Animal Migration, seasonal or periodic movement of animals in response to changes in climate or food availability, or to ensure reproduction. Migration most commonly involves movement from one area to another and then back again. This round-trip, or return migration, may be of a seasonal nature, as in the spring and autumn migrations of many birds. Or it may require a lifetime to complete, as in various species of Pacific salmon that are born in freshwater streams, travel to ocean waters, and then return to the stream where they were born to breed before dying.
Serengeti Animal Migration, Tanzania
Some migrations are nomadic in nature. Nomadic migrations involve irregular movement patterns that are dependent on temporary local conditions. For example, many of the large grazing animals that live in herds on the plains of eastern Africa move in response to varying local conditions of food and climate. In these migrations, the animals follow no regular route and do not return to any one place.
The wildebeest migration is such a phenomenon it involves movement of over 1 million animals crossing plains and rivers in mara migration.
Ostrich in the savannahs of the Loeli area
Another type of migration—removal migration, or one-way migration to new sites—is exhibited by migratory locusts of Africa and Asia. These locusts are well known for their enormous mass movements when their populations peak and food becomes scarce. They move to new areas, almost blackening the sky as they pass overhead. Rarely do they return to their place of origin.
Wildebeest migration in Masai Mara, Kenya
Irruption is a specific migratory cycle occurring in extreme climates. The best-known example of irruption is seen in lemmings of the Arctic tundra. “Once in about every 25 years Norway and Sweden are the scene of a migration which is one of the wonders of the natural world. The participants in this movement are tiny rat-like creatures, called popularly lemmings, and scientifically Myodes lemmus. The lemming is not more than six inches long, including a halfinch tail”
New York Times, November 7, 1886
The annual butterfly migration. Truly breathtaking, like being in an orange snowstorm
Flamingoes at Lake Nakuru
Many land birds migrate long distances. The most common pattern involves flying north to breed in the temperate or Arctic summer and returning to wintering grounds in warmer regions to the south. The primary advantage of migration is energetic. The longer days of the northern summer provide greater opportunities for breeding birds to feed their young. The extended daylight hours allow diurnal birds to produce larger clutches than related non-migratory species that remain in the tropics year-round. As the days shorten in autumn, the birds return to warmer regions where the available food supply varies little with the season.
West Estonia
Many types of fish migrate on a regular basis, on time scales ranging from daily to annual, and over distances ranging from a few meters to thousands of kilometers.
Up to 10,000 Stingrays migrating for the Summer
