Birds flying around at night is a common sight for many. But why do birds fly at night? Are all birds capable of nocturnal flight or are there limitations? This article dives into the fascinating world of avian nocturnal behavior to uncover the mysteries surrounding birds that fly after dark.
With over 10,000 species of birds in the world, it’s a complex topic with many variables at play. We’ll explore the science and research behind night vision, sleep patterns, migration, feeding, and more to understand the abilities and behaviors that allow some birds to take to the skies when the sun goes down. Whether you’ve spotted a night heron hunting after dusk or heard an owl hooting into the night, read on to satisfy your curiosity about these creatures of the night sky.
Key Takeaways:
- Many birds have special adaptations allowing excellent night vision.
- Migratory ability, feeding patterns, and sleep behaviors influence night flight.
- Owls, nighthawks, and other nocturnal species routinely hunt after dark.
- Diurnal birds rest at night, though they may sometimes fly short distances.
- Limitations in vision and flight style prevent some birds from migrating at night.
Nocturnal and Crepuscular Bird Species
While some birds like crows and sparrows are considered diurnal, meaning they are active during the daytime, others are nocturnal or crepuscular, meaning they are most active at night or during twilight hours at dawn and dusk.
Nocturnal bird species like owls, nighthawks, and whip-poor-wills do most of their hunting and moving around in the dark. Other examples of nocturnal birds include:
- Nightjars
- Goatsuckers
- Many species of shorebirds
Crepuscular birds are most active during the twilight hours of dawn and dusk. Examples include:
- American robins
- Rails
- Common nighthawks
- Owls
- Swallows
- Thrushes
- Flycatchers
So, while some birds settle down to roost and sleep at night, nocturnal and crepuscular species come alive after dark.
A Surprising Number of Birds Take Flight After Dark
While many birds sleep at night, around 30% of birds fly at night in North America. Owls, nighthawks, nightjars, rails, herons, cuckoos, and thrushes are all birds you may spot flying around after the sun goes down. Even small songbirds like warblers and sparrows migrate under the cover of darkness.
- According to estimates, well over 70% of birds are diurnal (active during the day), while the remaining 30% are nocturnal (active at night).
- 80% of migratory bird species in North America migrate at night.
- More than 50% of migratory birds will pass through certain areas on peak migration nights.
- Around 30% of North American bird species overall are nocturnal and fly at night.
So in summary, while the majority of birds are active during the daytime, a significant minority of approximately 30% of birds do fly at night in North America. This includes migratory species flying during migration seasons as well as resident nocturnal bird species that are active at night. The exact percentage likely varies by location and season.
Why Birds Migrate at Night
One of the main reasons birds take to the skies after dusk is migration. Many species migrate long distances to reach breeding grounds or overwintering sites, and nighttime offers cooler temperatures and calmer air that makes flying easier and more efficient.
Additional benefits of night migration include:
- Lower risk of overheating – Flying during hot daytime temperatures could cause birds to overheat and dehydrate. Cooler night air helps maintain ideal body temperature.
- Less turbulence – Daytime thermals and updrafts give way to calmer winds at night, allowing smoother passage.
- Avoidance of predators – Migrating at night reduces birds’ visibility to predatory raptors like hawks and eagles.
- Ability to use the stars and moon for navigation – Birds may use the stars as a celestial map to orient themselves during migration. Moonlight also aids navigation.
- Less energy expenditure – Flying uses less energy at cooler nighttime temperatures. Birds can conserve energy for the journey.
What Types of Birds Fly at Night?
While a majority of birds are diurnal (active during the daytime), there are quite a few nocturnal species that become active at night. Here are some of the most common:
- Owls – These predators have excellent night vision and hearing to hunt small mammals in the dark.
- Nighthawks – They swoop through the skies at night to catch insects.
- Nightjars – Related to nighthawks, they are also adept insect hunters after sunset.
- Herons – Some species hunt fish at night since it’s easier to spot prey.
- Rails – These marsh-dwelling birds often call and feed at night.
- Seabirds – Species like shearwaters may hunt at night then return to colonies.
- Cuckoos – Some migrate at night and have moon-related navigation abilities.
- Thrushes – Small songbirds like robins may migrate or sing at night.
How Do Birds See in the Dark?
Birds that fly at night often have special physical adaptations that allow them to see well in low light conditions:
- Large eyes to let in more light. Owls have huge eyes for their body size.
- Increased density of rod photoreceptors which detect dim light.
- Reflective eye tissue to make the most of ambient light.
- Ability to dilate pupils widely to allow more light into eyes.
- Narrow binocular vision to focus on prey against dark backgrounds.
Research shows that the night vision abilities of nocturnal bird species can be 100 times better than humans!
How Birds Fly at Night
Birds have anatomical and physiological adaptations that allow them to fly skillfully in dark nighttime skies, including:
- Excellent low-light vision – While humans are essentially blind at night, birds have evolved eyes with greater light sensitivity and more rod photoreceptor cells to improve night vision.
