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Bubo buboEurasian eagle-owl

By Jessie Cantrell

Geographic Range

Eagle owls primarily live in the Palearctic region, although they can travel as far south as the Oriental Region and Ethiopian Region and as far north as the far reaches of Siberia. They are found in North Africa, Europe, The Middle East, and Asia. ("The Eurasian Eagle Owl", 2002; Konig, et al., 1999; Parry-Jones, 1998; "Eurasian Eagle Owl", 2003)

Habitat

These owls can be found in many different kinds of habitats including wooded areas (coniferous forests), warm deserts, mountain ranges, and riverbeds. They prefer to live in rocky landscapes, especially when nesting. Eagle owls search for habitats with adequate food supply and proper nesting sites. Their habitats vary greatly, and they can also be found in open areas that have few trees like farmlands and grasslands. (; "Eurasian Eagle Owl", 2003; "The Eurasian Eagle Owl", 2002)

Physical Description

Eagle owls are the largest owls in the world, and they are best known for their large, striking, orange eyes. They are often called the Old World version of America's widely distributed great horned owl. They have prominent ear tufts and are primarily brown-black and tawny-buff in color. Their facial disk is heavily marked with black, gray, and white. Their upper parts are darker than their lower parts, which have black streaks, and their throat is white. It is interesting to note that these owls become paler in the northeastern geographic regions and get progressively darker as you move to the Pacific coast. Also, size tends to decrease from north to south, and east to west. ("The Eurasian Eagle Owl", 2002; Konig, et al., 1999; "Eurasian Eagle Owl", 2003; )

  • Sexual Dimorphism
  • female larger
  • Range mass
    1600 to 4200 g
    56.39 to 148.02 oz
  • Average mass
    2800 g
    98.68 oz
  • Range length
    58 to 71 cm
    22.83 to 27.95 in
  • Average length
    65 cm
    25.59 in
  • Range wingspan
    1.5 to 2 m
    4.92 to 6.56 ft

Reproduction

Both sexes are usually solitary but they pair up during courtship. They advertise potential breeding sites by digging a shallow depression into the earth and emitting a light staccato note and various clucking sounds. They also use these calls to keep track of their mate's location. People often hear them calling to each other. They keep the same partners for life. Eagle owls are very sensitive to their environment. If there is not enough food resources, will mate at a much slower rate and later into the year. When they have sufficient habitats and plentiful food, their mating rate increases significantly. ("The Eurasian Eagle Owl", 2002; Konig, et al., 1999; Parry-Jones, 1998; Penteriani, et al., 2002; "Eurasian Eagle Owl", 2003; )

Eagle owls form pairs in early fall and nest in late January and early February. They prefer to nest in crevices between rocks, sheltered cliff ledges, cave entrances, as well as abandoned nests of other large birds. Usually egg laying begins in late winter. They usually have one batch of eggs per year ranging from one to four white eggs. This number depends on the food availiable in their area. When the owlets hatch, they are brooded for about two weeks. In about three weeks the young begin to feed and swallow by themselves. By week five they can walk around the nesting area and begin to fly about 60 days, although for only a few meters. They leave the nest or are driven out in the fall (Sept-Nov.) Eagle owls are able to breed from the ages of 2-31 years. ("The Eurasian Eagle Owl", 2002; "Eurasian Eagle Owl", 2003; )

  • Breeding interval
    Breeding occurs once a year.
  • Breeding season
    The breeding season lasts from December to April.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    3
  • Range time to hatching
    2 to 3 months
  • Range fledging age
    20 to 24 weeks
  • Range time to independence
    9 to 12 months
  • Range age at sexual or reproductive maturity (female)
    1 to 3 years
  • Range age at sexual or reproductive maturity (male)
    1 to 3 years

Once the eggs are laid, they are incubated by the female alone. The male kills prey and feeds his mate. Once the eggs hatch, the male continues to bring food to the female for the next two weeks. During this time the female stays at the nest protecting her young from predators and teaching them how to eat on their own. All owls are imprinted by their mothers, which means they will imitate the first animal they see. This makes it difficult to release owls into captivity if they are not raised by an owl parent. If an owl sees a human when they are born, they think they are human too. ("Eurasian Eagle Owl", 2003; "The Eurasian Eagle Owl", 2002; Parry-Jones, 1998)

Lifespan/Longevity

Eagle owls have relatively long life spans once they reach adulthood. They have no real natural enemies. In the wild, they live for approximately 20 years, but they can live more than 60 years in captivity. ("The Eurasian Eagle Owl", 2002; Parry-Jones, 1998)

  • Range lifespan
    Status: wild
    68 (high) years
  • Range lifespan
    Status: captivity
    64 (high) years
  • Typical lifespan
    Status: wild
    10 to 20 years
  • Typical lifespan
    Status: captivity
    20 to 60 years

