There are a few reasons why birds might be active and flying around at night instead of during the day:
Nocturnal Birds
Some species of birds are nocturnal, meaning they are naturally active at night. Nocturnal birds have adaptations that allow them to see well in low light conditions, such as large eyes, light-sensitive receptors, and enhanced night vision. Some examples of nocturnal birds include owls, nighthawks, whip-poor-wills, and nightjars. These birds do most of their hunting, feeding, and migrating under the cover of darkness.
Owls
Owls are one of the most well-known nocturnal birds. They have excellent night vision and sensitive hearing that allows them to locate prey in darkness. Owls come out at dusk to hunt for rodents, insects, and other small animals. Their wings have evolved to be large and rounded, allowing them to fly silently in pursuit of prey. Many owl species roost during the day and only become active after sunset.
Nighthawks
Nighthawks are medium-sized nocturnal birds found throughout the Americas. As their name suggests, nighthawks are most active from dusk to dawn. They feed on flying insects like moths, beetles, and ants. Nighthawks have long, pointed wings ideal for fast, acrobatic flight maneuvers to capture insects mid-air. Their cryptic brown, grey, and black plumage helps camouflage them during the day when they roost on branches.
Whip-poor-wills
Whip-poor-wills are nocturnal birds that get their name from the loud vocalization they make at night. They inhabit forests and open woodlands and come out in the evening to swoop around catching large insects. Whip-poor-wills nest on the ground and rely on their camouflage to avoid predation during the day when they are vulnerable. Their wide mouth is adapted for catching insects in mid-flight.
Nightjars
Nightjars are a family of nocturnal birds including nighthawks, whip-poor-wills, and other allied species. They have long wings, short legs, and very short bills adapted for opening wide to catch insects. Nightjars have cryptic brown, grey, or black plumage that provides camouflage when they roost during the day. They come out at night to hunt insects, even drinking and bathing on the wing.
Migration
Some birds that are normally active during the day migrate at night. Nocturnal migration helps birds avoid overheating during the day, avoid predators, and take advantage of calmer winds after sunset. Many songbirds, shorebirds, and raptors migrate under cover of darkness. Using cues from the moon, stars, and magnetic fields, they navigate to their destination and rest and refuel during the day.
Songbirds
Many species of songbirds migrate at night, including warblers, thrushes, cuckoos, orioles, tanagers, and sparrows. Some songbirds like blackbirds form enormous flocks that travel together on migration. Flying at night allows them to cover more ground safely without overheating and exerting unnecessary energy during the hot daytime hours.
Shorebirds
Shorebirds like plovers, sandpipers, and whimbrels undertake nocturnal migrations in massive numbers. These birds stop to rest and feed in wetlands during the day and take off around sunset to navigate to their next destination. Flying at night reduces their vulnerability to predators like raptors that hunt during daylight.
Raptors
Many birds of prey including owls, hawks, eagles, falcons and vultures migrate at night. Large raptors like eagles and hawks conserve energy by soaring on thermal updrafts during the day and switching to powered flight at night when breezes are calmer. The cool night air creates better lift conditions that reduce the effort needed for long migratory journeys.
Disturbed Sleep
Sometimes normally diurnal birds become active at odd hours at night if their roosting or sleeping patterns are disrupted. This could be caused by light pollution, noise, predators, weather events, or other disturbances. Artificial lights and sounds cause confusion, while storms and predators like raccoons and cats can startle sleeping birds and force them to flee in darkness.
Light Pollution
Excessive artificial light from street lamps, signs, and buildings can adversely affect birds. Bright night lighting disorients birds and alters their biological clocks, leading to irregular sleep-wake cycles. Some end up awake and flying around artificially illuminated areas at night searching for food when they should be asleep.
Noise Pollution
High noise levels from traffic, machinery, or human activities can interrupt a bird’s rest. Birds are sensitive to noise pollution which can cause physiological stress. Loud disturbances may repeatedly awaken roosting and nesting birds, forcing them to take flight in the middle of the night.
Predators
Predatory threats can cause birds to flee their roosts in a panic. Nocturnal predators like owls, raccoons, and cats may attack nests or disturb sleeping birds, provoking a terrified mass exodus. Flocks erupting suddenly into night flight are trying to escape danger and reach safer areas.
Severe Weather
Sudden storms like gales, thunderstorms, hail, or heavy rain can startle and flush sleeping birds into the night. Seeking shelter from bad weather may put normally diurnal species aloft after dark. Bright city lights can disorient storm-driven landbird migrants, causing navigational mistakes.
Foraging
Some opportunistic birds will take advantage of artificial light to hunt for food at night. Nighttime lighting allows diurnal birds to extend their feeding hours after sunset. Urban songbirds like robins and thrushes will forage under streetlights where moths and insects congregate. Scavengers like gulls may also feed at all hours around cities where food waste is plentiful.
Extending Foraging Hours
Artificial lighting allows diurnal birds to prolong their active hours into the nighttime. Birds naturally follow predictable circadian rhythms synchronized to daylight. But street lamps and excessive lighting disrupt these rhythms and enable some species to remain active after dark.
Night Insects
Light fixtures attract night-flying insects which in turn draw in insectivorous birds. Some clever birds have learned that lamp posts create easy buffets of moths, beetles, midges, and other prey. Opportunistic species capitalize on these concentrated food sources by hunting under nighttime lights.
Scavenging
Gulls, pigeons, and other resourceful urban birds scavenge at all hours of day and night. Bright city lighting allows them to find and exploit tossed-out food scraps, waste piles, and dumpsters even after dark. For these adaptable scavengers, nighttime creates more opportunities to seek out meals.
Disorientation
Some instances of nocturnal flight are cases of disorientation rather than purposeful activity. Loss of navigational bearings can leave birds flying aimlessly after dark. Young fledglings become separated from parents and lost. Additionally, light pollution and artificial lights can entrap, ground, or even injure birds.
Fledgling Disorientation
Young birds on their first flights sometimes become disoriented and separated from their parents. Chasing prey or being chased by predators can also lead them astray. With limited flight experience, lost fledglings end up struggling to get their bearings at night.
Migratory Disorientation
Disoriented migrating birds may end up circling aimlessly after dark. Artificial light pollution can scramble navigational cues from moon, stars, and magnetic fields. Without proper bearings, exhausted migrants fly in endless loops trying to reorient themselves.
Artificial Light Entrapment
Bright artificial light sources can entrap, ground, or injure birds. When surrounded by illumination, the instinct is to fly straight into light. This can lead to collision with buildings or infrastructure. Circadian rhythms are disrupted and exhausted birds cannot escape the light.
Other Causes
Some additional reasons birds may fly at unusual nighttime hours include:
- Juveniles begging parents for food with constant chirping
- Territorial displays and chasing off intruders
- Nocturnal mating rituals like with woodcocks
- Displaced individuals seeking new shelter or habitat
- Escape attempts from enclosed areas like barns or garages
These activities stem from normal bird behavior but cause atypical nighttime flight. The reasons can range from mundane to serious, but help explain nocturnal activity.
Conclusion
While most birds are active during daylight, there are many reasons why they may end up flying around at night as well. Nocturnal species are adapted for nightlife. Migrating birds travel after dark. Disrupted sleep and foraging under artificial lights lead diurnal birds astray. Disorientation, weather, predators, and fledglings also contribute to night flights. So while unusual, nocturnal bird activity has many logical explanations behind it.
