Haliaeetus

Bald eagle Haliaeetus leucocephalus, copyright Andy Morffew.

Belongs within: Accipitridae.

Haliaeetus, the sea eagles, is a genus of large eagles found in the Old World and North America that feed predominantly on fish; species commonly have white heads, white tails and/or yellow beaks and feet.

Eagles of the sea
Published 28 November 2023

The bald eagle Haliaeetus leucocephalus may have a claim to be among the world’s most recognisable bird species. The status of this animal as the ornithological icon of the United States of America has led to its widespread depiction in that country’s popular media, in badges and logos, or in patriotic displays. Yet the bald eagle is just one of a broader group known as the sea eagles, and not even the most remarkable.

Steller’s sea eagle Haliaeetus pelagicus, copyright Pierpaolo Pessano.

The sea eagles and fish eagles comprise ten species, assigned to the accipitrid subfamily Haliaeetinae, found on all continents except South America and Antarctica. They vary in size from medium to very large, with Steller’s sea eagle Haliaeetus pelagicus among the contenders for largest living bird of prey. As suggested by their vernacular names, they are associated with water bodies, whether around the coast or alongside rivers and lakes. Fish is typically a major component of the diet, observed from a perch and then grabbed with the feet as it approaches the surface of the water rather than by diving (Thiollay 1994). Most species will also take other prey such as reptiles or small mammals, and carrion is often a favoured source of nutrition. Feet are relatively short and robust, with strongly curved claws and dense spicules on the underside of the toes.

White-tailed sea eagle Haliaeetus albicilla fishing, copyright du findest den Frank im Park.

Despite their superficial similarities, the sea eagles are not direct relatives of the other large eagles in the Aquilinae and other subfamilies. Instead, the Haliaeetinae appear likely to be connected to the kites of the subfamily Milvinae (Lerner & Mindell 2005). Among other things, members of both subfamilies share a characteristic fusion of the basal phalanges of the inner toe (mis-cited by many authors as the middle toe but the correct state was established by Olson, 1982). Historically, the species of Haliaeetinae have been divided between two genera, the larger sea eagles in Haliaeetus and smaller fish eagles in Ichthyophaga. However, more recent molecular studies have established the latter as paraphyletic to the latter (Lerner & Mindell 2005). Instead, the haliaeetines are basally divided between a tropical clade including the African and Indo-Australian species, and a boreal clade of temperate Eurasian and North American species. The conflict may be resolved in two ways, both of which I have seen enacted: whether to recognised all haliaeetines as a single genus Haliaeetus, or whether to restrict Haliaeetus to the boreal clade and recognise the tropical clade as Ichthyophaga.

Pallas’ fish eagle Haliaeetus leucoryphus, copyright rbhadury.

If restricted to the northern clade, Haliaeetus includes just four species. They are mostly dark brown in coloration, often with contrasting patches of white. Pallas’ fish eagle H. leucoryphus, found in central and southern Asia, has a sandy-coloured rather than white head and neck. Haliaeetus leucoryphus also differs from other species of Haliaeetus sensu stricto in having a dark-coloured beak and legs (like those of members of the tropical clade). In the other three species, the beak and feet are bright yellow. Molecular data corroborate the distinctiveness of H. leucoryphus by placing it outside the yellow-footed clade (Lerner & Mindell 2005).

The three yellow-footed species are the white-tailed sea eagle H. albicilla, Steller’s sea eagle H. pelagicus and the bald eagle H. leucocephalus. The bald eagle is found over most of North America and is mostly dark brown with a bright white head and tail. Two subspecies of bald eagle have been recognised, the southern H. l. leucocephalus and northern H. l. washingtoniensis, distinguished by the larger size of the latter. The white-tailed sea eagle is found over much of northern Eurasia, extending across the Atlantic into southern Greenland. It has a white tail like the bald eagle but its head is buff in coloration, contrasting less with the central body. Steller’s sea eagle has a range in northeastern Asia centering on the Sea of Okhotsk and Sea of Japan. It has a dark brown head and body, typically with bright white shoulders. A uniformly dark form historically recorded from Korea was once regarded as a distinct subspecies but is now thought to be a rare colour variant.

White-tailed sea eagle Haliaeetus albicilla, copyright Aleksandr Popov.

Like most large predators, sea eagle populations have experienced declines in the last century due to anthropogenic pressures. These have included direct persecution, loss of breeding habitat, and the build-up of toxins in prey species. However, protective measures in recent decades have led to rebounding numbers of bald and white-tailed eagles. Indeed, sea eagles now become abundant enough in places that concerns have been raised about their own impact on local seabird numbers (Hipfner et al. 2012). The question remaining to be answered is whether the eagles are indeed becoming overabundant, or whether conditions are simply approaching their earlier state before the eagles were removed.

