KONSTANZ — A study published in the journal Science on May 28, 2026, identified a strong magnetic signal in pigeons’ livers linked to specialized immune cells that aid navigation on overcast days. Researchers found that macrophages in the liver, which store iron from broken-down red blood cells, are superparamagnetic and appear essential to the birds’ ability to orient themselves when sunlight is unavailable.

Scientists used vibrating sample magnetometry and magnetic cell separation to analyze pigeon tissues and discovered the strongest magnetic response in the liver. In experiments, pigeons with intact liver macrophages released 19 kilometers from home on overcast days returned in about 70 minutes. When macrophages were temporarily depleted, the same birds flew erratically and did not return home until the sun reappeared the next day. On sunny days, however, even pigeons with depleted macrophages navigated directly home, confirming that pigeons rely on the sun as a primary guide when available.

“When scientists temporarily removed macrophages from pigeons and released them on overcast days, the birds ‘just couldn’t find their way,’” said Christian Kurts, Director at the Institute of Molecular Medicine and Experimental Immunology at the University Hospital Bonn. He added, “We didn't expect immune cells to act like sensors for magnetic fields at all. Our results reveal a previously unknown mechanism for magnetic perception in animals.”

The liver macrophages contain iron crystallized in oxide nanoparticles, making them responsive to magnetic fields. These cells are located near nerve fibers, suggesting a possible pathway for transmitting magnetic information to the brain. “That might be how they transmit their ‘magnetic sense’ to the brain and help the pigeons to navigate,” said study co-author Clivia Lisowski, a cell biologist at the University of Bonn.

Martin Wikelski, Director at the Max Planck Institute of Animal Behavior in Germany, said, “The magnetic sense has been this mystery for almost 100 years.” He added, “What looks like a 'gut feeling' in bird navigation may actually have a physical basis.”

More work is needed to verify that pigeons navigate using liver macrophages and to understand how signals reach the brain. Immune cells with magnetic properties have also been found in pigeons’ beaks and spleens.