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Monday, January 9, 2012
Every one of us knows the reason for migration. Birds are, to most people, the most obvious migrants. Their travels usually take them north in spring and south again in autumn. The northern land masses have a far greater are than the southern ones, so adequate breeding territories may be set up or, for sea birds, nest sites found near to food rich waters, also, the long hours of day light of the northern summer give more time for feeding hungry young than would be possible in short, tropical days.
Migration routes were probably established at the end of the Pleistocene period, and each species follows its own pattern of movements, led mysteriously but certainly, land marks, the stars and planets, and even by the Earth’s magnetic field. Some young birds learn their migration route from their parents. Others, such as young cuckoos, have no such guidance. Flying alone, they have only their innate knowledge of direction and distance to take them to their winter home, a strategy that gives them a chance to survive to be among the next year’s breeding population.