Many mysteries behind great migration

In the fall, the annual cycle of the seasons turns once more—and one of the great phenomena of this season is the migration of the birds.
Stand on the shore of one of our northern lakes some quiet evening. You will hear hundreds of tiny chirps above you as vast flights of small birds—sparrows, warblers, and the like—move toward the south.
For many, many years, men have wondered why the birds migrate as they do, and more to the point, how they do it. They are still wondering.
In the last 25 years or so, there has been a great deal of research done on this subject, with producing any clear-cut, simple answer.
We do know some things about bird navigation. For example, we know that many birds can—and do—navigate by the sun. A vast series of experiments has proven this beyond a doubt.
But birds also fly by night, and another set of experiments has shown that they also can navigate by the stars.
But birds also migrate in cloudy or foggy weather, so how do they do that?
One theory is that they can make use of the Earth’s magnetism. Another is that the bird’s inner ear—its balance—reacts somehow to the rotation of the Earth.
Scientists are continuing their experiments with modern methods, watching birds on radar screens, fitting some with tiny lights or miniature radios transmitters, and so on.
A vast amount of information has been collected but much of it is contradictory—and the real mystery is still there, waiting for some young scientists to solve it.
Who knows? When the answer comes, it may revolutionize the way we navigate our ships and aircraft.
Meanwhile, some of the migration distances are immense. We usually think of birds going south to, say, Florida. But the common bobolink, which you can see any day on our farms, goes to Argentina—and to the southern tip at that.
Bobolinks may cover 7,000 miles one way.
But the marathon migrant has to be the Arctic tern. This bird breeds in the very high Arctic of Canada, goes across the Atlantic to Britain, down the coast of Europe and Africa, and right on to the Antarctic—a 10,000-mile journey!
Although most birds migrate at fairly low altitudes, some flocks have been spotted at 20,000 feet.
Some also make some fantastic single flights. One that comes to mind is the Snow Goose, which leaves James Bay and doesn’t land until it gets to Louisiana—a distance of about 1,700 miles.
Birds are not the only animals that migrate. Many mammals, particularly grazing ones, migrate up and down mountains. The migration of the barren ground caribou, for instance, is very well-known.
Even a butterfly—the Monarch—migrates from here to California and Mexico, and then comes back in the spring.
How do they do it? We really don’t know all about it yet, by a long shot. There is a lot of information available, which is not in this article.
In another article, we can look at some other marvelous things about the great migrations.

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