Burrowing owl

Name and taxonomy

The scientific name of the burrowing owl is Athene cunicularia. The Spanish naturalist Juan Ignacio Molina described the bird in 1782. He worked from a specimen collected in Chile and called it Strix cunicularia. The second name comes from a Latin word for a burrower or a miner. The genus Athene dates from 1822 and the work of Friedrich Boie. That name honours the Greek goddess Athena, whose owl stood for wisdom.

Some authors once put the bird in a genus of its own, Speotyto. Bone structure and DNA place it with the little owls instead. Most authorities now treat it as a ground-living member of Athene.

Ornithologists recognise 18 subspecies, and two of those are extinct. The Antiguan bird died out around 1905 and the Guadeloupe bird around 1890. Most of the remaining forms live near the Andes or on Caribbean islands. Several differ so little in appearance that their status is still argued over.

Evolution and relatives

Athene is the genus of the little owls of Europe, Asia and North Africa. The burrowing owl is probably the branch of that group that took to the ground. Life in the open appears to have shaped the body plan. The legs are far longer than those of any other owl. Long legs let the bird sprint after prey and give it a push into the air.

A fossil form from the Pleistocene of the Bahamas has been named as a separate subspecies. Nobody knows whether it led to the modern Florida birds or died out on its own. Fossils of similar owls come from Barbuda, the Cayman Islands, Jamaica, Mona Island and Puerto Rico. Those island owls disappeared as the last ice age closed. Changing sea levels and habitat probably killed them, rather than people.

Appearance

An adult measures 19 to 28 cm long and weighs 0.14 to 0.24 kg. The wingspan runs 50.8 to 61 cm. That makes the bird a little larger than an American robin. The legs are grey and much longer than an owl's legs usually are. The tail is short in proportion to the body.

The head and wings are brown with white spots. The chest and belly are white, marked with brown spots or bars. White eyebrows arch over yellow eyes. A white patch on the chin swells when the bird is agitated. The bird bobs its head at the same time. The bill is dark yellow or grey, depending on the subspecies.

A young bird has fewer white spots above and little barring below. It carries a buff bar across the upper wing and a buff breast. The sexes look almost the same. Females tend to be heavier and males tend to measure longer in wing and tail. An adult male often looks paler, because sun outside the burrow bleaches his feathers.

Habitat and range

The burrowing owl wants open ground with short plants and few trees. Grassland, prairie, rangeland, farmland, badlands, chaparral and desert all suit it. It also uses airports, golf courses, fairgrounds and empty city lots. The one requirement is probably a hole in the ground it can move into.

The range reaches from southern British Columbia, Alberta, Saskatchewan and Manitoba to western Panama. A separate population holds central and southern Florida and some Caribbean islands. In South America the bird lives in every country. It skips the deep interior of the Amazon and the highest ranges of the Andes. Numbers rise again south of the Amazon, from southern Brazil down to Tierra del Fuego.

Most birds stay in one place all year. Canadian and northern American breeders move down to Mexico for the winter. Range has shrunk in North America since European settlement. In parts of South America it is spreading, because logging opens the forest up. The species is recorded in 40 countries on GBIF.

Diet and hunting

The burrowing owl appears to take a wider range of food than most owls. Invertebrates make up about one third of the diet and small vertebrates about two thirds. Animal Diversity Web counts arthropods as roughly 90% of the items taken. Grasshoppers, crickets, katydids, beetles and termites are the staples. The owl also eats mice, small birds, lizards, snakes, frogs, bats and earthworms.

A study in the Dominican Republic put invertebrates at about 53% of the diet. Other birds made up about 28%, reptiles about 15% and amphibians about 3%. The largest prey are birds such as eared doves, which can weigh nearly as much as the owl. Ground squirrels live alongside the owls, and the owls seldom touch them. Unlike other owls, this one eats fruit, including prickly pear and cholla cactus.

A hunting owl waits on a low perch and drops onto whatever moves. It also snatches insects in the air and hovers over cover to find small mammals. It will run down prey on foot across bare ground. Males range up to 9.6 kilometres from the nest, though most hunting stays inside 1.6 km. The owl also spreads mammal dung around the burrow mouth to draw dung beetles in. That trick probably turns the burrow entrance into a feeding station.

Behaviour and social life

This owl is out in daylight, which sets it apart from most of its family. It avoids the heat of the middle of the day. Hunting peaks around sunrise and sunset, when its night vision and hearing still work well. The bird flies in short low bursts and stays close to the ground. It walks, hops and runs after insects instead.

Burrows dug by colonial animals give the owls a loose colony of their own. Pairs sometimes nest close together in the same prairie dog town. A burrow runs 3 to 3.7 metres long and slopes down, so no sunlight reaches the end. Florida birds dig their own, about 1 metre deep and 2 to 3 metres long. Most tunnels curve, which keeps the nest chamber dark.

Owls bathe in a puddle or in falling rain. They also take dust baths and flick grit through the feathers to shift mites. When something reaches into the burrow, the bird makes a rattling, hissing noise. The sound is close to a rattlesnake, and it works on animals that know that danger. Researchers treat the copy as acoustic mimicry.

