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Science Frontiers ONLINE No. 55: Jan-Feb 1988 |
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Migrating Birds Collide With Magnetic Bump
Do birds utilize the earth's magnetic field for navigation? Many have so surmised; and there exists anecdotal evidence for it. A Swedish ecologist, T. Almberstam, decided to attempt scientific observations. At Norberg, in central Sweden, a huge deposit of magnetite creates a powerful magnetic anomaly. The deposit is 12 kilometers long by several wide. At low altitudes, the total magnetic intensity of the earth's field is 60% higher than normal. What happens when migrating birds fly into this magnetic bump?
"Although Almerstam found that many migrating birds showed no signs of avoiding the Norberg anomaly, and often managed to keep on the right course as they passed through it, there were definite indications that the birds' orientation might be affected under special circumstances. Some migrants flying at low altitudes, where the magnetic intensity was greatest and the inclination and declination distorted greatly, became disoriented briefly. They nervously landed and then circled around before taking off again. Other birds changed their altitude abruptly, dropping 100 metres in two minutes and breaking up their flock formations."
Certainly something is happening, but no one knows what.
(Anonmous; "Magnetic Anomaly Upsets Migrating Birds," New Scientist, p. 32, November 5, 1987.)