How do pigeons find their way home?

Scientists peek inside a pigeon's ear to understand how it reaches its destination

Melbourne: Homing pigeons are known for their uncanny ability to find their way home – navigating complex and changing landscapes. In fact, they do this so well they were used as a source of secure communication more than 2,000 years ago.

Julius Caesar reportedly sent news of his conquest of Gaul back to Rome via pigeons, as did Napoleon Bonaparte following his defeat by England in the 1815 Battle of Waterloo.
We know pigeons use visual cues and can navigate based on landmarks along known travel routes. We also know they have a magnetic sense called “magnetoreception” which lets them navigate using Earth’s magnetic field.

But we don’t know exactly how they (and other species) do this. In research published today in the Proceedings of National Academy of Sciences, David Simpson, School of Physics, Senior Lecturer, The University of Melbourne and his colleagues tested a theory that attempts to link magnetoreception in homing pigeons with tiny lumps of iron-rich material found in their inner ears.

“By using a new kind of magnetic microscope, we confirmed this isn’t the case. But the technology has opened the door for us to investigate the phenomenon in several other species,” he said.

Scientists have spent decades exploring the possible mechanisms for magnetoreception. There are currently two mainstream theories. The first is a vision-based “free-radical pair” model. Homing pigeons and other migratory birds have proteins in the retina of their eyes called “cryptochromes”. These produce an electrical signal that varies depending on the strength of the local magnetic field. This could potentially allow the birds to “see” Earth’s magnetic field, although scientists have yet to confirm this theory.

The second proposal for how homing pigeons navigate is based on lumps of magnetic material inside them, which may provide them with a magnetic particle-based directional compass. We know magnetic particles are found in nature, in a group of bacteria called magnetotactic bacteria. These bacteria produce magnetic particles and orient themselves along the Earth’s magnetic field lines.