The night skies have fascinated humans for as long as we've been around. Celestial bodies

have become actors in our myths and folklore, and from the stars and heavens we draw inspiration

and even religion. But the night skies have also taught us how to keep time in coordinating

our days and seasons. We have long used the night skies to live our lives more predictably

and make our way through the world more purposefully. But we're not the only ones.

I'm Jacob Job and you're listening to Scientific Americans Science Quickly. Today, part four

of our five-part series on the nighttime bird surveillance network, an informal but important

global audio dragnet that tracks some of the billions of migratory birds as they fly through

the night. If you're lucky and it's a clear night and the moon is illuminated, there are so many birds

migrating on average on these nights that if you use a telescope and look at the moon for a few

minutes, you're likely to see a bird high overhead flying and silhouette at it in front of the face of

the moon. Seeing birds fly in front of the moon or hearing the calls from above, I found really

really because it felt like I was tapping into this vast, mysterious pulse of the planet phenomenon

that was just so much bigger than me.

Migratory birds navigate to their summer and winter homes by way of the moon and stars.

On any given night during migration, there might be thousands of birds flying in the skies above you

and tens or hundreds of millions more moving across the continent.

We still don't fully understand the scope of this mass movement, but now,

science is turning to machines to unlock the secrets of nocturnal migration.

The nighttime bird surveillance network all started with one six-foot sound dish,

an expensive studio microphone on real-to-real tape, and a bunch of hay bales more than 60 years ago.

In time, the mics got a lot smaller, and the network grew and grew. Today, people all over the

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