How do birds navigate thousands of miles during migration?

The answer

Migratory birds use Earth's magnetic field as a biological compass, thanks to magnetite crystals in their beaks and light-sensitive proteins called cryptochromes in their eyes. The Arctic tern holds the record for the longest migration, traveling roughly 44,000 miles annually from Arctic to Antarctic and back. Birds also use the sun, stars, and landscape landmarks as supplementary navigational cues, and young birds appear to inherit a general migratory direction genetically.