Migratory bird

Migratory birds may ‘see’ Earth’s magnetic field. In European robins, the eye protein cryptochrome 4 changes its electron-spin chemistry under magnetic fields when lit. A 2021 Nature study showed it is magnetically sensitive, linking bird navigation to quantum mechanics.

In 1822, a stork was found in Germany with an African spear in its neck. It had flown from Africa wounded, providing decisive evidence that migratory birds travel between continents. Germans call such birds 'Pfeilstorch' (arrow stork).