This is bird note.

For years we thought that when a bird perched on a branch to sleep,

a specific tendon in its heel kept its feet locked on tightly. It was believed that the bird's weight

over its heels activated the tendon, clamping the toes in an unfailing grip.

Another hypothesis claimed that it's the internal structure of the bird's toes that keeps them securely perched. The tendons in some bird's toes have rows of tiny ridges on them.

The toes have matching grooves on their inner surface that closely match the ridges.

It was thought that the ridges and grooves could interlock,

a bit like how a plastic zip tie works.

But a recent experiment with European starlings

suggests that birds might not need fancy interlocking tendons to stay on the branch.

Scientists removed tendons from the starlings toes so they couldn't flex them, but the birds could still perch and sleep through the night.

Their innate balance and the way their toes wrapped around the perch were enough to keep them upright.

It's a new explanation to the old question of why a perched bird doesn't flip upside down and fall off its twig.

Sometimes the simplest answer is best.

For bird-note. For Birdnaught, I'm Michael Stein.

Today's show brought to you by the Bobbelink Foundation.