The Magnetic Mystery of Bird Migration

Scientists have known for decades that birds use Earth’s magnetic field to guide their migrations, but how they detect it has been a mystery. A recent German study published in the journal Science offers insight into this magnetic mystery of bird navigation.

Birds, as well as other animals, have immune cells called macrophages in their livers. Among other duties, these macrophages eliminate old red blood cells. As they digest these no-longer-needed red blood cells, they accumulate iron nanoparticles, making the macrophages superparamagnetic. In other words, they can detect Earth’s magnetic field as the bird passes through it.

To test whether these magnetic macrophages help birds navigate, the researchers used homing pigeons trained to fly 12.4 miles to their aviary. Pigeons without macrophages reached the aviary when the Sun was unobscured, but they got lost when the weather was overcast. This suggests that the birds use Earth’s magnetic field as well as the Sun to guide their flight. Using electron microscopy, the researchers observed that the macrophages were in contact with nerve cells, which could transmit magnetic information directly to the bird’s brain.

Solving the magnetic mystery of bird navigation can explain how birds that migrate at night find their way when the sky is overcast. It may also explain how sharks navigate and how bats migrate in the dark. Birds and other migrators use vision, magnetism, and other methods to find their way. God has designed into living things the features they need to survive.

— Roland Earnst © 2026

Reference: popsci.com