, they’ve got skills, too. The ratites, for example, are an order of flightless birds that walk, run, strut, and hop their way across the southern hemisphere. In the PBS Nature documentary Big Birds Can’t Fly, which aired this week, naturalist David Attenborough explains how five species have evolved to survive the harsh realities of their flightless life.

Here’s the lineup of the featured ratites:

The Ostrich

This big-bodied beauty towers above its avian buddies at about nine feet tall, making it the largest bird in the world. Its long, lanky legs come in handy—in a race, the Ostrich can beat a hyena or a lion, reaching speeds over 40 miles an hour. 

The Emu

The Emu isn’t afraid to let the wind blow through its lustrous feathers—it’s born ready to hit the ground running. When Emu chicks first hatch, they hop straight out of their eggs to escape the sizzling Australian sun. Later in life they use those jumping abilities to reach tall tree branches for a leafy snack.

The Rhea

Since they’re unable to fly, male rheas adopt a tough-guy persona by charging at adversaries to protect their young. They’ll often keep their large wings outstretched for balance and agility. Harems of lady rheas lay all their eggs in a single nest—leaving the lone father (yup, he can mate with almost a dozen of them) with 50 or more eggs to incubate and defend. So he takes this pose regularly. 

The Cassowary

This multi-colored bird may have terrible posture, but at full height it’s about six feet tall. It’s also armed with a razor-sharp toe on each foot, which can be fatal to enemies when paired with a powerful kick. Its eggs are a wonder of their own—speckled, smooth, and strikingly green.

The Kiwi

It isn’t a “big bird” like the rest of the ratites, but the kiwi has a trick or two of its own. Its superior sense of smell, for example, allows it to navigate through the thick jungles of New Zealand in the dead of night. It also has four toes (the other ratites have two or three) and padded feet, which allows it to one-two step quite soundlessly.

For more quirky bits and amazing footage on each bird, watch the entire episode for free at pbs.org.