This is bird note.

Even in the ruthless grip of winter, when the snow crunches beneath your boots,

an ember glows in the lilt of a black-capped chickadee.

Even in the northern states where the Arctic can seem too close for comfort,

springtime erupts from the song of a house finch.

Even now in February, when the air outside is brittle and painful, in winter some birds greet the sunrise with song.

We normally hear the dawn chorus in springtime,

when birds sing to define territory and attract mates.

The birds don't breed by warmth alone.

Day length is a far more reliable spark than weather.

And in February, as the days grow longer, birds begin to sing a

prelude to spring. It's not entirely clear how they measure day length, but we do know that photoreceptors in birds' brains sense the increasing light.

It triggers the production of hormones, which helps bring on the breeding season.

For bird note, I'm Michael Stein.