The December 2022 issue of IEEE Spectrum is here!

Close bar

Electromagnetic Interference Disrupts Bird Navigation, Hints at Quantum Action

Weak electromagnetic fields can throw off the magnetic orientation of robins and other songbirds

2 min read
Electromagnetic Interference Disrupts Bird Navigation, Hints at Quantum Action
European Robins, like the one in this photo, cannot use its magnetic compass when it is exposed to urban anthropogenic electromagnetic noise in the AM radiofrequency range.
Photo: Henrik Mouritsen

Repeated experiment failures have led to a most unexpected discovery about how songbird orientation may rely on the quantum phenomenon of electron spins. Researchers found out that very weak electromagnetic fields disrupt the magnetic compass used by European robins and other songbirds to navigate using the Earth's magnetic field.

Neither power lines nor cellphone signals are to blame for the electromagnetic field effect on the birds, according to the new study published in the 8 May 2014 edition of the journal Nature. Instead, the culprits consist of frequencies between 2 kHz and 5 MHz, such as AM radio signals and ordinary electronic equipment that might be found in businesses or private homes.

The discovery came about when researchers at the University of Oldenburg in Germany attempted to set up a typical experiment on the magnetic sense of birds, according to National Geographic's Phenomena blog. But the European robins they used in the studies kept flying in random directions rather than using their magnetic "sixth sense" to find their bearings—until the team came up with the idea of putting a Faraday cage around the birds' windowless huts to block the effects of nearby electromagnetic fields. Suddenly, the birds could navigate using their magnetic compass once more.

Researchers repeatedly tested the surprising finding for several years and added certain electromagnetic fields to test the sensitivity of the birds. That allowed them to narrow down the troublemaking frequencies to the 2 kHz - 5 MHz range, even if they couldn't pinpoint the devices or signals operating at such frequencies. Such background human-made noise is expected to be most disruptive for migrating birds flying above urban areas.

The surprise findings have left several mysteries for researchers. Such electromagnetic fields are much weaker than the lowest exposure limits recommended for humans by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and are also weaker than the minimum levels at which researchers expected any biophysical effects.

The results also support an intriguing idea about how quantum physics plays into the workings of birds' navigational systems. As Phenomena's Ed Yong explains, bird eyes contain a molecule called cryptochrome that can pass an electron to a nearby molecule when struck by light. The result is two unpaired electrons that can flip between up and down spin states—a quantum physics phenomenon. The Earth's magnetic field can influence the spin states in the pair of molecules and thereby trigger different chemical reactions.

Other experiments have shown that birds will ignore their magnetic compass and navigate according to the sun or stars under certain circumstances. An accompanying news article in the journal Nature suggests that birds may have evolved to learn when to ignore their disrupted magnetic compasses because of solar magnetic storms. Such storms occasionally disrupt the Earth's magnetic field and generate radiation at frequencies ranging from 20 kHz up to the MHz range—a range strikingly similar to the frequencies shown to disrupt the magnetic compass of birds.

The Conversation (0)

Deep Learning Could Bring the Concert Experience Home

The century-old quest for truly realistic sound production is finally paying off

12 min read
Vertical
Image containing multiple aspects such as instruments and left and right open hands.
Stuart Bradford
Blue

Now that recorded sound has become ubiquitous, we hardly think about it. From our smartphones, smart speakers, TVs, radios, disc players, and car sound systems, it’s an enduring and enjoyable presence in our lives. In 2017, a survey by the polling firm Nielsen suggested that some 90 percent of the U.S. population listens to music regularly and that, on average, they do so 32 hours per week.

Behind this free-flowing pleasure are enormous industries applying technology to the long-standing goal of reproducing sound with the greatest possible realism. From Edison’s phonograph and the horn speakers of the 1880s, successive generations of engineers in pursuit of this ideal invented and exploited countless technologies: triode vacuum tubes, dynamic loudspeakers, magnetic phonograph cartridges, solid-state amplifier circuits in scores of different topologies, electrostatic speakers, optical discs, stereo, and surround sound. And over the past five decades, digital technologies, like audio compression and streaming, have transformed the music industry.

Keep Reading ↓Show less
{"imageShortcodeIds":[]}