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Owl
Owl
from Wikipedia

Owl
Temporal range: Late Paleocene to recent 60–0 Ma
Eurasian eagle-owl (Bubo bubo)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Telluraves
Order: Strigiformes
Wagler, 1830
Families

Strigidae
Tytonidae
Ogygoptyngidae (fossil)
Palaeoglaucidae (fossil)
Protostrigidae (fossil)
Sophiornithidae (fossil)

      range of all species of owls, combined
Synonyms

Strigidae sensu Sibley & Ahlquist

Owls are birds from the order Strigiformes[1] (/ˈstrɪəfɔːrmz/), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers adapted for silent flight. Exceptions include the diurnal northern hawk-owl and the gregarious burrowing owl.

Owls are divided into two families: the true (or typical) owl family, Strigidae, and the barn owl and bay owl family, Tytonidae.[2] Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish. They are found in all regions of the Earth except the polar ice caps and some remote islands.

A group of owls is called a "parliament".[3]

Anatomy

[edit]
Tawny owl (Strix aluco), left, and western barn owl (Tyto alba), right, belonging respectively to the Strigidae and Tytonidae families
Burrowing owl (Athene cunicularia)

Owls possess large, forward-facing eyes and ear-holes, a hawk-like beak, a flat face, and usually a conspicuous circle of feathers, a facial disc, around each eye. The feathers making up this disc can be adjusted to sharply focus sounds from varying distances onto the owls' asymmetrically placed ear cavities. Most birds of prey have eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits the greater sense of depth perception necessary for low-light hunting. Owls have binocular vision, but they must rotate their entire heads to change the focus of their view because, like most birds, their eyes are fixed in their sockets. Owls are farsighted and cannot clearly see anything nearer than a few centimetres of their eyes. Caught prey can be felt by owls with the use of filoplumes—hairlike feathers on the beak and feet that act as "feelers". Their far vision, particularly in low light, is exceptionally good.

Owls can rotate their heads and necks as much as 270°. Owls have 14 neck vertebrae—humans have only seven—and their vertebral circulatory systems are adapted to allow them to rotate their heads without cutting off blood to the brain. Specifically, the foramina in their vertebrae through which the vertebral arteries pass are about ten times the diameter of the artery, instead of about the same size as the artery, as is the case in humans; the vertebral arteries enter the cervical vertebrae higher than in other birds, giving the vessels some slack, and the carotid arteries unite in a very large anastomosis or junction, the largest of any bird's, preventing blood supply from being cut off while they rotate their necks. Other anastomoses between the carotid and vertebral arteries support this effect.[4][5]

The smallest owl—weighing as little as 31 g (1+332 oz) and measuring some 13.5 cm (5+14 in)—is the elf owl (Micrathene whitneyi).[6] Around the same diminutive length, although slightly heavier, are the lesser known long-whiskered owlet (Xenoglaux loweryi) and Tamaulipas pygmy owl (Glaucidium sanchezi).[6] The largest owls are two similarly sized species; the Eurasian eagle-owl (Bubo bubo) and Blakiston's fish owl (Ketupa blakistoni). The largest females of these species are 71 cm (28 in) long, have a 190 cm (75 in) wing span, and weigh 4.2 kg (9+14 lb).[6][7][8][9][10]

Different species of owls produce different sounds; this distribution of calls aids owls in finding mates or announcing their presence to potential competitors, and also aids ornithologists and birders in locating these birds and distinguishing species. As noted above, their facial discs help owls to funnel the sound of prey to their ears. In many species, these discs are placed asymmetrically, for better directional location.

Owl plumage is generally cryptic, although several species have facial and head markings, including face masks, ear tufts, and brightly colored irises. These markings are generally more common in species inhabiting open habitats, and are thought to be used in signaling with other owls in low-light conditions.[11]

Sexual dimorphism

[edit]
A stamp from the Soviet Union, 1979

Sexual dimorphism is a physical difference between males and females of a species. Female owls are typically larger than the males.[12] The degree of size dimorphism varies across multiple populations and species, and is measured through various traits, such as wing span and body mass.[12]

One theory suggests that selection has led males to be smaller because it allows them to be efficient foragers. The ability to obtain more food is advantageous during breeding season. In some species, female owls stay at their nest with their eggs while it is the responsibility of the male to bring back food to the nest.[13] If food is scarce, the male first feeds himself before feeding the female.[14] Small birds, which are agile, are an important source of food for owls. Male burrowing owls have been observed to have longer wing chords than females, despite being smaller than females.[14] Furthermore, owls have been observed to be roughly the same size as their prey.[14] This has also been observed in other predatory birds,[13] which suggests that owls with smaller bodies and long wing chords have been selected for because of the increased agility and speed that allows them to catch their prey.[citation needed]

Another popular theory suggests that females have not been selected to be smaller like male owls because of their sexual roles. In many species, female owls may not leave the nest. Therefore, females may have a larger mass to allow them to go for a longer period of time without starving. For example, one hypothesized sexual role is that larger females are more capable of dismembering prey and feeding it to their young, hence female owls are larger than their male counterparts.[12]

A different theory suggests that the size difference between male and females is due to sexual selection: since large females can choose their mate and may violently reject a male's sexual advances, smaller male owls that have the ability to escape unreceptive females are more likely to have been selected.[14]

If the character is stable, there can be different optimums for both sexes. Selection operates on both sexes at the same time; therefore it is necessary to explain not only why one of the sexes is relatively bigger, but also why the other sex is smaller.[15] If owls are still evolving toward smaller bodies and longer wing chords, according to V. Geodakyan's Evolutionary Theory of Sex, males should be more advanced on these characters. Males are viewed as an evolutionary vanguard of a population, and sexual dimorphism on the character, as an evolutionary "distance" between the sexes. "Phylogenetic rule of sexual dimorphism" states that if there exists a sexual dimorphism on any character, then the evolution of this trait goes from the female form toward the male one.[16]

Hunting adaptations

[edit]

All owls are carnivorous birds of prey and live on diets of insects, small rodents and lagomorphs. Some owls are also specifically adapted to hunt fish. They are very adept in hunting in their respective environments. Since owls can be found in nearly all parts of the world and across a multitude of ecosystems, their hunting skills and characteristics vary slightly from species to species, though most characteristics are shared among all species.[17]

Flight and feathers

[edit]
External videos
video icon Experiment! How Does An Owl Fly So Silently?, from BBC Earth

Most owls share an innate ability to fly almost silently and also more slowly in comparison to other birds of prey. Most owls live a mainly nocturnal lifestyle and being able to fly without making any noise gives them a strong advantage over prey alert to the slightest sound in the night. A silent, slow flight is not as necessary for diurnal and crepuscular owls given that prey can usually see an owl approaching. Owls' feathers are generally larger than the average birds' feathers, have fewer radiates, longer pennulum, and achieve smooth edges with different rachis structures.[18] Serrated edges along the owl's remiges bring the flapping of the wing down to a nearly silent mechanism. The serrations are more likely reducing aerodynamic disturbances, rather than simply reducing noise.[19] The surface of the flight feathers is covered with a velvety structure that absorbs the sound of the wing moving. These unique structures reduce noise frequencies above 2 kHz,[20] making the sound level emitted drop below the typical hearing spectrum of the owl's usual prey[20][21] and also within the owl's own best hearing range.[22][23] This optimizes the owl's ability to silently fly to capture prey without the prey hearing the owl first as it flies, and to hear any noise the prey makes. It also allows the owl to monitor the sound output from its flight pattern.

