THE MAGIC OF MIGRATION

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SEASONS OF EARTH AND SKY

A "once in a lifetime" meteor shower.

By Fred Schaaf

North of Subtropical climates, the coming winter weather brings the threat of death to many plants and animals that are exposed to the elements. Some life preserves its next generation by planting seed or egg snugly in the ground or in underwater ooze.

Other animals preserve themselves by finding a burrow or den and entering the strange deep sleep of hibernation. But that still leaves numerous species that take the most spectacular option of all: they leave, en masse, by the millions and billions, for warmer lands.

This is the magic of migration. We all learn the basic concept as children, and have perhaps at least seen the southbound V's of Canada geese and heard their stirring calls. But familiarity breeds contempt, or at least indifference. And, as so often happens, what we think we know—the sun by day, the moon by night, what migration is—we really are amazingly ignorant about. It's time to shake off that supposed familiarity and to witness a fundamental wonder and mystery of nature anew.

Try to imagine the sheer number of birds, millions and billions, migrating south. Why don't most of us notice their throngs? One reason is that, in some cases, the full parade of a species may take many weeks to pass, without any one day having a spectacular concentration. A more common and fundamental reason is that most of us tend to grow virtually blind to whatever does not directly affect us. Another reason is that migration is funneled along certain preferred routes—ones that offer easier flight and, in many cases it seems, more recognizable landmarks. If you don't live near one of these routes, there may be far fewer migrants passing through your neighborhood. Yet another reason-one you might not suspect-is that most of bird migration takes place at night. You might think the experience of seeing flocks of birds passing in front of the moon in a telescope is extremely rare. In reality, it can be a relatively common experience if the observer is located along one of the major "flyways."

Birds aren't the only migrators. There are insects who also take a winter vacation. Most of these are shorter trips. But then there is the famous case of the monarch butterflies. Many of these orange butterflies journey from the northern United States and southern Canada to a mystical winter retreat all the way down in the mountains of Mexico. it's hard to believe anything so fanciful-looking and delicate is really a living creature, let alone one animated by an instinct powerful and knowing enough to carry it 1,500 miles or more across many and varied landscapes to reach a spectacularly specific location.

And that, of course, is the greatest mystery of migration: what guides it? The answer, after long scientific study of many species, seems to be many things. Some birds-the beautiful indigo bunting, for instance-rely heavily on sighting particular star patterns (like the Big Dipper). Other birds apparently are guided, in part, by the magnetic field of the Earth. Many use geographic landmarks as guides. Life is so gifted, we have to struggle to understand its many powers. But it is not at all difficult to be awed by marvels like migration.

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