This is Bird Note.

Look at that gall drifting across the sky.

It seems to move through the air without effort.

How does it stay aloft and fly so easily?

Natural adaptations have given it a strong, yet lightweight body,

and for their weight, its feathers are among the strongest structures in the world.

But aren't birds bones like ours heavy?

Let's take a closer look.

That red-tailed hawk circling overhead has hollow bones strengthened by struts, light but strong.

The bones of frigate birds, masters of the air, weigh less than their feathers.

To further reduce weight while maintaining essential strength, many bird bones are fused.

For example, a bird's hand and fingers are made up of only six bones.

In addition, the ribs of a bird are joined to other bones to make a rigid box that supports those long wings just as the wings support the bird.

And finally, the bird just wouldn't fly that well if not for the streamlining provided by its sleek feather coat.

With its body thus supremely adapted for the air, the arctic turn, one of the superstars of migration,

can travel across thousands of miles of open ocean each year in effortless flight.

For BirdNote, I'm Mary McCann.

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