A great horned owl with wet feathers, waiting out a rainstorm

The disadvantage of such feather adaptations for barn owls is that their feathers are not waterproof.[24] The adaptations mean that barn owls do not use the uropygial gland, informally the "preen" or "oil" gland, as most birds do, to spread oils across their plumage through preening.[25] This makes them highly vulnerable to heavy rain when they are unable to hunt.[26] Historically, they would switch to hunting indoors in wet weather, using barns and other agricultural buildings, but the decline in the numbers of these structures in the 20th and 21st centuries has reduced such opportunities.[24] The lack of waterproofing means that barn owls are also susceptible to drowning, in drinking troughs and other structures with smooth sides. The Barn Owl Trust provides advice on how this can be mitigated, by the installation of floats.[27]

Vision

[edit]

Eyesight is a particular characteristic of the owl that aids in nocturnal prey capture. Owls are part of a small group of birds that live nocturnally, but do not use echolocation to guide them in flight in low-light situations. Owls are known for their disproportionally large eyes in comparison to their skulls. An apparent consequence of the evolution of an absolutely large eye in a relatively small skull is that the eye of the owl has become tubular in shape. This shape is found in other so-called nocturnal eyes, such as the eyes of strepsirrhine primates and bathypelagic fishes.[28] Since the eyes are fixed into these sclerotic tubes, they are unable to move the eyes in any direction.[29] Instead of moving their eyes, owls swivel their heads to view their surroundings. Owls' heads are capable of swiveling through an angle of roughly 270°, easily enabling them to see behind them without relocating the torso.[29] This ability keeps bodily movement at a minimum, thus reduces the amount of sound the owl makes as it waits for its prey. Owls are regarded as having the most frontally placed eyes among all avian groups, which gives them some of the largest binocular fields of vision. Owls are farsighted and cannot focus on objects within a few centimetres of their eyes.[28][30] These mechanisms are only able to function due to the large-sized retinal image.[31] Thus, the primary nocturnal function in the vision of the owl is due to its large posterior nodal distance; retinal image brightness is only maximized to the owl within secondary neural functions.[31] These attributes of the owl cause its nocturnal eyesight to be far superior to that of its average prey.[31]

Hearing

[edit]
A great horned owl perched on the top of a Joshua tree at evening (twilight) in the Mojave Desert, U.S.

Owls exhibit specialized hearing functions and ear shapes that also aid in hunting. They are noted for asymmetrical ear placements on the skull in some genera. Owls can have either internal or external ears, both of which are asymmetrical. Asymmetry has not been reported to extend to the middle or internal ear of the owl. Asymmetrical ear placement on the skull allows the owl to pinpoint the location of its prey. This is especially true for strictly nocturnal species such as the barn owls Tyto or Tengmalm's owl.[29] With ears set at different places on its skull, an owl is able to determine the direction from which the sound is coming by the minute difference in time that it takes for the sound waves to penetrate the left and right ears.[32] The owl turns its head until the sound reaches both ears at the same time, at which point it is directly facing the source of the sound. This time difference between ears is about 30 microseconds. Behind the ear openings are modified, dense feathers, densely packed to form a facial ruff, which creates an anterior-facing, concave wall that cups the sound into the ear structure.[33] This facial ruff is poorly defined in some species, and prominent, nearly encircling the face, in other species. The facial disk also acts to direct sound into the ears, and a downward-facing, sharply triangular beak minimizes sound reflection away from the face. The shape of the facial disk is adjustable at will to focus sounds more effectively.[29]

The prominences above a great horned owl's head are commonly mistaken as its ears. This is not the case; they are merely feather tufts. The ears are on the sides of the head in the usual location (in two different locations as described above).

Talons

[edit]

While the auditory and visual capabilities of the owl allow it to locate and pursue its prey, the talons and beak of the owl do the final work. The owl kills its prey using these talons to crush the skull and knead the body.[29] The crushing power of an owl's talons varies according to prey size and type, and by the size of the owl. The burrowing owl (Athene cunicularia), a small, partly insectivorous owl, has a release force of only 5 N. The larger barn owl (Tyto alba) needs a force of 30 N to release its prey, and one of the largest owls, the great horned owl (Bubo virginianus), needs a force over 130 N to release prey in its talons.[34] An owl's talons, like those of most birds of prey, can seem massive in comparison to the body size outside of flight. The Tasmanian masked owl has some of the proportionally longest talons of any bird of prey; they appear enormous in comparison to the body when fully extended to grasp prey.[35] An owl's claws are sharp and curved. The family Tytonidae has inner and central toes of about equal length, while the family Strigidae has an inner toe that is distinctly shorter than the central one.[34] These different morphologies allow efficiency in capturing prey specific to the different environments they inhabit.

Beak

[edit]

The beak of the owl is short, curved, and downward-facing, and typically hooked at the tip for gripping and tearing its prey. Once prey is captured, the scissor motion of the top and lower bill is used to tear the tissue and kill. The sharp lower edge of the upper bill works in coordination with the sharp upper edge of the lower bill to deliver this motion. The downward-facing beak allows the owl's field of vision to be clear, as well as directing sound into the ears without deflecting sound waves away from the face.[36]

Camouflage

[edit]
The snowy owl has effective snow camouflage

The coloration of the owl's plumage plays a key role in its ability to sit still and blend into the environment, making it nearly invisible to prey. Owls tend to mimic the coloration and sometimes the texture patterns of their surroundings, the barn owl being an exception. The snowy owl (Bubo scandiacus) appears nearly bleach-white in color with a few flecks of black, mimicking their snowy surroundings perfectly, while the speckled brown plumage of the tawny owl (Strix aluco) allows it to lie in wait among the deciduous woodland it prefers for its habitat. Likewise, the mottled wood owl (Strix ocellata) displays shades of brown, tan, and black, making the owl nearly invisible in the surrounding trees, especially from behind. Usually, the only tell-tale sign of a perched owl is its vocalizations or its vividly colored eyes.

Behavior

[edit]
Comparison of an owl (left) and hawk (right) remex.
The serrations on the leading edge of an owl's flight feathers reduce noise
Owl eyes each have nictitating membranes that can move independently of each other, as seen on this spotted eagle-owl in Johannesburg, South Africa.

Most owls are nocturnal, actively hunting their prey in darkness. Several types of owls are crepuscular—active during the twilight hours of dawn and dusk; for example the pygmy owls (Glaucidium). A few owls are active during the day, also; examples are the burrowing owl (Speotyto cunicularia) and the short-eared owl (Asio flammeus).

Much of the owls' hunting strategy depends on stealth and surprise. Owls have at least two adaptations that aid them in achieving stealth. First, the dull coloration of their feathers can render them almost invisible under certain conditions. Secondly, serrated edges on the leading edge of owls' remiges muffle an owl's wing beats, allowing an owl's flight to be practically silent. Some fish-eating owls, for which silence has no evolutionary advantage, lack this adaptation.

An owl's sharp beak and powerful talons allow it to kill its prey before swallowing it whole (if it is not too big). Scientists studying the diets of owls are helped by their habit of regurgitating the indigestible parts of their prey (such as bones, scales, and fur) in the form of pellets. These "owl pellets" are plentiful and easy to interpret, and are often sold by companies to schools for dissection by students as a lesson in biology and ecology.[37]

Breeding and reproduction

[edit]

Owl eggs typically have a white color and an almost spherical shape, and range in number from a few to a dozen, depending on species and the particular season; for most, three or four is the more common number. In at least one species, female owls do not mate with the same male for a lifetime. Female burrowing owls commonly travel and find other mates, while the male stays in his territory and mates with other females.[38]

Evolution and systematics

[edit]
A great horned owl (Bubo virginianus) sleeping during daytime in a hollow tree

Recent phylogenetic studies place owls within the clade Telluraves, most closely related to the Accipitrimorphae and the Coraciimorphae,[39][40] although the exact placement within Telluraves is disputed.[41][42]

See below cladogram:

Telluraves
Accipitrimorphae

Cathartiformes (New World vultures)

Accipitriformes (hawks and relatives)

Strigiformes (owls)

Coraciimorphae

Coliiformes (mouse birds)

Cavitaves

Leptosomiformes (cuckoo roller)

Trogoniformes (trogons and quetzals)

Picocoraciae
Australaves

Cladogram of Telluraves relationships based on Braun & Kimball (2021)[43]

Some 220 to 225 extant species of owls are known, subdivided into two families: 1. true owls or typical owls family (Strigidae) and 2. barn-owls family (Tytonidae). Some entirely extinct families have also been erected based on fossil remains; these differ much from modern owls in being less specialized or specialized in a very different way (such as the terrestrial Sophiornithidae). The Paleocene genera Berruornis and Ogygoptynx show that owls were already present as a distinct lineage some 60–57 million years ago (Mya), hence, possibly also some 5 million years earlier, at the extinction of the non-avian dinosaurs. This makes them one of the oldest known groups of non-Galloanserae landbirds. The supposed "Cretaceous owls" Bradycneme and Heptasteornis are apparently non-avialan maniraptors.[44]

During the Paleogene, the Strigiformes radiated into ecological niches now mostly filled by other groups of birds. [clarification needed] The owls as known today, though, evolved their characteristic morphology and adaptations during that time, too. By the early Neogene, the other lineages had been displaced by other bird orders, leaving only barn owls and typical owls. The latter at that time was usually a fairly generic type of (probably earless) owl similar to today's North American spotted owl or the European tawny owl; the diversity in size and ecology found in typical owls today developed only subsequently.

