Owls are birds, and most owls are awake and hunt at night. As of November 2026, scientists recognize more than 200 kinds of owls, and they are sorted into two families: barn owls, and all the other owls, called typical owls. Linnaeus put owls and falcons in the same group, and that grouping lasted 130 years, partly because the two kinds of birds evolved similar features separately. Owls are well represented in the fossil record, with several families dating to the Paleocene era, about 58 million years ago. As of November 2026, the largest owl known to have existed lived in Pleistocene Cuba: Ornimegalonyx oteroi stood more than a meter tall and had the most powerful claws of all owls. The rest of this account looks at how living owls are engineered for the dark, beginning with the neck.
A Johns Hopkins team studied the bone structure and blood vessels in the heads and necks of snowy, barred and great horned owls that had died naturally, using dye-enhanced X-ray imaging and dissection. The artery that feeds an owl's brain runs through bony holes in the neck vertebrae; in owls these holes are about 10 times wider than the artery, leaving cushioning air pockets so the artery can move when the neck twists. An owl's vertebral artery enters its neck higher up than in other birds, at the 12th neck vertebra instead of the 14th, which gives the vessel more room and slack. When the team turned dyed owl heads, vessels under the jaw swelled and pooled the dye in reservoirs, unlike human arteries, which narrow as they branch; the researchers say these reservoirs let owls pool blood for their large brains and eyes while the head rotates. Small vessels link an owl's carotid and vertebral arteries, a link not usually seen in adult humans, and they let blood keep flowing to the brain even if one route is blocked during extreme neck rotation.
Owls have big eyes, but owls cannot see in total darkness. Owl eyes are shaped like tubes, not balls; owls have small skulls, so their big eyes, which need large corneas to collect light, could not grow outward and took a rod shape instead. Owl eyes have many more rods than cones, and an owl's retina holds a very high number of rods compared with other birds, which gives it a heightened sense of vision in dim light. Behind the retina is a mirror-like layer called the tapetum, which reflects light that the rods and cones did not absorb back through the eye, giving the receptor cells a second chance to catch it. An owl's eyes are fixed in its skull by a bony ring, so the owl has good two-eyed vision but must turn its head to see to either side, and an owl can turn its head far around to look behind it.
An owl's ears are holes in its head, hidden under feathers, and the ring of feathers around its face, called the facial disc, helps funnel sound to its ears. An owl's facial ruff and disc form parabolic troughs that lead to the ears and can increase sound pressure tenfold. Owls hear low-frequency sounds better than most birds do, and they are sensitive across a wide range of frequencies. The part of an owl's brain that handles hearing has more nerve cells than that of other birds of about the same size, and an owl's outer ear tube and inner ear are large, which helps it detect sounds well. An owl can hear a mouse step on a twig from about 75 feet (23 meters) away, and a great gray owl can find a rodent under the snow by sound. Owls are hard to study in the dark, and much of their socializing is done with their voices.
A sound from the right reaches the right ear first and is a little louder there, because the head partly blocks it from the left ear; owls, humans and other two-eared animals find where a sound comes from by using these differences. Konishi's team found that barn owls use the difference in arrival time between the two ears to judge a sound's horizontal direction, and the difference in loudness to judge its vertical direction. A barn owl's two ear openings are at different heights, which sharpens its ability to tell how high or low a sound is, and whenever a barn owl hears a sound, it turns its head to face the source. In the inferior colliculus, a part of the owl's midbrain, is a map of auditory space, and its space-specific neurons are each sensitive to sound from one direction. In 2001, Physics Today reported that Caltech researchers José Luis Peña and Masakazu Konishi found that barn owls use the neural equivalent of an AND gate to combine time-difference and intensity cues for locating sounds.
Many owls fly almost without a sound. Owl wings quiet the air in three ways: a stiff comb on the front edge of the outer feathers, soft fringes on the back edge, and a soft, downy covering on the feathers. Researcher Krista Le Piane examined feathers of 70 owl species, photographing and measuring the noise-cutting comb on the outermost wing feather; generally, the wider the comb, the less sound the wing makes. In her study, fish-eating owls had narrower wing combs, which means less noise-quieting, than owls that eat other kinds of prey, and owls that hunt mammals have wider wing combs than owls that hunt insects. Le Piane also found wider wing combs in owls that hunt at night, when sound cues matter most for finding prey, than in day-active owls such as snowy owls and burrowing owls. Silent flight matters less to owls that hunt over water or by day, and many of them lack the quieting feather features.
