For thousands of years, homing pigeons were the most sophisticated means of long-distance communication. The winners of the first Olympics were announced by homing pigeon. Julius Reuter started his news service with them. Cher Ami, an avian member of the U.S. Army Signal Corps, received the Croix de Guerre in World War I after completing a mission with a bullet in his breast.
How do the birds find their way home? Decades of studies with frosted lenses, magnetic coils or scent deprivation show they use pretty much every clue available. The most difficult one for us to comprehend may be the earth’s magnetic field. Birds see it, but what it looks like to them, nobody knows. Work by Roswitha and Wolfgang Wiltschko in Germany, among others, suggests that this sense relies on quantum mechanics—that is, birds detect something happening in the eye at a subatomic level. Light striking the retina seems to stimulate chemical reactions that produce pairs of molecules with electrons that are “entangled,” meaning they share certain quantum properties. One of those properties, called “spin,” is affected by a magnetic field. That effect could tell the bird which way is north.
Charles Walcott of Cornell, who began studying pigeons in the 1960s, says homing is “still a mystery”—a reminder that “it’s a mistake to think that we live in the same sensory world as other animals.”