Around the Paleogene-Neogene boundary (some 25 Mya), barn owls were the dominant group of owls in southern Europe and adjacent Asia at least; the distribution of fossil and present-day owl lineages indicates that their decline is contemporary with the evolution of the different major lineages of true owls, which for the most part seems to have taken place in Eurasia. In the Americas, rather, an expansion of immigrant lineages of ancestral typical owls occurred.

The supposed fossil herons "Ardea" perplexa (Middle Miocene of Sansan, France) and "Ardea" lignitum (Late Pliocene of Germany) were more probably owls; the latter was apparently close to the modern genus Bubo. Judging from this, the Late Miocene remains from France described as "Ardea" aureliensis should also be restudied.[45] The Messelasturidae, some of which were initially believed to be basal Strigiformes, are now generally accepted to be diurnal birds of prey showing some convergent evolution toward owls. The taxa often united under Strigogyps[46] were formerly placed in part with the owls, specifically the Sophiornithidae; they appear to be Ameghinornithidae instead.[47][48][49]

The ancient fossil owl Palaeoglaux artophoron

For fossil species and paleosubspecies of extant taxa, see the genus and species articles. For a full list of extant and recently extinct owls, see the article List of owl species.

Unresolved and basal forms (all fossil)

  • Berruornis (Late Paleocene of France) basal? Sophornithidae?
  • Strigiformes gen. et sp. indet. (Late Paleocene of Zhylga, Kazakhstan)[50]
  • Primoptynx (Early Eocene of Wyoming, U.S.)[51]
  • Palaeoglaux (Middle-Late Eocene of West-Central Europe) own family Palaeoglaucidae or Strigidae?
  • Palaeobyas (Late Eocene/Early Oligocene of Quercy, France) Tytonidae? Sophiornithidae?[citation needed]
  • Palaeotyto (Late Eocene/Early Oligocene of Quercy, France) Tytonidae? Sophiornithidae?[citation needed]
  • Strigiformes gen. et spp. indet. (Early Oligocene of Wyoming, U.S.)[45]
  • Ypresiglaux (Early Eocene of Essex, United Kingdom and Virginia, U.S.)[52]

Ogygoptyngidae

[edit]
  • Ogygoptynx (Middle/Late Paleocene of Colorado, U.S.)

Protostrigidae

[edit]
  • Eostrix (Early Eocene of United States, Europe, and Mongolia). E. gulottai is the smallest known fossil (or living) owl.[53]
  • Minerva (Middle – Late Eocene of western U.S.) formerly Protostrix, includes "Aquila" ferox, "Aquila" lydekkeri, and "Bubo" leptosteus
  • Oligostrix (mid-Oligocene of Saxony, Germany)

Sophiornithidae

[edit]
  • Sophiornis

Tytonidae

[edit]
  • Genus Tyto – the barn owls, grass owls, and masked owls, stand up to 500 mm (20 in) tall; some 15 extant species and possibly one recently extinct
  • Genus Phodilus – the bay owls, two to three extant species and possibly one recently extinct

Fossil genera

  • Nocturnavis (Late Eocene/Early Oligocene) includes "Bubo" incertus
  • Selenornis (Late Eocene/Early Oligocene) – includes "Asio" henrici
  • Necrobyas (Late Eocene/Early Oligocene – Late Miocene) includes "Bubo" arvernensis and Paratyto
  • Prosybris (Early Oligocene? – Early Miocene)

Placement unresolved

  • Tytonidae gen. et sp. indet. "TMT 164" (Middle Miocene) – Prosybris?

Strigidae

[edit]
A long-eared owl (Asio otus) in an erect pose
The laughing owl (Ninox albifacies), last seen in 1914
  • Genus Aegolius – the saw-whet owls, four species
  • Genus Asio – the eared owls, eight species
  • Genus Athene – two to four species (depending on whether the genera Speotyto and Heteroglaux are included or not)
  • Genus Bubo – the horned owls, eagle-owls and fish-owls; paraphyletic with the genera Nyctea, Ketupa, and Scotopelia, some 25 species
  • Genus Glaucidium – the pygmy owls, about 30–35 species
  • Genus Gymnasio – the Puerto Rican owl
  • Genus Gymnoglaux – the bare-legged owl or Cuban screech-owl
  • Genus Lophostrix – the crested owl
  • Genus Jubula – the maned owl
  • Genus Megascops – the screech owls, some 20 species
  • Genus Micrathene – the elf owl
  • Genus Ninox – the Australasian hawk-owls or boobooks, some 20 species
  • Genus Otus – the scops owls; probably paraphyletic, about 45 species
  • Genus Pseudoscops – the Jamaican owl
  • Genus Psiloscops – the flammulated owl
  • Genus Ptilopsis – the white-faced owls, two species
  • Genus Pulsatrix – the spectacled owls, three species
  • Genus Strix – the earless owls, about 15 species, including four previously assigned to Ciccaba
  • Genus Surnia – the northern hawk-owl
  • Genus Taenioptynx - the collared owlet
  • Genus Uroglaux – the Papuan hawk-owl
  • Genus Xenoglaux – the long-whiskered owlet

Extinct genera

Fossil genera

  • Mioglaux (Late Oligocene? – Early Miocene of West-Central Europe) – includes "Bubo" poirreiri
  • Intutula (Early/Middle – ?Late Miocene of Central Europe) – includes "Strix/Ninox" brevis
  • Alasio (Middle Miocene of Vieux-Collonges, France) – includes "Strix" collongensis
  • Oraristrix – the Brea owl (Late Pleistocene)

Placement unresolved

  • "Otus/Strix" wintershofensis: fossil (Early/Middle Miocene of Wintershof West, Germany) – may be close to extant genus Ninox[45]
  • "Strix" edwardsifossil (Middle/Late? Miocene)
  • "Asio" pygmaeusfossil (Early Pliocene of Odesa, Ukraine)
  • Strigidae gen. et sp. indet. UMMP V31030 (Late Pliocene) – Strix/Bubo?
  • the Ibizan owl, Strigidae gen. et sp. indet.prehistoric[54]

Symbolism and mythology

[edit]

Africa

[edit]

Among the Kikuyu of Kenya, it was believed that owls were harbingers of death. If one saw an owl or heard its hoot, someone was going to die. In general, owls are viewed as harbingers of bad luck, ill health, or death. The belief is widespread even today.[55]

South Asia

[edit]

In Hinduism, an owl is the vahana (mount) of the goddess Lakshmi, especially in the eastern region of India.[56] Owls are considered a symbol of wealth, prosperity, wisdom, good luck, and fortune. This is the reason why Owls are seen with Lakshmi, who is also the goddess of fortune, wealth, and prosperity. At the same time, owls are also associated with evil times in Hinduism. At times, Chamunda (fearsome form of Chandi) is depicted seated on an owl, her vahana (mount or vehicle). Hindus believe that owls are messengers of death.[57][better source needed]

East Asia

[edit]

China

[edit]

In China, owls are traditionally considered a sign of evil or misfortune, but are also seen as a symbol of good luck in military affairs, a symbol of protection and warding off evil spirits at funerals[58], and even as the incarnation of ancestors.[59] Owls are one of the most common birds in carvings and paintings on bronze, pottery, and funerary objects.

Japan

[edit]

In Japan, owls are regarded as lucky,[60] although in ancient times they were associated with death.[61]

Mesopotamia

[edit]

In Sumerian, Akkadian, and Babylonian culture, the owl was associated with Lilith.[62]

Europe

[edit]

The modern West generally associates owls with wisdom and vigilance. This link goes back at least as far as Ancient Greece, where Athens, noted for art and scholarship, and Athena, Athens' patron goddess and the goddess of wisdom, had the owl as a symbol.[63] Marija Gimbutas traces veneration of the owl as a goddess, among other birds, to the culture of Old Europe, long pre-dating Indo-European cultures.[64]

In medieval Europe, the owl was often used with more negative symbolism. The bird was associated with darkness, uncleanliness, and mourning. The bird was linked to the bubonic plague. Owls were even used as anti-Semitic caricatures of Jews.[65][66]

T. F. Thiselton-Dyer, in his 1883 Folk-lore of Shakespeare, says that

from the earliest period it has been considered a bird of ill-omen," and Pliny tells us how, on one occasion, even Rome itself underwent a lustration, because one of them strayed into the Capitol. He represents it also as a funereal bird, a monster of the night, the very abomination of humankind. Virgil describes its death howl from the top of the temple by night, a circumstance introduced as a precursor of Dido's death. Ovid, too, constantly speaks of this bird's presence as an evil omen; and indeed the same notions respecting it may be found among the writings of most of the ancient poets.[67]

Native American cultures

[edit]

People often allude to the reputation of owls as bearers of supernatural danger when they tell misbehaving children, "the owls will get you",[68] and in most Native American folklore, owls are a symbol of death.

