Owls have long captivated our imagination with their large, forward-facing eyes and ability to turn their heads almost all the way around. One of the most common owl myths is that they sleep with their eyes open.
If you’re short on time, here’s a quick answer to your question: Unlike us, owls can sleep with one eye open. This allows them to rest while still watching out for predators. However, they do fully close both eyes when in deeper stages of sleep.
In this comprehensive guide, we’ll explore the intriguing topic of how owls sleep in detail. We’ll cover owl sleeping habits, the reasons behind their ability to snooze with eyes open, the different types of sleep owls experience, whether certain species sleep differently, how to tell when an owl is asleep, and much more.
Owl Sleeping Habits and Behaviors
When Owls Are Most Active
Owls are nocturnal creatures, meaning they are most active at night. They typically start getting active around dusk when the sun begins to set. This is when they will leave their nests or perches to hunt for food under the cover of darkness.
According to the Cornell Lab of Ornithology, most owls spend the darkest hours of the night hunting, with activity peaks between midnight and dawn.
During the day, owls return to their nests and perches to sleep. They utilize cavities in trees, nest boxes, burrows underground, or dense foliage as shelter. Here, the owls can safely slumber away from predators until dusk approaches again.
An exception is the burrowing owl, which is sometimes active during the day when living in treeless areas lacking good roosting spots.
How Long Owls Sleep Each Day
As nocturnal hunters, owls tend to sleep for extended periods during the day. However, owl species can vary in their sleeping patterns. For example, barn owls typically sleep around 15 hours per day. In comparison, great horned owls usually get a whopping 20 hours of sleep in a 24-hour cycle according to the University of Michigan Museum of Zoology.
Owls have adapted the ability to snooze deeply despite potential threats like predators or noisy bird neighbors. Their feathers disguise owl plumage and help mask sounds while resting. If disturbed during slumber, owls may simply open an eye to check for disturbances or threats nearby.
| Owl Species | Sleep Hours Per Day |
| Barn Owl | about 15 hours |
| Great Horned Owl | up to 20 hours |
Where Owls Prefer to Sleep
Owls utilize cavities and covered spots as suitable sleeping sites. This includes tree hollows, nest boxes, burrows underground, dense foliage, or small caves. Sleeping in protected nooks with cover helps conceal owl plumage from potential predators during vulnerable resting periods.
Some examples of prime owl sleeping spot preferences:
- Burrowing owls dig underground burrows
- Barn owls nest in hollow trees, caves, or abandoned buildings
- Great gray owls use large tree cavities as nest sites
- Northern saw-whet owls roost in dense coniferous foliage
Interestingly, owls living in camouflaged sleeping quarters may feel comfortable enough to snore loudly! The echoing hoots of a saw-whet owl or the snores of a great horned owl emanating from a tree hollow are giveaways that an owl is fast asleep inside.
Why Owls Can Sleep with Eyes Open
Owls Are Vulnerable When Asleep
Owls are unique in their ability to sleep with their eyes open. This is an adaptation to help them survive, as they are vulnerable when sleeping. Owls have many predators, so they need to stay alert to danger even when getting some shut-eye.
Keeping their eyes open allows owls to quickly wake up and take flight if a predator approaches their roost.
Unihemispheric Slow-Wave Sleep
The reason owls can snooze with peepers wide open is due to their specialized sleeping habits. Owls, along with some other bird species, have the ability to engage in unihemispheric slow-wave sleep. This means one half of the brain sleeps while the other half remains awake.
The awake half makes sure the owl’s senses like sight, hearing, and smell remain active to monitor for threats.
Researchers have found that the sleeping hemisphere shows slow-wave sleep patterns, similar to deep non-REM sleep in humans. The awake hemisphere displays wake-like electrical activity. This alternating cycle allows the owl to achieve rest while not letting its guard down completely.
Nictitating Membrane Provides Protection
Another adaptation that permits owls to slumber with eyes agape is their nictitating membrane. This translucent inner eyelid acts like built-in goggles. It moves horizontally across the eye to moisten and protect it without obstructing vision.
The membrane shields the owl’s eyes from dust and damage as they sleep.
The nictitating membrane also gives the owl that wise wide-eyed look. Even with the membrane closed, the owl appears awake and alert. This adds to their air of mystery!
The Different Stages of Owl Sleep
Slow-Wave Sleep
Owls go through different stages of sleep just like humans do. The first stage is known as slow-wave sleep. During this stage, an owl’s brain waves become synchronized and slow down, indicating deep, restorative sleep.