Communication and senses

Adults use 13 recognised calls and young birds use only three. The young give a defence call, a food-begging whine and a distress call. The main song is a two-note coo-coooo, higher in pitch than a mourning dove. The male sings it to attract a mate, to hold ground and before mating.

A bird defending the nest screams, clucks and chatters. It also snaps its bill and flaps a wing to show distress. The rattlesnake imitation is probably the loudest signal of all, and it comes from inside the hole. Head bobbing with the white chin patch flared appears to be a visual warning.

The eyes face forward and give a field of view of about 110 degrees. The bird can turn its head about 270 degrees. Sharp hearing and good night vision make dawn and dusk the best hunting hours. Prairie dogs nearby give alarm calls, and the owls appear to use that warning.

Reproduction and life cycle

Nesting starts in late March or April in North America. In the south of the range the season can open as early as February. Most pairs are monogamous, though a male sometimes keeps two mates. Courtship includes song, preening and a gift of food from the male. Display flights climb to about 30 metres, hover, then drop fast.

The pair line the burrow with whatever they can carry. Cattle dung is the commonest lining, and some of it is left at the entrance. Researchers think the dung steadies the climate inside and draws in insects. The female adds one egg every day or two until the clutch is complete. A clutch runs from four to 12 eggs, and nine is usual.

She incubates for three to four weeks while the male brings her food. A chick weighs 8 to 9 grams when it hatches. Both parents feed the brood once the eggs open. The female stays close until the chicks can hold their own body heat. She starts hunting further out when they are about two weeks old.

Four weeks after hatching the young make short flights and leave the burrow. Parents keep feeding them for one to three months. Independence comes at about 53 days and breeding age at about 10 months. A wild bird usually lives 6 to 8 years, and the record is 11 years. Two thirds of young owls never reach adulthood.

Predators and threats

Badgers, coyotes, foxes, bobcats, weasels, skunks and opossums all kill burrowing owls. Snakes take eggs and young from the burrow. Larger birds of prey hunt the adults, including peregrine and prairie falcons. Red-tailed, Swainson's and Cooper's hawks take them too. In Florida, escaped pythons, boas and anacondas now eat them as well.

Feral and domestic cats and dogs kill many owls near towns. Cars kill birds that cross roads, because the owls fly low. Farmers fill in burrows in their pastures. Lice, fleas, mites and gapeworm all live on or in the birds.

The largest threat is the loss of the animals that dig the burrows. Poisoning programmes against prairie dogs and ground squirrels remove the owls' housing. Owl decline tracks prairie dog decline closely. Fewer holes also mean more owls in each hole, which makes a predator's work easier. Prairie dogs also act as alternative prey and as a warning system.

Population and conservation

The IUCN lists the burrowing owl as Least Concern. The species is common and widespread across the Neotropics, even in city parks. The northern picture is worse. Canada lists the bird as endangered and Mexico lists it as threatened. NatureServe ranks it S2B in Saskatchewan.

Colorado and Florida both treat it as a state threatened species. California calls it a species of special concern. In March 2024 seven groups petitioned California to list five populations under state law. The petition asked for endangered status in three coastal regions and threatened status in two others.

The owl is protected under the Migratory Bird Treaty Act in Canada, the United States and Mexico. It is also on Appendix II of CITES. Conservation groups dig artificial burrows where no digging animals remain. Those holes help in the short run but do not fix the problem. iNaturalist holds 46,673 observations of the species.

Relationship with humans

The burrowing owl lives close to people more readily than most owls. It nests beside roads, farms, houses and irrigation canals. Urban birds breed about as successfully as birds on open rangeland. City owls dig their own holes more often and react differently to people and dogs. Artificial burrows made of plastic pipe work well as nest sites.

Where building work threatens a colony, managers use passive relocation. They prepare a nearby site with burrows and perches months in advance. One-way trapdoors then stop the owls returning to the old holes. A colony can move across in a few nights if the work is done properly. Some groups argue that any removal has helped wipe out Californian colonies, because the owls stick to a site.

The bird does no harm to people. Birding festivals in late February bring visitors and money to owl country. Live burrow cameras let people watch nests online. Cape Coral in Florida holds the largest concentration of the owls in that state.

In culture and myth

The genus name probably carries the oldest story attached to this bird. Athene honours the Greek goddess Athena, and her owl was a sign of wisdom. A tetradrachm of about 500 BC shows a little owl holding an olive branch. A bronze of the fifth century BC shows Athena with the bird in her hand. The Roman goddess Minerva took over the same emblem.

The English name is plain description, and it appears to be slightly wrong. Most burrowing owls take over a hole rather than dig one. The Latin name says the same thing, because cunicularia means miner.

Modern American culture appears to treat the bird as a mascot of the open prairie. Festivals in the southern United States are built around the owls each February. Volunteer groups such as the Burrowing Owl Preservation Society campaign for them. Florida towns such as Cape Coral may now advertise their owl colonies to visitors.