How pigeons find their way home across hundreds of miles has puzzled scientists for decades. A new study published in the journal Science suggests the answer may lie in an unexpected organ: the liver. Researchers found that specialized immune cells in pigeon livers may act as magnetic sensors, helping the birds detect Earth’s magnetic field and navigate across long distances.
The discovery offers a new explanation for one of the most enduring mysteries in animal behavior. Scientists have long known that pigeons and migratory birds rely on Earth’s magnetic field during travel, but the biological mechanism behind that ability has remained unclear.
Previous theories suggested birds might sense magnetic fields through light-sensitive molecules in their eyes or tiny magnetic particles in their beaks. However, neither idea has received strong experimental support.
Iron-rich immune cells emerge as key suspects
The international research team included immunologists from the University of Bonn and University Hospital Bonn, physicists from the University of Duisburg-Essen, and ornithologists from the Max Planck Institute of Animal Behavior.
To identify potential magnetic sensors, researchers examined tissues from several organs, including the eyes, brain, beak, liver, and spleen. Using advanced magnetic analysis techniques, they found the strongest magnetic response in the liver.
Further investigation traced that response to macrophages, immune cells responsible for breaking down old red blood cells. As part of that process, the cells accumulate iron.
🔴 Pigeons' livers contain magnetic-sensing immune cells, study finds
Researchers from the University of Bonn and Max Planck Institute identified superparamagnetic macrophages in pigeon livers as central to magnetic navigation. When these immune cells were depleted, pigeons lost… pic.twitter.com/gMPQMkNH1E
— NewsTongue (@NewsTongueX) May 29, 2026
Researchers discovered that the iron forms tiny iron-oxide nanoparticles, making the cells highly responsive to magnetic fields.
“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,” said Christian Kurts, director of the Institute of Molecular Medicine and Experimental Immunology at University Hospital Bonn and a co-senior author of the study.
Navigation tests support the theory
To determine whether the cells influence navigation, researchers conducted experiments with trained homing pigeons released more than 20 kilometers (12.4 miles) from their aviary in Konstanz, Germany.
When researchers removed the liver macrophages, the birds struggled to find their way home on cloudy days when the sun was obscured. However, they successfully returned when the sun was visible, suggesting they relied on solar navigation cues instead.
The findings indicate that pigeons use multiple navigation systems and turn to magnetic sensing when visual guidance becomes limited.
A possible pathway to the brain
Researchers also investigated how magnetic information could travel from the liver to the brain.
Using electron microscopy, they found that the iron-rich macrophages sit close to nerve fibers. The arrangement suggests that magnetic signals may be transmitted through the nervous system before reaching the brain.
“These findings provide the first concrete evidence of how Earth’s magnetic field can be perceived within the body and passed on to the brain to guide movement,” said lead author Clivia Lisowski.
Implications beyond pigeons
Researchers said the discovery could reshape scientific understanding of animal navigation. It also raises questions about whether similar magnetic sensing systems exist in other species.
“Animal navigation is one of the most fascinating phenomena in nature,” said Martin Wikelski, director of the Max Planck Institute of Animal Behavior and a co-senior author of the study. “If immune cells are part of how birds sense direction, it would fundamentally change how we understand navigation.”
Future studies will examine how the brain processes these signals and whether other animals that travel long distances may rely on comparable biological mechanisms.
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