Songbirds are restless creatures, and scientists have learned to take advantage of that trait to study their migration. In one famous experiment, researchers place a bird in a cage equipped with sensors. When night falls, the bird jumps in the direction in which it would normally migrate, allowing researchers to determine where it would like to go. But in 2004, in a German lab at the University of Oldenburg, the classic experiment failed miserably. The European robins that the researchers were using simply wouldn't orient themselves in a single direction. "We tried to change the food the birds were getting, the light, the cages — just about anything," recalls biologist Henrik Mouritsen. "Nothing had any effect."

invisible lines of force disrupting bird migration

For the next three years, Mouritsen and his team tried to figure out why the robins weren't orienting. Nothing they tried seemed to work, until one of the scientists made a suggestion: maybe they should block the electromagnetic noise emanating from the electronics on campus, just to see. That night, the researchers covered the cages with aluminum screens and, against all odds, the birds started jumping again. This was the moment that the researchers realized what no one had ever considered: the invisible lines of force that electronics constantly emit around us were actually disrupting the orientation capabilities of small migratory songbirds.

"We are absolutely sure that the effect is real," Mouritsen says. And the intensities that are affecting the birds are "1,000 times below the World Health Organization guidelines." Today, the researcher speaks with authority, but back in 2007, Mouritsen was more than a little skeptical. "My immediate reaction was that this is highly unlikely to be the reason." So the scientists did a number of follow-up experiments — six years' worth — to confirm the results that were finally published today in the journal Nature.

Unfortunately, these experiments didn't determine which electronics are to blame. The disruption, Mouritsen says, could come from "basically anything you put into a plug." But the effect is only present in large urban or industrial areas, and around university campuses — locations in which humans tend to use a large number of electronics at once.

AM radio, not cell phone signals or power lines

The researchers did figure out that the interference doesn't come from cellphone signals or power lines, however, because their frequencies are too high and too low, respectively. Instead, the frequency band that seems to be at play is the 2 kHz-5 MHz range, which "originates primarily from AM radio signals and from electronic equipment running in university buildings, businesses, and private houses," the researchers write in the study. Furthermore, Mouritsen explains, "these disturbances are so small that a conventional physicist will tell you that they can't have any effect."

That's why he thinks the problem isn't one of conventional physics, but of quantum mechanics. "Theoretical predictions suggest that [the disruption] might be an effect of electron spins." Electromagnetic noise might be affecting electron spins in a molecule named cryptochrome, Mouritsen says — the eye protein that some scientists believe plays a pivotal role in avian magnetic orientation. This could cause the molecule's chemical properties to change, and the birds to lose all sense of direction at night. But the theory, Mouritsen warns, is "unproven."

losing all sense of direction

Nikita Chernetsov, a behavioral ecologist at the Russian Academy of Sciences who did not participate in the study, said in an email to The Verge that the findings are fascinating. "It raises the question of whether other functions of migratory birds are affected by this kind of noise, which has been widely believed to be harmless." For now, however, this is "probably not a big deal," he said, because a migrating bird that has entered an urban area "needs just to leave the city in any direction to regain [its migratory] ability."

This may be true, Mouritsen says, but humans should still consider limiting the level of electromagnetic noise present in cities and universities. "A lot of equipment is sending unnecessarily high levels of electromagnetic radiation, and it may be possible to reduce it." Yet, when asked if some birds might be avoiding cities as a result, Mouritsen replies that he doesn't know. "It's an interesting thought that may be true," he says. "I'm sure the birds would have been better off if one of their key compasses had never been disturbed."