Birds can combine the Sun, stars, landmarks, smell and Earth’s magnetic field. The balance differs by species, age and conditions. No single “built-in compass” explains every migration.
What we found
Young birds may inherit a general direction, while experienced birds learn routes and landmarks. Experiments with altered magnetic fields, artificial skies and displaced birds show that multiple senses contribute. This redundancy is useful: clouds can hide the Sun, unfamiliar terrain can remove landmarks, and magnetic information can be noisy. Navigation is therefore a flexible system rather than one magic ability. The Ridbusters then compare the wording with the original sources, look for the conditions of each observation and check whether another explanation could fit. That turns a surprising headline into a trail a young investigator can follow: claim, test, result and remaining uncertainty. Birds can combine the Sun, stars, landmarks, smell and Earth’s magnetic field.