Navigation systems of migratory birds suffer from electromagnetic fields
Electromagnetic radiation confuses migratory birds – they lose their orientation. Even weak waves can bring them off the right path.
Migratory birds do better than navigation instruments. Without maps, or the help of satellites, they reach their travelling goals with perfect accuracy, often over distances of many thousand kilometres. They orient themselves using the position of the Sun, and of the stars at night, as well as the Earth’s magnetic field. Still, their progress is not without interferences, as a team working around Henrik Mouritsen and Svenja Engels at the University of Oldenburg in Germany found out. Their results have been published in scientific magazine Nature.
Weak electromagnetic fields already suffice to trouble the sense of orientation of migratory birds. Mouritsen and his colleague established that the sensory system of European redbreasts fails them as soon as they are subjected to electromagnetic radiation in the mid-wave range.
The researchers locked redbreasts during the migration period in an especially prepared box – a funnel-shaped orientation cage. Normally, birds are then jumping in place at night in one direction, namely the one in which they would otherwise be flying. But the electromagnetic radiation present on the campus of the University of Oldenburg sufficed to disorient them.
Only once the researchers had protected the cages with aluminium plating were the redbeasts able to navigate again. Most surprisingly, the interferences did not stem from high-tension masts or from mobile-phone networks, but from electric equipment and were situated in radio wave range.
The scientists repeated their experiment in the countryside, where the electromagnetic radiation is usually less than in city. And indeed: in the environment of the country, the birds’ inner compass functioned perfectly.
These new insights put accepted scientific wisdom in question: “Until now, it was accepted that electromagnetic radiation below certain threshold values had no effect on biological processes,” Mouritsen says. But his experiments tell otherwise. “The results should make us think again,” he says. “As much about the survival chances of migratory birds as about the possible effects on humans.” These remain to be investigated.
Translated by Anne-Marie de Grazia
Original article in Der Spiegel, 05.08.2014