The magnetic sense: a mystery scientists spent decades trying to unravel
Many bird species can travel vast distances without losing their way. For a long time, scientists tried to understand how these birds navigate, as their routes often stretch for thousands of kilometers. It was known that birds can detect Earth’s magnetic field, but the exact mechanism remained unclear.
Several theories existed. One suggested that birds have magnetite crystals in their bodies that react to magnetic lines and send signals to the brain. Another linked navigation to special proteins in the eyes that can change their properties under the influence of light and the magnetic field. A third hypothesis was based on the principle of electromagnetic induction: the bird’s inner ear was believed to generate electric currents as it moves through a magnetic field.
Experimental approach: from the brain to sensory detection
In a new study, scientists decided to change the traditional approach. Instead of searching for magnetosensitive cells throughout the body, they began by analyzing brain activity. Pigeons were placed in an artificially created rotating magnetic field, while researchers monitored which areas of the brain responded to the stimulation.
Researchers used the C-FOS protein as a marker, which appears in active neurons. The bird brains were made transparent through a special process, then scanned with a laser to create a 3D map of neural activity. The experiments were conducted both in the dark and under illumination to rule out the influence of vision.
The results were clear: only the medial vestibular nuclei, which are linked to the inner ear, responded to the magnetic field. Areas responsible for vision and the trigeminal nerve remained unchanged. This ruled out hypotheses involving the eyes and beak in magnetoreception.
The inner ear: the key to navigation
Further analysis focused on the inner ear, specifically the ampullae of the semicircular canals. Using single-cell RNA sequencing, researchers identified a unique type of hair cell—type II. These cells contain specific ion channel proteins that make them sensitive to the slightest changes in electrical potential.
Interestingly, similar channels are found in sharks and rays, which are known for their ability to detect faint electrical signals. This discovery led scientists to suggest that in pigeons, type II hair cells may serve as biological electroreceptors.
When a bird flies and moves its head, fluid in the inner ear shifts, crosses magnetic field lines, and generates a weak electric current. These sensitive cells detect this signal and transmit the information to the brain.
Rethinking navigation: new horizons for science
The discovery that magnetic sense is integrated into the balance system explains many observed behaviors. For example, homing pigeons often circle in place before choosing a flight direction. It is now clear that such movements are necessary to activate their biological compass—head movements amplify the signal detected by the inner ear.
This research not only challenges previous hypotheses but also opens new avenues for studying migration in birds and other animals. Understanding how magnetoreception works could lead to innovative nature-inspired navigation technologies.
In addition, the results underscore the importance of a comprehensive approach in biological research. Rather than seeking individual sensors, it is more effective to analyze how entire systems operate and interact.
Did you know: what we know about the rock pigeon
The rock dove (Columba livia var. domestica) is one of the most widespread birds in the world. Its ancestors were domesticated by humans in ancient times, and since then, pigeons have become an integral part of urban landscapes. These birds are known for their remarkable homing ability, allowing them to return home from great distances—making them invaluable to postal services for centuries. Pigeons are highly trainable and possess excellent memory, which enables them to remember complex routes. In scientific research, the rock dove is often used as a model species to study behavior, navigation, and sensory systems. Thanks to their resilience and adaptability, pigeons have spread to nearly every continent except Antarctica. In culture and art, these birds symbolize peace and loyalty. Modern genetic studies are helping to shed light on the evolution and biological characteristics of this species. Interestingly, some pigeons can recognize human faces and even distinguish between paintings by different artists. Their unique navigational skills continue to fascinate scientists and inspire new discoveries.
