It's warm
When birds fly South for the winter it is called migration.
The main reason that birds fly south in the winter is because they can't stay in a cold place so they fly south to a warmer place during the winter.
Monarch Butterflies. They fly south for the winter like birds do.
migration
migration
Migration
They don't stay when it is snowing. Hasn't anybody learned that birds fly south in the winter?
Animals have What you and I would call a compass in there little heads. That's how birds know how to fly south for the winter. :)
No. Only some species are migratory.
Instinct
They fly to find better food supplies (and better weather).
because it is cold