Two hypotheses explain owls' silent flight. The stealthy hunting hypothesis says owls fly quietly so prey cannot hear them coming, and the prey detection hypothesis says quiet flight helps owls hear and track prey. Le Piane's results suggest both hypotheses are correct, depending on the owl: owls that hunt prey with good hearing, or that hunt at night, have feathers that reduce noise. Owl-inspired leading-edge serrations could be used on wind turbine blades, aircraft wings or drone rotors to help control airflow and cut noise. In tests of owl-inspired wing models, leading-edge serrations passively controlled the change from smooth (laminar) to turbulent airflow over the top of the wing at angles of attack between zero and 20 degrees, but serrated leading edges reduce aerodynamic performance below about 15 degrees angle of attack, while they can give noise reduction and aerodynamic performance above 15 degrees, which owl wings often reach in flight.
Owls have large wings for their body size, which lets them fly slowly, and a large owl such as a barn owl can fly as slowly as two miles per hour, gliding with little flapping. Most owls hunt by sitting and waiting on a perch, then dropping or gliding down; only light-winged owls such as the long-eared and short-eared owl hunt much in the air. The size of an owl's feet is usually a sign of how big a prey animal it can take, and owls eat many kinds of prey, from small mammals to birds, lizards and insects. Snowy owls lay more eggs in years when their prey, such as lemmings, is plentiful. Owls that depend on lemmings can increase sharply in a good lemming year, but the habitat cannot support the larger numbers for long, and owl numbers usually fall sharply when the prey declines.
Owls have no teeth, so they often swallow their food whole, and they cough up pellets of fur and bones that they cannot digest. Because the digestive juices of an owl's stomach are not as acidic, owl pellets contain the bones of the owl's previous meal, along with fur, feathers or insect parts. Taking apart an owl pellet shows what the owl ate, and scientists have found species they did not know lived in an area by digging through owl pellets. Many owls also hide extra food and come back to eat it later. An owl that sits still in daylight is not tame; it is trying to avoid attention by not moving. Owls help people by eating rodents such as mice and rats.
Most owls do not build their own nests, but use old nests of other birds or holes in trees. Burrowing owls often use burrows dug by other animals, such as prairie dogs, ground squirrels and badgers, rather than digging their own. Most owls stay in the same area all year, and very few kinds of owls migrate. Owls lay more eggs when there is plenty of food and fewer when food is scarce, and some owls skip breeding in years when food is scarce. In Washington State, scientists have built artificial burrows for western burrowing owls from corrugated drainpipes that lead to a nest chamber in a 55-gallon barrel. In Washington, burrowing owls seem drawn to farmland because prey is plentiful, but surveys show fewer young recruited and fewer adults returning there, suggesting farmland may act as a population sink.
BirdLife International's 1994 appraisal found 21 of 189 typical-owl species (11%) in danger of extinction and another 14 (7.4%) Near Threatened. Between 1966 and 2013, burrowing owls in North America declined by 33 percent, and removing burrowing mammals through pest control programs has been identified as the main cause of burrowing owl declines. Blakiston's fish owl is one of the world's rarest owls and, as of November 2026, is classified as Endangered, and as of November 2026 National Geographic reports that fewer than 2,000 remain, found in Russia and parts of Asia. In 1993 the U.S. Fish and Wildlife Service listed the Mexican spotted owl as threatened under the Endangered Species Act, and in 2004 it designated critical habitat for the owl. As of November 2026, the main threat to the Mexican spotted owl in the United States is the growing risk of very large wildfires that burn whole stands of trees.
Words to know
- tapetum: mirror-like layer
- vertebra: backbone bone
- serrations: toothed edges
- hypotheses: possible explanations
- colliculus: midbrain part
- Endangered: at risk
