Owls are a group of mostly nocturnal, raptorial birds (birds of prey) that are specialized for hunting and feeding on other animals. They constitute the order Strigiformes.
They are easily recognized by a prominent facial disc, a circular arrangement of feathers around each eye. Unlike most birds of prey that have eyes on the sides of their heads, owls have large, forward-facing eyes that provide them with binocular vision. This vision is particularly helpful while hunting in low-light conditions since it gives these birds a remarkable perception of depth.
These birds have exceptional neck mobility, capable of rotating the head up to approximately 270°. Moreover, they are also known for their near-silent flight, made possible by wing feathers with serrated edges and velvety surfaces that reduce noise during flapping of wings.
According to the IOC World Bird List, there are 249 extant species of owls in the world.
Size
The smallest owl of the world, the elf owl (Micrathene whitneyi), is 4.9 to 5.7 in (12.5 to 14.5 cm) long and has a wingspan of about 10.5 in (27 cm). It is also the lightest owl species, weighing only around 1.4 oz (40 g).
The largest and heaviest owls in the world 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 28 in (71 cm) long and have a wingspan of about 75 in (190 cm). They weigh around 148 oz (4.2 kg).
Description
These birds have a large, rounded head with a flat face. Their beak is short, curved, and downward-facing, with a hooked tip that helps them grip, tear, and cut prey. The face is easily recognized by a conspicuous ring of feathers around each eye, called the facial disc. This disc acts like a sound funnel, directing sound waves toward the ears. In many species, such as the barn owl (Tyto alba), the ears are asymmetrically placed, helping them locate the direction of sound more precisely.
Their eyes are fixed in their sockets, so they cannot move them as humans do. Instead, they rotate their head to shift their view, turning the head and neck up to about 270°. This flexibility is enabled by the presence of 14 cervical vertebrae, twice the number found in humans.
More than the beaks, the feet of owls are the most important weapon for catching and killing prey. The tips of the toes are equipped with curved, pointed claws called talons. They are made of keratin, and their sharp, hooked shape helps the owl pierce and lock onto prey.
Plumage
The feathers of owls are large, with many species having soft, serrated edges that reduce air turbulence and minimize sound during flapping of wings. Additionally, the surface of many flight feathers has a velvety texture that absorbs noise.
Their plumage is usually cryptic, having colors and patterns that help them blend into their surroundings. Depending on the habitat, the feathers mimic the tones and textures of tree bark, dry grass, woodland shadows, or snow. Some species, like the long-eared owl (Asio otus), have prominent ear tufts and facial markings for camouflage and visual signaling.
Taxonomy and Phylogeny
According to recent phylogenetic studies, the owl order, Strigiformes, is most closely related to the group Accipitrimorphae, which includes hawks and their relatives, as well as New World vultures.1 All living species of owls are classified under 2 families and 25 genera.
Family: Tytonidae (Barn owls)
Genus: Tyto
Species: Tyto tenebricosa (Greater sooty owl)
Species: Tyto multipunctata (Lesser sooty owl)
Species: Tyto inexspectata (Minahasa masked owl)
Species: Tyto nigrobrunnea (Taliabu masked owl)
Species: Tyto sororcula (Moluccan masked owl)
Species: Tyto manusi (Manus masked owl)
Species: Tyto aurantia (Golden masked owl)
Species: Tyto novaehollandiae (Australian masked owl)
Owls are found on all continents except Antarctica and a few remote oceanic islands, such as the Pitcairn Islands2 (South Pacific) and Tristan daCunha3 (South Atlantic).
These birds occupy most terrestrial habitats where they can find prey and safe roosting or nesting sites. For example, they live in forests and woodlands, open landscapes such as grasslands, and wet habitats such as marshes and reedbeds.4 Some species, such as the elf owl (Micrathene whitneyi), inhabit deserts, whereas the snowy owl (Bubo scandiacus)5 mainly inhabits the cold Arctic tundra.
Diet
Being birds of prey, owls have a carnivorous diet. Large owls, such as the great horned owl (Bubo virginianus), primarily eat hares and rabbits, but they also take larger birds, like grouse and ducks.6 In fact, this species has been recorded to supplement its diet with snakes, including venomous species.7
Medium-sized owls feed mostly on rodents, including mice, voles, and rats. Small owls mainly eat insects (such as beetles, moths, and grasshoppers), as well as small lizards, frogs, and mice.
Lifespan
Like most animals, an owl’s lifespan depends on its species and whether it lives in the wild or in captivity. Barn owls typically live 4 to 9 years in the wild, but can survive up to 15 years in captivity. The great horned owl usually lives around 13 years in the wild, but it has been recorded living up to 50 years in captivity.8 The Eurasian eagle owl (Bubo bubo), likely the longest living owl species, averages 10 to 20 years in the wild, with some individuals reaching up to 60 years in captivity.9
Reproduction and Life Cycle
These birds reproduce sexually, with males attracting potential mates with calls, display flights, and often by bringing prey as gifts to the female. Most species are seasonally monogamous, though in some, such as tawny owls, pairs remain together for life or multiple years.
Once a pair forms, they usually search for tree cavities, cliff ledges, or even nests abandoned by other birds to use as their own nesting sites. During mating, the male transfers his sperm to the female by a brief ‘cloacal kiss,’ and fertilization eventually occurs internally.
Females typically lay 1 to 10 smooth-textured eggs. In about a month, chicks emerge from the eggs, blind and sparsely covered with feathers. In a few more weeks, their eyes open and plumage starts to develop, a stage when they are called owlets. These owlets gradually leave the nest as fledglings with developing flight feathers, but they remain dependent on their parents. These fledglings eventually develop their full set of flight feathers and become sexually mature in 1 to 3 years, depending on the species.
Predators
Although owls are apex predators with few enemies, they are vulnerable to larger birds of prey, such as eagles and hawks. Occasionally, falcons, too, target young owls or smaller species.
Some species, such as the great horned owl, are known to kill and sometimes prey on smaller owl species. In rare cases, they have also been reported to cannibalize members of their own species.10
Many mammals, including foxes, coyotes, raccoons, martens, bobcats, and wildcats, target owl nests for eggs or fledglings. In fact, several snake species, such as garter snakes, frequently raid nests for eggs and owlets, especially in ground-nesting species.
