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Polemaetus bellicosusmartial eagle

By Will Overholt

Geographic Range

Martial eagles (Polemaetus bellicosus) are found throughout Sub-Saharan Africa, although they avoid dense forests and are absent from much of central Africa. (Burton and Burton, 2002; Machange, et al., 2005)

Habitat

Martial eagles prefer open habitats including savanna, steppe, semidesert and scrubby woodlands. These eagles require trees for nesting and are absent from arid or cleared areas, although there have been cases of martial eagles in the Karoo region of South Africa using power line supports to form nests. Martial eagles are spread sparsely throughout their geographical range punctuated with pockets of higher densities found in large protected areas, especially in South Africa and Zimbabwe. They can be found at all altitudes under 3000 meters. (Burton and Burton, 2002; Machange, et al., 2005; Thiollay, 1994; de Goede and Jenkins, 2001)

  • Range elevation
    0 to 3000 m
    0.00 to 9842.52 ft

Physical Description

Martial eagles are Africa’s largest eagle. Adults range in size from 78 to 96 cm in length, weighing between 3.1 and 6.2 kg, with a wingspan from 188 to 260 cm. The males are slightly smaller than females (76% of the size). The adults have brown upper-parts and have a short dark crest. The underparts are white with brown to black spots that extend to feathered legs. The bill is long, strongly hooked and black. The toes are bluish gray and armed with large curved talons. The wings are long and slightly pointed with dark tips and dark under-wing coverts, although the flight feathers are barred. The tail is short, lighter in appearance, and is also barred. Females have more spots on the underparts than males do. Juveniles have pale to white upper-parts and have pale wings with light under-wing coverts. (Burton and Burton, 2002; Ferguson-Lees and Christie, 2001; Thiollay, 1994)

  • Sexual Dimorphism
  • female larger
  • Range mass
    3.1 to 6.2 kg
    6.83 to 13.66 lb
  • Range length
    78 to 96 cm
    30.71 to 37.80 in
  • Range wingspan
    188 to 260 cm
    74.02 to 102.36 in

Reproduction

Martial eagles lack a mating dance although both sexes will make a loud, distinctive cry during mating periods. They form monogamous pairs and reportedly mate for life. (Burton and Burton, 2002)

Martial eagles nest in large trees or pylons often located on hill sides. The nest is a large structure (4 – 6 feet in diameter) made of sticks up to 1.5 inches in diameter and lined with green leaves. Pairs may build multiple nests (up to 7 nests in a given territory) and alternate between nests on successive years. The nests are often re-used from year to year with the female repairing parts of the structure and re-lining the interior with leaves. Mating seasons vary across the geographic range, although it generally occurs during the dry season: from February until November in South, Central and East Africa, from August till January in North East Africa, and in November in West Africa. Martial eagles more often breed once every two years, than once every year.

The female lays generally 1, sometimes 2 eggs. Incubation lasts for 45 to 50 days, and chicks fledge 90 to 100 days after hatching. Juveniles remain close to the nest for up to 6 months, and do not reach full independence until 2 to 3 years of age. Martial eagles reach reproductive maturity at 4 to 5 years of age. (Allan, 1996; Burton and Burton, 2002; Machange, et al., 2005; Simmons and Brown, 2006; Thiollay, 1994)

  • Breeding interval
    Martial eagles generally breed annually or biennially.
  • Breeding season
    The breeding season correlates with the dry season across the geographic range.
  • Range eggs per season
    1 to 2
  • Average eggs per season
    1
  • Range time to hatching
    45 to 50 days
  • Range fledging age
    90 to 100 days
  • Average fledging age
    96 days
  • Range time to independence
    2 to 3 years
  • Range age at sexual or reproductive maturity (female)
    4 to 5 years
  • Range age at sexual or reproductive maturity (male)
    4 to 5 years

The female incubates the egg for the 45 to 50 days it takes for a chick to hatch, although males have been observed incubating. Males rarely bring food to incubating females until the egg hatches, after which males will hunt and feed females for approximately 2 months. Chicks are born without feathers and become fully fledged after 90 days, and after which they attempt their first flight. Juveniles spend several years in the nest region before being chased off by the adults. (Brown, 1966; Burton and Burton, 2002; Thiollay, 1994)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • post-independence association with parents

Lifespan/Longevity

In the wild, martial eagles are expected only to live an average of 14 years, although one individual was recaptured 25 years after being banded. (Brown, 1966; Burton and Burton, 2002)

  • Range lifespan
    Status: wild
    25 (high) years
  • Average lifespan
    Status: wild
    14 years

Behavior

Martial eagles spend most of the time hunting or soaring high above the ground (generally invisible to the naked eye). With their large wings and broad tail they are excellent at soaring, although poor at maneuvering which helps explain why they avoid dense forests. These eagles hunt by attacking in a well controlled dive at a slanted angle and striking prey with their long legs. They often perch on dead branches and trees that give a wide view of the areas and generally return to these perches when resting. Although uncommon, they have been observed hunting from a perched position. Martial eagles are shy and often avoid humans. (Allan, 1996; Burton and Burton, 2002; Simmons and Brown, 2006; Thiollay, 1994)

  • Range territory size
    15 to 300 km^2

Home Range

A pair of adults can occupy a range up to 300 square kilometers, although in high densities a pair's territory is often less than 20 square kilometers. (Machange, et al., 2005; Thiollay, 1994)

