What are migratory birds?

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Certain species of birds, which live in cold places and migrate (change their habitat) to warmer places during the winter months are called migratory birds. Examples of such birds are the Arctic tern, the East Siberian Willow Warbler, the Siberian crane, the demoiselle crane, the wagtail, the rosy pastor, the Brahminy duck, the oriole, the common swallow, and the paradise flycatcher.

Some birds travel great distances such as the Arctic terns, which fly about 18,000 kilometres from the Arctic region to their winter homes in the Antarctic region, and the willow warblers, which travel 13,000 kilometres from Siberia to East Africa in the winter. There are also birds that travel shorter distances like the common swallow and the paradise flycatcher, which live in the Himalayas and move to south India and Sri Lanka for the winter. It has been established that birds have an in-built mechanism that helps them to use the sun and the stars as navigational aids during their long flights. But we still do not know how the birds know when to start on their journey, and how they return to the same locality year after year.