Researchers have discovered that certain radio waves can disrupt the magnetic compass of migratory birds. Other types of radio waves – particularly those used in mobile communication networks – do not affect the birds’ sense of orientation due to their high frequencies.
This critical finding supports the researchers’ theory that the magnetic compass sense in these birds is based on a quantum-mechanical effect. The radical pair mechanism, located in their eyes, is what they know as this.
The study, led by Professor Dr. Henrik Mouritsen of the University of Oldenburg and Professor Dr. Peter Hore of the University of Oxford, combined behavioral experiments with complex quantum-mechanical calculations on a supercomputer.
The goal was to delve deeper into the connection between the quantum-mechanical mechanism, suspected to underpin the birds’ magnetic sense, and the disruption of this mechanism by radio waves.
“Our experiments, together with detailed theoretical predictions, provide strong evidence that the compass magnetoreceptor in migratory birds is based on a flavin-containing radical pair and not a completely different sort of receptor, for example one based on magnetic nanoparticles,” explained Professor Mouritsen.
Magnetoreception refers to the ability of migratory birds and some other animals to use the Earth’s magnetic field for orientation.
Previously, in 2014, Mouritsen, Hore, and their colleagues demonstrated that electrosmog, the human-made electromagnetic noise generated by household electrical appliances in the AM radio waveband, impairs magnetoreception in migratory birds.
The experts proposed that this weak electrosmog, which is harmless to humans, affects the complex quantum-physical processes in certain cells in the retinas of migratory birds. These cells enable them to navigate using the Earth’s relatively weak magnetic field.
However, it remained unclear whether electrosmog also affects free-flying birds, such as long-distance migratory birds, whose numbers have been declining for unknown reasons.
In the current study, the researchers set out to investigate the cut-off frequency of radio waves above which the navigation of migratory birds remains unaffected.
Determining this value would let us draw conclusions about the properties of the actual magnetic sensor in the birds. This sensor is theorized to be a light-sensitive protein called cryptochrome 4, which possesses the necessary magnetic properties.
The initial theoretical prediction was that the cut-off frequency would lie somewhere between 120 and 220 megahertz in the Very High Frequency (VHF) range. To test this, the team conducted behavioral experiments with Eurasian blackcaps using different frequency bands within this range.
A study published in 2022 had already demonstrated that radio waves of a frequency between 75 and 85 megahertz interfere with the magnetic compass sense of these small songbirds The interference causes their magnetic compass to stop working when exposed to these radio frequencies. Conversely, they function properly without exposure.
In the current study, experiments conducted with frequencies between 140 and 150 megahertz and between 235 and 245 megahertz revealed that the radio waves in both these frequency bands did not affect the birds’ magnetic compass sense, confirming the scientists’ predictions.
Model calculations simulating the quantum-mechanical processes inside the cryptochrome protein enabled the researchers to narrow down the cut-off frequency even further, to 116 megahertz.
According to the simulations, radio waves above this frequency would only have a weak effect on the birds’ magnetic orientation. This prediction was confirmed by the results of the experiments.
Understanding magnetoreception is crucial for improving the protection of migratory birds. Increasing our knowledge will provide insights into the kind of electromagnetic radiation that drives birds off course. From there, we can take precautions to avoid using these forms of radiation in areas like nature reserves where migratory birds stop to rest.
Professor Mouritsen noted that while the radio waves used in radio and television broadcasting or CB radio play a decisive role in disrupting magnetoreception, mobile communications networks do not impair the birds’ magnetic sense. “The frequencies used here are all above the relevant threshold.”
This study marks a significant step forward in understanding the mysterious world of bird migration and the factors that influence their navigational abilities.
With the continued expansion of human-made electromagnetic fields, it is more important than ever to understand the impacts on wildlife and take necessary measures to mitigate any harmful effects.
Radio waves are a type of electromagnetic radiation, much like visible light, X-rays, or ultraviolet light, but with a much longer wavelength. Here’s a detailed overview.
The radio spectrum is divided into bands based on frequency:
There has been much debate and research about the potential health risks of radio waves, especially given the ubiquity of devices like cell phones. As of my last training cut-off in September 2021, the consensus among health organizations is that low-level exposure to radio frequencies does not cause adverse health effects.
Radio waves were first predicted by James Clerk Maxwell and later confirmed by Heinrich Hertz in the late 19th century. Their discoveries laid the foundation for the development of modern radio communication.
The study is published in the journal Proceedings of the National Academy of Sciences (PNAS).