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












“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 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.




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