How does it feel when you’re stuck at a crossroads, with no idea where to turn? You hit navigation on Google Maps and find your way. Sadly, pigeons are not as proficient at using GPS. What’s even the point of using such tech when you’ve got a built-in compass up in your inner ear? They have been used to send messages by ancient Egyptians and even during World War I. The Pigeon mailing service, called the Great Barrier Pigeongram Service, was also formed in New Zealand in 1897. Safe to say, they delivered well.
Pigeons can detect tiny electrical fields using their inner ears, basically providing them with an in-built compass. This explains their proficiency in migration and long-distance navigation. Scientists performed advanced brain mapping and single-cell RNA sequencing of inner-ear cells in pigeons. They found that the inner ear serves as the center of magnetoreception, or the ability to sense magnetic fields.
“This is probably the clearest demonstration of the neural pathways responsible for magnetic processing in any animal,” says Eric Warrant, a sensory biology researcher at the University of Lund in Sweden. Turtles and trout are also said to possess the ability to sense direction; however, little evidence of their mechanisms has been discovered.
Two leading hypotheses reveal how pigeons sense magnetic fields. One of them states that microscopic iron oxide particles in pigeon beaks can act as tiny compass needles, and the other one says that pigeons can see magnetic fields with their specialized retina. In a 2011 study, it was discovered that the vestibular system in the inner ear of pigeons is the organ that senses magnetic fields. These are an assortment of tubular fluid-filled canals that are perpendicular to one another and provide balance and stability.
David Keays, a neuroscientist at Ludwig-Maximilians-Universität München in Germany, developed the blueprint for an experiment to reveal how a pigeon’s brain responds to magnetic fields. Keay’s team exposed pigeons to magnetic fields slightly stronger than the Earth’s for just over an hour, during which the birds’ heads were immobilized. The magnetic field was rotated to mimic the motion of a pigeon’s head.
After this, the neuronal activation patterns of the pigeon were estimated by measuring a gene marker of cell activity in the pigeon’s brain using a technique called clearing. This data was compared against data from a control group that was not exposed to the magnetic field. The data showed that most neuronal activity arose in the brain areas that received inputs from the vestibular system and in other areas receiving information from sensory stimuli. This narrowed down the potential organs to the vestibular system.
Sharks and skates detect magnetic fields to locate prey. They do so using a protein sensitive to neural electrical activity, but with a 10-amino-acid modification that allows them to sense the electric currents generated by magnetic fields. Keays searched for such a modification in pigeons and found the same instance. Thus, when a pigeon bobs its head, it can detect the components of the magnetic field across three axes with the help of its vestibular system in the inner ear, allowing it to navigate. The prevalence of proteins sensitive to electromagnetic changes was high in the inner ear.
Finally, the pigeons were tested in the dark, and the absence of light had no effect on their perception, contradicting the retina-based model of magnetoreception. The next step is to knock out the genes needed for magnetoreception and see if that nullifies the ability.
Pigeons will probably be better off with a GoPro on their back showing how much of an expert they are in navigating the skies.
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