Characteristics and Behavior of Owls

Candace Berkeley, Product Manager 
Carolina Staff 

Updated April 2019 

Imagine being able to turn your head a full 270 degrees. For years, this range of motion and other unique physical characteristics and physiological adaptions of owls have allowed them to survive and even thrive in the wild. Owls have adapted to nearly every ecosystem on the planet. They are quite specialized predators, having eyes and ears that are designed for hunting and unique feathers that enable them to fly almost silently. 

Owls hunt throughout the night in deserted places such as cemeteries, run-down farms, and other open areas. The diet of many owls consists mainly of rodents and other small animals. Prey is usually eaten whole, but the whole prey is not digested. An owl's digestive tract compresses the undigested portions of the prey, such as fur and bone, into a compact pellet that the owl coughs up and expels through its mouth.

Instead of building nests, owls simply take over the abandoned nests of other birds. Barn owls frequently inhabit structures such as barns, belfries, and deserted buildings. They also nest in the crevices of cliffs, inside hollow trees, and inside dense evergreen trees during cold weather.

Human encroachment on owl territories has led to the decline of owl populations in the wild. Many owl species cannot adapt to changes in their ecosystems caused by humans. As a result, the future of many owls, including the popular barn owl, is in doubt.

Pygmy owls are threatened in their southwestern United States territories due to loss of habitat caused by growing towns and cities. Northern spotted owls have become threatened in the United States due to logging in the Northwest. Their long-term survival is questionable due to the loss of habitat and a low rate of successful reproduction.

Classification and evolution of owls

Owls belong to the phylogenetic class Aves. Two distinct families contain the more than 200 species of owls. The family Tytonidae contains approximately 17 known species of barn owls; the other species belong to the family Strigidae.

The oldest known owl fossils are from the Miocene, which occurred 38 to 54 million years ago. Based on the fossil evidence, these ancient owls evolved into the 2 families of modern owls. The oldest barn owl fossils found thus far are estimated to be at least 24 million years old. Fossil evidence indicates that giant barn owls once thrived in the Caribbean and Mediterranean regions between 10,000 and 30,000 years ago. These giants, known as Ornimegalonyx, were 2 to 3 times as large as modern barn owls and twice the size of modern great horned owls. Ornimegalonyx is thought to have preyed upon animals such as the giant sloth and giant rodents such as the capybara, which are over 4 feet long.

There are 134 known species of owls in the world, with the Eurasian eagle owl being the largest and the elf owl being the smallest. Although owls share many of the same characteristics, there are some notable differences in behavior between species. Two-thirds of owl species are nocturnal and the remaining third are diurnal.

Physical characteristics

Size

Unlike most species of birds, male and female owls of a given species are similar in appearance. Males and females are also generally the same size in the smaller species of owls. However, this is not the case in the larger species such as the great horned owl. Female great horned owls are up to 25 percent larger than the males of the species. Some theorize this facilitates egg incubation. However, it is also possible that the females are larger so that they can protect their nests from aggressive male owls. Of course, owls vary in both size and shape from one species to another. These adaptations allow owls to hunt their preferred prey with ease and effectively cope with their environment. 

Sight

Owls are widely believed to have the best night vision in the animal kingdom. Owls have large pupils and corneas that gather light very effectively. The cat is the only other animal that can come close to the owl's night vision capabilities. Owl eyes function in bright sunlight, too. However, it is believed that owls are not capable of seeing and interpreting a broad spectrum of colors.

Owls have extremely large eyes in proportion to the size of their heads. In some of the larger species, such as the great grey owl, the eyes are larger than those of most humans. Although owl eyes are well adapted for great visual acuity, there is a drawback. Unlike the eyes of most animals, owl eyes are more flat than spherical in shape. Due to this adaptation, owls have essentially given up the ability for eye movement. Their eyes are fixed in place by a bony structure called a sclerotic ring. As a result, they must turn their heads to move their eyes. However, owls can turn their heads around far enough to see directly behind them. The total range of head rotation for most owl species is an amazing 270 degrees. 

Hearing

Owls have extremely sensitive ears. It is believed that some owls can hear up to 10 times better than humans can. Owls need this ability to help them find prey that they cannot see with their keen eyes. Owls can hear tiny rodents scurrying around on the ground, even under thick snow. 

