Birds are extraordinary navigators, routinely finding their way across open oceans, featureless deserts, and unfamiliar terrain to reach precise destinations — sometimes the same backyard or nesting ledge they used the year before. They accomplish this using a layered toolkit of sensory cues that scientists have spent decades teasing apart. The sun serves as a daytime compass, its arc across the sky providing directional information. At night, migratory songbirds read the rotation of the star field around the north star. Olfactory cues — the smell of the landscape below — help some species build a navigational map, particularly homing pigeons and seabirds. And threaded through all of these is the magnetic sense: the ability to detect the Earth's magnetic field and use its inclination and intensity as a kind of invisible map. Past work suggests that some birds sense the magnetic field using a light-sensitive protein in the eye that is also sensitive to magnetic fields.
New research suggests another way birds may sense the magnetic field, at least in pigeons. This work revealed a dedicated neural pathway for processing magnetic information that is initially sensed within their inner ear’s balance system. They found specialized hair cells which may allow the pigeons to detect tiny electric currents from Earth's magnetic field.