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African fish eagle

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African fish eagle
Eagle at Chobe National Park, Botswana
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Icthyophaga
Species:
I. vocifer
Binomial name
Icthyophaga vocifer
(Daudin, 1800)

The African fish eagle (Icthyophaga vocifer) or the African sea eagle is a large species of eagle found throughout sub-Saharan Africa wherever large bodies of open water with an abundant food supply occur. It is the national bird of Malawi, Namibia, Zambia, and Zimbabwe. As a result of its large range, it is known in many languages.[3] Examples of names include: Vis Arend in Afrikaans, nkwazi in Chewa, aigle pêcheur in French,[4] hungwe in Shona, inkwazi in isiZulu, and ntšhu (pronounced "ntjhu") in Northern Sotho. This species may resemble the bald eagle in appearance; though related, the two species occurs on different continents, with the bald eagle being resident in North America.

Taxonomy

The African fish eagle is a species placed in the genus Icthyophaga (fish eagles). Its closest relative appears to be the critically endangered Madagascar fish eagle (I. vociferoides). Like all sea eagle species pairs, this one consists of a white-headed species (the African fish eagle) and a tan-headed one (Madagascar fish eagle). These are an ancient lineage of sea eagles; like other sea eagles, they have dark talons, beaks, and eyes[5] Both species have at least partially white tails even as juveniles. The vocifer is derived from its original genus name, so named by the French naturalist François Levaillant, who called it 'the vociferous one'.[6]

Description

African fish eagle in Lake Zway, Ethiopia

The African fish eagle is a large bird. The female, at 3.2–3.6 kg (7.1–7.9 lb) is larger than the male, at 2.0–2.5 kg (4.4–5.5 lb). This is typical sexual dimorphism in birds of prey. Males usually have wingspans around 2.0 m (6.6 ft), while females have wingspans of 2.4 m (7.9 ft). The body length is 63–75 cm (25–29.5 in). 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, except for 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, and the eyes are paler than the adult's. The feet have rough soles and are equipped with powerful talons to enable the eagle to grasp slippery aquatic prey. 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.[7][8][9] The call, shriller when uttered by males, is a weee-ah, hyo-hyo or a heee-ah, heeah-heeah.[8]

Distribution and habitat

This species is still quite common near freshwater lakes, reservoirs, and rivers, although it can sometimes be found near the coast at the mouths of rivers or lagoons. 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 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 in Central Africa, particularly the Rift Valley lakes.[10] This is a generalist species, requiring only open water with sufficient prey and a good perch, as evidenced by the number of habitat types in which this species may be found, including grasslands, swamps, marshes, tropical rainforests, fynbos, and even desert-bordering coastlines,[11] such as that of Namibia. The African fish eagle is absent from arid areas with little surface water.

Reproduction

An adult on the nest in Lake Baringo, Kenya
Egg

African fish eagles breed during the dry season, when water levels are low. They are believed to mate for life.[12][13] Pairs often maintain two or more nests, which they frequently reuse. Because nests are reused and built upon over the years, they can grow quite large, some reaching 2.0 m (6.5 ft) across and 1.2 m (3.9 ft) deep. The nests are placed in a large tree and are built mostly of sticks and other pieces of wood.

The female lays one to three eggs, which are primarily white with a few reddish speckles. Incubation is mostly done by the female, but the male incubates 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 often successfully rear two or three chicks.[14] Chicks fledge around 70 to 75 days old. Post-fledgling dependence lasts up to three months, whereafter the juveniles become nomadic and may congregate in groups away from territorial adults.[14] Those that survive their first year have a life expectancy of some 12 to 24 years.[12]

Diet

African fish eagle carrying off a catfish in Lake Baringo, Kenya
A juvenile catches a fish
An African fish eagle feeding on its prey, likely a mudfish Labeo sp., in Kruger National Park, South Africa

The African fish eagle feeds mainly on fish, which it swoops down upon from a perch in a tree, snatching the prey from the water with its large, clawed talons. The eagle then flies back to its perch to eat its catch. Like other sea eagles, the African fish eagle has structures on its toes called spiricules that allow it to grasp fish and other slippery prey. The osprey, a winter visitor to Africa, also has this adaptation. African fish eagles usually catch fish around 200 to 1,000 g (0.44 to 2.20 lb), but fish up to 4,200 g (9.3 lb) can be taken. If it catches a fish too heavy to allow the eagle to sustain flight, it will drop into the water and paddle to the nearest shore with its wings.[15] Mullets and catfish (Clarias) are common prey, though various fish such as cichlids, tilapias (Oreochromis), lungfish (Protopterus), and characins can be also taken.[16][17][18] Even African Tigerfish (Hydrocynus vittatus) can be preyed upon by fish eagles, especially while predating barn swallows (Hirundo rustica) in flight.[19]

