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Claim check

Do birds just know where to migrate?

Misleading

The words are defensible; the impression they create is not.

A first-year bird inherits a direction and roughly how long to fly it — which is not the same as knowing where to go. Displace a juvenile a few hundred kilometres and it flies the same heading into the wrong country; displace an adult and it corrects. Knowing where you are is learned by making the journey. And the magnetic compass is not a GPS: it gives direction, not position.

The claim as it circulates

“Migrating birds have an inbuilt instinct that tells them where to go. They follow the Earth’s magnetic field like a GPS and navigate to the same spot every year without being taught.”

Where you may have met it: Documentary narration, where "instinct" does the explaining; Popular science writing about magnetoreception, usually with a GPS comparison; School material on animal behaviour

Taking it apart

What was claimed
That migratory birds possess inherited knowledge of their destination, and navigate to it using the magnetic field in the manner of a satellite positioning system.
What was actually observed
Eleven thousand starlings displaced several hundred kilometres during autumn migration split by age: juveniles maintained the inherited compass heading from the release point and were recovered far outside the normal wintering range, while adults changed heading and reached their usual wintering areas. Separately, robins tested in altered magnetic fields reoriented when the vertical component was reversed but not when the horizontal component alone was, showing an inclination compass rather than a polarity one. And buntings raised without a rotating night sky failed to develop a star compass at all.
What the evidence supports
That a compass direction and an approximate duration are inherited, and are enough for a naive bird to arrive somewhere appropriate. That position-finding is a separate capability acquired through experience. That at least three compasses — magnetic, star and sun — are used and cross-calibrated.
What it does not support
Inherited knowledge of a destination. Anything resembling positioning: a compass tells a bird which way is poleward and nothing whatever about where it is. And the star compass is not inherited at all — it is learned in the nest from watching which point the sky turns around.

"Instinct" is the problem word. It sounds like an explanation and functions as a placeholder for one, and pulling it apart is what makes the subject interesting. What is inherited is a rule — fly this bearing for about this long — which is cheap, needs no teaching, and has an exact and testable failure mode. Perdeck found it by moving the birds.

The star compass makes the same point more sharply. A bird does not inherit Polaris. It inherits a procedure for finding whichever point the sky rotates around, and learns the answer as a fledgling. That is the better design: the pole star changes over thousands of years, and a rule does not have to be updated.

Go deeper

The claims underneath

Each one carries its own evidence, scope and caveats. Expand any of them to reach the studies.

A first-year bird follows an inherited direction; an adult can correct for being moved

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Displacement experiments separate two navigational capabilities. Juvenile migrants on their first journey maintain the inherited compass heading from wherever they are released and arrive at a correspondingly displaced destination. Experienced adults compensate, changing heading to reach their usual wintering area, which requires knowing their position relative to a goal rather than only a direction.

Who this applies to
starlings and chaffinches displaced during autumn migration in western Europe
Studied in
Sturnus vulgaris, Fringilla coelebs

You may have heard

“Birds instinctively know where to go”

What is inherited is a direction and roughly how long to fly it, which is enough to reach a plausible destination and no help at all if the bird is moved. Knowing where you are is a separate ability, and it is learned by making the journey. Move a young bird and it flies the same heading into the wrong country.

Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A large-scale displacement with more than eleven thousand marked birds and a clear, predicted difference between age classes recovered from independent reports.

How far it can be extended

The juvenile–adult split has since been found in several other migrant species, though the degree of correction varies.

Caveats

  • Recoveries depend on birds being found and reported, which varies by region and season.
  • Displacement is a severe manipulation with effects on condition and motivation that cannot be measured.
  • How adults determine position — the map component — is not answered by this result.

Still unanswered

  • What information does the adult map component actually use?

Last reviewed 2026-08-10

The evidence (1 study)

A bird’s magnetic compass tells poleward from equatorward, not north from south

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

European robins tested in coil systems reoriented when the horizontal component of the magnetic field was turned, but reversing the horizontal component alone did not reverse their heading; reversing the vertical component did. The compass therefore responds to the inclination of the field lines relative to gravity rather than to magnetic polarity, distinguishing poleward from equatorward directions.

Who this applies to
night-migrating songbirds, established in the European robin
Studied in
Erithacus rubecula, Aves

You may have heard

“Birds follow the Earth’s magnetic field like a GPS”

Two errors in one sentence. A compass gives direction and GPS gives position — knowing which way is poleward tells a bird nothing about where it is. And the bird’s compass is not the kind in a hiker’s pocket: it reads the angle the field makes with the ground rather than which end points north.

Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A direct manipulation with the diagnostic control: separating the horizontal and vertical components tells the two candidate mechanisms apart, and the result is unambiguous.

How far it can be extended

The inclination compass has since been demonstrated in many migratory bird species; it is not universal among animals with magnetoreception.

Caveats

  • Cage orientation measures intention rather than a flight path.
  • The receptor mechanism remains contested, with cryptochrome and magnetite hypotheses both unresolved.
  • An inclination compass gives no useful signal at the magnetic equator, where the field lines are horizontal.

Still unanswered

  • Which receptor actually detects the field, and where is it?

Last reviewed 2026-08-10

The evidence (2 studies)

Young birds learn which way is north by watching the sky turn

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Indigo buntings tested under a planetarium sky oriented by the pattern of stars around the axis of celestial rotation rather than by specific constellations, and rotating the artificial sky rotated their headings. Birds reared without exposure to a rotating sky failed to orient by stars; birds reared under a sky rotating about an arbitrary star treated that star as the pole.

Who this applies to
indigo buntings under planetarium conditions
Studied in
Passerina cyanea

You may have heard

“Birds are born knowing the stars”

What is inherited is a rule — find the point the sky turns around — rather than a chart. That is a better design than inherited constellations, because the pole star changes over thousands of years and the rule does not have to.

Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A developmental manipulation with a clean prediction: rear a bird under a sky turning about the wrong star and it should adopt the wrong pole, which is what happened.

How far it can be extended

Star-compass calibration from rotation has been shown in several night-migrating species since, though the developmental window differs.

Caveats

  • A planetarium sky is brighter and simpler than a real one.
  • Captive rearing is a severe manipulation with effects beyond the visual environment.
  • A star compass supplies direction only, and is unavailable under cloud.

Still unanswered

  • How do birds arbitrate between star, magnetic and sun compasses when they disagree?

Last reviewed 2026-08-10

The evidence (2 studies)

Go deeper

Bird migration

Move a young bird 500 km and it flies the same heading into the wrong country. Move an adult and it corrects.

Last reviewed 2026-08-10