There are few observable traits distinguishing migrating animals from non-migratory species. Many birds, such as Arctic terns, mallards and bar-tailed godwits migrate across vast distances, while some of their close relatives remain in the same place all year. There are species of birds, fish, mammals, and even reptiles and amphibians that migrate each year.
Birds are perhaps the most famous migratory creatures. Roughly 1,800 of the world’s 10,000 living species of birds migrate long distances annually. Some species vary their migratory behavior depending on their location. For example, many hawks migrate, but those living in the southern United States are often able to find food year round, so they do not leave their summer hunting grounds.
Reptiles and amphibians are not well adapted to long-range journeys. Nevertheless, these cold-blooded critters often move between breeding territories and feeding territories, or winter ranges and summer ranges. For example, American toads spend the breeding seasons near small puddles and aquatic sites where they can deposit eggs. However, during the summer, the toads move into the surrounding forests to feed.
Several of the large mammals native to the African plains engage in long, complex migratory journeys. Each year, about 1.7 million wildebeests migrate to find food sources. Impala, gazelle and other mammals make similar journeys.