Eurasian eagle-owl

Name and taxonomy

Carl Linnaeus gave the eagle-owl its first scientific name in 1758. He placed it in the genus Strix, where he put most owls. André Duméril set up the genus Bubo in 1805, and the species belongs there now. Bubo holds about ten living species, and most of them are large owls. About 12 subspecies of the eagle-owl are accepted today.

German speakers call the bird Uhu, a name copied from its call. Spanish speakers call it buho real, and Swedish speakers berguv. Norwegians know it as hubro, and Finns as huuhkaja. In much of Europe and Asia people simply call it the eagle-owl.

Evolution and relatives

The genus Bubo probably arose in Africa, on the evidence of fossils and of where its species live today. The pharaoh eagle-owl and the Indian eagle-owl were both treated as subspecies of this bird until recently. Genetic work split them off, and the pharaoh bird differs by about 3.8% in its mitochondrial DNA. The great horned owl of North America grew out of early eagle-owls that crossed into that continent. It is much smaller, carries yellow eyes and shows horizontal bars below rather than upright streaks.

The snowy owl also belongs to this group and split from it at least 4 million years ago. Genetic tests place the snowy owl closer to the great horned owl than to the eagle-owl. In captivity the species has produced hybrids with the Indian eagle-owl, and with the great horned owl. Fossils from southern France show that Middle Pleistocene eagle-owls were larger than the birds alive now. Eight owls once placed in Bubo now sit in the genus Ketupa with the fish owls.

Appearance

The upper parts are mottled tawny-buff, freckled and streaked with black-brown. The underside is paler, with heavy dark streaks on the breast and fine wavy bars on the belly. Two ear tufts stand on the head, and in Spanish birds their feathers run 63.3 to 86.6 millimetres long. The facial disc is tawny and only weakly framed, unlike the deep dish of a barn owl. The iris is usually orange, and in some European birds it burns almost blood-red.

The bill and the talons are black, and feathers cover the legs down to the toes. Adults measure 56 to 75 cm long, and the tail alone runs 22.9 to 31 cm. The wingspan is 131 to 188 cm, wider than that of any other owl in Europe. Females weigh 1.75 to 4.6 kg and males 1.2 to 3.2 kg, so the female is the larger sex. One British female had a middle claw of 57.9 mm, as long as the hind claw of a golden eagle.

Habitat and range

The eagle-owl ranges over about 32,000,000 square kilometres of Europe and Asia. It reaches the Iberian Peninsula in the west and Magadan in the Russian Far East. It is absent only from the wet rainforest of Southeast Asia and from the high Arctic tundra. Cliffs, gullies and rocky slopes with scattered trees hold the densest populations. A nest set among rocks or on a steep slope is hard for a ground predator to reach.

Birds breed at sea level and as high as 2,100 metres in the Alps. In the Himalayas they reach 4,500 metres, and on the Tibetan Plateau 4,700 metres. Farmland suits them only where the fields are rough, lightly worked or left fallow. Some pairs settle beside towns, and at least five have nested in Helsinki since 2005. Feral rabbits in the city gave those Helsinki owls a steady food supply. GBIF holds records of the species from 83 countries.

Diet and hunting

The eagle-owl takes mostly small mammals, and voles, rats, rabbits and hares fill most meals. It also kills birds, from crows and ducks to other owls. Reptiles, amphibians, fish and large insects round out the list. It eats whatever is common near its territory, so the diet shifts from place to place. European hares supply the greatest weight of food across much of the natural range.

The bird hunts from a perch and in low flight over open ground. It prefers open country to closed woodland when it hunts. It kills with its feet, and the talons hold the prey while the grip does the work. Fur, feathers and bone come back up later as a pellet. Rare animals turn up in the diet too, among them the European mink and the great bustard.

Behaviour and social life

An adult lives alone or with its mate and holds one territory for the rest of its life. A territory covers about 15 to 80 square kilometres. The male sings from rock pinnacles and ridges along the edge of his ground. Males attacked stuffed owls set near their borders, and struck hardest at models with a puffed white throat. Females reacted far less strongly to the same models.

The flight is direct, with shallow beats and long fast glides. The bird sometimes soars on rising air, which is unusual for an owl. It roosts by day on a ledge or in a tree and moves little. Crows mob it when they find it out in daylight. The species does not migrate, though five tagged adults moved over 20 km from their nests after breeding.

Communication and senses

The male's territorial song is a deep two-note hoot with the stress on the first note. The female answers higher and longer, and a pair often calls in turn. The song runs at 250 to 350 hertz, deeper than that of the great horned owl. Calling peaks from October to February, first over territory and then over courtship. In one Spanish study the birds started no earlier than 29 minutes after sunset.

