Robins' inbuilt navigators pecked to bits by AM radio

Humans often claim to be able to sense wireless fields by way of headaches – the so-called WiFi syndrome – but pity the European Robin, whose navigational abilities may be spoiled by electromagnetic radiation.

That's the suggestion put forward in this paper in Nature.

The frequencies the researchers looked at had nothing to do with WiFi however: what they found is that radio noise in the range 50 kHz to 5 MHz is what upsets the birds. Within that range, the biggest allocation is AM radio, from 530 kHz to 1,710 kHz.

“When European robins, Erithacus rubecula, were exposed to the background electromagnetic noise present in unscreened wooden huts at the University of Oldenburg campus, they could not orient using their magnetic compass,” the abstract states.

The robins' magnetic navigation is pretty neat, actually: it's believed to depend on a magneto-sensitive nerve called the trigeminal nerve, which senses how iron in birds' beaks aligns with the Earth's magnetic field. Science has a discussion here.

The researchers formed a belief that radio noise might interfere with birds' magnetic sensitivity when they found that inside a faraday cage in an otherwise noisy environment, birds could align themselves correctly (the robins, Science explains, are so anxious about their migrations that they'll try to escape from cages from whichever wall is pointing in the appropriate direction). Drop the shielding, and they become confused again.

Their seven-year investigation culminated in the construction of a double-blind test, with volunteers working in noise-screenable wooden huts with screens either turned on or off, but without knowing who was working in which environment. As study leader Henrik Mouritsen of the University of Oldenburg told Science: “The conditions were repeated with different generations of students, and experiments were blinded on all levels.”

Finally, to work out what noise sources caused the most disruption, they tested robins exposed to different frequencies. Unsurprisingly, since AM radio is ubiquitous and loud, that was one of the culprits. Frequencies used by RFID tags were also fingered, which the researchers note is emitted at much, much lower levels.

The good news for the robins is that evolution already allows for disruption to their magnetic sense. Since they've always been exposed to things like noise from solar storms and the variability of the Earth's magnetic field, robins on the wing switch to other cues to overcome the short-term loss of magnetic navigation. ®