The Greatest Migration was not one year. It was from 1940-1970.
622
It allows them to travel to areas of greatest resources to survive.
1975
The telegraph
Arctic Tern (the world's greatest migrator, arctic to antarctic. Caribou
Midwest
The Arctic tern holds the long-distance migration record for birds. The bird is recorded for travelling between Arctic breeding grounds and the Antarctic each year.
There is no migration in Antarctica: it is not home to any animal.
Arctic Tern (the world's greatest migrator, arctic to antarctic. Caribou
The wildebeest migration in the Masai Mara typically occurs between July and October, with the peak of the migration occurring in August and September. However, the timing of the migration can vary slightly from year to year depending on factors such as rainfall and grass growth.
It is called the Hegira.
Migration