The unique hearing system of owls allows them to pinpoint the location of even the faintest sounds. Their ears are not lined up symmetrically like those of most animals. Having ears that are not lined up even with one another allows the owl to determine precisely from where a sound is coming. When an owl hears something that gets its attention, it turns its head left and right and up and down until it homes in on the sound. 

Owl faces are shaped elliptically, like a satellite dish. This facial shape, which is very apparent in barn owls and great grey owls, and its facial feathers, allows owls to focus sounds directly on their ears. The elliptical face and offset ears of an owl work together to form a highly sensitive and precise hearing system. 

Feet and talons

Owls use their powerful feet and sharp talons to snare their prey. Their talons are adapted to piercing through tough animal hides and holding heavy weights without breaking. The bones in their feet are strong enough to withstand the impact made by snatching or striking prey at high speeds. Most owl species have feathers covering the top surface of their feet to protect them from the cold. The soles of their feet, which are rough and knobby to improve grip, have extra blood vessels to radiate excess heat. 

The grip strength of owls' feet is among the greatest of all raptors. In the book Owls, author Kim Long tells the story of a biologist who experienced this strength the hard way. The biologist was gripped by a great horned owl and could not be freed from its clutches until its leg tendons were severed.

Feathers

Owls, like most birds, have 2 types of feathers. Contour feathers are the outer layer of feathers that provide protection from the environment and enable flight. Down is the inner layer of fluffy feathers that trap air to provide insulation from cold weather. Owls have far less down than most species of birds have. However, their contour feathers have special barbules that take the place of down. Their dense feathers give owls the illusion of having thick bodies, but their featherless bodies are surprisingly small. Their dense feathers also provide insulation, allowing owls to withstand severe cold without storing much body fat or continually eating. 

Newly hatched owls do not have flight feathers. Instead, they are covered with downy feathers to keep them warm. As the owlets (owl chicks) grow, their down feathers are replaced with juvenile feathers. These feathers typically do not have the same markings as adult feathers have. Owlets will get their first adult flight feathers after they are a few months old. 

Mature owls have feathers that can be considered drab colored when compared to those of other species of birds. However, the drab coloration serves to camouflage owls from predators and prey. Owls sometimes use their plumage to protect themselves from attack by condensing their feathers and closing their eyes. They can also fluff up their feathers to bluff and frighten possible attackers.

Owl flight

Owls are powerful fliers because their wings are relatively large in proportion to the size of their bodies; also, their skeletons—like those of all birds—are lightweight. 

Their large wings are also perfectly suited to hauling heavy prey through the air. Some owls have the physical endurance to hover in the air like a hummingbird for brief periods of time to catch prey, while others, like the Great Grey Owl, rarely fly more than a short distance before retreating to the sanctuary of a perch to conserve energy.

Predation

Owls are quite specialized predators, having eyes and ears designed to easily locate prey and unique feathers that enable them to fly almost silently. They hunt through the night, mainly consuming rodents and other small animals. Prey is usually consumed whole, but the whole prey is not digested. An owl's digestive tract compresses the undigested portions of the prey, such as fur and bone, into a compact pellet that the owl coughs up and expels through its mouth. Using their keen vision and hearing, most owls silently swoop down upon their unsuspecting prey and grab them with their talons. However, flammulated owls are one exception to this rule. These nocturnal owls, which feed almost exclusively on insects, use their bills to catch their prey in flight. Other owls pluck birds out of the air with their talons. Although owls do not dive into water after prey, they will skim its surface to snag fish or snakes. Some owls have even been observed standing on the shore of streams and plucking fish out of the water with their talons . 

Owls such as great grey owls, boreal owls, and hawk owls sometimes attack prey which has tunneled under snow. These owls use their keen hearing to locate their buried prey. If the owl misses its target, it may simply stomp around in the snow until the prey has been flushed out of hiding. 

Great horned owls have a crude, but effective, method of flushing tree squirrels out of their nests. These owls slam into the side of the nests with enough force to send the terrified squirrels scurrying for better cover. However, at least one unlucky squirrel usually ends up in the clutches of the hungry owl.

Hunting patterns are often developed by owls when they observe their prey coming back to the same place time after time. Great horned owls have been observed making repeated raids on colonies of ducks that return to a specific area to nest. Barn owls sometimes follow a methodical hunting schedule when prey is readily available. They hunt 3 times a day, with the first hunt at around sunset, the second hunt at around midnight, and the third hunt at around sunrise. 

