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Aquila pomarinalesser spotted eagle

By Jasmine Jackson and Meron Mengestab

Geographic Range

Lesser spotted eagles are found across the Palearctic and Ethiopian regions. During the breeding season, lesser spotted eagles (Aquila pomarina) inhabit areas of western Europe. Their primary breeding areas are in northern Germany, Estonia, Lithuania, and Slovakia. In winter (typically during the month of September), lesser spotted eagles migrate to the warmer climates of South Africa and Mozambique. The specific location of their winter habitat is dependent on the location of their breeding grounds.

Greater spotted eagles and lesser spotted eagles show very similar migration patterns during both the breeding and wintering seasons. This may contribute to the commonly noted hybridizations between these two species. (Hedenström, 1997; Meyburg, et al., 2004a; Meyburg, et al., 2000; Väli and Löhmus, 2004; Väli, et al., 2004)

Habitat

Lesser spotted eagles live primarily in patchy woodland areas, meadows, fields, and natural grasslands, often in moist environments. Although forests are not used as primary habitat, they often build nests near forest edges. Lesser spotted eagles have been found in African dry mountain and grassland savanna habitats during their winter migration. Within these dry mountain habitats, their range typically extends to a maximum elevation of 2,200 meters. (Väli and Löhmus, 2004)

Lesser spotted eagles generally hunt by walking along the ground. However, they typically nest and perch in the branches of forest trees. When nesting and perching, lesser spotted eagles often use branches closer to the ground rather than higher in the trees. (Väli and Löhmus, 2004)

  • Range elevation
    2,200 (high) m
    ft

Physical Description

Lesser spotted eagles are medium-sized birds (body length 54 to 65 cm), generally smaller than steppe eagles (Aquila nipalensis) (60 to 81 cm) and greater spotted eagles (A. clanga) (59 to 71 cm). The largest of these three species are steppe eagles, weighing 1.8 to 3.8 kg. Thus, despite their relatively large size, lesser spotted eagles only weigh 1.2 to 2.2 kg, with an average of 1.6 kg. Greater spotted eagles are just slightly heavier (1.4 to 3.2 kg) than lesser spotted eagles.

Adult lesser spotted eagles also are distinguished by their yellow eyes, whereas adult steppe eagles and greater spotted eagles have brown eyes. Juveniles of all three species have brown eyes. The head and wings of lesser spotted eagles are a lighter shade of brown compared to the rest of its body; in steppe eagles and greater spotted eagles, the entire body is a dark shade of brown. Lesser spotted eagles also have a small head and beak for an eagle. Like other eagles in the genus Aquila, lesser spotted eagles have a white V mark on their rump. Finally, differences in the shape of the wings cause lesser spotted eagles to appear to have a longer tail (96.6 to 123.75 cm) than other closely related species. Lesser spotted eagles have narrower wingspans (145 to 165 cm), whereas greater spotted eagles have broader wingspans. (Burton, 1983; Christie, 2001; Clark, 2000; Meyburg, et al., 2004a; Scott, 1976)

These closely related eagle species can be most readily distinguished during their juvenile stages. In each species, juvenile birds differ greatly compared to adults. For example, juvenile greater spotted (A. clanga) and lesser spotted (A. pomarina) eagles have numerous white spots on upper wing coverts (a set of feathers that covers other feathers) and on their backs. Greater spotted eagles have more abundant spots than lesser spotted eagles. It is these spots that give the "spotted eagles" their common names. (Burton, 1983; Christie, 2001; Clark, 2000)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    1.2 to 2.2 kg
    2.64 to 4.85 lb
  • Average mass
    1.6 kg
    3.52 lb
  • Range length
    54 to 65 cm
    21.26 to 25.59 in
  • Range wingspan
    145 to 165 cm
    57.09 to 64.96 in

Reproduction

Lesser spotted eagles are considered monogamous birds. Currently there is no clear evidence of partner fidelity, however most birds return to the same nest every year. (Del Hoyo, et al., 1994)

