Migration occurs when living things move from one biome to another. In most cases organisms migrate to avoid local shortages of food, usually caused by winter.
Birds often migrate (see bird migration for more details). The longest known migration is that of the Arctic Tern, which migrates from the Arctic to the Antarctic and back each year.
Whales, butterflies, moths, and lemmings are also known to migrate. The periodic migration of flocks of locusts is a phenomenon recorded since Biblical times.
Human migrations on the largest scale are discussed under two entries at Wikipedia:
Human migration discusses mass migrations in history and in modern times.
Völkerwanderung ("the wandering of the peoples") more specifically discusses the movements of Germanic peoples during the Age of Migrations in Europe that separated Antiquity from the Middle Ages.
