What happens to robins in winter?

   If you live in a place where winter is cold, you know that robins disappear before the snow falls. They fly away south to warmer country where they can find plenty of worms and insects to eat. In spring the robins come back. This moving back and forth is called migration.
   Many kinds of birds migrate in huge flocks. Each kind follows just about the same path each year. Some travel only a few hundred miles. Others fly immense distances. Often a bird will find its way back to its old nesting place year after year.
   How can we be so sure the same bird comes back? We can be sure if the bird wears a label. Naturalists actually do put labels on birds. They fasten tiny aluminum bands to the birds' legs. Each band has a different number. Every year naturalists catch birds and look at the bands. They can tell by the number whether a particular bird has come back to its old home.
   Why don't the birds get lost? One kind of bird guides itself by the stars. The positions of the stars give it directions, just as the Pole Star tells us which way is north. Scientists still have to find out whether all birds are guided in this same way.