Lesser spotted eagles breed once per year. The pair builds a platform nest, generally in a tall tree. Egg laying begins after the nest is complete in late April to early May. It is believed that males are responsible for defending the immediate vicinity around the nest. Lesser spotted eagles lay one to two eggs, but typically only one survives. The older or stronger sibling usually attacks the weaker one. Eggs are laid in the second half of April and between May 23 and 27. The egg incubation period ranges from 36 to 41 days. Fledglings have been observed in the middle of July, with a fledging period up to eight weeks. No information is available on the time to independence for lesser spotted eagles; however, golden eagles require 32 to 80 days after fledging before they are independent of their parents. Juvenile lesser spotted eagles do not reach reproductive age until they are 3 to 4 years old. (Allen, 1982; Del Hoyo, et al., 1994)

  • Breeding interval
    Lesser spotted eagles breed once yearly.
  • Breeding season
    Breeding season is between late March or beginning of April and late August.
  • Range eggs per season
    1 to 2
  • Average eggs per season
    2
  • Range time to hatching
    36 to 41 days
  • Average time to hatching
    38 days
  • Range fledging age
    6 to 8 weeks
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Range age at sexual or reproductive maturity (male)
    3 to 4 years

Lesser spotted eagle females lay two eggs and stay with them continuously while males forage for food. After the eggs hatch, both parents tend the helpless, altricial young until fledging occurs, typically after 8 weeks. Siblicide is common in this species, thus only one offspring typically survives to fledge. (Del Hoyo, et al., 1994)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • male

Lifespan/Longevity

Lesser spotted eagles have a maximum lifespan of 20 to 25 years. Threats include local conditions of their habitat, prey abundance, deliberate poisoning, and hunting. Average annual mortality is 35% per year for juveniles, 20% for immature birds, and 5% for adults. Because of these threats, the average lifespan of lesser spotted eagles typically ranges from 8 to 10 years. (Del Hoyo, et al., 1994)

  • Range lifespan
    Status: wild
    20 to 25 years
  • Typical lifespan
    Status: wild
    8 to 10 years

Behavior

Lesser spotted eagles are arboreal, meaning they live in trees. They are diurnal and perform all activities (e.g., hunting and flying) during the day and sleep at night. They are typically solitary birds. However, during the breeding season they often are seen in breeding pairs consisting of a single male and a single female. As a migratory species, lesser spotted eagles spend the breeding season in Europe and then migrate to Africa during the winter.

Lesser spotted eagles are highly territorial. They will fight other birds that come too close to their nests. Males are more aggressive than females, and typically only show territorial behavior towards other males. Female lesser spotted eagles often visit the nests of other females during breeding season. The reason for these nest visits is not known. Lesser spotted eagles are the only raptors that leave their own nests to go to another. Genetic testing of these females indicates that they are not closely related individuals. (Meyburg, et al., 2007; Meyburg, et al., 2000; Väli and Löhmus, 2004)

Home Range

The home range of lesser spotted eagles is typically 1800 km^2, but can range from 1200 to 2500 km^2. Currently, exact territory size is unknown. (Hedenström, 1997; Meyburg, et al., 2000; Väli and Löhmus, 2004; Väli, et al., 2004)

Communication and Perception

Lesser spotted eagles usually fly alone or in pairs. However, they often live with other eagles during the winter, especially greater spotted eagles. Lesser spotted eagles do sometimes hunt with other birds of the same species. They have strong eyesight that they use in finding prey, and good tactile senses used to perch on branches. They walk on the ground when hunting for food. The primary forms of communication in lesser spotted eagles are vocalizations and hearing (acoustic senses) when communicating with mates and with their young. Like most birds, lesser spotted eagles perceive their environments through auditory, visual, tactile and chemical stimuli. (Tingay and Katzner, 2010)

Food Habits

Although lesser spotted eagles are most often seen alone or in pairs, they often hunt in intraspecific groups. Lesser spotted eagles are carnivorous birds of prey. They generally eat small mammals (Order Rodentia), small birds (Class Aves), amphibians (Order Anura), reptiles (Order Squamata), and occasionally insects (Class Insecta). It is known that lesser spotted eagles often feed on voles (Family Cricetidae). A recent experimental study on pesticide effects demonstrated that lesser spotted eagles that fed on pesticide-infected voles often died. During the winter months, these birds often feed on termites (Order Isoptera). This distinguishes this species from greater spotted eagles, which more often eat carrion during the winter. (Bildstein, 2006; Christie, 2001; Clark, 2000)