It also feeds on birds, especially waterbirds such as ducks, cormorants, grebes, darters, hatchlings of herons and egrets,[18] and greater and lesser flamingos. Other prey include small turtles and terrapins, baby crocodiles, Nile monitors, skinks, frogs, insects (especially termites),[20] and carrion. Occasionally, it may even take mammalian prey, such as hyrax, monkeys, rats, hares, and dik diks.[21][17][22] It has also been observed feeding on domestic fowl (chickens). The African fish eagle is known to steal the catch of other bird species, a practice known as kleptoparasitism. Targeted species are usually large wading birds such as Goliath herons, hammerkops, and shoebills, as well as kingfishers, pelicans, ospreys, and other fish eagles, which usually hunt large fish and take a long time to handle them.[21][23][18]

Relationship with humans

Conservation

This species is listed as least concern by the IUCN.[1] The estimated population size is about 300,000 individuals with a distribution area of 18,300,000 km2.[24]

Heraldry

In the form of the Zimbabwe Bird, it is the national bird of Zimbabwe and appears on the Zimbabwean flag. The bird also figures in the coats of arms of Malawi, Namibia, Zambia, and South Sudan, and on the Zambian flag.

References

  1. ^ a b BirdLife International (2020). "Haliaeetus vocifer". IUCN Red List of Threatened Species. 2020: e.T22695115A174556979. doi:10.2305/IUCN.UK.2020-3.RLTS.T22695115A174556979.en. Retrieved 12 November 2021.
  2. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ^ "African Fish Eagle (Haliaeetus vocifer) - Birds.com: Online Birds Guide with Facts, Articles, Videos, and Photos". Birds.com. Retrieved 2012-12-12.
  4. ^ "African Fish Eagle videos, photos and facts - Haliaeetus vocifer". ARKive. Archived from the original on 2012-12-27. Retrieved 2012-12-12.
  5. ^ Wink, M.; Heidrich, P.; Fentzloff, C. (1996). "A mtDNA phylogeny of sea eagles (genus Haliaeetus) based on nucleotide sequences of the cytochrome b gene" (PDF). Biochemical Systematics and Ecology. 24 (7–8): 783–791. doi:10.1016/S0305-1978(96)00049-X.
  6. ^ Fourie, Pieter J (2010). Media Studies: Policy, Management and Media Representation. Juta and Company Ltd. p. 370. ISBN 978-0-7021-7675-3.
  7. ^ "African fish eagle - Wilkinson's World". wilkinsonsworld.com. Retrieved 18 April 2018.
  8. ^ a b "Fish Eagle". The Booking Company. Archived from the original on 2012-03-25. Retrieved 2012-12-12.
  9. ^ "Art Of The Wild by Roger Brown.: Cry of the African Fish Eagle". Artofthewildrogerbrown.blogspot.com. 2011-05-10. Retrieved 2012-12-12.
  10. ^ "African Fish Eagle {Haliaeetus vocifer}". Sa-venues.com. Retrieved 2012-12-12.
  11. ^ "BBC Nature - African fish eagle videos, news and facts". Bbc.co.uk. 1970-01-01. Retrieved 2012-12-12.
  12. ^ a b Wildscreen. "African Fish Eagle". eol.org. Encyclopedia of Life. Retrieved 11 April 2016.
  13. ^ Orban, David. "Haliaeetus vocifer African fish eagle". Animal Diversity Web. University of Michigan. Retrieved 11 April 2016.
  14. ^ a b Botha, André; et al. (2012). Eagles and Farmers (PDF). Birds of Prey Programme, Endangered Wildlife Trust. ISBN 978-0-620-11147-8. Archived from the original (PDF) on 18 February 2017. Retrieved 11 April 2016. {{cite book}}: |website= ignored (help)
  15. ^ Kemp, A. C. and J. S. Marks (2020). African Fish-Eagle (Haliaeetus vocifer), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.affeag1.01
  16. ^ Whitfield, A. K. & Blaber, S. J. M. 1978. Feeding ecology of piscivorous birds at Lake St Lucia, Part 1: Diving birds. Ostrich 49:185-198.
  17. ^ a b STEWART, KATHLYN, et al. "Prey diversity and selectivity of the African fish eagle: data from a roost in northern Kenya." African Journal of Ecology 35.2 (1997): 133-145.
  18. ^ a b c "Haliaeetus vocifer (African fish eagle)". Animal Diversity Web.
  19. ^ O'Brien, G. C., et al. "First observation of African tigerfish Hydrocynus vittatus predating on barn swallows Hirundo rustica in flight." Journal of fish biology 84.1 (2014): 263-266.
  20. ^ "African Fish Eagle | the Peregrine Fund".
  21. ^ a b "The African fish eagle". Encounter.co.za. Archived from the original on 2013-01-17. Retrieved 2012-12-12.
  22. ^ Sumba, Seraphine JA. The biology of the African fish eagle with special reference to breeding in Queen Elizabeth National Park, Uganda. Diss. 1983.
  23. ^ John, Jasson, and Woo Lee. "Kleptoparasitism of Shoebills Balaeniceps rex by African Fish Eagles Haliaeetus vocifer in Western Tanzania." Tanzania Journal of Science 45.2 (2019): 131-143.
  24. ^ "African Fish Eagle (Haliaeetus vocifer) - BirdLife species factsheet". Birdlife.org. Retrieved 2012-12-12.
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