According to the Apache and Seminole tribes, hearing owls hooting is considered the subject of numerous "bogeyman" stories told to warn children to remain indoors at night or not to cry too much, otherwise the owl may carry them away.[69][70] In some tribal legends, owls are associated with spirits of the dead, and the bony circles around an owl's eyes are said to comprise the fingernails of apparitional humans. Sometimes owls are said to carry messages from beyond the grave or deliver supernatural warnings to people who have broken tribal taboos.[71]

The Aztecs and the Maya, along with other natives of Mesoamerica, considered the owl a symbol of death and destruction. In fact, the Aztec god of death, Mictlantecuhtli, was often depicted with owls.[72] There is an old saying in Mexico that is still in use:[73] Cuando el tecolote canta, el indio muere ("When the owl cries/sings, the Indian dies"). The Popol Vuh, a Mayan religious text, describes owls as messengers of Xibalba (the Mayan "Place of Fright").[74]

The belief that owls are messengers and harbingers of the dark powers is also found among the Hočągara (Winnebago) of Wisconsin.[75] When in earlier days the Hočągara committed the sin of killing enemies while they were within the sanctuary of the chief's lodge, an owl appeared and spoke to them in the voice of a human, saying, "From now on, the Hočągara will have no luck." This marked the beginning of the decline of their tribe.[76] An owl appeared to Glory of the Morning, the only female chief of the Hočąk nation, and uttered her name. Soon after, she died.[77][78]

According to the culture of the Hopi, a Uto-Aztec tribe, taboos surround owls, which are associated with sorcery and other evils.[citation needed]

The Ojibwe tribes, as well as their Aboriginal Canadian counterparts, used an owl as a symbol for both evil and death. In addition, they used owls as a symbol of very high status of spiritual leaders of their spirituality.[79]

The Pawnee tribes viewed owls as the symbol of protection from any danger within their realms.[79]

The Puebloan peoples associated owls with Skeleton Man, the god of death and the spirit of fertility.[79]

The Yakama tribes use an owl as a totem, to guide where and how forests and natural resources are useful with management.[79]

Rodent control

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A purpose-built owl-house or owlery at a farm near Morton on the Hill, England (2006)

Encouraging natural predators to control rodent population is a natural form of pest control, along with excluding food sources for rodents. Placing a nest box for owls on a property can help control rodent populations (one family of hungry barn owls can consume more than 3,000 rodents in a nesting season) while maintaining the naturally balanced food chain.[80]

Conservation issues

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The snowy owl is very endangered in Scandinavia[81] and Finland, where it is found only in northern Lapland.[82]

Almost all owls are listed in Appendix II of the international CITES treaty (the Convention on Illegal Trade in Endangered Species of Wild Fauna and Flora) with four species listed in Appendix I. Although owls have long been hunted, a 2008 news story from Malaysia indicates that the magnitude of owl poaching may be on the rise. In November 2008, TRAFFIC reported the seizure of 900 plucked and "oven-ready" owls in Peninsular Malaysia. Said Chris Shepherd, Senior Programme Officer for TRAFFIC's Southeast Asia office, "This is the first time we know of where 'ready-prepared' owls have been seized in Malaysia, and it may mark the start of a new trend in wild meat from the region. We will be monitoring developments closely." TRAFFIC commended the Department of Wildlife and National Parks in Malaysia for the raid that exposed the huge haul of owls. Included in the seizure were dead and plucked barn owls, spotted wood owls, crested serpent eagles, barred eagles, and brown wood owls, as well as 7,000 live lizards.[83]

In addition to hunting, other threats to owl populations are habitat loss, pesticides, viruses, and vehicle collisions.[84][85]

References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
Owls are nocturnal in the order Strigiformes, comprising approximately 200 divided into two families: the typical owls (Strigidae) and the barn owls (Tytonidae). Found on every continent except , they are renowned for their silent flight—largely unique among birds of prey—large forward-facing eyes, and specialized adaptations that make them efficient nighttime hunters. These birds exhibit remarkable anatomical features suited to low-light conditions and stealthy predation. Their eyes are tubular and fixed in place, providing enhanced vision in dim light—up to 100 times more sensitive than human vision—while a protects them from debris during hunts. Asymmetrical ear openings and a concave facial disk act as sound funnels, allowing owls to pinpoint prey locations with precision, even under snow or cover. Their flight feathers feature serrated (comb-like) leading edges on the primaries, fringed trailing edges, and soft velvety surfaces that dampen turbulence and reduce noise, enabling near-silent flight and preventing detection by prey. Additionally, their zygodactyl feet—with two toes forward and two backward—deliver a powerful grip on struggling quarry. Owls occupy diverse habitats worldwide, from dense forests and grasslands to urban edges and deserts, often nesting in tree cavities, abandoned buildings, or ground burrows. As apex or mesopredators, they primarily feed on small mammals like and rabbits, alongside birds, , reptiles, and occasionally , helping regulate pest populations in ecosystems. Most species are monogamous and territorial, with breeding seasons varying by region; females lay clutches of 2–12 eggs, which they incubate while males provide food. Though many are nocturnal, some, like the , hunt by day, showcasing the order's adaptability.

Taxonomy and evolution

Fossil record

The fossil record of owls (Strigiformes) begins in the late epoch, approximately 60 million years ago, shortly after the Cretaceous-Paleogene that eliminated non-avian dinosaurs. The earliest known strigiform is Berruornis orbisantiqui, represented by fragmentary remains including a from deposits near , , indicating a large-bodied, owl-like comparable in size to modern eagle owls. This species, assigned to the extinct family Sophiornithidae, exhibits transitional features such as a robust structure bridging primitive avian traits and more derived strigiform morphology, suggesting early predatory adaptations in forested Paleocene environments. Another pivotal early taxon is Ogygoptynx wetmorei from mid- to late-Paleocene fissure fillings in southwestern , , dating to around 60 million years ago and recognized as the oldest named owl genus in the . This species, the type of the extinct family Ogygoptyngidae—considered among the earliest true owls— is primarily known from a well-preserved , though referred cranial material reveals primitive strigiform skull features, including large orbital regions and a basicranial structure lacking advanced auditory specializations seen in later forms. The hypotarsus of the shows eroded but distinct crests, indicative of grasping capabilities suited to perching and predation, while overall limb proportions suggest initial adaptations for agile flight in a post-extinction recovery landscape. During the Eocene epoch (approximately 56–34 million years ago), the Protostrigidae emerged as a diverse group of proto-owls across North America, Europe, and Asia, characterized by intermediate traits such as strong first and second toes for prey capture and a widened medial condyle on the tibiotarsus for enhanced leg stability. Fossils like those of Eostrix and Minerva from early Eocene sites, including the Green River Formation in Wyoming, display symmetrical temporal fenestrae (ear openings), a primitive condition implying diurnal hunting rather than the nocturnal sound localization enabled by later asymmetry. Bone structures, including elongate wing elements and a furcula adapted for flight muscle attachment, provide evidence of evolutionary refinements in aerial predation, transitioning from diurnal, hawk-like behaviors to more specialized nocturnal strategies in subsequent lineages. The Sophiornithidae, spanning the Paleocene to early , represent additional transitional forms with chicken-sized bodies and predatory morphologies, as seen in European fossils like those from the Phosphorites du in . These birds bridge early strigiforms and more advanced owls through features such as a flattened internal condyle on the tibiotarsus, differing from later taxa, and overall skeletal proportions indicating a shift toward silent flight via fringed primary feathers inferred from bone imprints. This in structures—combining primitive avian flight capabilities with emerging raptor-like grasping—underscores the gradual development of owl-specific adaptations for low-light hunting, ultimately giving rise to modern families like Tytonidae and Strigidae.

