This is Bird Note.

Many birds migrate at night.

It might sound strange to travel in the dark,

but the birds have their reasons.

At night, the air is less turbulent,

so it's a bit easier to fly.

That's Julia Wang from the Cornell Lab of Ornithology.

And especially for woodland species that might not be as agile.

It's easier to fly at night.

It's also typically cooler at night,

so it's easier to off-put the heat that's generated

when you're flying really, really far distances.

But migrating at night also means that birds can get disoriented

by bright lights and collide with the building.

All of this light pollution coming from major centers

of buildings, homes, residences,

poles, birds generally into an area

where they're more likely to deal with collisions

and other urban threats.

Julia is the project leader for Birdcast,

which provides forecast for bird migration

so that people know when they should keep their lights off.

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