Migrating birds posses a sixth sense that allows them to detect the difference between magnetic and true north, new research suggests.
By measuring the variation, which changes depending on location, the birds can navigate in a way that defeated human sailors for centuries, scientists believe.
Every orienteering enthusiast knows that while a compass needle points north under the influence of the Earth’s magnetic field, the North Pole as viewed on a map can be one or more degrees further east or west.
When navigating using a map and compass, this ‘declination’ has to be accounted for, especially when travelling long distances.
Scientists have now shown that at least one species of migratory bird, the reed warbler, can sense declination and use the information to plot its longitudinal point on Earth.
Dr Richard Holland, from the University of Bangor in Wales, said: “How birds have resolved the longitudinal problem has been a scientific mystery.”