Migration refers to periodic or seasonal movements of animals over a relatively long distance, from one habitat or climate to another. Migrations may be made by particular individuals, or by an entire population of a species. Migration is an extremely "expensive" undertaking for animals to make, in terms of the energetic costs of the extensive movements from one place to another. Migration can also be a risky venture, during which animals are exposed to predators, the possibility of becoming irretrievably lost, and other natural hazards. However, there are also substantial benefits to be gained by migrating. These are usually associated with having access to a seasonal abundance of food in certain kinds of habitats. It is because of the opportunity to exploit such abundant resources that many species of animals have adopted the extraordinary behavioral attribute of migration.

Individuals of some species undertake regular short-distance migrations, usually to...