Cities Disrupt Bird Migration, Report Finds
Electronics and AM radio signals might disrupt the internal magnetic compasses of migratory birds, suggests a study published in Nature. According to the magazine, decades of experimentation have shown that migratory birds orient themselves using an internal compass guided by Earth’s magnetic field. Cites, researchers conclude, have significant effects on bird migration patterns due to electromagnetic fields emitted by radio towers.
Henrik Mouritsen, biologist at the University of Oldenburg, Germany, and co-author of the report featured in Nature, says that European robins are especially sensitive to magnetic imbalance. According to Mouritsen, robins located in large cities crowded with electromagnetic noise (unlike robins at rural sites) could not orient themselves in their proper migratory directions.
“If birds can’t use one of their most significant compasses when they are in towns, what effect will that have on survival?” Mouritsen asked in an interview with the magazine.
In an effort to point to a solution, Mouritsen electrically grounded shelters designed to attract migratory birds to cut out electromagnetic noise in the range from 50 kHz to 5 MHz—a range that includes AM and shortwave radio transmissions but not the lower-frequency emissions from electrical grid or higher-frequency FM radio, television, or cell phone transmissions. He then covered the shelters in aluminum plates, reducing the intensity of noise by about two orders of magnitude. Under those conditions, birds were able to orient themselves, the report concluded. The actual biophysical mechanism within birds that is sensitive to electromagnetic noise remains unclear.
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Published June 19, 2014