When hunting, lesser spotted eagles usually perch on low branches or hunt their prey by walking along the forest floor. Unlike many other birds of prey, they rarely search for prey while flying. Lesser spotted eagles migrate long distances and stop at many places for water and to hunt. (Bildstein, 2006; Christie, 2001; Clark, 2000)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • insects

Predation

Lesser spotted eagles and greater spotted eagles have no natural predators and show no evident anti-predation adaptations. The primary threat to lesser spotted eagles is humans. Humans are a danger to lesser spotted eagles because of chemical usage, such as Azodrin, an organophosphorous insecticide used to prevent small animals from feeding on crops. Raptors, including lesser spotted eagles, often die from feeding on these poisoned animals. Another human impact on lesser spotted eagles is through hunting. (Mendelssohn and Paz, 1977; Meyburg, et al., 2004b)

Lesser spotted eagles are often shot by hunters as they migrate to their wintering grounds. Declines in habitat availability also have been reported in Germany and other areas due to increased agriculture.

Another cause of mortality in lesser spotted eagles is siblicide. If there are two or three eggs in a nest, typically the offspring that hatches first kills the others by knocking them out of the nests, attacking them, or by eating food before their siblings have a chance to eat. As a result, most lesser spotted eagles only raise one to two offspring successfully.

It has been suggested that lesser spotted eagle eggs may be eaten by other animals, particularly snakes (Order Squamata); however, this has not been clearly documented. In greater spotted eagles, eggs are eaten by American minks (Neovison vison). Therefore, it is possible that minks may also prey on lesser spotted eagle eggs. (Ingram, 1959; Meyburg, et al., 2004b)

Ecosystem Roles

Eagles in the genus Aquila may be beneficial to farmers by eating rabbits (Family Leporidae) and other rodents (Order Rodentia), small birds (Class Aves), insects (Class Insecta), and reptiles (Order Squamata) that threaten crops. (Bildstein, 2006; Clark, 2000)

Lesser spotted eagles do not usually contract West Nile Virus. However, this virus is occasionally transmitted from mosquitoes (Family Culicidae). When this occurs, it is typically fatal. Lesser spotted eagles that contract West Nile Virus usually are infected when migrating to Africa for the winter. These birds typically do not survive to return to Europe the following season. (Meyburg, et al., 2004b)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Eagles in the genus Aquila may benefit to farmers by feeding on small animals that threaten crops. These include rodents (Order Rodentia) such as rabbits (Family Leporidae), small birds (Class Aves), insects (Class Insecta), and reptiles (Order Squamata). (Christie, 2001; Clark, 2000)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Aquila pomarina on humans. At one point, scientists thought that migrating birds, including lesser spotted eagles, may transmit viruses such as the avian bird flu and West Nile virus to humans. However, birds in the Order Falconiformes do not carry the antibodies necessary to transmit these viruses. (Seidowski, et al., 2010)

Conservation Status

The conservation status of lesser spotted eagles is considered to be of least concern. Lesser spotted eagles are not considered vulnerable or threatened, because according to the Red List, the range that lesser spotted eagles occupy is large. Declines in lesser spotted eagle populations have been documented, but these declines are occurring relatively slowly.

Humans are a threat to lesser spotted eagles by hunting them during migration periods. Loss of breeding habitat also contributes to population declines. (Tingay and Katzner, 2010)

Contributors

Jasmine Jackson (author), Radford University, Meron Mengestab (author), Radford University, Christine Small (editor), Radford University, Rachelle Sterling (editor), Special Projects.

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

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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

diurnal
  1. active during the day, 2. lasting for one day.
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

forest

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

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).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

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.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

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

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

tactile

uses touch to communicate

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

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

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.

visual

uses sight to communicate

References

Allen, P. 1982. Can captive breeding save birds of prey. New Scientist, 95: 376.

Bergmanis, U. 1996. On the taxonomy of lesser spotted eagle Aquila pomarina and greater spotted eagle A. clanga. Pp. 199-207 in B Meyburg, R Chancellor, eds. Eagle Studies. Berlin: World Working. Group Birds of Prey.

Bildstein, K. 2006. Migrating Raptors of the World: Their Ecology and Conservation. Ithaca, N.Y.: Comstock Publishing Associates.

Burton, P. 1983. Vanishing Eagles. New York: Dodd, Mead, & Company.

Christie, D. 2001. Raptors of the World. Princeton, New Jersey: Princeton University Press.