Systematics of Haliaeetus
<==Haliaeetus Savigny 1809 [=Haliaetus Vieillot 1818; incl. Blagrus Blyth 1846; Haliaeetinae]CC10
    |  i. s.: H. aguiaF43
    |         H. maceiE42
    |         H. piscator Milne-Edwards 1871 [=Haliaetus (l. c.) piscator]M02
    |         H. ponticerianusE42
    |--+--H. leucoryphusLM05
    |  |--H. pelagicus (Pallas 1811)LM05, I92
    |  `--+--H. albicilla (Linnaeus 1758)LM05, M02 (see below for synonymy)
    |     |    |--H. a. albicillaUSDI77
    |     |    `--H. a. greenlandicusUSDI77
    |     `--H. leucocephalusLM05 (see below for synonymy)
    `--+--+--H. leucogaster (Gmelin 1788)LM05, CC10 (see below for synonymy)
       |  `--H. sanfordiLM05
       `--+--+--H. vociferLM05
          |  `--H. vociferoidesLM05
          `--IchthyophagaLM05
               |--I. humilisLM05
               `--I. ichthyaetusLM05
Inorganic: Haliaeetus pelagicus minilorientalus Okamura 1987O87

Haliaeetus albicilla (Linnaeus 1758)LM05, M02 [=Falco albicillaM02, Vultur albicillaF17; incl. Haliaetus angustipes Jánossy 1983M02, Haliaeetus brevipes (l. c.)M02, *Haliaeetus nisusCC10, Falco ossifragusF17, Pygargus vulturinusF17]

Haliaeetus leucocephalusLM05 [=Falco leucocephalusJ23; incl. Ichthyophaga australis Harrison & Walker 1973WH02, H. australisCC10]

Haliaeetus leucogaster (Gmelin 1788)LM05, CC10 [=Falco leucogasterCC10, Haliaetus leucogasterCC10, Ichthyaetus leucogasterCC10; incl. *Blagrus dimidiatusCC10, Haliaeetus leucogaster pallidus Mathews 1912CC10, Haliaeetus sphenurus Gould 1838CC10]

*Type species of generic name indicated

References

[CC10] Checklist Committee (OSNZ). 2010. Checklist of the Birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica 4th ed. Ornithological Society of New Zealand and Te Papa Press: Wellington.

[E42] Ewer, W. 1842. List of a collection of birds from India. Proceedings of the Zoological Society of London 10: 91–93.

[F17] Forster, T. 1817. A synoptical catalogue of British birds; intended to identify the species mentioned by different names in several catalogues already extant. Forming a book of reference to observations on British ornithology. Nichols, Son, and Bentley: London.

[F43] Fraser, L. 1843. On the collection of birds brought to England by Mr. Bridges. Proceedings of the Zoological Society of London 11: 108–121.

Hipfner, J. M., L. K. Blight, R. W. Lowe, S. I. Wilhelm, G. J. Robertson, R. T. Barrett, T. Anker-Nilssen & T. P. Good. 2012. Unintended consequences: how the recovery of sea eagle Haliaeetus ssp. populations in the Northern Hemisphere is affecting seabirds. Marine Ornithology 40: 39–52.

[I92] Iwahashi, J. (ed.) 1992. Reddo Deeta Animaruzu: a pictorial of Japanese fauna facing extinction. JICC: Tokyo.

[J23] James, E. 1823. Account of an Expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and ’20, by order of the Hon. J. C. Calhoun, sec’y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party vol. 1. H. C. Carey & I. Lea: Philadelphia.

[LM05] Lerner, H. R. L., & D. P. Mindell. 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37: 327–346.

[M02] Mlíkovský, J. 2002. Cenozoic Birds of the World. Part 1: Europe. Ninox Press: Praha.

[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.

Olson, S. L. 1982. The distribution of fused phalanges of the inner toe in the Accipitridae. Bulletin of the British Ornithologists’ Club 102 (1): 6–12.

Thiollay, J. M. 1994. Family Accipitridae (hawks and eagles). In: Hoyo, J. del, A. Elliott & J. Sargatal. 1994. Handbook of the Birds of the World vol. 2. New World Vultures to Guineafowl pp. 52–205. Lynx Edicions: Barcelona.

[USDI77] United States Department of the Interior. 1977. Endangered and threatened wildlife and plants—republication of list of species. Federal Register 42: 36420–36431.

[WH02] Worthy, T. H., & R. N. Holdaway. 2002. The Lost World of the Moa: Prehistoric life of New Zealand. Indiana University Press: Bloomington (Indiana).

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