The word for a bird that is active at night is “nocturnal.” Nocturnal birds are species that are awake and hunt for food during the nighttime hours rather than during the day. Some examples of nocturnal birds include owls, nighthawks, and nightjars. These birds have special adaptations that allow them to see, hear, and hunt in low light conditions. Their nocturnal behavior helps them avoid competition for food and habitat with daytime birds. In this article, we’ll take a deeper look at what defines a nocturnal bird, which bird species are considered nocturnal, and the unique adaptations that allow these nighttime creatures to thrive.
What Makes a Bird Nocturnal?
For a bird to be considered fully nocturnal, it must meet two key criteria related to its activity patterns:
- It is awake and active during the nighttime hours when light levels are low.
- It sleeps and rests during the daylight hours.
Many nocturnal birds cannot see well during the bright light of day, and sunlight can actually damage their sensitive eyes that are adapted for low light. Staying asleep and inactive during daylight hours helps protect nocturnal species from predators that hunt using vision. Then, under the cover of darkness, these species emerge to hunt using their specialized night vision and hearing.
Some birds may show mixed nocturnal/diurnal activity, meaning they exhibit periods of activity both at night and during the day. However, true nocturnal birds are exclusively active at night. This chronobiology – the internal clock regulating cycles of rest and activity – is an important adaptation to avoid competition with daytime species and take advantage of the rich nighttime ecology.
Examples of Nocturnal Bird Species
Many types of birds around the world exhibit fully nocturnal activity patterns. Some of the most common and well-known nocturnal birds include:
Owls
Owls are certainly the most iconic nocturnal birds. Species like the barn owl, great horned owl, and barred owl only hunt at night. Owls have several key adaptations for their after-dark activity, including:
- Exceptional night vision
- Special feather adaptations that allow silent flight
- Asymmetrical ear placement to precisely locate prey
- Talons and hooked bills for catching prey
There are over 200 owl species worldwide, and they are found on every continent except Antarctica. Their nocturnal prowess makes them expert nighttime hunters.
Nighthawks
Nighthawks are medium-sized nocturnal birds found throughout North and South America. These cryptic birds nest on the ground and have mottled brown, black, and white camouflage plumage. They are sometimes observed flying over cities at night as they hunt for insects. Unique adaptations like a wide mouth and small beak allow them to scoop up bugs while flying at high speeds.
Nightjars
Nightjars are a family of nocturnal birds found worldwide. There are over 80 species, including whip-poor-wills, common nighthawks, and Egyptian nightjars. In addition to excellent night vision, nightjars have other adaptations like large eyes, muted plumage, and expansive wings designed for silent flight. Their camouflage and stealthy hunting allow them to avoid detection, even in daylight when roosting.
Parrots
While most parrot species are active during the daytime, there are several nocturnal parrot species worldwide. The kakapo of New Zealand is a large, flightless nocturnal parrot. The owl parrot of Central and South America is another example. These parrots developed nocturnality to help avoid predation and competition from daytime birds.
Potoos
Potoos are a family of nocturnal birds found in Central and South America. They have enormous mouths perfect for capturing night-flying insects. Potoos perch upright on tree branches where their mottled brown plumage disguises them as part of the tree during daylight hours.
Frogmouths
Named for their large, frog-like mouths, frogmouths are tropical nocturnal birds found in Asia, Australia, and Africa. They have wide, heavy bills for capturing insects, rodents, and other small prey. During the day, frogmouths perch motionless, perfectly camouflaging themselves as broken tree branches.
Oilbird
The oilbird of South America is a unique nocturnal species that navigates and locates its fruit diet by echolocation, much like bats do. Oilbirds get both their common name and scientific name, Steatornis, from the oil produced by their chicks that was historically used for cooking and lamp oil fuel.
Penguins
While not often thought of as nocturnal, penguins actually demonstrate crepuscular behavior, meaning they are active primarily around dawn and dusk. Staying out of the bright midday sun helps penguins avoid overheating and predation from aerial hunters that rely on sight. Some penguins have special adaptations to help them see well in low light.
Unique Adaptations for Nocturnality
To thrive under the cover of darkness, nocturnal birds have evolved specialized physical and behavioral adaptations to help them survive in dimly lit surroundings. Some of the most important adaptations that allow birds to live at night include:
Enhanced Night Vision
Excellent night vision is an absolute necessity for nocturnal avian hunters. Most nocturnal birds, like owls, have very large eyes relative to their skulls to maximize their light gathering power. Their eyes also have more rods than cones – specialized photoreceptor cells that excel at night vision rather than colored vision. Some species also have eyes with tubular-shaped pupils that can open extra wide to let in more light.
Light-Colored Feather Markings
While most of their plumage is camouflage-colored, some nocturnal birds have highlighted patches of light-colored feathers, like the facial disks of owls. These markings help the birds locate one another in dense darkness. Light patches also reflect sound waves towards the birds’ ears to slightly amplify hearing.
Silent Flight Adaptations
Stealth hunting is important for nighttime predators trying to surprise prey. Owls and nightjars possess specialized fringed flight feathers that dampen and muffle the sound of their wings. This allows silent flight that does not disturb potential prey or reveal the bird’s location.
Enhanced Hearing
In lieu of visual cues, nocturnal birds rely heavily on auditory information from their environment. They have excellent high-frequency hearing, aided by facial disks and feathers that funnel sound into their ears. Asymmetrical ear placement also enhances the ability to pinpoint tiny sounds in 3D space, critical for hunting.
