Do migratory birds sleep while flying? Facts & Explanation

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Many birds migrate from one country to another. Migration happens when conditions change and become unfavorable for survival. Since many species travel vast distances, you may wonder if the birds stop off on the way to rest and if the birds sleep while in flight.

There are species of birds that can sleep even when flying. This is known as unihemispheric sleep and it allows the birds to shut off half the brain while remaining aloft. Magnificent Frigatebirds and Alpine Swifts are birds that have been shown to sleep in this way while flying during migration.

Read on to learn more about how migratory birds can sleep during flight, and other strategies they use during migration to increase their chances of survival.

Do migratory birds sleep while flying?
Do migratory birds sleep while flying?

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Do migratory birds sleep while flying?

Some species of birds can sleep even while in flight. This phenomenon has been found for the Magnificent Frigatebird, where an individual bird can remain flying while shutting one eye and letting one brain hemisphere rest.

The process where a bird can sleep by having one hemisphere in a state of sleep and the other awake is known as unihemispheric slow-wave sleep (USWS). Migratory birds such as the Alpine Swift, can also sleep in flight in this way.

During flight, some birds may very briefly also engage in bihemispheric SWS (BWS), in which both brain hemispheres are asleep. It seems that USWS is more common.

How much and the type of sleep the birds enter in flight may be influenced by how they are migrating. In other words, birds that are flying in a V-formation may require more alertness to ensure they don’t collide with other members of the flock.

The V-formation is important for aerodynamic effectiveness, and allows the birds to fly efficiently from place to place. It does rely on individuals not colliding with each other during flight.

Scientists have found that birds sleeping while flying do sometimes also enter REM sleep, but do so for less than 5 seconds at a time. On land, sleeping birds are in REM sleep for close to 6 seconds at a time.

Besides birds sleeping while in flight, species may land and stop over at various places along the migration route. This explains why there are many migration hotspots during the annual spring and fall migration of birds.

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Migration hotspots and resting

Birds flying in a V-formation
Birds flying in a V-formation

Some parts of the United States are known as migration hotspots. These are usually places found along the coast, along rivers, or on the Great Lakes shoreline.

Birds may take the first opportunity, after crossing water, to land and refuel. Such hotspots are important in helping many migratory birds to rest and regather their strength for the next phase of their journey.

These hotspots are places where many migratory birds may choose to wait for a day or two before continuing on with their migration journey.

Many songbirds that migrate can be seen in hotspots during times of migration. Other surprising hotspots are green areas within cities. For example, Central Park in New York City provides a good place for birds to stop over, rest, and feed, during migration. 

Aside from the usual stopover spots on land, birds may stop off on ships. This is quite common when birds are crossing oceans and seas, and may happen more when weather conditions become adverse. The birds may rest for a while on a ship before continuing on their trip. 

Sleep-deprivation in birds

Research on Pectoral Sandpipers has found that these birds can function fine on very little sleep. These findings are relevant when studying sleep in migratory birds.

The results suggest that even long-distance migrants could be able to fly for many hours without needing to rest or sleep at all.

In fact, scientists have discovered that the White-crowned Sparrows sleep only one third what they normally do while on migration.

Besides how much sleep a bird needs when migrating, the timing of migration is also important. Different species may migrate at different times, either at night, or during the daytime. 

Do birds migrate during the day or the night?

Many bird species actually migrate at night. They may use the stars and magnetic north to make sure they are moving in the correct direction. There are benefits to flying at night. It does help protect birds from attacks by diurnal birds of prey like hawks and eagles.

It is also thought that the atmosphere may be more stable at night, making flight easier. This does, however, depend on the type of bird and on what the weather conditions happen to be.

For instance, raptors are diurnal migrants. They migrate during the day. A good reason for doing this is that these birds use thermals to help with flight.

In fact, the birds may even wait until there are strong thermals before setting out on their migration. Thermals are updrafts of warm air that help provide increased buoyancy for the birds.

This means they can soar and glide more and flap less. Since wing flapping uses more energy, taking advantage of thermals means a more efficient use of energy for the birds.

Birds frequently call when flying in migration. This is believed to help the birds remain in contact with their flock members. The contact calls during migration are usually different from calls made at other times. This has been the case for warblers and buntings studied during migration flight. 


Some migratory bird species do sleep while flying. Commonly the birds use unihemispheric sleep where one hemisphere of the brain rests while the other remains alert and active. Birds can even briefly enter REM sleep.

Flying birds may also use bihemispheric sleep at times where both hemispheres of the brain are asleep. Migrating birds may be able to function on very little sleep.

There are also bird species that do stop and rest at various hotspots on land during migration. This allows these birds a chance to eat and refuel before continuing on their migration route.

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Rae Osborn

Rae Osborn is an avid bird watcher and holds a doctorate in Biology. Her interests in birds began as a child growing up in South Africa. She has continued to study birds and has bird watched in the United States and South Africa.

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