# Why do birds migrate?

> Birds migrate to follow food and suitable breeding conditions as seasons change — moving between rich feeding areas and safe nesting sites. Some species fly thousands of kilometres twice a year. Migration trades long dangerous journeys for access to rich feeding and safe nesting areas as seasons shift.

**Category:** Conservation  ·  **Updated:** 2026-07-05

## Key takeaways
- Migration follows food and breeding seasonality.
- Arctic tern ~70,000 km annual route record.
- Navigation combines magnetic, celestial and learned cues.
- Stopover habitat loss kills migrants mid-route.
- Climate mismatch can desynchronise food and chicks.
- Flyway protection needs international cooperation.

## Answer
Migration is an energy trade-off: long flights are costly, but staying in a food-scarce winter range can mean starvation. Arctic terns may travel roughly 70,000 km annually — the longest migration of any animal.

Birds navigate using the sun, stars, Earth’s magnetic field and learned landmarks. Juveniles often migrate without parents, suggesting inherited route maps.

Habitat loss along “flyways”, window collisions, hunting and climate-driven timing mismatches (arriving before insects hatch) are major threats. WARN’s habitat appeals address forest and wetland loss that removes stopover fuel for migrants.

## Energy trade-off
Staying in food-scarce winter range risks starvation — migration costs fat and mortality from storms and predators but access to summer abundance repays investment. Short-distance migrants move altitudinally or regionally; long-distance cross oceans and continents. Body mass doubles in some species pre-migration — hyperphagia at stopover sites. Without intact wetlands to refuel, birds cannot complete crossing — dead in exhausted condition on beaches documented globally.

## Navigation mechanisms
Experiments with displaced birds show magnetic compass sense — magnetite or cryptochrome proteins proposed. Star patterns learned in youth; sun compass adjusted for time of day. Olfactory cues help homing pigeons. Juvenile cuckoos migrate to Africa without parents — genetic programme plus landscape cues. Climate change disrupts synchrony — arrival before insect hatch leaves chicks starving — phenological mismatch research documents declines in pied flycatchers and others.

## Flyway conservation
East Asian-Australasian Flyway loses tidal flats to reclamation — critically endangers curlews and godwits. Americas flyway loses stopover forest in Central America — coffee farm shade matters. Mediterranean hunting pressure kills millions of songbirds illegally each year. Window glass on skyscrapers kills migratory warblers in cities — lights at night disorient. Single country protection insufficient — treaties like CMS coordinate but enforcement weak.

## WARN habitat link
Migration success depends on chain of habitats — breeding forest, stopover wetland, winter mangrove. WARN habitat appeal funds partner forest and wetland work in tropical range countries where orangutan and parrot habitats overlap migratory stopovers for Palearctic birds wintering in same regions. Rescue of individual exhausted migrants helps locally; flyway protection addresses population scale — donors need both short and long geographic horizon.

## FAQ
### Why do birds migrate?
To follow food and suitable breeding conditions as seasons change — escape starvation in harsh winters.

### Which bird migrates the farthest?
Arctic tern — roughly 70,000 km annually pole to pole.

### How do birds navigate?
Sun, stars, Earth's magnetic field and learned landmarks — combined cues.

### Do young birds migrate alone?
Many species — juveniles often migrate without parents using inherited route programmes.

### What threatens migratory birds?
Flyway habitat loss, glass collisions, illegal hunting, climate timing mismatches.

### What is a flyway?
Broad migration route linking breeding and wintering areas across countries.

## Sources
- [National Audubon Society — migration](https://www.audubon.org)

Human-readable page: https://worldanimalrescuenetwork.org/answers/why-do-birds-migrate