Upper bound for broadband radiofrequency field disruption of magnetic compass orientation in night-migratory songbirds

Abstract

Overview

Night-migratory songbirds possess a light-dependent magnetic compass, thought to rely on photochemical formation of radical pairs in cryptochrome (Cry) proteins found in the retina. The disruption of magnetic orientation by weak radiofrequency (RF) electromagnetic fields has been considered a diagnostic test for this radical-pair mechanism and a possible clue to the specific radicals involved.

Findings

• Predictions indicated that frequencies between 120 and 220 MHz might disrupt magnetic compass orientation via a flavin-tryptophan radical pair in Cry.
• The study found that RF noise within 140–150 MHz and 235–245 MHz did not interfere with the magnetic orientation of Eurasian blackcaps (Sylvia atricapilla).
• Analyses of internal magnetic interactions suggest the RF susceptibility of flavin-containing radical-pair sensors is nearly constant up to 116 MHz, but birds’ sensitivity to RF fields sharply declines (by about two orders of magnitude) at frequencies above 116 MHz.
• Notably, prior work confirmed that 75–85 MHz RF fields can disrupt magnetic orientation in blackcaps.

Conclusion

These findings strongly support the hypothesis that the magnetic compass in migratory birds operates via a radical pair mechanism, specifically in cryptochrome proteins. Furthermore, this work underscores that broadband RF fields below 116 MHz can meaningfully disrupt biological magnetoreception—highlighting the biological sensitivity to certain electromagnetic frequencies and the real potential for health and ecological risks related to EMF exposure.