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Haliaeetus vociferAfrican fish eagle(Also: African fish-eagle)

By David Orban

Geographic Range

Found throughout sub-Saharan Africa, African fish eagles range from Mauritania, Mali, Niger, Chad, Sudan, and Eritrea in the north, to the Atlantic Ocean in the west, the Indian Ocean in the east and to South Africa in the south. Non-breeding (wintering) areas are located in southwestern Africa (Namibia, Botswana, and South Africa), parts of central Africa (Cameroon, Equatorial Guinea, Gabon, the Republic of the Congo, and the Democratic Republic of the Congo), and parts of western Africa (Sierra Leone, Guinea, Liberia, Côte d'Ivoire, and Ghana). Generally, African fish eagles can be found between the latitudes of 17°N and 35°S. Adults are usually sedentary, but may move about locally in response to changing environmental conditions such as drought, flooding events, or changes in food supply. (Ferguson-Lees and Christie, 2001; Ferguson-Lees and Christie, 2005)

Habitat

African fish eagles are found primarily along bodies of water throughout sub-Saharan Africa; these include rivers, lakes, floodplains, coasts, estuaries, mangrove lagoons, and swamps. African fish eagles also frequent stocked dams and alkaline lakes. Individuals have been observed at elevations up to 4000 m. However, they usually remain under an elevation of 1500 m. (Ferguson-Lees and Christie, 2001; Ferguson-Lees and Christie, 2005)

  • Range elevation
    4000 (high) m
    13123.36 (high) ft
  • Average elevation
    under 1500 m
    ft

Physical Description

Adult African fish eagles are large, readily recognizable raptors, with their pure white head, neck, chest, and tail, dark chestnut brown body, and black primaries and secondaries. They have broad, rather long wings (wingspan from 175 to 210 cm), and a fairly short, rounded tail. The face is largely bare and yellow, as is the cere; the eyes are dark, and the feet are yellow. The mass of an adult African fish eagle ranges from 2.1 to 3.6 kg and the length can range from 63 to 77 cm. Females are larger and bulkier (about 10 to 15%) than males, and African fish eagles tend to be slightly larger in the southern parts of Africa. (Brown, 1980; Ferguson-Lees and Christie, 2001; Ferguson-Lees and Christie, 2005; Hollamby, et al., 2004)

Juveniles are quite different than adults; their plumage is mostly brown, with white feathers scattered throughout in no particular pattern. They have white patches on the chest, base of the tail, and primary bases, and the face is dull grayish. The tail also tends to be longer in juveniles than in adults. (Brown, 1980; Ferguson-Lees and Christie, 2005)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • Range mass
    2.1 to 3.6 kg
    4.63 to 7.93 lb
  • Range length
    63 to 77 cm
    24.80 to 30.31 in
  • Range wingspan
    175 to 210 cm
    68.90 to 82.68 in

Reproduction

African fish eagles are monogamous and most often mate for life. Breeding is seasonal, and both sexes participate in nest building, incubation, and rearing of chicks. (Brown, 1970; Ferguson-Lees and Christie, 2001)

There have been instances of non-breeding pairs of African fish eagles, with no reasons attributed to this behavior. (Brown, 1960)

African fish eagles breed once yearly, with breeding seasons varying according to where the African fish eagles reside. Along the equator, breeding can occur most months. In southern Africa, April through October is the typical breeding season, where it is June through December for coastal eastern Africa and October through April for western Africa. (Ferguson-Lees and Christie, 2001)

Usually two eggs are laid, but clutch sizes ranging from one to four eggs have been observed. If there is more than one egg per clutch, they are usually laid 2-3 days apart, and usually only 1 chick survives as a result of siblicide. Young hatch between 42 and 45 days, and fledge between 64 and 75 days. African fish eagles are usually independent from their parents after 6 to 8 weeks post-fledging. It has been said that only 5% of African fish eagle young reach adulthood. (Brown, 1960; Brown, 1970; Brown, 1980; Ferguson-Lees and Christie, 2001)

  • Breeding interval
    African fish eagles breed once yearly.
  • Breeding season
    Along the equator, breeding can occur most months. In southern Africa, April through October is the typical breeding season, where in coastal eastern Africa it is June through December, and in western Africa it is October through April.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    2
  • Range time to hatching
    42 to 45 days
  • Range fledging age
    64 to 75 days
  • Range time to independence
    16 to 18 weeks

African fish eagles usually construct one to three nests in tall trees near waterways; nest are commonly built in acacias, smooth-barked trees, or euphorbias. Both sexes participate in nesting behavior. Nests usually have a diameter of 120-150 cm and a depth of 30-60 cm (but can be as big as 200 cm in diameter and 150 cm deep). Nests are lined with grass, leaves, papyrus, reed, and sometimes even weaver nests. Both sexes participate in incubation and rearing of chicks; females primarily incubate and shade the chicks whereas the male does most of the hunting for his mate and offspring. Adults may continue to feed offspring for an additional six weeks post fledging. (Brown, 1960; Brown, 1970; Ferguson-Lees and Christie, 2001)