Clark, W. 2000. A Field Guide to the Raptors of Europe, the Middle East, and North Africa. New York, N.Y.: Oxford University Press.

Del Hoyo, J., A. Elliott, J. Sargatal. 1994. Handbook of the Birds of the World. Volume Two. Barcelona: Lynx Edicions.

Hedenström, A. 1997. Predicted and observed migration speed in lesser spotted eagle Aquila pomarina. Ardea, 85: 29-36.

Ingram, C. 1959. The importance of juvenile cannibalism in the breeding biology of certain birds of prey. American Ornithologists' Union, 76/2: 218-226.

Lõhmus, A., V. Ülo. 2001. Interbreeding of the greater spotted eagle Aquila clanga and lesser spotted eagle A. pomarina. Acta Ornithoecologica, 4/2-4: 377-384.

Mayburg, B., C. Mayberg. 2009. Annual cycle, timing and speed of migration of a pair of lesser spotted eagles Aquaila pomarina - A study by means of satellite telemetry. Eulenarten, BD/6: 63-85.

Mendelssohn, H., U. Paz. 1977. Mass mortality of birds of prey caused by Azodrin, an organophosphorous insecticide. Biological Conservation, 11/3: 163-170.

Meyburg, B., C. Meyburg, T. Belka, O. Sreiber, J. Vrana. 2004. Migration, wintering and breeding of a lesser spotted eagle (Aquila pomarina) from Slovakia tracked by satellite. Journal of Ornithology, 145/1: 1-7.

Meyburg, B., W. Scheller, C. Meyburg. 2000. Migration and wintering of the lesser spotted eagle Aquila pomarina: A study by means of satellite telemetry. Journal fur Ornithologie, 136/4: 183-193.

Meyburg, B., T. Langgemach, K. Graszynski, J. Böhner. 2004. The situation of the lesser spotted eagle Aquila pomarina in Germany: The need for an action plan and active conservation. Pp. 601-613 in R Chancellor, B Meyburg, eds. Raptors Worldwide. Berlin, Germany: World Working Group on Birds of Prey and Owls.

Meyburg, B., C. Meyburg, F. Franck-Neumann. 2007. Why do female lesser spotted eagles (Aquila pomarina) visit strange nests remote from their own. Journal of Ornithology, 148/2: 157-166.

Scott, R. 1976. The Birdwatcher's Key: A Guide to Identification in the Field: 382 Species. London: Frederick Warne.

Seidowski, D., U. Ziegler, J. von Rönn, K. Müller, K. Hüppop, T. Müller, C. Freuling, R. Mühle, N. Nowotny, R. Ulrich, M. Niedrig, M. Groschup. 2010. West Nile Virus monitoring of migratory and resident birds in Germany. Vector-Borne and Zoonotic Diseases, 10/7: 639-647.

Steenhof, K., I. Newton. 2007. Assessing nesting success and productivity. Pp. 181-191 in D Bird, K Bildstein, eds. Raptor Reseach and Management Techniques. Surrey B.C.: Hancock House.

Tingay, R., T. Katzner. 2010. The Eagle Watchers: Observing and Conserving Raptors around the World. Ithaca, N.Y.: Comstock Publushing Associates.

Treinys, R., D. Dementavièius. 2004. Productivity and diet of lesser spotted eagle (Aquina pomarina) in Lithuania. Acta Zoologica Lituanica, 14/2: 83-87.

Väli, Ü., A. Löhmus. 2004. Nestling characteristics and identification of the lesser spotted eagle Aquila pomarina, greater spotted eagle A. clanga, and their hybrids. Journal of Ornithology, 145/3: 256-263.

Väli, Ü., R. Treinys, A. Lõhmus. 2004. Geographical variation in macrohabitat use and preferences of the lesser spotted eagle Aquila pomarina. The International Journal of Avian Science, 146/4: 661-671.

Ülo, V., V. Dombrovski, R. Treinys, B. Ugis, S. Daróczi, M. Dravecky, V. Ivanovski, J. Lontkowski, G. Maciorowski, B. Meyburg, T. Mizera, R. Zeitz, H. Ellegren. 2010. Widespread hybridization between the greater spotted eagle Aquila clanga and the lesser spotted eagle Aquila pomarina. Biological Journal of the Linnean Society, 100/3: 725-736.

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