Great horned owls have been known to prey on domestic animals such as cats, small dogs, and fowl. Even domesticated birds as large as turkeys have fallen prey to the Great horned owl. These owls have also been known to torment farmers who have poorly designed chicken coops by somehow opening the coop and snatching the chickens inside while they sleep.

Diet

Most owls are active year-round and most species eat every day. Owls have a low percentage of body fat during the warm months of the year. However, during the cold months, the percentage of body fat does increase in some owl species such as the snowy owl. These fat reserves provide energy when food is scarce. 

Metabolism

The rate of metabolism (turning food into energy) in owls is generally quite high. As a result, owls must eat frequently, which also means that they must hunt frequently. Small owls, such as the elf owl, have extremely high metabolisms that require them to consume enough prey to equal half of their body weight every day. Larger owls have slower metabolisms and eat less than smaller owls do in proportion to their body weight. The Snowy owl has a metabolism which at times greatly differs from that of all other owls. It might fast for over a month during winter due to the scarcity of prey. During the fasting period, the snowy owl relies heavily on its fat reserves to keep it going. 

Owls, like most birds, cannot chew their food and usually eat their prey whole. Most of the time, they do not separate edible parts of the prey from the inedible ones. However, when they have caught something that is too big to swallow whole, they will pick the animal apart before consuming it. Large owls, such as the great horned owl, commonly attack prey near their own size or even larger. Examples include foxes, skunks, weasels, and even smaller owls. The tiny pygmy owl has been known to attack and kill quail, which are twice its weight.

Certain types of prey might not be available to owls at different times of the year due to hibernation, migration, or other reasons. Because of this, most owls are opportunistic hunters, eating anything available in times of need. However, many owl species do prefer rodents. For example, barn owls will pass up an easy kill to dine on their preferred rodent delicacy. 

Most of the time older owlets are friendly to their younger siblings. They may help feed the younger chicks and help them keep warm. However, owlets sometimes cannibalize their younger or weaker siblings if food is scarce. This often occurs when there is a wide gap between the ages of the oldest and youngest chicks in a nest. 

Owl prey

Here is a partial list of owl prey. Bear in mind that larger species of owls generally eat larger prey (like squirrels) and smaller species of owls generally eat smaller prey (like insects).

Nesting

Barn owls are renowned for making nests in man-made structures, but most other owl species seek out shelter away from the influence of people. The cavities of rotten trees, or trees hollowed out by woodpeckers, often host owl nests. Owls also readily seek out the abandoned nests of other species of birds, such as eagles, hawks, or crows. Some owl species even use the cover provided by caves and niches in rocks. Great horned owls can run squirrels out of their nest, squash it flat, and take it. Once a suitable nesting place has been found, it may be used for many years.

When owls do construct their own nests, the quality of workmanship is shoddy. Many nests are hastily constructed out of discarded owl feathers and the feathers and fur of their prey. As an exception to this, the burrowing owl chooses instead to nest in holes dug into the ground insulated with grass, plant stalks, and other material to provide protection for their young.

Courtship and reproduction

Courtship

Male barn owls use a special call to attract females to their territory. The courtship often involves the male and female chasing each other in flight while both call out loudly to one another. Male barn owls also exhibit a special courtship behavior known as “moth flight.” During this ritual, the male hovers in front of a perched female to display the distinctive white areas on its chest and belly. 

Another mating ritual performed by owls involves the male repeatedly flying from a female’s nest to his own to get her attention. If the female is impressed, she will respond with a unique mating call similar to that of chicks begging for food. The male responds to this call by bringing a freshly caught animal as an offering to the female. The acceptance of this offering often leads to copulation. 

Some owls, such as screech owls, appear to be monogamous throughout life. However, the pair-bond relationship of other owl species may last for only one brood. Barn owls raise multiple broods in a single year if there is an abundance of prey. They may pick different mates for each brood. Barn owls may also have more than one brood if an early brood is lost to disease, malnutrition, predators, or catastrophic weather.

The incubation of young

Owls usually begin a nesting phase during the mating period, but they are not known for being diligent or skillful nest builders. A lot of owls simply take over the nest that some other bird or animal has made. Once a good nest is found, owls may use it year after year. 

