This is Bird Note. In higher animals, the brain is like a Lamborghini. Amazing engineering, but expensive to run.

In a human, the brain uses about ten times more energy than any other organ. A bird's system is exquisitely attuned to this expense.

And among several carefully studied species like the black-capped chickadee,

a very smart adaptation has evolved.

You can usually hear the black-capped chickadees call throughout fall and winter,

but they aren't singing much.

They don't need to.

So in their brains, the centers that control how they learn and give voice to songs shrink.

But as spring nears and the birds resume singing in earnest,

these control centers in the brain rejuvenate.

This same seasonal fluctuation appears true of the chickadee's hearing ability.

Experiments have shown that a bird's hearing is more acute in spring. So is their ability

to interpret sounds. This may help male birds tell the difference between a neighboring

male he already knows and an interloper who's infringing on his territory.

And more finely attuned hearing can also help a female bird rate the songs of males she hears

so she can pick out the best partner.

All of which means that seasonal changes in the gray matter itself put birds' brains in a class by themselves.

For Bird Note, I'm Mary McCann.