Some Birds Can Sleep While Flying — Nature’s Most Surprising Survival Skill
It may sound like science fiction, but it’s a scientifically documented truth: some birds can sleep while flying. This phenomenon has fascinated ornithologists and biologists for decades. In environments where stopping could mean death or danger, this ability helps certain bird species survive long migrations and harsh conditions.
Let’s explore how some birds can sleep while flying, why they do it, and what it reveals about the wonders of evolution.
🧠 What Is Unihemispheric Slow-Wave Sleep?
The secret behind how some birds can sleep while flying lies in a unique biological process called unihemispheric slow-wave sleep (USWS). In simple terms, one half of the bird’s brain stays awake while the other half rests.
- One eye remains open while the other closes.
- The active brain hemisphere manages flight and navigation.
- The resting half goes into a sleep-like state.
This allows the bird to remain alert to dangers while giving its brain a chance to rest — a true marvel of nature.
🌍 Which Birds Can Sleep While Flying?
Not all birds have this superpower. The most well-known example comes from the frigatebird — a large seabird that can stay in the air for weeks.
Other birds believed to use USWS during flight include:
- Swifts
- Albatrosses
- Petrels
Frigatebirds, in particular, have been observed sleeping in short bursts of about 10 seconds while gliding over the ocean.
🔬 Scientific Discoveries
Researchers placed EEG (electroencephalogram) devices on the heads of frigatebirds to record brain activity during long flights.
Findings:
- Birds spent less than 45 minutes sleeping per day during flight.
- Most sleep occurred during ascending air currents.
- Confirmed that some birds can sleep while flying using only one brain hemisphere at a time.
These results were published in Nature Communications and mark one of the most remarkable discoveries in avian neuroscience.
🧭 Why Do Birds Sleep in the Air?
So why would some birds sleep while flying?
- Predator avoidance: Less risk of attack in open skies.
- Migration efficiency: Saves time during long-distance flights.
- Energy conservation: Gliding takes less effort than flapping.
In highly competitive ecosystems, every advantage matters — and sleep-on-the-go is one of the most extreme.
📚 Fun Fact:
Humans experience something similar during microsleeps (short sleep episodes during monotonous tasks). However, unlike birds, we lose all awareness during sleep.
🧳 Where Can You See This?
- Galápagos Islands — home to many frigatebirds
- Tropical Oceans — look up during seabird migrations
- Hawaii and Southeast Asia — nesting regions for some migratory species
Next time you see a seabird soaring effortlessly above the waves, you might be watching one that’s asleep mid-flight!
