Eagles are powerful birds of prey that soar majestically through the skies during the day. But when night falls, do these raptors continue hunting under the cover of darkness? If you’re short on time, here’s a quick answer: Eagles have excellent daytime vision to spot prey from afar, but their eyesight deteriorates sharply at night, making successful night hunting nearly impossible.
In this detailed guide, we’ll explore whether various eagle species hunt after dark. We’ll look at how their vision, sleep patterns, and activity levels change between day and night. And we’ll highlight fascinating nocturnal behaviors exhibited by some eagles.
Eagle Vision Capabilities By Day and Night
Eagles Have Telescopic Day Vision to Spot Prey
When it comes to eyesight during the day, eagles have vision that is nothing short of superhero-like. With eyes that are almost as big as a human’s, eagles have some of the largest and most powerful eyes in the avian world. Their eyes are designed to spot prey from distances of over a mile away.
Here are some key facts about an eagle’s incredible daytime vision:
- Eagles have two foveae or centers of focus in each eye that allow them to see straight ahead and to the side simultaneously.
- Their eyes are situated on the sides of their head giving them a field of view of up to 270 degrees – much wider than humans.
- Eagles have both monocular and binocular vision. They can use each eye independently or together for depth perception.
- With two times more photoreceptors than humans, eagles have superior visual acuity and can spot prey movement from distances over 10 times farther away than people.
- Special pigments in their eyes called oil droplets filter light, sharpen their vision, and enhance color separation.
- Eagles can see colors on the spectrum that humans can’t like ultraviolet light.
- An eagle eye has a larger lens and higher density of photoreceptors leading to telescopic vision 4-8 times stronger than a person.
Researchers have discovered that eagles have such advanced day vision that they can spot a rabbit moving almost 2 miles away. With these special adaptations, it’s no wonder eagles are such effective hunters during daylight hours.
Eagle Eyes Don’t Function Well in Low Light Conditions
Given their exceptional day vision, it may be surprising to learn that eagles actually have rather poor eyesight at night or in low light conditions. Here’s a look at why eagle eyes don’t work well after dark:
- Eagles have a high density of cones but very few rods which are the photoreceptors needed for night vision.
- Their eyes lack a tapetum lucidum – a special reflective coating that amplifies dim light in many nocturnal animals like owls.
- Oil droplets that sharpen day vision block light from reaching the retina at night.
- Eagles have smaller pupils relative to their eyes which limits light intake in dark conditions.
- Their eyes are optimized for distant rather than close-up vision making it hard to spot prey in low light.
According to the Cornell Lab of Ornithology, eagles see only about as well as humans do after dusk. Their eyes are adapted to see detail and color when light is abundant, not to amplify limited light sources.
So while eagles are formidable hunters during the day, they are far less effective after dark.
Sleep Cycles of Eagles
Most Eagles Sleep at Night
Like most diurnal birds, a majority of eagle species tend to be inactive at night when they cannot effectively hunt, and instead sleep to conserve energy (reference). Bald eagles, golden eagles, African fish eagles, harpy eagles, and most other eagles predominantly rest and sleep at night.
Eagles build sturdy nests high up in trees or on cliffs and outcroppings to sleep safely at night. The elevated locations help protect adult eagles as well as vulnerable chicks and fledglings from potential nocturnal predators on the ground.
Their claws also lock tightly around branches while sleeping to prevent accidental falls.
Since eagles rely heavily on keen daytime vision to spot and capture prey, their eyes are not adapted for efficient night hunting. Low visibility at night combined with reduced activity of typical eagle prey animals are likely reasons why most eagles evolved to sleep after dusk and resume hunting at dawn.
Some Eagles May Exhibit Nocturnal Activity
A small number of eagle species have been observed exhibiting some levels of nighttime activity, although not necessarily hunting.
For example, Steller’s sea eagles and white-tailed eagles are occasionally active at night, sometimes even bringing nesting material to their eyries after dark (reference). But this is still quite rare compared to their primarily diurnal habits.
One theory is that the extreme northern latitudes where these eagles reside experience prolonged summer daylight hours. This may allow for extra waking hours while still maintaining regular sleep cycles aligned with nighttime in the darkest months.
More research is needed to fully understand any nocturnal tendencies in these northern eagle species.
In contrast, the large and powerful crowned eagle of sub-Saharan Africa has been confirmed to occasionally hunt at night, especially juveniles (reference). With formidable talons and wing cords strengthened to lift heavy prey, crowned eagles may be physically equipped to overpower animals like hyraxes in any light conditions.
Hunting and Feeding Behaviors of Eagles
Eagles Are Diurnal Hunters
Eagles are diurnal raptors, meaning they are active hunters during the day. Their vision and hunting strategies are adapted for daytime conditions. An eagle’s eyes have evolved to detect subtle movements from great distances during daylight hours.
Their incredible eyesight enables them to spot potential prey animals moving through brush or grass.
Since eagles are visual hunters, they rely heavily on sunlight to illuminate potential prey. Their pupils dilate widely to let in light and their retinas are densely packed with photoreceptors for detecting movements.
While eagles can see some on moonlit nights, their visual acuity dramatically decreases after dusk.
In addition to exceptional vision, eagles have evolved physical attributes for daytime hunting. Their broad wings and short, powerful wingbeats allow them to swiftly stoop down and grab unsuspecting prey.
Their strong talons and hooked beaks are perfectly designed for swiftly killing animals during daytime conditions.
Exceptions Where Eagles Show Nocturnal Behavior
While eagles are diurnal by nature, some exceptions exist where eagles exhibit unusual nocturnal behavior. For instance, young eagles under one year old have been observed making awkward nighttime attempts at hunting.
Likely, these juvenile eagles have an underdeveloped hunting skills and struggle catching prey during the day.
Additionally, migrating eagles have been documented making overnight migratory flights. It’s hypothesized that eagles migrate at night when thermal updrafts are unavailable to help them soar during the daytime. However, eagles do not hunt while migrating at night.
Finally, eagles have been recorded taking opportunistic bites at bats as they emerge at night. However, this behavior is likely playful antics, not determined hunting efforts.
Other Nocturnal Scavenging Opportunities
While active night hunting goes against an eagle’s innate diurnal nature, they will readily scavenge prey at night. For example, eagles may take advantage of night lighting near cities to scavenge roadkill along highways.
Additionally, eagles will scavenge remains from other predator’s kills such as those made by owls or coyotes.
Eagles are well known for stealing fish from ospreys and otters. If an osprey or otter makes a catch at night, eagles have been observed scavenging these fresh kills under the cover of darkness. However, the eagles did not actively hunt the fish themselves.
In rare cases, eagles have been documented scavenging human trash in urban areas at night. However, these cases likely represent desperate or struggling eagles taking advantage of easy human food sources.
Conclusion
To summarize, the majority of eagles do not hunt at night when their vision is compromised by darkness. These raptors are active hunters during the day, relying on keen eyesight to spot small prey animals from high vantage points.
However, some eagle species may show limited nocturnal behaviors like soaring, calling out, nest maintenance, or scavenging already dead animals under the right conditions. But successful night hunting requiring precise sight to chase and catch live prey in flight is essentially impossible for these daytime specialists.