- Rapid adaptation to changing light – Birds’ pupils can quickly adjust to dilate and let in more light in dark conditions. Intraocular fluid also changes to improve night focus.
- Keen hearing – Birds use finely tuned hearing to detect prey, predators, landmarks, and other auditory cues at night. Owls have asymmetrical ear placement to precisely locate sounds.
- Ultraviolet vision – Some birds may be able to see ultraviolet wavelengths that stand out better against the night sky.
- Nocturnal radar – Owls have specialized facial discs with small stiff feathers that funnel sound to their ears, acting like radar to locate prey in the dark.
- Excellent maneuverability – Birds have superb aerial agility and flight control, allowing them to fly adeptly through dark skies and dodge obstacles. Their streamlined bodies and tapered wings provide aerodynamic flight.
Challenges Birds Face When Flying at Night
Despite their adaptations for nocturnal flight, birds do face challenges when aloft on dark nights, including:
- Reduced visibility in low light – Even with excellent night vision, details and obstacles can be harder to discern.
- Disorientation in overcast conditions – Heavy cloud cover blocks out the moon and stars used for celestial navigation.
- Risk of collision – Communication among flock members can become difficult in the dark, increasing the chance of midair collisions.
- Inclement weather – Precipitation, fog, and storms can be dangerous for night migrators. Lightning is especially hazardous.
- Predation – Some predators like owls are adept night hunters, preying on migratory songbirds.
- Artificial light pollution – Bright city lights and illuminated skyscrapers can disorient and attract/deter birds.
- Fatigue – Flying at night over long distances is physically draining. Birds need ample rest periods.
- Lack of food/water – Finding nourishment at night is more difficult, so birds must stock up in advance.
Despite the difficulties, billions of birds manage the feat of nightly migration each year, relying on their specialized senses, capabilities, and navigation strategies to traverse great distances under cover of darkness. Their ability to fly skillfully at night is a marvel of avian biology.
Why Don’t Some Birds Fly at Night?
While many birds do migrate and forage at night, some species are not active after dark for various reasons:
- Not nocturnal – Birds like crows, sparrows, finches, and blackbirds are diurnal, meaning they are awake and active during the daytime. They return to their roosts to sleep at night.
- Not migratory – Non-migratory resident species have no need to travel great distances, so they stay put and sleep at night.
- Heavy bodies – Larger birds like ostriches, turkeys, chickens, and peacocks are too heavy for efficient night flight and the risks that come with it.
- Predator avoidance – Some small bird species that are preyed upon heavily avoid being active at night when predators hunt.
- Limited night vision – Birds like penguins adapted to bright daylight have limited night vision, making night flight difficult.
- Young birds – Juvenile birds on their first migration may not have the experience or stamina for prolonged night travel.
- Exhaustion – Even migratory birds must rest at night after flying all day. Night flights are intermittent with rest.
- Unsafe weather – Stormy, windy, or foggy weather can make night flight dangerous even for nocturnal species.
- Bright moonlight – Some birds avoid migration on brightly moonlit nights to evade predation.
Examples of birds that don’t fly at night
Not all birds that migrate do so exclusively at night. Some species fly during the day as well, including:
- Hawks
- Eagles
- Falcons
- Cranes
- Storks
- Pelicans
- Swans
- Geese
- Ducks
These diurnal migrants have strong soaring and gliding flight, allowing them to ride daytime thermals and updrafts to help conserve energy over long journeys. They avoid migration during evenings when thermals die down.
Some migratory birds like shorebirds also migrate short distances back and forth from foraging sites at dawn and dusk, taking advantage of crepuscular hours.
How Far Do Birds Migrate at Night?
Migration distances covered during nighttime flights vary widely depending on the species:
- Short-distance migrants – Some species such as blackbirds, crows, and sparrows may migrate just a few hundred miles between breeding and wintering grounds. Their nightly flights cover anywhere from 30 to 100 miles.
- Medium-distance migrants – Thrushes, warblers, and shorebirds may migrate 500 to 1,500 miles between ranges. They can fly 200 or more miles per night.
- Long-distance migrants – Extreme marathon migrants like the arctic tern make huge journeys of over 20,000 miles annually between Arctic and Antarctic regions. Their nonstop transoceanic flights may cover 500 miles or more per night.
The distances birds can fly in one night depend on factors like fat stores, weather conditions, and the need to stopover and rest/refuel. But equipped with energy reserves and favorable winds, some birds can fly astonishing distances of hundreds of miles in a single overnight flight.
Do Birds Sleep While Migrating at Night?
It was long thought that migrating birds flew nonstop all night, but research shows many species alternate between flying and napping:
- Studies of recorded bird calls show migratory birds sleep and fly intermittently at night.
- Electroencephalogram recordings by Nature communications indicate cyclical periods of slow-wave sleep while aloft at night.
- Creative University researchers observed birds napping in flight by closing one eye at a time and keeping half their brain asleep.
