Mystery of pigeons solved. Scientists now know how they use Earth’s magnetic field

The results of a new study suggest that pigeons sense magnetic poles thanks to special sensors located in their livers. This breakthrough discovery sheds new light on the mysteries of bird navigation and helps us better understand the mechanisms behind migration, one of the greatest natural phenomena on Earth.

Sun, stars, scents, or an internal magnetic compass

Scientists have long known that birds use a wide range of strategies to find their way from breeding grounds to wintering areas and back again. Some journeys cover thousands of kilometers and take place under challenging weather conditions, yet they are completed successfully. How is this possible?

We know that starlings and pigeons use the position of the sun as a biological compass. New World warblers and European robins prefer observing the night sky, particularly the North Star. Storks and cranes identify landmarks in the landscape, while shearwaters rely on scent maps that reflect changes in the chemical composition of the air.

One of the most fascinating forms of avian navigation is the ability to detect Earth’s magnetic field, observed in species such as feral pigeons, European robins, and garden warblers. Until now, researchers believed that this sense was primarily based on light-sensitive proteins located in the retina and magnetic receptors associated with the nervous system.

Pigeons: masters of navigation

Feral pigeons have become iconic subjects in the study of animal orientation and navigation for good reason. They are easy to breed, cooperate well with humans, and are famous for their remarkable homing instinct. Even when transported 500 or 1,000 kilometers away from their nest, they can find their way back. Humans used this ability for communication long before the invention of radio and the internet.

Previous studies on pigeons showed that these intelligent birds use many different cues for navigation: Earth’s magnetic field, the position of the sun, scents, distinctive landmarks, and perhaps even infrasound. However, the exact workings of their magnetic compass remained a mystery.

The secret weapon: macrophages in the liver

German scientists set out to explain magnetoreception in pigeons using a wide range of physical, morphological, functional, and genetic tests. They discovered that the ability to sense Earth’s magnetic field depends on macrophages located in the birds’ livers.

Macrophages are immune system cells found in organs such as the lungs, liver, spleen, and lymph nodes. They help the body remove microorganisms and dead cells. By breaking down red blood cells, they release iron from hemoglobin, which, according to the researchers, may explain their superparamagnetic properties. Detailed tissue analyses revealed that the pigeons’ livers responded most strongly to external ferromagnetic stimuli, far more strongly than muscles or the beak.

To confirm the theory of a liver-based GPS system in pigeons, the scientists conducted a field experiment. Thirty-four birds were trained to fly along a 19-kilometer route over a German village located at the foothills of the Alps. In some individuals, however, the macrophages were depleted beforehand using clodronate liposomes.

What happened? Under overcast conditions, pigeons lacking active macrophages were unable to return home. However, as soon as the sun emerged from behind the clouds, they found their way without difficulty. The control group performed perfectly under all conditions.

The experiment demonstrates the remarkable ingenuity of nature, which has equipped pigeons with a whole range of navigational mechanisms to cope with different circumstances. According to the study’s authors, the superparamagnetic macrophage model may also be present in other animals, including sharks, bats, and blind mole-rats.

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Source:

Clivia Lisowski et al., Homing pigeon navigation relies on superparamagnetic macrophages under overcast conditions. Science, 392, 985-991 (2026). DOI: 10.1126/science.ady2486