Communication and Perception

Martial eagles are silent for most of the year, although during mating season they cry kwi-kwi-kluee-kluee. Like all birds, martial eagles perceive their environment through visual, auditory, tactile, and chemical stimuli. (Burton and Burton, 2002)

Food Habits

Martial eagles eat a variety of medium sized mammals, birds, and lizards generally weighing between 1 – 5 kilograms, determined by whatever is available in their territories, including animals much larger than 5 kilograms. In a study in the Cape Province of South Africa, Cape hares (Lepus capensis) were the dominant prey making up 50% of all kills, followed by striped polecats (Ictonyx striatus), genets (Genetta tigrina and G. genetta), ground squirrels (Xerus inauris) and mongooses (Mungos mungo, Helogale parvula, Herpestes ichneumon, and Galerella sanguinea). In some cases game birds and waterfowl make up a large portion of their diet. These include primarily francolins (Francolinus species), bustards (Otididae), and guinea fowls (Numidae). In other areas, martial eagles prey primarily upon rock hyraxes (Procavia capensis). To a lesser extent, martial eagles have hunted: Vervet monkeys (Chlorocebus pygerythrus), baboons (Papio species, especially P. Anubis), small antelopes including: Thomson’s gazelles (Eudocas thomsoni), young impala (Aepyceros melampus), duikers (Cephalopus species), jackals (Canis species), snakes, and monitor lizards (Varanus niloticus, V. exanthematicus). These eagles have been seen killing and eating prey up to 35 kilograms. (Boshoff, et al., 1990; Machange, et al., 2005; Thiollay, 1994)

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

Predation

There are no known occurrences of predation on martial eagles, although humans will kill martial eagles if they are perceived as pests. (Machange, et al., 2005)

Ecosystem Roles

Martial eagles are apex predators and can be used as an indicator of ecosystem health. They also likely keep prey populations in check. (Machange, et al., 2005; de Goede and Jenkins, 2001)

Economic Importance for Humans: Positive

While the results are not clear, it has been suggested that in the Karoo region of South Africa, martial eagles benefit small-stock farmers by managing populations of small grazing mammals that compete with their own domestic grazing animals. In general though, these eagles are very rare outside of protected areas and avoid humans. (Burton and Burton, 2002; de Goede and Jenkins, 2001)

Economic Importance for Humans: Negative

Martial eagles are thought to be the most severely persecuted raptor in South Africa since it sometimes feeds on domesticated poultry, small lambs, and goats. However, a study in Nambia reported these predations make up a small portion (< 1%) of an eagles diet even in areas dominated by small ranchers. Unfortunately, many farmers use poison to ward off predators and many eagles are harmed in this non-specific, deadly method. (Boshoff, et al., 1990; Machange, et al., 2005; de Goede and Jenkins, 2001)

  • Negative Impacts
  • crop pest

Conservation Status

According to the IUCN Red List, martial eagles are near threatened and their populations are declining throughout their geographic range. Locally, West Africa populations are declining and their presence is rare. In Namibia, martial eagles are endangered due to a decline of 80% in their population over a five year period, where there are approximately only 350 pairs in the country. The population decline can be attributed to shooting and poisoning from local farmers and ranchers, electrocution from nesting on power lines, drowning from attempting to drink at steep-sided reserves, and starvation from the extermination of common food sources. (Burton and Burton, 2002; Machange, et al., 2005; Simmons and Brown, 2006; Thiollay, 1994; de Goede and Jenkins, 2001)

Contributors

Will Overholt (author), Florida State University, Emily DuVal (editor), Florida State University, Rachelle Sterling (editor), Special Projects.

Glossary

Ethiopian

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

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

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).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

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

sedentary

remains in the same area

sexual

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

tactile

uses touch to communicate

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

Allan, D. 1996. Photographic Guide to Birds of Southern, Central, and East Africa. Cape Town, South Africa: Struik Publishers.

Boshoff, A., N. Plamer, G. Avery. 1990. Regional variation in the diet of Martial Eagles in the Cape Province, South Africa. South African Journal of Wildlife Research, 20/2: 57.

Brown, L. 1966. Observations on some Kenya Eagles. Ibis, 108/4: 531.

Burton, M., R. Burton. 2002. Martial Eagle. Pp. 1586 in P Bernabeo, ed. International Wildlife Encyclopedia, Vol. 12, 3 Edition. Tarrytown, New York: Marshall Cavendish Corporation.

Ferguson-Lees, J., D. Christie. 2001. Raptors of the World. New York, New York: Houghton Mifflin Company.

Machange, R., A. Jenkins, R. Navarro. 2005. Eagles as indicators of ecosystem health: Is the distribution of Martial Eagles in the Karoo, South Africa, influenced by variations in land-use and rangeland qualilty?. Journal of Arid Environments, 63/1: 223.

Simmons, R., C. Brown. 2006. Birds to Watch in Nambia: red, rare, and endemic species. Windhoek, Namibia: National Biodiversity Programme.

Thiollay, J. 1994. Martial Eagle. Pp. 225 in J del Hoyo, A Elliot, J Sargatal, eds. Handbook of the Birds of the World, Vol. 2, 1 Edition. Barcelona, Spain: Lynx Edicions.

de Goede, K., A. Jenkins. 2001. Electric Eagles of the Karoo. Africa -- Birds & Birding, 6/4: 62.

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