Curiosities: How do birds migrate?
The essential skills of bird migration are orientation — knowing north from south, and east from west — and navigation, having some sort of “map” to establish the location you’re aiming for, says Stanley Temple, emeritus professor of conservation.
A Sandhill Crane in flight.
Birds usually orient themselves by observing the sun and the stars – although some can also sense Earth’s magnetic field.
Orientation is not enough by itself: to find your way to the right location, you also need navigation – in this case using a mental map of where you’re going. The mental map may have inherited and learned components, Temple says.
“The inherited map plays a role in the many birds that do a first migration completely on their own, without associating with other individuals, using a well-developed innate map,” he says.
Other species learn the appropriate migration route by following experienced birds, or even the ultra-light airplanes that have guided hand-reared whooping cranes.
“Birds also employ redundant orientation systems,” Temple says. “They will normally use the most accurate directional clue, but will fall back on a less accurate clue if necessary. If celestial navigation is the primary way to orient, and it’s overcast, they may shift to geomagnetism, landmarks, or other, less accurate techniques that will still get the job done.”