The Road Back

By Alan Anderson

ANIMALS IN MIGRATION by Robert T. Orr. 303 pages. Macmillan. $12.50.

Despite occasional collisions with man-made obstacles like the Empire State Building, one of which recently claimed the lives of hundreds of southbound warblers, birds are easily the fleetest, most accurate and far-ranging of migrants. Even the smallest feathered creature in North America, the .09-oz. calliope hummingbird, buzzes 6,000 miles each year from British Columbia to Mexico City and back. The ruddy turnstone and bristle-thighed curlew fly more than 2,000 miles nonstop from Alaska to the Hawaiian islands on their way to the South Pacific. The long-distance champion of them all is the Arctic tern, which makes an annual round trip of 22,000 miles.

Frogs, toads and salamanders also migrate, if only a mile or two. Many snakes go into something like hibernation; to find the best location for doing so, they move short distances, seeking not a change of climate but a warm spot for the winter. In one choice den in an anthill in Manitoba, 257 snakes of three species were once found.

Hitchhiking Barnacles. A California ornithologist and mammalogist, Author Orr describes the quirks and patterns of migration that scientists have brought to light, mostly during the past quarter-century. He notes that barnacles hitchhike to new climes by attaching themselves to whales, sailfish and ships' bottoms. Like some commuters who are forced to transfer from train to bus or taxi, Adelie penguins migrate using an integrated transport system. They toddle across the bleak Antarctic icecap on foot, swim in the icy sea and cruise lazily on drifting ice floes.

The homing ability of some migrating animals is uncanny. A bat living in Arizona's Colossal Cave was removed 28 miles and freed; it found its way home in less than four hours. A coho salmon raised in a California hatchery was shifted to a different stream when it was a year old. At spawning time the next year, the fish appeared back in its old tank. From the sea, it had found and ascended its home stream, crossed under U.S. Highway 101 by culvert, swum through a storm sewer and up to a flume, finally wriggled through a right-angled 4-in. drainpipe, knocking off its wire cap, and leaped across a wire net that surrounded the drain.

Piratical Hawks. Navigators of the animal world use a wide variety of clues for orientation. Some birds make use of the coastline, the sun or, more commonly, the stars. There is a theory that others are guided by the slight force of the earth's magnetic field. Some animals seem to depend upon old-fashioned topographic features, which they pick up with their own sonar. Eels, according to studies reported by Orr, have so keen a sense of smell that they could detect half a teaspoon of alcohol diluted in 42-mile-long Lake Constance.

Some of the most absorbing details in Orr's book deal with the ways in which different migrators may interrelate--often bloodily. Birds crossing the eastern Mediterranean in late summer and early fall, for example, must face the threat of the Eleonora's falcon. Some 3,000 pairs of these piratical hawks have timed their breeding season--when they require maximum food to feed their young--to match the migrating patterns of European warblers and other small birds. Swooping in upon their helpless prey high over the water, the falcons take an estimated annual toll of nearly a million birds. Fortunately this is but a small fraction of the billion or so migrants that beat their way between Europe and Africa each year.

o Alan Anderson

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