Overview
- The study, published May 28, 2026, reports that removing iron-laden liver macrophages stopped homing pigeons from orienting on overcast days while leaving sunny-day returns intact.
- Researchers found the liver held the strongest magnetic signal because macrophages break down red blood cells and store iron as ferritin and oxide nanoparticles that show superparamagnetic behavior.
- The team tested 34 trained pigeons on a 19-kilometer route, comparing control birds with a group given a macrophage-depleting treatment and tracking their flights with GPS.
- Key limitations remain: the depletion method acted systemically so effects cannot be attributed solely to liver cells, the proposed nerve pathway to the brain has not been traced, and some lab magnetic tests used stronger fields than Earth’s.
- Authors and outside experts say targeted liver-specific manipulations, direct neural tracing, and independent replication in other species are needed before this proposed immune-cell magnetoreceptor model is accepted.