Hailed for their supposed wisdom and their appetite for pesky rodents but derided as pests and subjects of superstition, owls (families Tytonidae and Strigidae) have had a love/hate relationship with humans since the beginning of recorded history. There are over 200 species of owls, and they might date back to the days of dinosaurs.
Fast Facts: Owls
- Scientific Name: Tytonidae, Strigidae
- Common Names: Barn and bay owls, true owls
- Basic Animal Group: Bird
- Size: Wingspans from 13-52 inches
- Weight: 1.4 ounces to 4 pounds
- Lifespan: 1-30 years
- Diet: Carnivore
- Habitat: Every continent except Antarctica, most environments
- Conservation Status: Most owls are listed as Least Concerned, but a few are Endangered or Critically Endangered.
There are about 216 species of owls divided into two families: Barn and Bay owls (Tytonidae) and the Strigidae (true owls). Most owls belong to the group of so-called true owls, with large heads and round faces, short tails, and muted feathers with mottled patterns. The remaining dozen-plus species are barn owls, which have heart-shaped faces, long legs with powerful talons, and moderate size. Except for the common barn owl, which is found worldwide, the most familiar owls in North America and Eurasia are the true owls.
More than half of the owls in the world live in the neotropics and sub-Saharan Africa, and only 19 species reside in the United States and Canada.
One of the most remarkable things about owls is that they move their entire heads when looking at something rather than moving their eyes, like most other vertebrates. Owls need large, forward-facing eyes to gather scarce light during their nocturnal hunts, and evolution couldn't spare the musculature to allow these eyes to rotate. Some owls have astonishingly flexible necks that let them turn their heads three-quarters of a circle, or 270 degrees, compared to 90 degrees for the average human being.The tawny owl is just one of the more than 225 owl species in the world. Nick Jewell/Flickr/CC by 2.0
Habitat and Distribution
Owls are found on every continent except Antarctica, and they also inhabit many remote island groups including the Hawaiian islands. Their preferred habitats vary from species to species but include everything from arctic tundra to marshlands, deciduous and conifer forests, deserts and agricultural fields, and beaches.
Diet and Behavior
Owls swallow their prey-insects, small mammals and reptiles, and other birds-whole without biting or chewing. Most of the unfortunate animal is digested, but the parts that can't be broken down-such as bones, fur, and feathers-are regurgitated as a hard lump, called a "pellet," a few hours after the owl's meal. By examining these pellets, researchers can identify what a given owl has been eating and when. (Baby owls don't produce pellets since their parents feed them soft, regurgitated food in the nest.)
Although other carnivorous birds, such as hawks and eagles, hunt during the day, most owls hunt at night. Their dark colors make them nearly invisible to their prey and their wings beat almost silently. These adaptations, combined with their enormous eyes, put owls among the most efficient night hunters on the planet.
As befitting birds that hunt and kill small prey, owls have some of the strongest talons in the avian kingdom, capable of seizing and grasping squirrels, rabbits, and other squirmy mammals. One of the largest owl species, the five-pound great horned owl, can curl its talons with a force of 300 pounds per square inch, roughly comparable to the strongest human bite. Some unusually large owls have talons comparable in size to those of much bigger eagles, which may explain why even desperately hungry eagles usually won't attack their smaller cousins.
In popular culture, owls are invariably depicted as extremely intelligent, but it's virtually impossible to train an owl, while parrots, hawks, and pigeons can be taught to retrieve objects and memorize simple tasks. People think owls are smart for the same reason they think kids who wear glasses are smart: Bigger-than-usual eyes convey the impression of high intelligence. This doesn't mean owls are especially dumb, either; they need lots of brain power to hunt at night.
Reproduction and Offspring
Owl mating rituals involve dual hooting, and once paired, a single male and female will remain together through the breeding season. Some species stay together for an entire year; others remain paired for life. They don't typically build their own nests, instead, they take over nests abandoned by other creatures. Owls can be aggressively territorial, especially during the breeding season.
Mother owls lay between one and 11 eggs over a few days period, with an average of five or six. Once laid, she does not leave the nest until the eggs hatch, some 24-32 days later, and, although the male feeds her, she does tend to lose weight over that period. The chicks hack themselves out of the egg with an egg-tooth and leave the nest (fledge) after 3-4 weeks.
No one is sure why, on average, female owls are slightly larger than males. One theory is that smaller males are more agile and therefore more suited to catching prey, while females brood young. Another is that because females don't like to leave their eggs, they need a larger body mass to sustain them for long periods without eating. A third theory is less likely but more amusing: Since female owls often attack and drive off unsuitable males during mating season, the smaller size and greater agility of males prevent them from getting hurt.CGander Photography/Getty Images
It's difficult to trace the evolutionary origins of owls, much less their apparent kinship with contemporary nightjars, falcons, and eagles. Owl-like birds such as Berruornis and Ogygoptynx lived 60 million years ago during the Paleocene epoch, which means it is possible that the ancestors of owls coexisted with dinosaurs toward the end of the Cretaceous period. The strigid family of owls broke off from tyronids and first appeared in the Miocene epoch (23-5 million years ago).
Owls are one of the most ancient terrestrial birds, rivaled only by the game birds (e.g., chickens, turkeys, and pheasants) of the order Galliformes.
Most of the species in the International Union for Conservation of Nature (IUCN) are listed as Least Concern, but a few are listed as Endangered or Critically Endangered, such as the Forest Owlet (Heteroglaux blewitti) in India; the Boreal Owl (Aegolius funereus) in North America, Asia, and Europe; and the Siau Scops-Owl (Otus siaoensis), on a single island in Indonesia. Ongoing threats to owls are hunters, climate change and habitat loss.
Owls and Humans
It isn't a good idea to keep owls as pets, and not just because that's illegal in the U.S. and most other countries. Owls eat only fresh food, requiring a constant supply of mice, gerbils, rabbits, and other small mammals. Also, their beaks and talons are very sharp, so you'd also need a stock of bandages. If that weren't enough, an owl can live for more than 30 years, so you'd be donning your industrial-strength gloves and flinging gerbils into its cage for many years.
Ancient civilizations had widely divergent opinions about owls. The Greeks chose owls to represent Athena, the goddess of wisdom, but Romans were terrified of them, considering them bearers of ill omens. The Aztecs and Mayans hated and feared owls as symbols of death and destruction, while many Native American tribes scared their children with stories of owls waiting in the dark to carry them away. The ancient Egyptians had a kinder view of owls, believing that they protected the spirits of the dead as they traveled to the underworld.
- Askew, Nick. "List of Owl Species." BirdLife International, June 24, 2009.
- BirdLife International. "Micrathene " The IUCN Red List of Threatened Species: e.T22689325A93226849, 2016. whitneyi.
- BirdLife International. "Bubo ." The IUCN Red List of Threatened Species: e.T22689055A127837214, 2017.scandiacus (errata version published in 2018)
- BirdLife International. "Heteroglaux ." The IUCN Red List of Threatened Species: e.T22689335A132251554, 2018.blewitti
- BirdLife International. "Aegolius ." The IUCN Red List of Threatened Species: e.T22689362A93228127, 2016. funereus
- BirdLife International. "Otus ." The IUCN Red List of Threatened Species: e.T22728599A134199532, 2018.siaoensis
- Lynch, Wayne. "Owls of the United States and Canada: A Complete Guide to their Biology and Behavior." Baltimore: The Johns Hopkins University Press, 2007.