AM Radio Can Disorient Birds

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Certain radio stations are bad for birds, according to a new study in Nature that finds AM radio signals disorient songbirds migrating at night.

The study shows how even weak electromagnetic fields produced by AM radio signals can throw off a small animal — begging the question what are other electromagnetic fields doing to them, not to mention to the rest of us?

Electronic pollution, or as the researchers call it, “electrosmog,” is a growing problem that is only expected to get worse as more of us plug or tune into radio stations, TVs, computers and countless other electrical devices. It’s a reminder that not all pollution is visible to us.

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Biologist Henrik Mouritsen, a professor at the University of Oldenburg, and his colleagues determined that AM affects birds after studying European robins. These birds have an internal magnetic compass that helps them to find their way even when other cues, such as visual ones, are poor. At night, the internal magnetic compass is key to the birds finding their way.

Mouritsen and his team housed the birds in windowless huts. The researchers figured out a way to easily turn on and off the birds’ exposure to background urban electromagnetic signals.

With the electrosmog, the birds could not orient themselves properly. Without it, they were good to go.

You can see how the researchers set up this unusual experiment (which sort of looks like sticking birds safely in covered salad bowls) in this video:

The researchers further determined that only certain electromagnetic noise bothered the birds. It was in the frequency range of two to five kilohertz megahertz, putting it right in the range of AM radio signals.

“These perturbations do not originate from power lines or mobile networks,” Mouritsen said.

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He added that the identified magnetic component is much weaker than the lower exposure limits currently recommended by guidelines adopted by the World Health Organization.

What then could the implications be for humans?

In an accompanying “News & Views” piece in the same journal, Joseph Kirschvink mulled over that very question. Kirschvink is in the Division of Geological and Planetary Sciences at the California Institute of Technology. He’s also a researcher at the Tokyo Institute of Technology.

Kirschvink notes that human tissues contain biological magnetite, which has geomagnetic sensitivity.

“Many people claim to be bothered by radio transmissions, and some have even moved to live in radio frequency ‘quiet zones’ around radio telescopes,” he wrote. “Modern-day charlatans will undoubtedly seize on this study as an argument for banning the use of mobile phones, despite the different frequency bands involved.”

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“However,” he continued, “if the effect reported by the authors stands the acid test of reproducibility, we might consider gradually abandoning our use of this portion of the electromagnetic spectrum and implementing engineering approaches to minimize incidental low-frequency noise, to help migratory birds find their way.”

In other words, don’t buy stock in AM radio anytime soon. Like the non-avian dinosaur relatives of birds, it’ll probably go extinct before long.

Photo: European Robins like this cannot use their internal magnetic compass when they are exposed to urban electromagnetic noise in the AM radio frequency range. Credit: Henrik Mouritsen.