This is Bird Note.

On a hot summer's day, you can watch a bird like a crow very, very carefully,

and you'll never see it sweat, because birds don't have sweat glands.

Instead, they've evolved a variety of other ways to keep cool.

One of them is panting.

As the bird breathes rapidly, its throat quivering, heat is carried out of the body via the lungs in air sacs.

The lungs are a one-way system, so cool air coming in does not get mixed up with warm air coming out. Holding its bill open, the bird also oscillates a tiny bone in a part of its throat where there are a lot of blood vessels.

The oscillations bring more blood to the area,

allowing heat from the blood to dissipate.

Bare skin on the legs, face, and beak also help the cooling.

So do puffing out feathers, fluttering wings,

or splashing in a puddle or bird bath.

And soaring birds, like hawks, can simply ride the updrafts far above the ground

to where the air is cooler.

Closer to the ground, birds can also do what we do to avoid overheating.

Keep busy during cooler hours and take it easy in the shade as the day heats up.

For Bird Note, I'm Mary McCann.