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

Lifespan/Longevity

The lifespan of African fish eagles in the wild is expected to be between 16 and 24 years. (Brown, 1970; Ferguson-Lees and Christie, 2001)

  • Range lifespan
    Status: wild
    16 to 24 hours

Behavior

African fish eagles are diurnal. They are often observed in pairs perched on mostly horizontal branches that are near to or overhanging a body of water. Most of their time is spent surveying the area, and they spend less than 10 minutes per day fishing, except when raising young. (Brown, 1980; Ferguson-Lees and Christie, 2001)

Courtship displays in African fish eagles include aerial diving, swooping, and calling. In some instances, the pair will lock talons and perform a whirling dive together. (Brown, 1960)

During times of extreme food concentration or food scarcity, the density of African fish eagles can reach high numbers. Juveniles have been observed in groups of 30 around fisheries. (Ferguson-Lees and Christie, 2001)

  • Range territory size
    1.1 to 5 km^2

Home Range

Breeding pairs hold an average territory size of 1.1 km along the shoreline of a freshwater lake and an average territory size of 3.4 km along a river shoreline. Immature fish eagles, which are often out-competed intra-specifically for shoreline territories, may occupy an area of 5 sq km in shrubby grassland. Density of African fish eagles usually reflects available perches and amount of food resources. (Krueger, 1997)

Communication and Perception

African fish eagles communicate vocally with members of the same species or other avian competitors to establish and maintain territories. When calling, whether perched or in flight, they throw the head back and give loud, far-carrying, distinctive calls that sound like “Weeah kyow-kow-kow.” Male African fish eagles tend to have higher pitched calls than females. (Brown, 1960; Brown, 1980; Ferguson-Lees and Christie, 2005; Krueger, 1997)

Duets between a breeding pair are often heard. Duetting is more common at the start of the breeding season and facilitates a close bond between the pair. (Brown, 1960; Brown, 1970; Ferguson-Lees and Christie, 2005)

Like other eagle species, African fish eagles will display or call when under threat from solicitors or intruders. African fish eagles perceive their environment through visual, auditory, tactile and chemical stimuli. (Brown, 1960)

  • Other Communication Modes
  • duets

Food Habits

African fish eagles’ primary food source, as the name implies, is fish. An individual may consume half a pound of fish per day. Common fish species preyed upon include tilapia (Oreochromis esculentus), catfish (Clarius), lungfish (Protopterus aethiopicus), tigerfish, and mullet, all of which are captured along the water’s surface. Aquatic birds such as cormorants (Phalacrocorax carbo), grebes, darters (Anhinga melanogaster rufa), and hatchlings of herons and egrets (Ardea alba, Bubulcus ibis, Ardea intermedia) may also become prey to fish eagles. They also hunt flamingos (Phoeniconaias minor, Phoenicopterus ruber) in alkaline lakes, where abundance of fish is limited. Rarely, they will hunt terrestrial mammalian prey such as hyraxes or monkeys, reptile prey such as crocodile hatchlings, terrapins, or monitor lizards, or amphibians such as bullfrogs. (Brown, 1960; Brown, 1970; Brown, 1980; Ferguson-Lees and Christie, 2001; Green, 2009; Harper, et al., 2002)

Typical foraging by African fish eagles involves soaring followed by diving to the water’s surface to catch fish with their talons. It often requires several attempts before a successful catch occurs, with only one in 7 to 8 attempts ending in success. Only fish up to 2 kg can be easily lifted away; anything larger is usually dragged to land and then consumed. (Ferguson-Lees and Christie, 2001; Green, 2009)

African fish eagles have been known to steal food from other predatory birds such as hammerkops (Scopus umbretta), kingfishers, pelicans (Pelecanus), herons, and other birds of prey, such as osprey (Pandion haliaetus) or other fish eagles. African fish eagles may also hunt or scavenge terrestrial prey; however when terrestrial hunting does occur, it is likely due to the eagle’s immaturity. (Brown, 1960; Brown, 1970; Green, 2009; Harper, et al., 2002)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • carrion

Predation

Snakes and Nile monitors (Varanus niloticus) have been known to prey upon the eggs of African fish eagles. African fish eagle parents will also guard against monkeys and baboons, but tend to not be concerned about nearby humans. (Brown, 1970; Sumba, 1988)

Other birds of prey, such as the tawny eagle (Aquila rapax) have been known to steal food from African fish eagles. (Brown, 1960)

Ecosystem Roles

African fish eagles are a tertiary predator in their ecosystem, at the top of the food chain. (Hollamby, et al., 2006)

Economic Importance for Humans: Positive

African fish eagles prey upon many species such as catfish and cormorants that are other major predators of young or small fish. This in turn has a positive effect on the fishing industry for the region. (Brown, 1970)

