Every year, birds leave their nests and fly thousands of miles—across oceans, continents, even entire hemispheres. The Arctic tern alone racks up nearly 50,000 miles annually. Some birds return to the same patch of land every time, sometimes the same tree.
How the hell do they do that?
Researchers have been trying to figure that out for decades. “We know that birds use a variety of cues to keep their migratory direction,” said Miriam Liedvogel, director of the Institute of Avian Research in Germany, in an email to Live Science.
How Do Migrating Birds Know Where They’re Going? Science Still Isn’t Totally Sure.
They use sight and smell to navigate when the terrain is familiar. Some memorize rivers or coastlines. Others follow scent trails. In one study, seabirds lost their way over open water after scientists blocked their sense of smell—but still flew fine over land.
For orientation, birds also rely on light. During the day, some species use a built-in sun compass, blending their circadian rhythm with the sun’s position to track direction. At night, many shift to the stars, watching how constellations rotate around Polaris, like natural-born astronomers.
If the skies are cloudy or they’re flying through storms, they fall back on something even stranger: Earth’s magnetic field. Birds have a sense called magnetoreception, which helps them detect the field’s direction and strength. Oxford chemist Peter Hore believes it comes from cryptochrome, a molecule in birds’ eyes that reacts to magnetic fields in the presence of blue light.
Other studies suggest birds also have magnetite, a magnetic mineral, in their beaks. These particles might act like tiny compasses, feeding data to the brain through a network of nerves.
On top of that, birds can read polarized light, patterns created when sunlight scatters through the atmosphere, to figure out where the sun is hiding, even on overcast days.
All of this works alongside instinct. Liedvogel said the urge to migrate—and which direction to fly—is genetically programmed. Birds inherit it from their parents, though researchers are still trying to decode the exact genes behind it.
And while people keep trying to relocate birds for conservation purposes, it doesn’t always go well. They just leave. “If you displace them,” Hore said, “they simply fly back.”
The post How Do Birds Navigate the Skies While Migrating? appeared first on VICE.
