Navigation map has to be learned by migration-naïve Eurasian reed warblers.

Migration-naïve Eurasian reed warblers do not use a functional innate magnetic map during their first migration, as shown by their unaltered orientation under virtual magnetic displacement.

• Why it matters: Understanding whether young birds possess an inherited magnetic map is crucial for revealing how migration navigation develops and whether innate mechanisms guide initial migration or if experience is necessary.
• What they did: Researchers trapped juvenile Eurasian reed warblers in early autumn, kept them in captivity over winter, and tested their orientation in natural and displaced magnetic fields in spring, totaling 6 birds.
• The result: The birds did not change their orientation under virtual magnetic displacement, indicating that a functional magnetic map is not innate but develops through migratory experience in this species.