How do birds know where to migrate?
Migrating birds carry a navigation kit: a magnetic sense tied to a protein in their eyes, sun and star compasses, and an inborn sense of direction.
Quick Answer
Birds navigate with several built-in tools. Many can sense Earth’s magnetic field, and research points to a light-sensitive protein in their eyes, cryptochrome 4; in a 2021 Nature study, the version from night-migrating European robins was more magnetically sensitive than the versions from chickens and pigeons. Birds also steer by the sun and by the stars: in planetarium experiments, indigo buntings found north from the point the night sky rotates around. Much of the plan is inborn, which is how young birds can migrate without a guide. The results are astonishing: Arctic terns fly more than 71,000 km a year, and in 2022 a young bar-tailed godwit flew 13,560 km nonstop from Alaska to Tasmania in 11 days.
By the Numbers
Key Facts
- Magnetic sense
- Linked to cryptochrome 4, a light-sensitive protein in birds’ eyes
- Star compass
- Birds find north from the point the night sky rotates around
- Longest migration
- Arctic terns: more than 71,000 km a year
- Longest nonstop flight
- 13,560 km, Alaska to Tasmania, by a young bar-tailed godwit in 2022
A bird’s navigation toolkit
- Magnetic compass
A light-sensitive protein in the eye, cryptochrome 4, appears to let birds sense Earth’s magnetic field.
- Sun compass
By day, birds use the sun’s position, adjusted for the time of day.
- Star compass
At night, many find north from the point the stars rotate around.
- Inborn direction
Young birds inherit a sense of which way to go, so some make their first migration without an experienced guide.
A compass in the eye
In 2021, researchers reported in Nature that cryptochrome 4 from European robins, a night-migrating songbird, is magnetically sensitive, more so than the same protein from chickens and pigeons. The finding supports the idea that birds sense Earth’s magnetic field through a quantum chemical reaction in their eyes.
Navigating by the stars
In classic planetarium experiments, ornithologist Stephen Emlen showed that indigo buntings orient using the point in the night sky around which the stars turn. When he rotated the planetarium sky around a different star, the birds changed direction to match.
Record-breaking journeys
Tiny 1.4-gram trackers revealed that Arctic terns fly more than 71,000 km a year between the Arctic and Antarctic. In 2022, a young bar-tailed godwit flew 13,560 km from Alaska to Tasmania without landing once, the longest nonstop bird flight on record.
Myth vs. Fact
MythYoung birds just follow the flock.
FactMany young birds migrate using an inborn sense of direction; a juvenile godwit set the nonstop record on its first migration.
MythMigration mostly happens by day.
FactMost songbirds migrate at night, navigating partly by the stars.
The Bottom Line
Birds migrate with a built-in toolkit: a magnetic sense tied to a protein in their eyes, sun and star compasses, and an inborn sense of direction. Together they guide journeys of thousands of kilometers, sometimes without a single stop.
Sources & Further Reading
- Nature — Xu et al., Magnetic sensitivity of cryptochrome 4 from a migratory songbird (2021)
- PNAS — Egevang et al., Tracking of Arctic terns reveals longest animal migration (2010)
- Guinness World Records — The record-breaking bird that flew from Alaska to Australia without stopping
- BirdNote — Migrations: Indigo Bunting, Master Stargazer
- BirdCast — Bird migration forecasts in real time