Ornithology: Fighting the Birds

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As long as any Dutchmen can remember, the airspace over their crowded lowlands has swarmed with birds. But the birds have increasing competition. Part of the sky over The Netherlands has been invaded by commercial air routes; another part has been taken over by the military. And the birds are fighting back. In the past seven years the Dutch Air Force has recorded 413 bird-plane collisions. Commercial airplanes have had their share of bird trouble too, but they make no reports lest they frighten passengers. Circumstances have forced the Dutch to become world leaders in anti-bird research, but the problem is serious in many other places, and it tends to get worse.

At jet speeds a bird's soft body becomes a hard projectile that can easily whack a hole in the edge of a wing; jet engines suck up birds like giant vacuum cleaners and suffer serious internal damage. One Dutch military pilot was almost killed when his jet inhaled five gulls on take-off and crashed into a barrier. Another crashed after vacuuming a flock of partridges. In 1959, 25% of Dutch military aircraft was out of action because of bird trouble.

Distressed Dialect. To the rescue came "The Birdman of The Hague," Zoologist Johann D. F. Hardenberg of the Ministry of Agriculture's fauna department. Called in by the Air Force and Amsterdam's airport, Hardenberg's first move was to import an American invention, a loudspeaker playing the tape-recorded distress calls of American herring gulls. It was an imaginative effort, but it did not work. Dutch herring gulls apparently speak a dialect all their own and are not alarmed by the screams of their American cousins. When Dr. Hardenberg recorded distressed Dutch gulls and a Jeep carrying his loudspeaker patrolled the runway of Leeuwarden military air base, the gulls merely flew up ahead of the noise in temporary terror and then landed behind it. Dr. Hardenberg's riposte was to line the runway with 23 loudspeakers, which sounded off with ghastly screams that kept the gulls 500 ft. away.

By 1966, ten air force bases will use this system, playing the distress calls of sparrows, peewits, whatever bird is causing trouble. Nearly all birds, says Hardenberg, are frightened away by their own distress calls. Only ducks don't seem to care, and magpies are actually attracted to the loudspeakers.

Frightening Racket. Commercial airports do not use the full Hardenberg system. When birds get thick along a runway, a Jeep broadcasting the appropriate distress calls drives out to clear the way so the jetliners can take off safely. There are no permanent loudspeakers to make a racket that scares away nervous passengers as well as birds.

Since Dr. Hardenberg started his work, bird accidents at Dutch airports have sharply decreased; but in-flight accidents have increased sharply and for no apparent reason. Most of them occur in spring or fall when birds are migrating, but some birds congregate dangerously at other times. Coping with migratory birds, says Hardenberg, calls for close cooperation between aviation experts and ornithologists. Pilots should get bird information along with weather forecasts, he says, and the movements of birds should be followed closely throughout Europe. Studies are now under way to see whether radar can watch for dangerous birds as it does for thunderstorms.