**A Pigeon That Loses the Sun Does Not Necessarily Lose Its Way Home**
A pioneering study published in *Science* on 28 May 2026 suggests that homing pigeons might depend on a magnetic sense located in the liver instead of the brain or beak, as earlier studies indicated. This sense appears to be particularly vital when the sky is cloudy.
The paper, “Homing pigeon navigation relies on superparamagnetic macrophages under overcast conditions,” was spearheaded by Clivia Lisowski at the University of Bonn and University Hospital Bonn, with senior authors Christian Kurts and Martin Wikelski, along with physicist Ulf Wiedwald.
**What the Team Actually Did**
The revelation was intentional. Researchers targeted the liver and spleen, realizing these organs gather iron from the breakdown of old red blood cells. They employed magnetic cell-sorting technology to pinpoint which pigeon organs emitted a significant magnetic signal.
The liver exhibited the most robust signal, with iron concentrated in superparamagnetic macrophages clustered around nerve endings. Curiously, immune cells were recognized as detectors of magnetic fields.
**Why the Cloudy-Day Detail Matters**
Removing these macrophages in pigeons trained to navigate from over 20 kilometers indicated that treated pigeons struggled on cloudy days but excelled on sunny days. This trend suggests that the liver’s magnetic sense acts as a backup when the sun is hidden.
Lisowski characterized the finding as proof of how Earth’s magnetic field can be sensed and influence movement, spotlighting a mechanism and pathway rather than asserting it as the only navigation method for pigeons.
**An Older, Contradictory Chapter in This Story**
In 2012, research showed that iron-rich cells in pigeon beaks, once believed to be sensors, were actually macrophages. These discoveries contradicted prior assertions but laid the groundwork for comprehending magnetoreception in various contexts.
The liver findings involve the same category of cells but suggest functional importance for navigation. It highlights that the reduction of specific cells leading to behavioral shifts is essential for substantiating the study.
**Not Everyone Is Convinced**
The study has sparked doubt. Joseph Kirschvink deemed the mechanism unrealistic, and neuroscientist Pascal Malkemper pointed out that the evidence is correlational without confirming a causal pathway.
This does not undermine the findings but emphasizes that it is a single study, requiring replication by independent laboratories to authenticate results. Magnetoreception research has produced outcomes that have not withstood further examination.
**What the Study Does Not Show**
The paper does not assert that it has uncovered pigeons’ sole or primary magnetic sense. Existing research frequently centers on light-dependent mechanisms involving retinal proteins called cryptochromes. If validated, the liver macrophage discovery serves as a backup system for when visual and solar signals are scarce, enhancing rather than replacing other navigation techniques.