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. The biggest owls weigh up to about 9 pounds (4 kilograms). Let's look at how an owl is built, starting with its 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. Owls cannot move their eyes around. An owl can turn its head far around to look behind it, and it bobs and sways its head to judge distance.

Now let's look at the eyes. 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. Behind an owl's 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 retina holds a very high number of rods compared with other birds, which gives it a heightened sense of vision in dim light.

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. 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.

Now let's see how owls work out where a sound is coming from. 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.

Let's turn to the wings. 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. Silent flight matters less to owls that hunt over water or by day, and many of them lack the quieting feather features. Owl-inspired leading-edge serrations could be used on wind turbine blades, aircraft wings or drone rotors to help control airflow and cut noise.

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. Owls eat many kinds of prey, from small mammals to birds, lizards and insects, and a few owls eat fish, while a snowy owl's favorite food is lemmings. 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. Owls are hard to study in the dark, and much of their socializing is done with their voices; owls also 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.

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
• vertebrae: backbone bones
• serrations: toothed edges
• Paleocene: ancient era
• pellets: fur-and-bone balls
• Endangered: at risk