Camouflage Plumage
Mottled blacks, browns, grays, and tawny buff colors allow nocturnal birds to blend into their environments at night. This camouflage also disguises roosting birds from predators during the daytime when vision is a bigger threat. Some species have dark backs and pale undersides to aid camouflage from different vantage points.
Hooked Bills and Talons
Sharp hooks, curved talons, and exquisitely coordinated reflexes give nocturnal predators the tools they need to seize and kill prey in an instant. These hunting adaptations are essential assets for birds that cannot rely on vision alone when pursuing fast-moving prey at night.
Wide Mouths and Large Gapes
The oversized mouths of nightjars, frogmouths, and potoos allow them to easily scoop up moths, beetles, crickets, and other night-flying insects. Their flexible upper jaw also expands their gape wide to capture and swallow sizable prey.
Nocturnality in Bird Species Around the World
While the tropics harbor the greatest diversity of nocturnal birds, night-loving avian species can be found on every continent. Here is an overview of some nocturnal birds in key regions worldwide:
Africa
Africa is home to dozens of nocturnal bird species like fiery-necked nightjars, Egyptian nightjars, and various owls including Verreaux’s eagle-owls, pearl-spotted owlets, and marsh owls. Within this diverse assemblage are specialists like the cave-dwelling Cape eagle-owl and the ostrich-like nocturnal kori bustard.
Asia
The forests and jungles of Asia hide an array of nocturnal birds. Malaysian nightjars, large-tailed nightjars, Oriental bay owls, brown wood owls, and collared owlets all inhabit this region. The Philippines have a high diversity of night birds as well, including the Philippine eagle-owl and frogmouths like the tawny and Mindoro frogmouths.
Australia
Australia’s remote outback suits the cryptic behaviors of nocturnal birds well. Birds like the tawny frogmouth, Australian owlet-nightjar, spotted nightjar, and barking owl inhabit this island continent. The kakapo, a flightless nocturnal parrot, evolved in isolation in New Zealand before the arrival of mammals.
Europe
Despite its highly populated landscape, Europe still supports some nocturnal avian predators like the Eurasian eagle owl, Tengmalm’s owl, and nightjars such as the European nightjar. These birds carve out secretive lives in remnants of primeval forest and moorlands that still exist across Europe.
North America
Owls like the great horned, barn, and barred owl rule the night across much of North America alongside nighthawks, poorwills, chuck-will’s-widows, and common nightjars. Secretive species like the spotted owl and buff-collared nightjar hide within specific habitats in the American Southwest.
South America
South America contains the highest diversity of nocturnal birds on any continent. Owls like the striped owl, black-banded owl, and tropical screech owl fill the nights alongside oilbirds, potoos, and over a dozen unique nightjar species in ecosystems like scrub forest, savannah, and rainforest.
Threats Facing Nocturnal Birds
Though skilled at evading predators, nocturnal birds face other threats in both their natural environments and interactions with humans. Some key threats confronting night birds include:
Habitat Loss
Deforestation and development that destroys forests and wetlands used by nocturnal birds for nesting and roosting sites has put pressure on many populations. Fragmentation of their habitat can isolate groups and lead to inbreeding.
Environmental Toxins
Pesticides, heavy metal poisoning, and other toxins have impacts on nocturnal birds, both direct and indirect through the food chain. For example, chemicals can thin egg shells or accumulate to toxic levels in bird tissues over time.
Climate Change
Changing weather and temperature extremes related to climate change can negatively impact nocturnal bird populations. Unseasonal weather events can limit prey availability while nesting birds and chicks are vulnerable to increased storms, flooding, and drought.
Collisions
Nocturnal birds that live near human infrastructure like roads, cell towers, and wind turbines are prone to colliding with these structures, especially in poor visibility conditions. Ill-placed lighting can also disorient and ground night flyers.
Invasive Species
Introduced predators like rats, cats, and snakes can prey on ground and cavity nesting nocturnal birds, targeting eggs and chicks. Exotic species also compete with native nocturnal birds for food and other resources.
Conservation Efforts
Protecting remaining habitat strongholds and mitigating human hazards are top priorities for ensuring the future of vulnerable nocturnal bird populations. Some key conservation strategies include:
- Designating protected reserves and parks to safeguard intact habitat.
- Managing forests and other ecosystems to support natural prey abundance.
- Enacting policies that require bird-friendly building designs.
- Researching sustainable solutions to risks like chemical pollution.
- Controlling populations of invasive predators.
- Educating the public to foster appreciation for nocturnal birds.
Bolstering support for nocturnal bird conservation ensures healthy, balanced ecosystems both during the day and after dusk. The unique attributes of these nighttime avians are worth protecting.
Conclusion
Birds that are awake and active primarily during the night earn the descriptive label of “nocturnal.” These species have evolved a suite of specialized visual, auditory, and behavioral adaptations that allow them to live in dim environments and avoid competition from other birds active during daylight hours. Iconic nocturnal birds include various owls, nighthawks, nightjars, and others. While scattered worldwide, hotspots of diversity occur in the tropics of Central and South America. Ensuring healthy nocturnal bird populations requires protecting habitat and mitigating artificial threats ranging from climate change to unnatural lighting. Preserving pockets of darkness benefits the unique avian denizens of the night.