Overview
Scientific Name: Haliaeetus vocifer
Local Name
Luganda : MAKWANZI
Lugisu : KISILILI
Lunyankole : EKIHUNGU
Lugbara: YUKU
Brief Summary
Biology
The African fish-eagle is a proficient hunter, with live fish accounting for the bulk of its diet. It typically hunts from a high perch on a waterside tree, where it can watch for fish moving close to the water’s surface. Once prey is sighted, the fish-eagle launches from its perch, swoops low over the water, and at the critical moment throws both feet forward to seize hold of its target with powerful talons. Small fish are carried through the air into a tree but larger catches are dragged through the water to the shoreline. Despite only one in every seven or eight fishing attempts being successful, the African fish-eagle rarely spends more than ten minutes per day actively hunting. Aside from fish, this efficient raptor will also take the young of water birds such as the lesser flamingo, and very occasionally will go for monkeys, crocodile hatchlings, frogs and insects. Except for the odd dead fish, fully mature African fish-eagles rarely feed on carrion unless food is particularly scarce. Adult African fish-eagles are normally seen in pairs, but on large productive lakes, nests and roosts may be only a few hundred metres apart, and many birds can be found together in one area. The stick nests are usually built in a tree close by water and are used year after year, growing in size over time with the addition of reeds, papyrus heads, bulrushes and sometimes weaver nests. Calling and duetting, whilst perched or soaring, is an integral part of the breeding display, and is combined with dramatic aerial dives and falls, with pairs interlocking talons in mid air. The female normally lays one to three eggs in the nest, which are incubated for around 44 days before hatching. Until the chicks fledge after around 65 to 75 days, it is necessary for the adults to spend considerably more time hunting for food, compared with other times of the year. Although in captivity African fish-eagles can live for more than 40 years, in the wild those that are fortunate to survive the first year have an estimated life expectancy of 12 to 24 years.
Description
With its distinctive plumage and evocative cry, the African fish-eagle is probably the most familiar bird of prey in Africa. Perched majestically on a high branch, the contrast between the white upper-body and tail, the chestnut belly, and the black wings, is unmistakable. Much less striking is the almost scruffy appearance of the immature African fish-eagle, with its generally dark-brown plumage and white mottling. Although after the first year the plumage begins to resemble that of the adult, it will take at least four to five years and numerous moults to reach full maturity. The clear, ringing call weee-ah hyo-hyo-hyo, made with the head thrown back, has to be the most characteristic and evocative sound of African watersides.
Distribution
Range
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.
Physical Description
Morphology
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.
Range mass: 2.1 to 3.6 kg.
Range length: 63 to 77 cm.
Range wingspan: 175 to 210 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; female larger
Ecology
Habitat and Ecology
Behaviour: This is an afrotropical species (17°N to 35°S), common to be abundant throughout its range except in waterless areas. It is generally sedentary but can be nomadic in response to resource shortages (e.g., drought, flood or prey scarcity), and has been recorded traveling up to 200km from the natal site. Habitat The species occupies a range of aquatic habitats from sea level to 4000m, ideally areas of calm water, such as swamps, lakes, rivers, floodplains and estuaries. Juveniles that are dispersing can cross vast dry areas and will roost and feed on carcasses en-route. Diet The speciesâ diet consists primarily of fish, but it will also take other available taxa as well as carrion when prey is scarce. Juveniles are known to feed at large mammal carcasses alongside vultures and Tawny Eagles Breeding Site The species nests near water, in tall acacias or other suitable trees, and occasionally on rock outcrops. Nests are up to 1.5m in diameter and are composed of sticks and papyrus, lined with rush heads and occasionally, weaver nests. Breeding can occur at any time within Equatorial regions, but spans April – October in southern Africa; June – December in the east; and October â“ April in the west.
Systems
- Terrestrial
- Freshwater
- Marine
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.
Range elevation: 4000 (high) m.
Average elevation: under 1500 m.
Habitat Regions: temperate ; tropical ; terrestrial ; freshwater
Terrestrial Biomes: savanna or grassland
Aquatic Biomes: lakes and ponds; rivers and streams; coastal ; brackish water
Wetlands: marsh ; swamp
Other Habitat Features: riparian ; estuarine
This fish-eagle is associated with a diverse range of aquatic habitats from rivers, lakes and dams to swamps and mangrove lagoons.
Dispersal
Movements and dispersal
Trophic Strategy
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.
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
Primary Diet: carnivore (Piscivore )
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.
Known Predators:
- Nile monitors (Varanus niloticus)
- Snakes
- Primates
Life History and Behavior
Behavior
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.
Communication Channels: visual ; acoustic
Life Expectancy
Lifespan/Longevity
The lifespan of African fish eagles in the wild is expected to be between 16 and 24 years.
Range lifespan
Status: wild: 16 to 24 hours.
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.
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.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
African fish eagles usually construct one to three nests in tall trees near waterways; nests 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); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
LC
Least Concern
Red List Criteria
Version
3.1
Year Assessed
2013
Assessor/s
BirdLife International
History
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.
Threats
Major Threats
The species is not known to be directly persecuted by humans, even though it is very numerous and probably a direct competitor for fish. Neither is it particularly affected by habitat loss. In some regions a build-up of organochlorine pesticides in water bodies and therefore in their fish prey, could result in eggshell thinning. This has been recorded in South Africa (Ferguson- Lees and Christie, 2001) and Zimbabwe (del Hoyo et al., 1994) but has not yet had any significant impact on the population.
While wetland degradation and water pollution has affected African fish-eagles in some areas, this species has benefited considerably from the construction of large dams, particularly in Southern Africa. Given that its population appears to be stable and widely distributed, the African fish-eagle is not considered to be under any significant threat.
Management
Conservation
There are no known conservation measures in place for the African fish-eagle.
Relevance to Humans and Ecosystems
Benefits
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
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
