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

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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

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.

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)

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)