- Some birds fly with their heads turned and tucked under a folded wing to rest one brain hemisphere.
- In-flight naps allow birds to restore energy and stay alert on long migrations.
So while they don’t sleep continuously, birds have evolved the incredible ability to grab power naps while flying through the night, resting half their brain at a time to maintain aerodynamic control.
How High Do Birds Fly When Migrating at Night?
Birds migrate at a range of altitudes based on factors like weather, winds, and geography:
- Songbirds often migrate at lower altitudes below 3,000 feet. Flying low allows them to spot food sources and resting places.
- Larger birds like geese, pelicans, and hawks may migrate between 3,000 to 10,000 feet altitude. They ride thermals and updrafts at these heights.
- Birds migrating over mountains fly at higher altitudes above 10,000 feet to clear the peaks.
- Transoceanic migrants may fly at very high altitudes up to 20,000 feet to take advantage of strong tailwinds.
- When flying into headwinds, birds fly lower to the ground to escape unfavorable winds.
- Inclement weather like rain or storms causes birds to fly lower to the ground for safety.
- On calm nights, migrants may fly at lower altitudes under 1,000 feet.
So optimal migration altitude depends on many factors, but most birds fly under 10,000 feet, with songbirds staying lowest and shorebirds and waterfowl flying highest. But when necessary, some remarkable migrants can fly miles above the earth.
How Do Birds Know When to Begin Migrating?
Birds rely on a mix of internal rhythms and external cues to know when to start their migratory journeys:
- Changes in day length – As days shorten after the solstice, hormonal changes prompt hyperphagia (excessive eating) to store fat.
- Cooling temperatures – A drop in temperatures triggers migration urges in many species.
- Genetics – Migration timing is innate and programmed genetically over successive generations.
- Availability of food – Scarcity of food sources motivates migration to regions of abundance.
- Changes in weather – The onset of rainy or stormy weather may spur birds to migrate.
- Molting – Completing the energy-intensive feather molt signals readiness for migration.
- Orientation of stars/moon – Shifting night sky patterns help signal the timing of migration.
- Maturation – Young birds may not migrate until they have fully matured and are ready for the journey.
- Social cues – Birds may take their migration timing cues from older individuals in the flock.
These internal rhythms and environmental signals help birds instinctively know when the time is right to take off and migrate south or north for the season. Their ability to keep track of the seasons and determine optimal departure times is a marvel of nature.
How Do Birds Know Where to Migrate?
Birds rely on a combination of innate genetic programming and learned environmental cues to determine where to migrate each season:
- Genetic imprinting – Migration routes and destinations are imprinted genetically over generations. Young birds inherit this innate knowledge.
- Learned traditions – Juveniles learn migration particulars like stopover sites and routes by traveling with experienced adults.
- Environmental cues – Birds use changing seasonal cues around them to determine when to move and where.
- Celestial navigation – The stars provide a map for determining cardinal directions during migration.
- Geomagnetic sensitivity – Birds sense magnetic fields to maintain their bearing as they migrate.
- Landscape recognition – Visual landmarks like mountains, rivers, coastlines, and manmade structures provide guidance.
- Odor cues – Birds may use winds carrying odor molecules to identify important stopover and breeding sites.
- Memory – After their first migration, birds remember sites and routes for subsequent seasonal journeys.
- Weather patterns – Birds may follow prevailing winds, temperatures, and storm systems that guide them along established flyways.
So, migration destinations are engrained genetically and refined through generational knowledge, giving birds an internal GPS and map to follow between seasonal ranges year after year.
Wrapping Up
So, while many remarkable species migrate immense distances at night, others stick close to home and only fly during the relative safety of daylight hours. The habits of each species have evolved to match their lifestyles and environments. So, next time you see a bird flying at night, take a moment to appreciate the remarkable abilities that allow some birds to rule the night skies. Their nocturnal lives reveal just how adaptable and impressive our avian neighbors can be!
FAQs: Do birds fly at night
What are nocturnal birds?
Nocturnal birds are the species of birds that are active during the night and sleep during the day. They have the ability to see at night and hunt for food.
Why do birds fly around at night?
Birds fly around at night mainly to find food. The darkness provides them with an advantage as they can easily spot their prey and catch it.
Can birds see at night?
Yes, birds can see at night. They have the ability to see in low light conditions, allowing them to navigate and find food during the night.
What are the reasons why birds migrate and fly at night?
Birds migrate and fly at night for several reasons. Flying at night helps them avoid predators and take advantage of cooler temperatures. Additionally, flying during the night is safer as there is less air traffic.
Are there any small birds that fly around at night?
Yes, there are small birds that are active at night. Examples include night herons and some species of wading birds.
Do birds sing at night?
Some birds do sing at night. This behavior is more common during the breeding season when males use their songs to attract mates and establish territories.
Can birds fly at night even without any light?
Birds can fly at night even without any light as they have good vision in low light conditions. However, they do rely on moonlight or artificial light sources to some extent.