Authors: Bo Leberecht, Siu Ying Wong, Baladev Satish, Sara Döge, Jakob Hindman, Lalitha Venkatraman, Shambhavi Apte, Katrin Haase, Isabelle Musielak, Glen Dauta, Ilia A. Solov’yov, Michael Winklhofer, Henrik Mouritsen, and P. J. Hore
Year: 2023
Publication: Proceedings of the National Academy of Science
Publication Link: https://www.pnas.org/doi/10.1073/pnas.2301153120
Keywords: radical pair mechanism, magnetoreception, bird migration, electrosmog, hyperfine interaction
Abstract: Night-migratory
songbirds have a light-dependent magnetic compass sense, the mechanism of which is thought to depend on the photochemical formation of radical pairs in
cryptochrome (Cry) proteins located in the retina. The finding that weak radiofrequency
(RF) electromagnetic fields can prevent birds from orienting in the Earth’s magnetic
field has been regarded as a diagnostic test for this mechanism and as a potential source
of information on the identities of the radicals. The maximum frequency that could
cause such disorientation has been predicted to lie between 120 and 220 MHz for a
flavin–tryptophan radical pair in Cry. Here we show that the magnetic orientation
capabilities of Eurasian blackcaps (Sylvia atricapilla) are not affected by RF noise in
the frequency bands 140 to 150 MHz and 235 to 245 MHz. From a consideration of
its internal magnetic interactions, we argue that RF field effects on a flavin-containing
radical-pairsensor should be approximately independent of frequency up to 116 MHz
and that birds’ sensitivity to RF disorientation should fall by about two orders of magnitude
when the frequency exceeds 116 MHz. Taken together with our earlier finding
that 75 to 85 MHz RF fields disrupt the magnetic orientation of blackcaps, these results
provide compelling evidence that the magnetic compass of migratory birds operates by
a radical pair mechanism.