Classification and families

Owls belong to the order Strigiformes, which is divided into two extant families: Tytonidae, comprising barn owls, and Strigidae, encompassing all other owls, commonly referred to as true owls. The family Tytonidae includes two genera: Tyto (barn owls, grass owls, and masked owls; 17 species) and Phodilus (bay owls; 2 species), totaling 19 species. Strigidae is more diverse, containing 30 genera and 229 species, resulting in a total of 248 extant owl species worldwide (as of 2025). Key morphological distinctions between the families include the heart-shaped facial discs and comb-like serrations on the middle toe of Tytonidae species, which aid in grooming facial feathers, in contrast to the rounder facial discs and generally stronger, more robust talons of Strigidae species. Representative examples include the common barn owl (Tyto alba) from Tytonidae and the Eurasian eagle-owl (Bubo bubo) from Strigidae. Within Strigidae, several subfamilies are recognized, such as Striginae, which includes typical smaller owls like screech owls and wood owls, and Buboninae, encompassing larger such as eagle-owls and fishing owls. Recent taxonomic revisions in owl classification have been driven by , revealing in some Strigidae genera and leading to splits or lumping, particularly in the 2010s and 2020s, such as re-evaluations of relationships within the typical owl clades.

Physical description

Size and morphology

Owls exhibit a wide range of sizes across their more than 200 species, reflecting adaptations to diverse ecological niches. The smallest owl is the (Micrathene whitneyi), which measures 12–14 cm in length and weighs 35–55 g, with a wingspan of approximately 27–33 cm. At the opposite end of the spectrum, the (Bubo blakistoni) represents one of the largest, reaching lengths of 60–75 cm and weights up to 4.6 kg, supported by a wingspan of 178–190 cm. Wingspan variations further highlight this diversity; for instance, pygmy owls (Glaucidium spp.) have wingspans around 30 cm, while the great gray owl (Strix nebulosa) extends to 137–153 cm. In many species, manifests as females being larger than males, often by 20–30% in body mass. The general body morphology of owls is characterized by a compact, rounded that aids in maneuverability and silent flight, paired with a disproportionately large head that accommodates their fixed, tubular eyes. This structure includes a short for balance, a relatively short but highly flexible , and powerful legs equipped with strong, zygodactyl toes for grasping prey. The rounded body form contributes to their streamlined profile during low-altitude flights. Skeletal features in owls emphasize lightweight construction and enhanced mobility. The skull is reinforced through specialized articulations between the cervical vertebrae and the occipital region, enabling head rotation of up to 270 degrees without vascular compromise. The furcula, formed by the fusion of the clavicles, provides structural stability to the pectoral girdle during flight. Compared to many other birds, owls possess a reduced sternal spine on the keel-shaped sternum, which may facilitate a lower center of gravity and quieter wingbeats. Overall, the owl skeleton constitutes about 7–9% of body weight, with numerous fused elements enhancing rigidity while minimizing mass.

Plumage and coloration

Owls possess specialized feather structures adapted for both functionality and concealment. Their are notably soft and feature fringed edges, with comb-like serrations on the leading edges of the primaries that reduce air turbulence during flight. These adaptations contribute to the owls' characteristic silent flight, enabling stealthy approaches to prey. Contour feathers include barbules near the skin, providing insulation against extremes. The of owls typically exhibits mottled patterns in shades of brown, gray, and white, which serve as cryptic against natural backgrounds such as bark and foliage. These colorations disrupt the bird's outline, making it difficult for predators or prey to detect them during rest or hunting. Variations occur across and individuals, including sexual differences where females may show more barring or tones in some cases, and age-related changes such as juveniles often displaying paler, fluffier with finer streaking compared to adults. A distinctive feature of owl is the , composed of stiff, radiating s that form a disc around the eyes to funnel sound toward the ears. In the Tytonidae family, such as barn owls, this disc is heart-shaped, while in the Strigidae family, encompassing most other owls, it is more rounded. These arrangements enhance auditory localization without compromising the overall provided by the surrounding mottled patterns. Owls undergo annual molting, typically post-breeding season, where feathers are replaced over a period of up to three months in a sequential pattern to preserve flight capability and effectiveness. are shed gradually—often from the innermost primaries outward, except in barn owls where the pattern starts centrally—ensuring no large gaps form that could expose the bird or hinder aerial maneuverability. This methodical replacement maintains the mottled coloration and insulating properties throughout the process.

Sexual dimorphism

Owls exhibit reverse sexual size dimorphism (RSD), a characteristic pattern in which females are larger than males across most species in the order Strigiformes. This dimorphism is particularly pronounced in the family Strigidae (true owls), where females can be up to 30% heavier than males, as seen in the great horned owl (Bubo virginianus), with females averaging 1.7 kg compared to 1.3 kg in males. In contrast, the family Tytonidae (barn owls) shows a less extreme degree of RSD, with female body mass approximately 18% greater than males based on Storer's index calculations from measurements of weight and wing dimensions. The larger female size is primarily linked to the physiological demands of egg production, which requires substantial energy reserves, and to the physical capacity for defending territories and nests against predators. While size differences are consistent, plumage coloration dimorphism is more variable and often subtle, serving adaptive roles in and . In many , females possess duller, more mottled plumage to blend with nesting substrates during incubation, reducing visibility to threats; for instance, female barn owls (Tyto alba) exhibit darker, more spotted underparts compared to the paler males. Rare exceptions include the (Bubo scandiacus), which displays minimal overall dimorphism in size relative to other strigiforms but marked color differences, with females retaining brown barring for ground camouflage while males are nearly pure white. Behaviorally, RSD facilitates a sexual division of labor, with smaller, more agile males specializing in hunting small, elusive prey to provision incubating females and chicks, enhancing reproductive efficiency. This pattern is more evident in Strigidae, where prey size variation drives greater size divergence, than in Tytonidae, which target similar small mammals regardless of sex. Evolutionarily, RSD in owls has arisen through favoring sex-specific adaptations for reproduction, including female size for brooding large clutches and male nimbleness for foraging, rather than for ornamental traits.

Physiological adaptations

Flight and feathers

Owls achieve remarkably silent flight through specialized adaptations in their feathers and overall morphology, which minimize aerodynamic during nocturnal . The primary feathers feature serrated leading edges that disrupt and reduce turbulence-generated by breaking up large vortices into smaller, less audible ones. These serrations, resembling comb-like structures, effectively lower the intensity of broadband produced by air passing over the surface. Complementing this, the trailing edges of the are fringed and covered in a velvety down, which absorbs residual waves and dampens frictional between feathers during flapping. This combination results in flight levels up to 10-20 decibels lower than those of comparably sized non-owl birds, enabling stealthy approaches to prey. Owls are unique among birds of prey (raptors) in possessing these highly effective silent flight adaptations; most other raptors, such as hawks, eagles, falcons, and vultures, lack them and produce audible wing noise during flight. Among owl species, the Barn Owl (Tyto alba) is widely regarded as having particularly silent flight. The wing structure of owls further supports efficient, low-noise flight suited to their predatory lifestyle. Broad, rounded wings with a low aspect ratio and reduced wing loading—typically 0.2–0.5 grams per square centimeter across species—allow for slow gliding speeds as low as 2-5 meters per second and enhanced maneuverability in cluttered forest environments. This design provides a high lift-to-drag ratio, facilitating sustained hovering or near-hovering during prey detection without excessive energy expenditure. In contrast to diurnal raptors like hawks, which possess pointed, high-aspect-ratio wings optimized for high-speed dives exceeding 50 meters per second, owl wings emphasize stealth and control over velocity. These adaptations collectively enhance energy efficiency for nocturnal activities, as the low minimizes the power required for prolonged low-speed flight, conserving metabolic resources during extended hunting bouts. By reducing drag and noise without compromising lift, owls can maintain silent patrols over territories for hours, a critical advantage in energy-limited nighttime .