As the mating season draws near, female owls begin acting as if they are brooding even before there are eggs. After an egg is fertilized (usually within a day or two), it goes through several stages of development. The developing egg, which is known as the yolk, initially picks up several coatings of albumen (egg white). It then gets two coatings of a material that forms the familiar hard shell.

As soon as the first egg forms a shell, another egg begins to develop. The first egg may be ready to lay as early as one day after copulation. Initially, eggs are laid individually every 1 to 2 days, but the cycle becomes erratic after the first few eggs have been laid. Younger chicks are more vulnerable to starvation because it becomes harder to feed the entire brood as the number of hatched chicks increases. Several days or even weeks can separate the oldest egg from the newest. 

During the incubation process, female owls rarely leave the nest except to defecate and get water. To help with incubation, female owls have a sparsely feathered brood patch on their bellies that has a higher percentage of blood vessels than other parts of the skin. Blood flow through these vessels creates a good source of heat for the eggs. 

Although most owls begin incubating eggs as soon as the first is laid, others may wait for hours or days to begin. When the incubation begins immediately, some chicks hatch far sooner than others. This can lead to the older chicks helping to brood and feed the younger chicks. When prey is scarce, however, it can lead to the older chicks cannibalizing the younger ones.

The rearing of young

Like all birds, owls are born with an egg tooth. This structure helps them chip away from within and break the tough eggshell. This tooth drops off 1-2 weeks after hatching. Although owls are born blind and have only a thin coat of down to protect them from cold weather, a thicker coat appears within a couple of weeks. 

It doesn’t take long for owls to develop strength and alertness. Barn owl chicks are notorious for their curious, wandering behavior. 

Owlets often beg vocally for food. Since more predators lurk nearby, those owlets on the ground are much quieter than those nested in trees. 

The parents of young owls provide them with food soon after they have hatched. Many species provide insects to their young in the early stages and whole rodents once the chicks become large enough. Spotted owls rip off the heads of their prey so that digestion and owl pellet production are easier for the chicks. In some species, such as great horned owls, the parents provide larger and larger prey as the owlets increase in size. 

Many young owls take their first flight, or fledge, by the time they are 2 months old. Once an owl begins flying, parental support dries up. The parents may chase the young away or simply abandon their nests. The young are subsequently forced to feed themselves.

Mortality and disease

Adult owls are near the top of the food chain and are not threatened by many animals. Large raptors, such as eagles, may attack owls if food is scarce. Likewise, large owl species may attack smaller ones on occasion. 

Owlets are much more vulnerable, however. The more chicks in a given brood, the less likely all will survive disease, malnutrition, or catastrophic weather. Predators of owlets include snakes, squirrels, possums, and ravens. (All of these animals are preyed upon by species of larger owls.)

The influence of humans can also lead to chick mortality. Chicks often die directly from human interference, such as deforestation and illegal hunting. Owls also frequently fly into cars, windows, or clotheslines. The mere presence of humans may cause the parents to abandon the nest and the young. Long-term studies have shown that the survival rate of owl chicks goes down as the number of humans in the area goes up. 

Young adult owls are also vulnerable because of their lack of hunting experience. They could be pushed by their parents or other adults into unfamiliar hunting territory inhabited by other hostile adult owls. At least half of all young adult owls die before they reach their first birthday. The odds of survival increase greatly as they gain size and experience. 

How long can owls live?

Most owls in the wild live about 10 years. However, owls can live much longer if conditions are favorable. Great horned owls in the wild have been observed to live for 19 years, whereas long-eared owls have lived up to 27 years. Owls can live for many more years in captivity than they would in the wild. The record for longevity in captive great horned owls is 38 years, which is twice as long as the record age for longevity in the wild. 

Diseases and parasites

Feather lice can torment owls and can also pose health problems. Owls are also susceptible to a variety of parasitic worms. Fleas and flies pester owls, but they only hang around because of the decomposing materials typically found in owl nests. 

Hepatosplentitis infectiosa strigum is a virus that is fatal to many owls, but some species, such as barn owls, have become immune to it. Owls are also vulnerable to pneumonia and tuberculosis. Pigeons, which are preyed upon by some species of owls, carry a parasitic protozoan that may cause a thick deposit to form in the throats of owls. This deposit can eventually cause an owl to choke to death.

