How migrating birds find a direction
Migrating birds can combine several directional cues, including the Sun, stars, Earth's magnetic field and familiar landmarks. Different species and situations rely on different combinations. Navigation is therefore not one universal built-in map, and knowing which way is north is not the same as knowing where a destination lies.
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Direction and location are separate problems
A compass provides a direction. A map-like sense provides information about position relative to a destination. Successful migration can require both, along with suitable timing and the ability to respond to conditions.
Birds use combinations of celestial, magnetic and landscape cues. Experience can matter, and some young birds begin with inherited directional programmes rather than a fully learned route.
No single cue explains every migration. A method useful on a clear night may be unavailable under cloud, while landmarks are useful only where they can be recognised.
- Compass cues help establish a heading.
- Position information helps relate a heading to a destination.
- Experience can refine routes and responses.
Research continues on the detailed sensory mechanisms, especially magnetic sensing. The well-supported point is that bird navigation draws on multiple sources of information.