Other sounds include a laughing series of notes, a harsh bark and loud bill-clicking. A flared white throat patch works as a visual signal at close range. Sight matters more than hearing here, because the ear openings are simple and the facial disc is shallow. As in other owls, one ear opening sits higher than the other, which helps place a sound. Fringed feathers quieten the wingbeat, as in other owls.

Reproduction and life cycle

Pairs usually stay together for life and renew the bond with courtship each winter. The male shows the female possible nest sites and scrapes a shallow hollow at each one. Eagle-owls build nothing, so the eggs lie on bare rock, on soil or in another bird's old nest. Cliff ledges, crevices, caves and the ground under a bush all serve as nest sites. Laying starts in late winter, and the mean date in the Italian Alps was 27 February.

A clutch holds one to four white eggs, and rarely as many as six. Each egg weighs about 75 to 80 grams. The eggs arrive three days apart, and the female alone sits on them. The first chick hatches after 31 to 36 days. The male carries food to the nest through the whole of that period.

Owlets open their eyes at four days old and swallow small prey whole at about three weeks. They walk well at five weeks and take short flights at seven weeks. They leave the nest at five to six weeks and fly weakly by about eight weeks. The young depend on their parents for 20 to 24 weeks in all. Most birds first breed at two or three years old, once they hold a territory.

Predators and threats

A healthy adult eagle-owl has no natural predator. Eggs and small owlets are at risk from ground hunters, and the female guards them closely. Most eagle-owls that are found dead were killed by people or by human structures. Electrocution on power poles was the leading cause of death in 68% of 25 published studies. Across those studies it caused 38.2% of recorded deaths on average.

In Finland, electrocution accounted for 39% of deaths and vehicle collisions for 22%. Spanish records of 1,476 dead owls put 313 of them down to deliberate persecution. Gamekeepers and landowners shot and poisoned the bird for centuries because it kills game. Wind turbines kill some birds where turbines stand near good hunting ground. Insulating the pylons steadies local numbers, because floaters then fill the empty territories.

Population and conservation

The IUCN lists the Eurasian eagle-owl as Least Concern. The world population is put at 250,000 to 2,500,000 birds. Europe alone holds 19,000 to 38,000 breeding pairs. The trend is downward, and human activity is the reason. The species sits on Appendix II of CITES, which controls international trade.

Persecution wiped the bird out of Luxembourg in 1903 and Belgium in 1943. Germany had lost its breeding birds by the 1960s. More than a thousand owls were then released in the Eifel, at about US$1,500 a bird. Those birds now breed as well as wild ones, though many still die on power lines. Sweden's population also grew from a series of releases, and the Low Countries were repopulated from the east.

Relationship with humans

The eagle-owl kills nobody, and it attacks people at the nest less often than many smaller owls. A cornered bird raises its wings into a half circle, puffs up and snaps its bill. Some females feign an injury to draw a climber away from the eggs. Farmers gain from the owl, because it takes rats, mice and pigeons. Tame birds have been flown to keep gulls from nesting on buildings.

Falconers keep the species, and escapes are common in Britain. Between 1994 and 2007, 73 escaped eagle-owls were never logged as recovered. About 12 to 40 pairs were thought to live in the United Kingdom in 2016. People argue over whether those British birds are native returns or escapes. Fossils from Meare Lake Village show the species in Britain about 2,000 years ago.

In culture and myth

Germany calls the bird the Uhu, and the name follows the shape of its call. Finland named its national football team Huuhkajat, the Finnish word for eagle-owls. A wild eagle-owl landed in the Helsinki Olympic Stadium in 2007 and stopped a match for six minutes. The city named the bird its citizen of the year that December. Gamekeepers once tethered a live eagle-owl as a decoy, because crows and hawks mob it on sight.

Greek myth gave Athena an owl of her own, though hers was the small Athene noctua. Athens stamped that owl on its silver tetradrachm from about 510 BCE. To Roman writers, an owl that called above a house warned of a death inside. In medieval Europe the owl stood for plague, for mourning and for darkness. Hindu tradition gives an owl to Lakshmi, the goddess of wealth, as her mount.

The Kikuyu of Kenya treat an owl seen or heard as the sign of a coming death. Chinese bronzes carry owls, and the bird stood for both evil and luck in war. Japan once read the owl as a death sign and now sells it as a charm. British folklore holds no eagle-owl stories, which suggests the bird had gone before those tales formed.