The puzzle of magnetic resonance effect on the magnetic compass of migratory birds

TL;DR

This paper critically examines the magnetic resonance hypothesis for migratory birds' magnetic compass, finding that RF field amplitudes used in experiments are too weak to affect radical-pair mechanisms, questioning the current understanding of magnetoreception.

Contribution

The paper provides a detailed analysis showing that RF fields in experiments are insufficient to influence radical-pair based magnetoreception, challenging existing models.

Findings

RF field amplitudes are too small to affect radical-pair spins

Current physical agents cannot explain RF effects on bird navigation

Questions the validity of the radical-pair model for magnetoreception

Abstract

Experiments on the effect of radio-frequency (RF) magnetic fields on the magnetic compass orientation of migratory birds are analyzed using the theory of magnetic resonance. The results of these experiments were earlier interpreted within the radical-pair model of magnetoreception. However, the consistent analysis shows that the amplitudes of the RF fields used are far too small to noticeably influence electron spins in organic radicals. Other possible agents that could mediate the birds' response to the RF fields are discussed, but apparently no known physical system can be responsible for this effect.