The next time someone calls you bird-brained, you should assume that you are being complimented on your sense of direction.
Pigeons, in particular, are known for their innate homing ability, having been used as messengers since ancient times. We know that pigeons have some kind of internal magnetic compass, but exactly what it is and how it works has remained a mystery.
Now scientists are one step closer to decoding the birds' magnetic sense. Writing in the journal Science, Le-Qing Wu and J. David Dickman at Baylor College of Medicine described what happened when they put seven pigeons in an artificial magnetic field and observed their brains.
Wu and Dickman put the pigeons in a completely dark room, clamped their heads in place, connected their brain stems to electrodes, and used a Tesla coil to cancel out the effects of the Earth's magnetic field and to induce a new one. Then they fiddled with the angle and the intensity of the magnetic field and watched which parts of the pigeons' brains lit up.
Ultimately, Wu and Dickman identified 53 neurons in the pigeons' brain stems that responded to magnetic stimuli.
"The cells responded to the angle and intensity of the magnetic field. Some cells were more sensitive depending on what direction we aimed the magnetic field around the bird’s head," Dickman said in a Baylor press release.
Of course, being able to tell which way is north is not the same thing as knowing your position on the globe. (If you doubt this, have a friend blindfold you and drop you in a boat in the middle of the ocean with just a compass. You'll quickly realize that, even though you can determine your bearing, you still have no idea where you are. You'll also realize that you need better friends.)
Pigeons seem to have both an internal compass and an internal map. Dickman and his colleagues believe that pigeons encode the information from these magnetically attuned nerve cells to spatial maps in the memory centers of their brains.
"Birds give us a unique opportunity to study how the brain develops these spatial maps and the receptors that feed into it because they have such a great ability to navigate," said Dickman in the press release.