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, CĂ´te 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.
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.
- Habitat Regions
- temperate
- tropical
- terrestrial
- freshwater
- Terrestrial Biomes
- savanna or grassland
- Aquatic Biomes
- lakes and ponds
- rivers and streams
- coastal
- brackish water
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.
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.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
- female larger
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.
There have been instances of non-breeding pairs of African fish eagles, with no reasons
attributed to this behavior.
- Mating System
- monogamous
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.
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
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.
- Parental Investment
- altricial
- male parental care
- female parental care
-
pre-hatching/birth
-
provisioning
- male
- female
-
protecting
- male
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- male
- female
-
protecting
- male
- female
-
provisioning
-
pre-independence
-
provisioning
- male
- female
-
protecting
- male
- female
-
provisioning
Lifespan/Longevity
The lifespan of African fish eagles in the wild is expected to be between 16 and 24
years.
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.
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.
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.
- Key Behaviors
- flies
- diurnal
- motile
- sedentary
- territorial
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.
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.
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.
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.
- 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 (
Tilapia esculenta
), 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 rufa
), and hatchlings of herons and egrets (
Egretta 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
.
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.
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.
- 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.
Other birds of prey, such as the tawny eagle (
Aquila rapax
) have been known to steal food from African fish eagles.
Ecosystem Roles
African fish eagles are a tertiary predator in their ecosystem, at the top of the
food chain.
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.
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.
- 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.
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.
Additional Links
Contributors
David Orban (author), Michigan State University, Pamela Rasmussen (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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).
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- freshwater
-
mainly lives in water that is not salty.
- 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.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- brackish water
-
areas with salty water, usually in coastal marshes and estuaries.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- estuarine
-
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
- 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.
- 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.
- monogamous
-
Having one mate at a time.
- 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).
- 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
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- 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.
- male parental care
-
parental care is carried out by males
- female parental care
-
parental care is carried out by females
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- 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
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- 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
- carrion
-
flesh of dead animals.
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
References
Brown, L. 1970. African Birds of Prey . Boston: Houghton Mifflin.
Brown, L. 1980. The African Fish Eagle . Great Britain: Bailey Bros. and Swinfen.
Brown, L. 1960. The African Fish Eagle Haliaeetus vocifer especially in the Kavirondo Gulf. Ibis , 102: 285-297.
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 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 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.