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Why do pigeons have a good sense of direction?

A wide variety of animals detect magnetic fields. This sensory ability helps birds and insects migrate and turtles remember the locations of rich feeding areas.

When a pigeon bobs its head, its inner-ear loops provide information to the brain about the magnetic field. This helps them navigate long distances back to the location they identify as home. (Photo: Wikimedia Commons)

Scientists have long known that pigeons navigate using the Earth’s magnetic field. However, several questions remain unresolved about this process. For instance, how do pigeons detect magnetic fields? Which brain circuits process the information? And where in the body is this sensory system located?

Now, a new study has provided some clues which can help answer these questions. It has found that pigeons can sense the Earth’s magnetic field by detecting tiny electrical currents in their inner ears.

The analysis, ‘A global screen for magnetically induced neuronal activity in the pigeon brain’, was published in the journal Science on November 20.

Note that apart from pigeons, a wide variety of animals detect magnetic fields. This sensory ability helps birds and insects migrate and turtles remember the locations of rich feeding areas.

How was the study carried out?

Led by Professor David Keays of Ludwig-Maximilian University (Germany), a team of scientists first created an experiment to find how pigeons respond to the magnetic field. For this, they exposed six pigeons to a magnetic field slightly stronger than Earth’s.

“The birds’ heads were immobilised and the magnetic field was continually rotated to simulate the heads’ motions with respect to Earth’s geomagnetic field,” according to a report in Nature.

Then, scientists mapped the brain activity of these pigeons to see which neurons responded to the magnetic field. They subsequently compared the maps of brain activity of pigeons exposed to the magnetic field to those which were not exposed to the magnetic field.

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What did the study find?

The results showed that the vestibular nuclei — a brainstem area that gets information from the inner ear — are activated by magnetic fields in pigeons.

“The signals went to the mesopallium, a part of the brain that integrates sensory information, and also to the hippocampus — a key region for spatial orientation and navigation,” according to a report in Science.

The scientists also performed a technique called single-cell sequencing in vestibular system cells to look for molecules involved in detecting electric currents. They found a high prevalence of proteins sensitive to electromagnetic changes, the Science report said.

In other words, when a pigeon bobs its head, its inner-ear loops provide information to the brain about the magnetic field. This helps them navigate long distances back to the location they identify as home.

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However, more research is required to ascertain the findings of the new study. Ulrich Müller, a neuroscientist at Johns Hopkins University (the US), told Nature that while the analysis was “compelling”, genetic studies need to be conducted to validate the findings.