Vision

Owls have tubular-shaped eyes, a morphology that contrasts with the spherical eyes of most vertebrates and enhances light-gathering capacity for nocturnal activity. These eyes are disproportionately large relative to body size, comprising up to 5% of an owl's body weight compared to about 1% in humans, allowing for a larger and improved low-light performance. This large eye size constrains the available cranial space for the brain, resulting in relatively small brain volume—often occupying one-third or less of the skull—compared to birds with higher encephalization quotients. Consequently, owls exhibit average or below-average cognitive abilities among birds, relying on instinctual sensory processing rather than flexible cognition, with poor performance in captive tests of problem-solving such as puzzle tasks relative to corvids or parrots. The tubular structure, supported by a bony ring called the scleral ossicle, fixes the eyes in place within the , preventing but providing structural stability for sharp focus. The retina of an owl's eye features a high density of rod photoreceptor cells, which are specialized for detecting low levels of light and motion in dim conditions, enabling vision in environments as dark as 0.001 lux. In contrast, cone cells, responsible for color discrimination and detail in bright light, are far less numerous—often comprising less than 10% of photoreceptors—leading to diminished color perception overall. This rod-dominated retina prioritizes sensitivity over acuity, with owls exhibiting dichromatic color vision primarily sensitive to blue and green wavelengths around 437 nm and 547 nm, as demonstrated in behavioral discrimination tests on tawny owls. Owls' visual field spans approximately 110 degrees horizontally, with a binocular overlap of about 50 degrees that facilitates for prey assessment. Due to the immobility of their eyes, owls compensate by rotating their heads up to 270 degrees, leveraging specialized neck vertebrae to scan surroundings effectively. Compared to diurnal birds, owls exhibit limitations in and color resolution; their maximum resolution is roughly equivalent to 20/60 in terms during daylight, with poor fine-detail detection at distances beyond a few meters due to the elongated and low . This trade-off favors nocturnal hunting efficiency but results in functional for reds and , restricting their chromatic range to shorter wavelengths.

Hearing

Owls possess asymmetrical structures that enhance their ability to localize sounds in three dimensions, particularly for vertical . The openings are unequally sized and positioned at different heights on the , with one typically higher and more vertical than the other, allowing for precise detection of interaural time differences (ITDs) and intensity differences (IIDs) that vary with sound elevation. This asymmetry is most pronounced in species like barn owls ( alba), where the left opening is often larger and the right one more offset, optimizing cues for pinpointing prey from above or below. The , composed of specialized feathers, funnels sound waves toward the ears, amplifying low-level noises and aiding in directional focusing. Owls exhibit acute sensitivity to low frequencies, spanning approximately 200 Hz to 12 kHz, which enables detection of subtle rustling or movement from concealed prey. This range is particularly tuned for sounds in the 4-8 kHz band, where thresholds can reach as low as -14 dB SPL, allowing owls to hear prey under layers of , leaves, or that would muffle higher frequencies. Such sensitivity surpasses that of many diurnal birds, prioritizing the faint, noises produced by small mammals over ultrasonic or infrasonic extremes. In complete darkness, owls' hearing provides superior prey localization compared to other senses, enabling strikes with remarkable precision. For instance, barn owls can pinpoint a source within 1-2 degrees of accuracy in and , even when visual cues are absent, as demonstrated in controlled acoustic tests. This capability allows them to accurately target hidden or obscured prey, such as voles beneath , by integrating temporal and cues without relying on sight. Neural processing in owls features enlarged auditory centers in the , particularly the , which map spatial sound cues into a topographic representation of auditory space. Dedicated pathways separately analyze ITDs in the nucleus laminaris and IIDs in the lateral superior olive, converging to form neurons with highly selective receptive fields for specific directions. This specialized architecture, evolved for nocturnal hunting, ensures rapid and precise localization by encoding elevation through spectral filtering and via binaural disparities.

Talons and beak

Owls are equipped with powerful talons that serve as primary tools for capturing and subduing prey. These consist of sharp, curved claws on zygodactyl feet, featuring four toes arranged with two facing forward and two backward for a secure grip; like ospreys, the outer toe is reversible among raptors, allowing owls to shift to an anisodactyl configuration (three forward, one back) for perching or enhanced opposability during hunting. This adaptability enables precise piercing and holding, with large species like the (Bubo virginianus) exerting up to 500 pounds per square inch (psi) of pressure to crush bones or sever spinal cords. The complements these talons as a specialized structure for processing food, characterized by a short, downward-curving with a hooked tip and sharp cutting edges, but lacking teeth typical of mammals. This design facilitates tearing flesh from larger prey items, though owls predominantly swallow smaller prey whole, relying on an expandable and to handle ingestion without extensive mastication. Following digestion, the beak indirectly aids in prey preparation by allowing initial dismemberment when necessary, contributing to the formation of pellets—compact masses of indigestible remains like bones, fur, and feathers. These materials are compressed in the and regurgitated through the mouth approximately 12–18 hours after feeding, providing a non-invasive method for waste expulsion. Talons and s exhibit variations across owl taxa, reflecting dietary specializations. Members of the Strigidae family, which includes most owl species, often possess larger, more robust talons suited for tackling sizable mammalian or avian prey, enhancing their piercing capability compared to the generally smaller-clawed Tytonidae. morphology correlates with prey type, with broader, stronger bills in species consuming harder foods, while fish-specializing owls in Strigidae, such as the (Ketupa blakistoni), feature particularly thick talons for grasping slippery aquatic targets.

Distribution and habitat

Global range

Owls occupy a near-cosmopolitan distribution across all continents except and are absent from some remote oceanic islands, reflecting their adaptability to diverse environments. With approximately 254 recognized worldwide, their highlights a concentration of diversity in and subtropical regions, where evolutionary pressures have favored . For instance, supports around 52 , underscoring the ' role as hotspots for owl and variety. Continental patterns reveal varying richness: north of hosts 19 , primarily in temperate and boreal zones, while harbors about 49 and over 100, with the latter's extensive landmass and gradients driving higher counts. Regional endemics exemplify localized evolution, such as the red owl ( soumagnei), also known as the Madagascar grass owl, which is confined to the island's forests. These distributions are shaped by historical biogeographic events and current ecological limits. Post-glacial recolonization has influenced European ranges, with species like the barn owl (Tyto alba) expanding northward from Iberian refugia after the around 20,000 years ago. Human activities have induced contractions in isolated populations, as seen in the little owl (Athene noctua) across parts of due to and agricultural intensification over recent decades. Most owls are non-migratory residents, but exceptions include the (Asio flammeus), which performs seasonal migrations across continents in response to prey availability.

Habitat types

Owls occupy a wide array of habitats worldwide, ranging from dense forests to open arid regions and aquatic environments, with adaptations enabling them to exploit specific ecological niches. In forested areas, species such as the barred owl (Strix varia) thrive in mature mixed woodlands, particularly deciduous and coniferous stands near water bodies, where large trees provide essential cover and prey abundance. In contrast, burrowing owls (Athene cunicularia) are specialized for open, arid landscapes like deserts, grasslands, and prairies, utilizing sparsely vegetated expanses that facilitate ground-dwelling and burrowing behaviors. Wetland and riparian zones are critical for fish owls, including the Blakiston's fish owl (Bubo blakistoni), which inhabit dense forests along rivers, lakes, and non-freezing streams, relying on proximity to water for foraging on aquatic prey. Microhabitats play a pivotal role in owl survival, particularly for roosting and nesting, with preferences varying by species and family. Many owls, such as those in the Strigidae family, roost in tree cavities, cliff ledges, or dense foliage during the day to avoid detection, while barn owls (Tyto alba) often select artificial structures like barns, silos, or church steeples for seclusion. Nesting sites similarly reflect habitat versatility; Tytonidae species like barn owls favor open cavities in buildings or trees without extensive nest-building, whereas others, including burrowing owls, excavate or repurpose ground burrows originally dug by mammals. This microhabitat use allows owls to persist in fragmented landscapes, though loss of such sites can limit populations. Owls demonstrate remarkable altitudinal flexibility, occurring from sea level to elevations exceeding 2,500 meters in mountainous regions like the , where species such as the Himalayan owl (Strix nivicolum) inhabit coniferous and forests between 1,000 and 2,650 meters. Some generalists, including the (Bubo bubo), extend to over 4,000 meters in alpine zones, adapting to varying oxygen levels and temperatures. Urban environments also support adaptable species like the (Athene noctua), which occupies parks, gardens, and suburban areas with a mix of open ground and structures, tolerating human proximity where prey remains available. Habitat specialization underscores the diversity within owl taxa, with some species tightly linked to particular ecosystems while others exhibit broad tolerances. The , or Tengmalm's owl (Aegolius funereus), is highly specialized for old-growth boreal coniferous forests, preferring dense stands of and with large trees for nesting cavities and subnivean prey access. In opposition, the barn owl serves as a generalist, occurring across grasslands, farmlands, and woodlands globally, as long as open areas adjoin roosting sites. These specializations influence vulnerability to habitat alteration, with forest specialists facing greater threats from than generalists in agricultural mosaics.

