Researchers have known for many years that birds navigate using Earth’s magnetic field. It has always been assumed however that ‘electrosmog’, also known as AM radio waveband electromagnetic interference, was harmless. Now, an accidental discovery by Henrik Mouritsen, biologist and Lichtenberg Professor at the University of Oldenburg has called that assumption into question.

Mouritsen noticed that the robins, which are kept in wooden huts on the Oldenburg University campus, were unable to use their built in magnetic navigation systems. Moritsen’s colleague, the electrophysiologist Dr. Nils-Lasse Schneider, proposed covering the wooden huts and orientation cages with sheets of aluminum.

The aluminum did not interfere with the Earth’s magnetic field, but it reduced the electromagnetic interference or “electrosmog” from reaching the inside of the huts. The researchers report that the birds navigation problems cleared up immediately.

“Our measurements of the interferences indicated that we had accidentally discovered a biological system that is sensitive to anthropogenic electromagnetic noise generated by humans in the frequency range up to five megahertz”, Mouritsen said in a statement.

After seven years of research, the Oldenberg scientists in cooperation with Prof. Dr. Peter J. Hore of Oxford University, have shown that the robins magnetic compass fails at just a thousandth of the value considered harmless by the World Health Organization (WHO).

The research is described in detail in the paper “Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird” published in the May 15th edition of the journal Nature.

“In our experiments we were able to document a clear and reproducible effect of human-made electromagnetic fields on a vertebrate. This interference does not stem from power lines or mobile phone networks. The effects of these weak electromagnetic fields are remarkable: they disrupt the functioning of an entire sensory system in a healthy higher vertebrate,” says Mouritsen.

Devices in the range described by Mouritsen include nearly all modern electronic devices. As would be expected, the amount of ‘electrosmog’ is much less in rural areas than it is in urban environments. The researchers demonstrated this by repeating their experiments just a mile outside city limits. In that setting the robins were able to function normally without aluminum screening.

“Thus, the effect of anthropogenic electromagnetic noise on bird migration is localised. However these findings should make us think – both about the survival of migratory birds as well as about the potential effects for human beings, which have yet to be investigated”, concludes Mouritsen.