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Magnetic navigation idea fails to fly.

Magnetic naviation idea fails to fly

What was to blame when half the 12,000 homing pigeons released in Denmark didn't show up in Germany at the end of a race this month? "Solar flares," said a spokesman for the association that released them. His explanation that solar flares had disrupted the earth's magnetic field and interfered with the pigeons' navigation shows just how commonly accepted the idea of magnetic navigation in pigeons is. Yet newly released data from the scientist who started it all, published eight years after his death, show no support for the existence of magnetic navigation in pigeons.

In 1971, William Keeton of Cornell University in Ithaca, N.Y., taped magnetic bars to the backs of some homing pigeons and normal bars to others. He found that when the sky was overcasat and the pigeons couldn't use the sun to guide them, the birds with magnetic bars often couldn't navigate well. Keeton proposed that pigeons use the earth's magentic field to navigate, an idea that quickly caught on and has since been applied to other animals.

Keeton was perturbed, however, by what he called a "disturbing variability found in the results," and he spent the last eight years of his life doing experiments to account for that variability, even as the idea was gaining support in scientific circles. Keeton died in 1980 before publishing the results of these follow-up experiments, but his data were analyzed by researcher Bruce Moore of Dalhousie University in Halifax, Nova Scotia, and published in the July PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol. 85, No. 13).

The only valid statistical inference that can be drawn from those data is that the magnets have no effect on the pigeons' navigation, Moore reports. "If [Keeton's] early conclusions now require reexamination, it is appropriate that it should be his own later findings that again call our attention to the problem," he says.

Theoretically, if pigeons were sensitive to changes in the magnetic field, they could tell something about their position because the earth's magnetic field changes with latitudinal position. "But detailed magnetic charts show no usable information, because there are variations in local magnetic fields," Moore says.

Many experiments similar to Keeton's conducted by other scientists over the last 17 years have produced conflicting results, and almost all laboratory experiments have been negative, Moore says. Nevertheless, there are many strong believers in magnetic navigation in pigeons, he says.

Even if pigeons don't sense magnetic fields, other animals may. The evidence of bacteria sensing magnetic fields is "rock solid," while the idea that humans sense magnetic fields has been refuted by many researchers, Moore says. "For everything in between it's an open questions," he adds.

And what about the pigeons missing in action over Denmark? "In most large races most birds get home, but in a big race it's not unusual for a large fraction of the birds to get lost," Moore says. Races in which many birds are lost are common enough to have earned the name "busts," and studies of such races have shown no correlation between birds getting lost and magnetic storms, he says.
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Title Annotation:research on magnetic navigation in pigeons
Author:Vaughan, Christopher
Publication:Science News
Date:Jul 23, 1988
Words:523
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