Nesting habits

Barn owls are renowned for making nests in manmade structures, but most other species of owl seek out shelter away from the influence of man. The cavities of rotten trees, or trees hollowed out by woodpeckers often host owl nests. Owls also readily seek out the abandoned nests of other species of birds such as eagles, hawks, or crows. Some owl species also use the cover provided by caves and niches in rocks to provide them with protection from the elements. Great horned owls run squirrels out of their nest, squash it flat, and take it as their own. Once a suitable nesting place has been found, it may be used for many years. 

When owls do construct their own nests, the quality of workmanship is shoddy at best. Many nests are hastily constructed out of discarded owl feathers and the feathers and fur of their prey. 

Barn owls typically don't even attempt to build a nest. The only comfort and protection that barn owl chicks get is from the regurgitated owl pellets that are strewn around the nesting area. Owl nests become coated with excrement and uneaten animal parts, making them very filthy compared to the nests of other species of birds. 

Burrowing owls do try to provide a good nest for their young. These birds nest in holes dug in the ground insulated with grass, plant stalks, and other material, which provides protection for their young.

Mobbing

Raptors such as owls don't always have it easy just because they are on top of the food chain. Smaller birds attack and pester owls caught flying in the open or roosting. Many types of birds may join the owl assault, which is known as mobbing. Songbirds most commonly attack owls, but birds as large as crows and as small as hummingbirds join in, also. 

The harassment that occurs during mobbing usually consists of repeated dives as well as loud vocal calls designed to alert others to the owl's presence. Sometimes birds physically attack, plucking at the owl's eyes and feathers or clawing at its body. Owls are seldom hurt by these attacks and seem to ignore the mobbing behavior of other birds.

Owls in society and culture

Throughout history, owls have been linked to unnatural forces, evil, and death. Ancient Babylonians believed that the hoot of an owl at night came to represent the cries of a woman who died during childbirth. In Hungary, the owl was referred to as the bird of death. Owls were official symbols of death for ancient Egyptians. The hieroglyphic for the owl also symbolized darkness, cold, and a state of passivity.

Ancient Romans considered the sight of an owl an extremely unlucky omen. According to legend, the only way to negate the effects of this omen was to catch the owl, burn it, and then scatter its ashes in the Tiber River. It has been said that before Julius Caesar was murdered, owls were heard making their mournful cries.

However, not all societies and cultures have assigned negative attributes to owls. Buddhists have long thought the owl to be an enemy of ignorance and a representation of isolation and the need for deep meditation. In Athens, owls represented a force of mystery, but one associated with good. The owl was the symbol of the Greek goddess Athena, goddess of night, war, wisdom, and the liberal arts.

In many ancient cultures, owning or carrying a piece of an owl as a charm was thought to provide special protection from evil spirits and health problems, such as epilepsy and rabies. Other ancient cultures believed that energy, wisdom, and bravery might be imparted to the carrier of owl charms. Different cultures used different parts of owls in their charms, including the feet, feathers, eyes, heart, bones, or even the entire owl.

There are many natural areas named after owls in the United States. Lakes, rivers, bays, swamps, and mountain ranges contain "owl" in their names. There are at least 2 towns in the United States named "Owl”—one is in Arizona and the other is in California. You can also visit Owls Head, Maine, and Owlsville, New York.

Owl watching

Many birdwatchers are fanatical about observing owls. Some even invest in infrared equipment for night viewing. Owls can become very spooked by humans and may abandon their nests and young if people get too close. Owl calls may upset the birds causing them to flee their territory. 

A good way to observe owls without disturbing them is to listen to their calls instead of trying to see them up close. Owl calls are very species-specific, so precise identification of owl species is possible using this technique. The best way to observe owls up close is at zoos and aviaries. 

Owl houses

Because of the declining numbers of some owl species, conservationists are now trying to create nesting and roosting structures. Owl boxes are popular with barn owls. Other owl species, especially the larger ones, are more reluctant, but they have been observed raising young in manmade nests. 

Because they help keep the rodent population down, barn owls are well liked by farmers. Some barns are even purposely designed to include owl entry doors and nesting rooms.

With their unique attributes and capabilities, owls provide fascinating insight into predator-prey dynamics, food chains, physiological adaptations, human impact, and more. Engage your students and bring important science concepts to life by studying this extraordinary bird.

With their unique attributes and capabilities, owls provide fascinating insight into predator-prey dynamics, food chains, physiological adaptations, human impact, and more. Engage your students and bring important science concepts to life by studying this extraordinary bird.

Get started by dissecting owl pellets.

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