Chimney swifts are small birds that are uniquely adapted to spend most of their lives on the wing. Unlike many other bird species, chimney swifts can sleep while flying! Here’s an overview of how chimney swifts are able to sleep during flight:
Do chimney swifts really sleep while flying?
Yes, chimney swifts have the remarkable ability to sleep while flying. They are able to enter short periods of deep sleep lasting up to 10 seconds while airborne. Chimney swifts spend the night flying actively and can sleep while flying to get the rest they need.
How are chimney swifts able to sleep in flight?
Chimney swifts have several key adaptations that allow them to sleep in flight:
- Unihemispheric slow-wave sleep – Chimney swifts can turn off one hemisphere of their brain to rest, while the other hemisphere remains awake to maintain flight.
- Swift flight style – Their swift, stiff-winged flight pattern is efficient and does not require constant active control.
- Short sleep cycles – They only sleep for brief periods of 10 seconds or less at a time.
- Swift claws – Their feet have evolved to be permanently clenched around perches, so they don’t need muscle control to grip.
What happens when a chimney swift sleeps in flight?
When chimney swifts go into short sleep cycles while airborne, here is what happens:
- One hemisphere of their brain goes into slow-wave sleep mode.
- The eye connected to the sleeping hemisphere will close briefly.
- Their flight pattern remains steady due to stiff wings requiring little active control.
- Claws stay tightly clenched around perches or each other in group flight.
- After 10 seconds or less they become fully alert and aware again.
Chimney swifts alternate which side of the brain sleeps during flights to get rest for both hemispheres.
When do chimney swifts sleep while in flight?
Chimney swifts primarily sleep while flying during their long migratory journeys in spring and fall. They migrate hundreds or thousands of miles between their breeding and wintering grounds.
Chimney swifts also sleep in flight during their nightly roosting rituals. Instead of settling down to sleep like other birds, chimney swifts spend the night flying actively in large communal flocks. They can sleep in brief bouts while circling together through the night.
Why do chimney swifts sleep while flying?
There are two key reasons chimney swifts evolved the ability to sleep in flight:
- Spending almost their entire lives airborne – Chimney swifts eat, mate, and even gather nesting materials while in flight. Staying aloft for their entire existence, except for nesting, necessitates adapting to sleep during flight.
- Long migrations – Chimney swifts need to be able to sleep during their migratory journeys that can cover thousands of miles. Sleeping during flights enables them to get proper rest.
Sleeping while flying allows chimney swifts to devote more time to aerial feeding and mating while still getting the sleep they require.
How much do chimney swifts sleep overall?
Chimney swifts sleep around 4-6 hours per day on average. However, this sleep is broken up into very short bursts of unihemispheric sleep lasting only up to 10 seconds at a time. They get their necessary total sleep through the accumulation of hundreds of micro-naps while in flight.
How is chimney swift sleep different from regular sleep?
Chimney Swift Sleep | Regular Sleep |
---|---|
Only half the brain sleeps at once | Both hemispheres sleep |
Sleeps for up to 10 seconds | Sleep cycles last ~90 minutes |
Happens while flying | Occurs while mostly still |
Eyes partially open | Eyes fully closed |
Chimney swift unihemispheric sleep is very different from regular sleep in mammals and other birds in many ways related to their specialized flying lifestyle.
Do other birds sleep while flying?
Chimney swifts are not the only type of bird capable of sleeping in flight. Other birds that can sleep while airborne include:
- Common swifts
- Alpine swifts
- Frigatebirds
- Ducks and geese
- Great frigatebirds
- Shearwaters
However, chimney swifts and common swifts are the only two bird species known to enter regular slow-wave sleep while flying. The other birds can engage in lighter restful states to get some rest during flight.
Conclusion
Chimney swifts are fascinating birds that have evolved the remarkable capacity to sleep while flying. By sleeping with half their brain at a time in short bursts, they obtain the rest needed to support their highly aerial lifestyles. Their ability to sleep on the wing enables chimney swifts to spend virtually their whole lives flying, only landing to nest and roost.