How do birds use light as a signal for migration?

Birds use light as a signal to know when it’s time to fly somewhere new, just like you use the sun to tell if it's morning or night.

Some birds watch the sun and the stars while they're flying. It’s like using a map in the sky! When it gets darker, they might follow the stars, kind of like how you follow the moon when you’re playing hide-and-seek at night.

Some birds also use light to know when to start their journey. For example, if there’s not enough sunlight, it means winter is coming, and it's time to fly south to find warmer places, just like you might put on a jacket when the days get shorter.

Imagine your bedroom has a little light that turns on in the morning. When that light comes on, you know it's time to wake up! Birds have their own kind of “light” that tells them when to start flying.