Signals too small to sense: Physical and information-theoretic limits to induction-based magnetoreception in birds

TL;DR

This paper investigates the physical and information-theoretic limits of induction-based magnetoreception in birds, concluding that electromagnetic induction in the semicircular canals is unlikely to provide sufficient directional information, but RF waves could disrupt navigation.

Contribution

It provides a quantitative analysis showing the physical plausibility limits of induction-based magnetoreception and suggests RF interference as a potential disruptor, refining understanding of avian magnetic sensing mechanisms.

Findings

Induction in semicircular canals likely insufficient for directional sensing.

RF electromagnetic waves of tiny amplitude could disrupt magnetoreception.

Physical constraints limit the viability of induction-based mechanisms.

Abstract

A recent study [Science 2025, eaea6425] proposes that magnetoreception in pigeons may arise from electromagnetic induction within the semicircular canals of the inner ear. In this framework, motion through the geomagnetic field is suggested to generate an induced electromotive force that leads to ion redistribution in the endolymph, activation of voltage-gated calcium channels, and subsequent engagement of downstream neural circuits. In this work, we examine the physical plausibility of this mechanism using a toy model of the induction process combined with an information-theoretic analysis. We find that, under idealised assumptions, Faraday induction in the semicircular canals would not generate a signal of sufficient informational content to support the extraction of directional magnetic field information from the geomagnetic field. However, the model supports the possibility of inferences due to radio-frequency (RF) electromagnetic waves of a miniscule amplitude, thereby providing a potential rationalisation of their disruptive effect on avian compass navigation. We stress that our analysis does not call into question the experimental evidence for magnetically responsive pathways within the vestibular system of pigeons. Rather, it constrains the class of viable physical mechanisms, indicating that a functionally competent magnetosensory system likely relies on different sensing principles or, if induction-based, on a different sensing architecture, while highlighting induction as a potential interference pathway of RF electromagnetic fields.