> Though the effect of weak electromagnetic fields <br />> <http://www.who.int/peh-emf/about/WhatisEMF/en/> has been a <br />> hotly contested issue -related to the safety of cell phones and <br />> the like- there existed no reliable scientific evidence of weak <br />> electromagnetic fields affecting behavioral processes. <br />> Furthermore, if the cages worked because they screened out <br />> confounding sources of weak electromagnetic activity, why had <br />> unscreened huts worked without Faraday cages elsewhere in the <br />> past -Had something changed_ <br />> Finished with their brain experiment, Schneider and Mouritsen <br />> decided to run a quick test. They assigned students to release <br />> robins in both huts over subsequent days. Without letting the <br />> students know, the scientists repeatedly disconnected and <br />> connected the cages' grounding screws in each hut. <br />> As the students observed the robins, they saw no discernible <br />> pattern in the birds' ability to orient to north at some moments <br />> but not at others. Then Schneider and Mouritsen revealed the <br />> schedule on which they'd been grounding and ungrounding the <br />> shielding cages?and the patterns aligned perfectly. The simple <br />> turn of a screw turned on and off the birds' orientation <br />> mechanism. <br />> Intrigued, the team next measured electromagnetic disturbances <br />> inside the huts, grounded and ungrounded. The noise detected in <br />> the ungrounded huts was broadband in frequency, in the range of <br />> AM radio, and it was low?a hundred to a thousand times below the <br />> guidelines adopted by the World Health Organization <br />> <http://www.who.int/peh-emf/publications/risk hand/en/> to <br />> protect human health. Yet mystifyingly it proved enough to <br />> disable the birds' magnetic compass. <br />> Then came the clincher, one more layer of proof. The scientists <br />> intentionally added broadband, low-level noise inside the <br />> screened huts. Disturbances no stronger than those equivalent to <br />> AM radio frequencies were enough to switch off the birds' <br />> magnetic compasses. <br />> -Powerful Effects on Songbirds- <br />> The scientists were astonished. "We were seeing powerful effects <br />> on songbirds, yet billions of migratory songbirds nevertheless do <br />> arrive at their destinations every season," says Mouritsen. "And <br />> you can listen to AM radio everywhere. So how could these signals <br />> be disturbing birds?" <br />> The scientists took their experiment out of town. In the middle <br />> of a field outside of Oldenburg, far from any electric and <br />> electronic equipment, they reran their experiment. The level of <br />> noise in the unscreened but in the field approximated that in the <br />> screened but in Oldenburg. Birds took off toward the north. <br />