Every spring, millions of birds migrate from the temperate regions of the world, to breed. These regions have abundance of food where they can rear their hungry chicks. The biggest migrations are to the northern parts of North America, Europe and Asia. There is some migration to the southern hemisphere also. For example, the double-banded dotted flies from Australia to New Zealand to breed. The American Golden Plover undertakes a non-stop flight of 3325 kilometres from Alaska to Hawaii. In the northern hemisphere, wild geese fly north to their breeding grounds in spring, and fly south in the autumn. Migration is mainly triggered by changes in the length of the day, which cause a change in the bird’s hormonal balance. Now the question is — how do the birds find their way while migrating from one place to another, and then manage to return to their original place? Young birds learn about migration from their parents. They make the first migration with the older birds, which have made the trip before. The bigger birds familiarise their young ones with the migration route. Landmarks such as mountains, lakes and coastlines, guide some birds. Others may use the Sun and stars to navigate. When the sky is cloudy, they often get lost. Scientists are yet to discover, how these migratory birds find their way. Birds are not the only ones to migrate. Many fishes, mammals, flying insects, locusts, and eels also migrate.