Using measurements from ESA's Earth Explorer Swarm mission, scientists have developed a new tool that links the strength and direction of the magnetic field to the flight paths of migrating birds.

Migrating animals have for a long time been tracked by recapturing tagged individuals. More recently, radio-telemetry, which requires an observer to physically follow the tagged animal, has been used.

When people think of migration, they often think of the animals in the world that travel huge distances. Some of these migrations are amazing. They involve thousands or millions of animals and are ...