Behavior

Eagle owls are primarily solitary animals except during the mating period. They fiercely defend their territory against other owls and will only overlap territories slightly if food is sparce. Eagle owls prefer to stay within the same territory unless they are forced to leave due to food shortages or if they are driven out by other owls. Despite their large size, they are very elusive creatures, which makes them difficult to study in their natural habitats. Eagle owls spend most of their days roosting high in trees remaining relatively inactive. They are nocturnal and become active at dusk and remain so throughout the night. When food is rare, they will hunt during the day. ("The Eurasian Eagle Owl", 2002; )

  • Range territory size
    15 to 80 km^2
  • Average territory size
    42.5 km^2

Communication and Perception

Eagle owls are known for their loud calls. They are heard far more than they are seen. They use their various hoots and clucks to let others know they have entered or are entering certain territories. Different hoots represent different moods and are easily recognizable between each member of the species. Also, eagle owls are able to decipher the size and distance of intruders based on the intensity of their call. They also use a low gutteral hoot to attract mates. It's interesting to note that even though eagle owls are difficult to study, they (like other owls) cough up what is known as an owl pellet after their stomach goes through the digestive process. These owl pellets contain the hair, feathers, and bones of prey they were unable to digest. These pellets are very useful to scientists because they help them understand the food habits of these elusive birds. ("The Eurasian Eagle Owl", 2002; Parry-Jones, 1998)

Food Habits

Eagle owls are carnivores. They are primarily nocturnal hunters and have various hunting techniques. They take their prey in flight or on the ground. They prefer to hunt in open spacious locations rather than forests. Most owls are very capable hunters and the eagle owl is no exception. Owl wings have evolved to make very little noise when flapping. With their night vision, advanced hearing, and silent flight they are the hit men of their territory. Their prey usually has no idea they were being stalked. They feed on almost anything they can catch including rats, mice, voles, beetles and even large prey like deer fawns and foxes. They will also feed on other birds such as crows, ducks, and even other owls. Dominant prey can vary from habitat to habitat but is most often small rodents. ("The Eurasian Eagle Owl", 2002; Parry-Jones, 1998)

  • Animal Foods
  • birds
  • mammals
  • reptiles
  • insects

Predation

Once eagle owls reach adulthood, they are at a very low risk of predation. They are at the top of the food chain in their niche. They are not a major food source for any other species. The only time they are at risk of predation is during their early years. They are at risk from any predator too large for them too eat. Fortunately, the mother stays with the young for most of this period and keeps the predators at bay. Due to their striped, spotted, and varied coloring, they are extremely well camouflaged, especially when perching in the trees. (Parry-Jones, 1998)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Eagle owls are at the top of their food chain. They are particularly useful in keeping the number of rodents down in their various ecosystems. The removal of this species can cause the rodent population in a given area to grow significantly. Therefore, they may be a keystone predator. (Konig, et al., 1999; Parry-Jones, 1998; )

Economic Importance for Humans: Positive

Eagle owls are economically beneficial to farmers that want to keep the number of rodents down on their land. Many birdwatchers will also pay to get a glimpse of this rare bird in its natural habitat as well as in zoos. ("The Eurasian Eagle Owl", 2002; "Eurasian Eagle Owl", 2003)

  • Positive Impacts
  • ecotourism
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse affects of the eagle owl on humans.

Conservation Status

Eagle owls are considered rare but not yet threatened. Their numbers are steadily declining due to habitat loss from human encroachment. ("Eurasian Eagle Owl", 2003)

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Jessie Cantrell (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

The Peregrine Fund. 2003. "Eurasian Eagle Owl" (On-line). The Peregrine Fund. Accessed March 21, 2003 at http://www.peregrinefund.org/Explore_Raptors/owls/eagleowl.html.

Centre for the Conservation of Specialized Species. 2002. "The Eurasian Eagle Owl" (On-line ). The Centre for the Conservation of Specialized Species. Accessed 3/21/03 at http://www.conservationcentre.org/scase21.html.

Konig, C., J. Becking, F. Weick. 1999. Owls: A Guide to the Owls of the World. New York, NY: Yale University Press.

Parry-Jones, J. 1998. Understanding Owls: Biology, Management, Breeding, Training. New York, NY: David and Charles.

Penteriani, V., M. Gallardo, P. Roche. 2002. Landscape structure and food supply affect eagle owl (Bubo bubo) density and breeding performance: a case of intra-population heterogeneity. Journal of Zoology, 257: 365-372.

Woburn Safari Park, "Woburn Safari Park" (On-line ). Amazing Animal Facts. Accessed 3/21/03 at http://www.woburnsafari.co.uk/animalfacts.asp?aID=11.

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