An owl’s eyes will usually close partially, but not completely, during slow-wave sleep. Their nictitating membrane, which is a transparent inner eyelid, will move across the eye to keep it moistened and protected.
Slow-wave sleep is critical for owls to feel well-rested. It allows their bodies to repair muscles, bones, and other tissues. This is when most physical recovery occurs after a long night of hunting and flying. Slow-wave sleep also consolidates memories from the day to improve learning.
An owl needs adequate time in this stage each day to function at optimal levels.
Rapid Eye Movement Sleep
The second stage of sleep is called rapid eye movement (REM) sleep. In this stage, an owl’s eyes will often fully close as their eyeballs begin to move quickly under their eyelids. Their brain waves also become more active, similar to when they are awake.
It is during REM sleep that owls dream and consolidate memories related to learned skills like flying and hunting.
REM sleep is crucial for owls’ mental health and cognitive function. Lack of REM sleep can impair their ability to focus and process information. Owls need a healthy amount of REM sleep each day to perform hunting-related tasks efficiently.
During the nesting season, female owls especially require adequate REM sleep to successfully incubate eggs, protect hatchlings, and teach fledglings to hunt and fly.
Differences in Sleep Between Owl Species
Forest-Dwelling vs. Grassland Owls
Studies show that forest-dwelling owls like barred owls sleep longer during the day compared to grassland owls like short-eared owls or burrowing owls (Audubon). The dense tree cover provides more protection and shelter for forest owls, allowing them to sleep deeply and for longer stretches of time.
Grassland owls tend to take shorter daytime naps and remain more alert to threats in their open habitats.
In one study, researchers found that forest-dwelling barred owls slept on average 10 hours during the day, while short-eared owls in grasslands slept only around 3 hours on average (Audubon). The ability to remain vigilant likely aids the survival of grassland owl species that lack protective cover.
Diurnal vs. Nocturnal Owls
Most owls are nocturnal, meaning they are active at night and sleep during the day. However, some tropical and desert owl species like the Northern hawk owl or the burrowing owl are diurnal – active during the day and sleeping at night.
Diurnal owls only sleep around 7-8 hours per night since they need to be awake to hunt and eat during daylight. In contrast, nocturnal owls like barn owls may sleep 10-12 hours or more during the day to conserve energy for nighttime activity (NestWatch).
Their sleep patterns align with their natural hunting behaviors and habitat conditions.
Owl Nestlings Sleep More
While adult owls have varied sleep patterns, research shows that baby owl nestlings tend to sleep up to 20 hours a day for proper growth and development (Audubon). Their energy demands are high and sleep allows their body and brains to develop rapidly during the first few months of life.
One study of barn owl chicks found they slept over 90% of the time during their first month after hatching. Their total sleep decreased to around 15 hours per day by the time they fledged and left the nest (Journal of Mammalogy).
More sleep in early life stages enables survival later on as juvenile owls start hunting.
How to Tell if an Owl is Asleep
Eyes Half-Closed
One of the most notable signs that an owl is sleeping is that its eyes will be partially closed. Owls have unique eyes compared to other birds – their eyes are tube-shaped and cannot move side to side. This means owls must turn their entire head to change their viewpoint.
When asleep, owls will often keep their eyes open halfway with the nictitating membrane covering the eye. The nictitating membrane helps protect and moisten the eye. So if you see an owl with its eyes half-shut and barely open, it’s likely the owl is asleep.
Fluffed-Up Feathers
Another indicator an owl is sleeping is its feathers will appear fluffed up. Owls have thick, soft plumage that helps insulate them. When an owl is sleeping, its feathers will look messier and more disheveled as the owl relaxes its muscles.
The feathers essentially act as a blanket to keep the sleeping owl warm and cozy. An owl with ruffled, puffy feathers is a strong sign it is catching some Zzz’s.
Stillness
Owls are extremely alert and attentive birds when awake. They are constantly observing their surroundings and can rotate their heads 270 degrees. When an owl is sleeping, it will remain completely still and its head will face forward. The lack of movement is a dead giveaway that the owl is asleep.
In contrast, an awake owl will swivel its head and twitch frequently. If you spot an owl sitting perfectly motionless for an extended period, chances are high it is in sleep mode.
Conclusion
As mysterious nighttime creatures, owls continue to entrance us with their otherworldly ways. Now that you know the tricks behind how owls sleep, you can better understand their daily rhythms and behaviors.
The next time you spot an owl snoozing with an eye partially open, you’ll know they’re simply resting while standing guard against danger. Their ingenious ability to unihemispherically sleep likely evolved to help these feathered raptors survive in the wild.
