ELI5: Why do birds migrate?

Imagine it's playtime all the time, but the toy store runs out of toys! That's kind of like what happens to birds in the winter.

Birds need two really important things: food and a good place to build a nest and raise their babies.

• In the summer, many places are full of yummy insects, berries, and seeds for birds to eat. It’s also warm enough to build nests and keep baby birds cozy.

• But when winter comes, things change! The weather gets cold, ice and snow cover the ground, and many of those yummy insects disappear or go into hiding. This means birds can't find enough to eat!

• Also, it's too cold for baby birds to survive.

Here's why they do it:

• Food: They fly to places where there's still plenty of food during the winter.
• Warmth: They go to places that are warmer, so they don't freeze.
• Breeding: When spring comes, they often fly back to their original homes to build nests and have babies because those places are perfect for raising a family during the summer.