Behavior and ecology

Daily activity and movement

Owls exhibit primarily nocturnal or crepuscular circadian rhythms, with the majority active during twilight or nighttime hours to align with their hunting and sensory adaptations. Approximately 69% of owl species hunt nocturnally, 22% are crepuscular, and only 3% are diurnal, reflecting evolutionary pressures for low-light foraging efficiency. A notable exception is the (Surnia ulula), which is predominantly diurnal, hunting actively during daylight in boreal forests due to its reliance on visual prey detection similar to diurnal raptors. During daylight, owls roost to conserve energy and avoid detection, typically in solitary positions or, in some species like the (Asio otus), in communal groups of up to several dozen individuals during winter for and predator vigilance. Roost sites often feature dense foliage or cavities where plumage provides effective against daytime predators such as hawks or corvids. Daily movement patterns include excursions that can span up to 10 km, as observed in species like the (Strix occidentalis), allowing access to dispersed resources while returning to secure roosts. Territoriality is maintained year-round, particularly in resident species, through defensive postures—such as ruffling feathers to appear larger and assuming a stance—and vocalizations that signal boundaries and deter intruders. Home range sizes typically vary from 1 to 10 km², influenced by prey availability; for instance, barn owls (Tyto alba) show smaller ranges in high-prey areas (around 1–6 km²) and larger ones (up to 20 km²) where resources are scarce. Movement patterns differ by region and species: many tropical owls, such as the (Pulsatrix perspicillata), remain sedentary within stable forest habitats year-round, exhibiting minimal dispersal due to consistent food supplies. In contrast, northern species like the (Bubo scandiacus) display irruptive migrations, sporadically traveling hundreds of kilometers southward during food shortages, such as lemming population crashes in the , rather than following predictable routes.

Hunting strategies

Owls employ a variety of hunting modes adapted to their environments and prey availability, primarily relying on stealth and precision to capture elusive targets. The most common strategy among many species is the perch-and-pounce method, where the owl perches motionless on an elevated vantage point, listens for prey sounds, and then silently glides or drops onto the target below. This ambush tactic leverages the owl's asymmetrical ear structure and to pinpoint noise sources with millimeter accuracy, even in complete darkness. In contrast, some diurnal or crepuscular species, such as the (Asio flammeus), use a hover-and-strike approach, patrolling low over open grasslands while hovering briefly to scan and then diving sharply to seize prey. Burrowing owls (Athene cunicularia), adapted to ground-level habitats, often employ ground-probing or on foot, walking, hopping, or running to pursue and capture prey directly. Prey detection in owls integrates acute hearing for initial localization with vision for final confirmation, enabling strikes with high precision. Hearing provides the first cue through sensitivity to low-amplitude rustling sounds in the 5-10 kHz range, allowing owls to triangulate prey positions vertically and horizontally within 1-2 meters, even under cover like snow or vegetation. Vision then refines the approach during descent, with owls adjusting flight paths mid-strike to compensate for prey movement, achieving accuracy to within 60 cm in controlled studies of barn owls (Tyto alba). This sensory fusion is critical in low-light conditions, where auditory cues dominate, and visual input ensures talon deployment aligns precisely with the target. Foraging efficiency varies by species and conditions but generally ranges from 20-50% success per strike attempt, reflecting the challenges of nocturnal hunting and evasive prey. Barn owls, for instance, succeed in about 25-30% of perch-initiated attacks, with rates improving when auditory signals persist during approach. Eastern screech-owls (Megascops asio) achieve higher rates, capturing up to 56% of attempts through repeated pounces after initial misses. Adaptations enhancing efficiency include silent that minimize detection noise and the ability to hover or circle persistently, increasing encounter opportunities without alerting prey. Differences in hunting strategies are pronounced between owl families, with Tytonidae (barn owls) favoring more aerial pursuits and Strigidae emphasizing ambush tactics. Barn owls often quarter fields in low, buoyant flight to intercept moving prey mid-air, capitalizing on their exceptional directional hearing. In Strigidae, species like great horned owls (Bubo virginianus) predominantly use perch-and-pounce from dense cover, waiting for auditory or visual cues before a sudden descent, which suits forested or varied terrains. These family-specific approaches reduce while optimizing energy use in diverse habitats.

Diet and prey

Owls are predominantly carnivorous predators within the order Strigiformes, with small mammals such as and forming the primary component of their diet in most , often accounting for 60-80% of prey biomass as determined through pellet analysis studies. For instance, in barn owls (Tyto alba), small mammals constitute 74-100% of the diet across numerous regional investigations, highlighting their role as key controllers. Other prey items include birds, , reptiles, amphibians, and occasionally , with dietary specialization evident in certain taxa; fish owls (Ketupa spp.) primarily target aquatic prey like salmonids, while some tropical incorporate more reptiles. As opportunistic carnivores occupying higher trophic levels, owls exhibit dietary flexibility influenced by prey availability and seasonality. In temperate regions, small owls such as little owls (Athene noctua) shift toward greater insect consumption—up to 12% of the diet—in summer months when abundance peaks, supplementing their mammalian intake during breeding periods. This adaptability ensures nutritional balance, as owls require high-protein diets to support their metabolically demanding lifestyles, including nocturnal activity and reproduction. Pellet regurgitation, a key aspect of their digestive process, allows non-invasive dietary reconstruction; analyses of these indigestible remains have quantified substantial prey volumes, with a single barn owl family consuming 2,000-4,000 items annually to meet energy needs. Prey selection in owls closely correlates with predator body size, enabling efficient capture and consumption relative to their physical capabilities. Larger species, such as Eurasian eagle-owls (Bubo bubo), routinely prey on sizable lagomorphs like hares, which can exceed 2 kg, comprising a significant portion of their intake in open habitats. Conversely, diminutive pygmy owls (Glaucidium spp.) target smaller , including beetles and , which form a substantial dietary fraction during warmer seasons, reflecting their limited gape and hunting constraints. This size-based partitioning minimizes and underscores the ecological diversity within Strigiformes.

Breeding and reproduction

Owls exhibit predominantly mating systems, with pairs often forming long-term bonds that can last multiple breeding seasons, though some display or sequential under favorable conditions. This supports cooperative , where males perform courtship displays such as food presentations to attract and maintain pair bonds. , with females typically larger than males, facilitates division of labor by enabling females to better cover eggs and broods while males focus on agile hunting. Breeding seasonality varies by latitude and environmental cues; in temperate zones, most species initiate reproduction in late winter or spring (January to April), aligning with increasing prey availability, whereas tropical owls often breed year-round or opportunistically in response to food abundance. Clutch sizes generally range from 2 to 7 eggs, laid at intervals of 1-3 days, with the number influenced by prey density—larger clutches occur in resource-rich years to maximize reproductive output. Females alone incubate the eggs for 20 to 35 days, beginning with the first egg laid, during which time males provision the female with food to sustain her energy demands. Most owl species do not construct nests, instead utilizing natural tree cavities, cliffs, abandoned nests of other birds, ground burrows dug by mammals, or even artificial structures for shelter. Eggs are laid directly on the substrate without added lining, reflecting an to opportunistic nesting that conserves for . Upon hatching, altricial owlets are brooded by the female for warmth and protection, while the male delivers prey to the nest, with both parents increasingly sharing feeding duties as chicks grow. Fledging occurs after 3 to 10 weeks, depending on species, followed by extended post-fledging care lasting several months, during which parents teach hunting skills and continue provisioning until juveniles achieve independence. is heavily modulated by food availability, with low prey levels leading to reduced sizes, higher nestling mortality, or skipped breeding seasons.

