African fish eagle

Appearance

The African fish eagle is a large bird, and the female, at 3.2–3.6 kg is larger than the male, at 2–2.5 kg. This is typical of sexual dimorphism in birds of prey. Males usually have a wingspan of about 2 m, while females have wingspans of 2.4 m. The body length is 63–75 cm.

The adult is very distinctive in appearance with a mostly brown body with a white head like the bald eagle and large, powerful, black wings. The head, breast, and tail of African fish eagles are snow white, with the exception of the featherless face, which is yellow. The eyes are dark brown in colour.

The hook-shaped beak, ideal for a carnivorous lifestyle, is yellow with a black tip. The plumage of the juvenile is brown in colour, and the eyes are paler compared to the adult. The feet have rough soles and are equipped with powerful talons in order to enable the eagle to grasp slippery aquatic prey.

Distribution

This species is still quite common near freshwater lakes, reservoirs, and rivers, although they can sometimes be found near the coast at the mouths of rivers or lagoons. As their name implies, African fish eagles are indigenous to sub-Saharan Africa, ranging over most of continental Africa south of the Sahara Desert. Several examples of places where they may be resident include the Orange River in South Africa and Namibia, the Okavango Delta in Botswana, and Lake Malawi bordering its namesake country Malawi, Tanzania and Mozambique. The African fish eagle is thought to occur in substantial numbers around the locations of Lake Victoria and other large lakes that are found in Central Africa, particularly the Rift Valley lakes. The African fish eagle is a generalist species, requiring only open water with sufficient prey and a good perch. This is evident by the number of habitat types that this species may be found in, including grassland, swamps, marshes, tropical rainforest, fynbos and even desert bordering coastlines, such as that of Namibia. The African fish eagle is absent from arid areas with little surface water.

Status

This species is listed as "Least Concern" by IUCN. The estimated population size is about 300,000 individuals with a distribution area of 18,300,000 km2.

Behavior

While this species mainly subsists on fish, it is opportunistic and may take a wider variety of prey such as waterbirds. Its distinctive cry is, for many, evocative of the spirit or essence of Africa. The call, shriller when uttered by males, is a "weee-ah, hyo-hyo" or a "heee-ah, heeah-heeah".

Reproduction

Breeding season for African fish eagles is during the dry season, when water levels are low. African fish eagles are believed to be monogamous – in other words, they mate for life. Pairs will often maintain two or more nests, which they will frequently re-use. Because nests are re-used and built upon over the years the nests can grow quite large, some reaching 2 m across and 1.2 m deep. The nests are placed in a large tree and are built mostly of sticks and other pieces of wood.

The female lays 1 to 3 eggs, which are primarily white with a few reddish speckles. Incubation is mostly done by the female, but the male will incubate when the female leaves to hunt. Incubation lasts for 42 to 45 days before the chicks hatch. Siblicide does not normally occur in this taxon, and the parents will often successfully rear two or three chicks. Chicks fledge at approx 70 to 75 days. Post-fledgling dependence lasts up to three months, whereafter the juveniles become nomadic, and may congregate in groups away from territorial adults. Those that survive their first year have a life expectancy of some 12 to 24 years.

Food

The African fish eagle feeds mainly on fish, which it will swoop down upon from a perch in a tree, snatching the prey from the water with its large clawed talons. The eagle will then fly back to its perch to eat its catch. Like other sea eagles, the African fish eagle has structures on its toes called spiricules that allows it to grasp fish and other slippery prey. The osprey, a winter visitor to Africa, also has this adaptation. Should the African fish eagle catch a fish over 1.8 kg it will be too heavy to allow the eagle to get lift, so it will instead drag the fish across the surface of the water until it reaches the shore. If it catches a fish that is too heavy to even allow the eagle to sustain flight, it will drop into the water and paddle to the nearest shore with its wings. The African fish eagle is known to peculate other bird species of their catch. This behaviour is known as kleptoparasitism. It will also feed on waterfowl such as ducks, small turtles and terrapins, baby crocodiles, greater flamingos and lesser flamingos, lizards, frogs and carrion. Occasionally, it may even carry off mammalian prey, such as hyraxes and monkeys. It has also been observed feeding on domestic fowl.