BirdNote® Navigating by the Earth’s Magnetic Field
Air Date: Week of March 2, 2012
Modern technology has made it easy for us humans to get around. All we need to do is plug in our coordinates to a GPS, and we’re good to go. But, as BirdNote®’s Michael Stein reports, migrating birds have some unusual ways of charting their flight path.
GELLERMAN: It's Living on Earth, I'm Bruce Gellerman.
[BIRD NOTE® THEME]
GELLERMAN: Getting around these days is easy to do. Just tap in your destination on the old GPS, and you're good to go. Migratory birds, on the other hand, have other ways of finding their way, as BirdNote®’s Michael Stein reports.
[BOBOLINKS SINGING AND CALLING]
STEIN: How do birds navigate? They steer by landmarks and by the sun and stars. A keen sense of smell helps some birds chart their course. And, it turns out, migrating birds also find their way by responding to the magnetic field of the earth.
[BOBOLINKS SINGING AND CALLING]
STEIN: These bobolinks we’re hearing orient themselves to Earth’s magnetic north with the help of iron-rich magnetic crystals inside their upper beaks. Homing pigeons also carry these magnetoreceptors, as do robins and other birds.
[WHINNY OF AMERICAN ROBIN]
STEIN: But that’s not the only way birds use the earth’s magnetic field to help them on their way. Light hitting a specific protein in a bird’s eye may trigger a chemical reaction that varies depending on the direction of the earth’s magnetic field. And “birds may actually see Earth’s magnetic field in the form of changing dark areas across one eye.”
STEIN: This sensitivity explains why night-flying birds need to recalibrate their magnetic sense every day by the light of the setting sun. In an experiment in central Illinois, 18 thrushes were fitted with radio transmitters and exposed to a misaligned magnetic field. When released after dark, the birds headed west. Birds not exposed to the false geomagnetic field headed north. On subsequent days, however, the misdirected birds reoriented themselves to follow their true course.
STEIN: I’m Michael Stein.
GELELRMAN: To see some Bobolink photos, point your compass to our website LOE dot org.
Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Bobolink song and calls recorded by D.S.Herr; whinny of American Robin recorded by G.A. Keller; and song of Bobolink recorded by A.A. Allen.
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