As top carnivore, the African fish eagle is commonly a reference to the health of an aquatic ecosystem, since anything happening at lower levels of the food web will affect the fish eagle through biomagnification. Ecologists, conservationists, and fish farmers can evaluate the strength of a fish eagle population to establish fish crop population, pollution in the waterways, and habitat alteration, since each of these factors will have a more dramatic effect on top carnivores.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

The diet of African fish eagle is comprised mainly of fish, some of which are reintroduced or farmed for commercial fishing or fish farming. They have also been known to prey upon the catch of fishermen, ranging from less than .4% to as much as 1% of the total catch. Since many Africans live in poverty, these losses can be detrimental to them. (Cooke and Wilde, 2007; Eltringham, 1975)

  • Negative Impacts
  • crop pest

Conservation Status

The estimated current population size is 300,000. However the species remains common and widespread throughout sub-Saharan Africa, in suitable habitat. (Butchart, et al., 2009)

Ecologically, African fish eagle populations are negatively impacted by limited fish sources, land changes in terms of perching or nesting trees near waterways, and aquatic vegetation changes that alter fishing practices of the eagle. Pesticides and other pollutants may also pose a threat to African fish eagles through biomagnification. Eggshell-thinning due to a buildup of organochlorine pesticides (from fish) may begin to cause problems in some parts of its range. (Ferguson-Lees and Christie, 2001; Harper, et al., 2002; Steyn, 1983)

Contributors

David Orban (author), Michigan State University, Pamela Rasmussen (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

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.

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.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

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

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

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.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

freshwater

mainly lives in water that is not salty.

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

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.

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.

piscivore

an animal that mainly eats fish

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

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

swamp

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

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

Brown, L. 1960. The African Fish Eagle Haliaeetus vocifer especially in the Kavirondo Gulf. Ibis, 102: 285-297.

Brown, L. 1970. African Birds of Prey. Boston: Houghton Mifflin.

Brown, L. 1980. The African Fish Eagle. Great Britain: Bailey Bros. and Swinfen.

Butchart, S., J. Ekstrom, M. Harding. 2009. "BirdLife International (2009) Species factsheet" (On-line). African Fish-eagle (Haliaeetus vocifer). Accessed July 27, 2009 at http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3361&m=0.

Cooke, S., G. Wilde. 2007. The Fate of Fish Released by Recreational Anglers. Pp. 181–234 in S Kennelly, ed. By-catch Reduction in the World’s Fisheries, Vol. 7, Reviews: Methods and Technologies in Fish Biology and Fisheries. Netherlands: Springer.

Eltringham, S. 1975. Territory size and distribution in the African fish eagle. Journal of Zoology London, 175: 1-13.

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

Ferguson-Lees, J., D. Christie. 2005. Raptors of the World. Singapore: Princeton Field Guides.

Green, J. 2009. Birds of the Nile. Pp. 705-720 in H Dumont, ed. The Nile: Origin, Environments, Limnology and Human Use, Vol. 89, Monographiae Biologicae. Netherlands: Springer.

Harper, D., R. Childress, M. Harper, R. Boar, P. Hickley, S. Mills, N. Otieno, T. Drane, E. Vareschi, O. Nasirwa, W. Mwatha, J. Darlington, X. Escute-Gasulla. 2003. Aquatic biodiversity and saline lakes: Lake Bogoria National Reserve, Kenya. Hydrobiologia, 500: 259-276.

Harper, D., M. Harper, M. Virani, A. Smart, R. Childress, R. Adatia, I. Henderson, B. Chenge. 2002. Population fluctuations and their causes in the African Fish Eagle, (Haliaeetus vocifer (Daudin)) at Lake Naivasha, Kenya. Hydrobiologia, 488: 171-180.

Hollamby, S., J. Afema-Azikuru, W. Bowerman, K. Cameron, C. Dranzoa, A. Gandolf, G. Hui, J. Kaneene, A. Norris, J. Sikarskie, S. Fitzgerald, W. Rumbeiha. 2004. Methods for capturing African Fish eagles on water. Wildlife Society Bulletin, 32(3): 680-684.

Hollamby, S., J. Afema-Azikuru, S. Waigo, K. Cameron, A. Gandolf, J. Sikarskie. 2006. African fish eagle nest site characteristics within Uganda. African Journal of Ecology, 44: 109-112.

Krueger, O. 1997. Population density and intra- and interspecific competition of the African Fish Eagle Haliaeetus vocifer in Kyambwra Game Reserve, southwest Uganda. Ibis, 139: 19-24.

Steyn, P. 1983. Birds of Prey of Southern Africa. Dover, New Hampshire: Tanager Books Inc.

Sumba, S. 1988. Nestling growth in the African fish eagle in Uganda. African Journal of Ecology, 26: 315-321.

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