Vocalizations and communication

Owls produce a variety of vocalizations primarily for territorial defense, mate attraction, and alarm signaling, with distinct differences between the two main families: Strigidae (true owls) and Tytonidae (barn owls). In Strigidae, hooting serves as a key territorial call, often performed by males to advertise presence and deter intruders, while Tytonidae species rely more on hissing and screeching for alarm purposes. Pairs of many owl species engage in duets, where males and females alternate calls to strengthen pair bonds and coordinate territory defense. Hooting in Strigidae is characterized by low-frequency sounds that facilitate long-distance transmission, typically carrying 1-2 kilometers in open conditions due to minimal absorption by air. These calls are species-specific, enabling identification and mate recognition; for example, the great horned owl (Bubo virginianus) produces a rhythmic series of deep hoots described as "hoo-h'HOO-hoo-hoo," which males use to claim territories. In contrast, Tytonidae alarms like the barn owl's (Tyto alba) high-pitched screech or "k-r-r-r-r-ick" are sharper and more piercing, designed for immediate threat responses rather than broad advertisement. Beyond vocalizations, owls employ non-vocal signals during threat displays and . Wing-clapping, a sharp snapping sound produced by rapidly bringing the wings together, is common in species like the (Asio flammeus) and barn owl during aerial displays to intimidate rivals or attract mates. Bill-snapping, where the mandibles clash audibly, occurs in both families as a defensive when agitated, such as near nests, and is particularly frequent in nestlings of Strigidae species like the . These vocal and non-vocal signals play crucial ecological roles across life stages and environments. Territorial hoots and duets aid mate attraction by signaling fitness and availability, while chick begging calls—often piercing screams or whimpers—prompt parental provisioning, as seen in juvenile great horned owls that vocalize persistently for food. Call characteristics vary by habitat to optimize transmission; in dense forests, owls like the (Strix aluco) produce lower-frequency, softer hoots to penetrate vegetation with less attenuation, whereas open-habitat species such as barn owls use higher-pitched screeches that carry effectively over distances without obstacles.

Cultural and ecological roles

Symbolism in mythology

Owls have held diverse symbolic roles across ancient mythologies, often embodying wisdom, death, or protection due to their nocturnal habits and piercing gaze. In , the (Athene noctua) served as the sacred companion of , the goddess of wisdom and strategic warfare, symbolizing keen intellect and foresight; this association is evident in Athenian coinage from the 6th century BCE, where the owl appeared alongside Athena's image to represent the city's intellectual prowess and divine favor. Conversely, in Roman traditions, owls were viewed as harbingers of doom, with their hoots foretelling death or disaster, as recorded in accounts of omens preceding the demise of figures like and . In various African folklore traditions, particularly among the Tsonga and in Zimbabwean beliefs, owls similarly signify ill omens, embodying evil spirits or impending calamity, leading to practices where their appearance prompts protective rituals. Yet, in , the owl (uluka) acts as the , or mount, of , the goddess of wealth and prosperity, representing vigilance and the wise stewardship of fortune to ward off misfortune. However, in Indian culture more broadly, owls are often considered symbols of foolishness or stupidity, contrasting with their association with wisdom in Western traditions. Cross-culturally, owls appear in funerary and motifs, linking them to the soul's journey. In ancient Egyptian , the owl hieroglyph (G17) denoted the sound "m" and was tied to through words like mwt (to die), while owls were believed to guide souls in the , possibly inspiring the ba-bird concept of a human-headed soul migrating post-mortem; mummified owls found in tombs reinforced their role as protective intermediaries against illness or judgment. In Mesoamerican, particularly , owls were sacred to Mictlantecuhtli, the skeletal god of the and ruler of Mictlan, often depicted with owl feathers in his headdress to symbolize the bird's silent, night-bound dominion over and the southern direction. In modern symbolism, owls persist in literature and heraldry as emblems of enigma and acuity. William Shakespeare's Macbeth employs the owl's shriek as a "fatal bellman," an ominous signal of King Duncan's murder, drawing on Elizabethan superstitions where an owl's cry over a home heralded death. In heraldry, dating from the late 13th century, the owl typically signifies wisdom and vigilance, depicted affronté (facing forward) to emphasize its watchful nature, as seen in arms like those of the Seyvile family. Psychologically, owls evoke the nocturnal mystery of the , influencing and media as archetypes of hidden knowledge and transformation. Their silent flight and symbolize and , as explored in archetypal analyses where owls bridge the conscious and unconscious realms, fostering themes of amid obscurity in contemporary visual .

Human interactions and rodent control

Humans have long recognized the value of owls, particularly barn owls (Tyto alba), in controlling populations that damage crops and stored grain. A breeding pair of barn owls with their offspring can consume 1,000 to 3,000 annually, making them an effective natural alternative to chemical rodenticides. This predation focuses on small mammals like mice, voles, and rats, which constitute the bulk of their diet. In agricultural contexts, such as vineyards and fields, farmers install nest boxes to attract barn owls and encourage their use as biological control agents. For instance, in California's Napa Valley, winegrowers initiated owl box programs in the 1980s to manage rodent pests, leading to widespread adoption where about 80% of surveyed vineyards report improved control without increased pesticide use. Historically, barn owls have been encouraged to nest in structures like s to curb infestations, a practice that gained traction in the 19th century as awareness of their predatory habits grew. Today, modern eco-farming initiatives expand on this by strategically placing nest boxes in farmlands, which boost local owl populations and enhance biocontrol efficacy. These installations not only reduce damage but also minimize environmental risks associated with rodenticides, such as secondary poisoning of . Studies in agricultural landscapes demonstrate that such programs can significantly lower pest pressures, supporting sustainable pest management. Beyond , owls interact with humans in other ways, including , where larger species like the (Bubo bubo) are trained and flown for hunting or educational purposes. However, these interactions are not without conflicts; habitat loss from urban expansion and fragments owl territories, while vehicle strikes pose a major mortality risk, accounting for many documented owl deaths. Conservation efforts, including programs, help mitigate these issues by bolstering populations in human-modified landscapes.

Conservation status

Owl populations worldwide exhibit varied trends, with approximately 50% of species considered stable and 30% showing declines according to the assessment as of 2025. This assessment covers around 250 species in the orders Strigiformes and Tytonidae, highlighting that while many common species like the maintain steady numbers, others face significant reductions driven primarily by habitat loss. For instance, the (Strix occidentalis caurina) has seen its populations decline by 65-85% across study areas in the since the 1990s, with annual rates of 2-9% in monitored sites. Regionally, owl populations in and are predominantly declining due to agricultural intensification and , as evidenced by the common barn-owl (Tyto alba), which is decreasing in but increasing in parts of . In contrast, some tropical show stability or slight increases within protected areas, such as certain forest owls in Southeast Asian reserves where conservation efforts have bolstered numbers. The snowy owl (Bubo scandiacus), with a global breeding population estimated at 14,000-28,000 adults, has declined by over 30% in the past three generations across its and range. Monitoring owl populations relies on standardized methods to track these trends accurately. Common techniques include pellet analysis to assess diet and territory use, camera traps for detecting occupancy in remote areas, and breeding bird surveys that combine auditory and visual detections during nesting seasons. Additionally, autonomous recording units and mark-recapture protocols provide demographic data on survival and reproduction rates, particularly for elusive . Among vulnerable species, the (Bubo philippensis) is classified as Vulnerable, with a global population estimated at 2,500-10,000 individuals and ongoing declines of 20-35% over three generations due to pressures. Similarly, the ferruginous pygmy-owl (Glaucidium brasilianum) numbers around 20 million mature individuals but is suspected to be decreasing overall. These examples underscore the importance of continued monitoring to inform conservation priorities for at-risk owl taxa.

Threats and protection

Owls face significant threats from human activities that disrupt their habitats and food sources. , primarily driven by for , , and urban development, reduces nesting sites and hunting grounds for many species, particularly old-growth forest dwellers like the . Secondary poisoning from anticoagulant rodenticides, used widely for , accumulates in prey such as , leading to lethal effects in owls that consume contaminated animals; this issue affects species across regions, including barn owls in and spotted owls in . exacerbates these pressures by altering prey availability through shifts in populations and , potentially reducing overwinter survival for boreal species and increasing vulnerability in temperate zones. Additional risks include collisions with human infrastructure and exploitation through . Owls frequently collide with wind turbines, especially during migration, contributing to mortality in raptor populations including barn owls and kestrels, while vehicle strikes pose a common urban hazard, entangling or injuring species like great horned owls. Illegal trade for the pet market targets exotic and rare owls, such as eagle owls in , driven by demand in countries like and , leading to poaching and weakening wild populations despite international prohibitions. Conservation efforts focus on legal protections and targeted interventions to mitigate these threats. In the United States, the safeguards species like the by designating critical habitats and restricting logging in key areas, supporting recovery through federal management plans. Internationally, the regulates trade in vulnerable owls, such as the and certain subspecies, by listing them in appendices that prohibit commercial exploitation of wild-caught individuals. Success stories include habitat preservation for burrowing owls in , where state-funded land acquisitions and relocation programs have stabilized local populations amid urban expansion. In the , restrictions on second-generation rodenticides since the early 2020s, including bans on non-professional use implemented in 2023, have reduced secondary poisoning incidents in owls by limiting environmental persistence of these chemicals.

References

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