Most robins migrate south during the winter, while some stay behind and live in colder temperatures. While the south is warmer during the winter, it is the search for food that causes a robin to migrate.
The food source for a robin is more available in the warmer temperatures than in cold ones. Robins consume fruit during the winter and earthworms during the spring. The temperature at which these foods are available occurs in different regions during certain parts of the year. In addition to migrating to a different region, the robin continues to wander during the winter as its food source becomes more scarce due to decreasing temperatures and increased consumption from other birds.