German scientists have proved for the first time that the electromagnetic "noise" emitted by electronic devices can disorientate migratory birds in an urban environment.
It has long been debated whether manmade electric and magnetic fields have an impact on biological processes, including human health, but until now there has been no scientific proof.
A seven-year-long study by University of Oldenburg researchers found that European robins, who usually orientate themselves on migration paths using internal compasses guided by the Earth's magnetic field, become confused by the electromagnetic radiation in cities.
Their research paper, entitled "Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird" is published in the journal Nature.
In order to identify which part of the brain processes compass information, scientists kept robins in wooden huts to monitor how they navigated during flight.
However, once the experiment was moved to huts on the university campus in the city of Oldenburg, the robins lost the ability to orientate themselves properly.
"I tried all kinds of stuff to make it work, and I couldn't make it work until one day we screened the wooden hut with aluminium," said Henrik Mouritsen, co-author of the paper.
When the aluminium plates electrically "grounded" the birds, the electromagnetic noise was reduced from 50kHz (the range of broadband) to 5Hz (AM radio transmissions) and the birds' internal compasses were restored, allowing them to find their way again as they flew.
To validate the results, the scientists spent seven years conducting double-blind tests and the initial results were independently replicated.
While it cannot be said that electromagnetic noise will definitely affect all birds in all cities, other scientists have seen similar results.
John Phillips, a sensory biologist at Virginia Tech who studies spatial memory and navigation in mice and newts, told Nature: "These effects are real. You wouldn't study a vision mechanism with flashbulbs going off at irregular intervals."
A number of people have claimed they are allergic to the electromagnetic signals produced by Wi-Fi networks, a condition known as "Electromagnetic Sensitivity". Symptoms include acute headaches, heart palpitations, tinnitus, eye problems and a feeling of burning skin.
Many of them in the US migrate to live in Green Bank, a tiny remote town in West Virginia where all electromagnetic devices including mobile phones and satellite TV are banned.