How do animals navigate during long migrations?

Animals use multiple overlapping systems to navigate during migration. Many birds, fish, and sea turtles detect Earth's magnetic field through magnetite crystals in their tissues or light-sensitive proteins in their eyes, giving them a built-in compass and even a positional map. Birds also rely heavily on the sun's position during the day and star patterns at night. Salmon famously use their sense of smell to return to the exact stream where they hatched. Beyond these internal tools, animals also learn landmarks, follow coastlines or mountain ranges, and use infrasound or barometric pressure cues. Many species combine innate genetic programming with learned experience, meaning young animals are born with a general directional tendency but refine their routes over time.