Scientists at the Max Planck Institute of Animal Behavior uncovered that liver macrophages in homing pigeons store magnetic iron particles. The discovery came after an immunologist noted similar structures in mouse spleen macrophages, sparking a cross‑disciplinary test in bird livers. Researchers used magnetometers and electron microscopy to confirm iron‑laden cells adjacent to neurons today.

To test function, 34 pigeons were trained on a 19‑km eastward path. Researchers injected 18 birds with clodronate liposomes to deplete liver macrophages. On cloudy days, drug‑treated birds drifted off course and returned only after skies cleared, while sham‑injected controls flew straight home during the experiment no disturbances in behavior.

These results suggest that liver‑resident iron cells act as a magnetic compass. The team ruled out drug side‑effects by releasing treated birds on sunny days, where navigation remained intact. Experts view the study as a proof‑of‑concept, urging further work to map how ferritin‑laden macrophages transmit signals to nearby neurons within the nervous system.

While the mechanism remains unconfirmed, the finding opens avenues for bio‑inspired navigation systems. If ferritin‑based magnetoreception proves universal, it could explain magnetic sensing in species from bees to whales. For now, the study provides a concrete link between immune cells and spatial orientation, challenging decades of speculation about animal magnetism in the broader context of biological sensing research.