Aquilinae

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Aquilinae
Crowned Eagle (Stephanoaetus coronatus), at Ndumo Nature Reserve, KwaZulu-Natal, South Africa (28842574882).jpg
Crowned eagle (Stephanoaetus coronatus) in South Africa.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Subfamily: Aquilinae
Genera

About 10, see article

The Aquilinae are a subfamily of eagles of the family Accipitridae. The general common name used for members of this subfamily is "booted eagle", although this is also the common name of a member of the subfamily. [1] At one point, this subfamily was considered inclusive with the Buteoninae (commonly known as buzzards or buteonine hawks) based probably on some shared morphological characteristics. [2] However, research on the DNA of the booted eagles has shown that they are a monophyletic group that probably have had millions of years of separation from other extant forms of accipitrid. [1] [3] [4]

Contents

Description

The formidable bearing and talons are evident on even modestly sized booted eagles such as African hawk eagles. African hawk-eagle (Aquila spilogaster).jpg
The formidable bearing and talons are evident on even modestly sized booted eagles such as African hawk eagles.

The Aquilinae consists of medium-sized to very large species. Modern species range in mass from the recently recognized pygmy eagle (Hieraaetus weiskei) of Papua New Guinea, which weighs about 500 g (1.1 lb) to the martial eagle (Polemaetus bellicosus) and golden eagle (Aquila chrysaetos), which both weigh about 4.2 kg (9.3 lb) on average. [5] [6] In wingspan, extant Aquilinae range from the pygmy eagle, with a median of 1.18 m (3 ft 10 in), to the wedge-tailed eagle (Aquila audax) and martial eagles, which average about 2.15 m (7 ft 1 in) and 2.12 m (6 ft 11 in) in wingspan, respectively. Total length can vary from 38 to 106 cm (15 to 42 in), in the pygmy and wedge-tailed eagles, respectively. [5] [7] [8] [9] The record sizes for wild booted eagles are 7.7 kg (17 lb) for a golden eagle in body mass and 2.84 m (9 ft 4 in) for a wedge-tailed eagle in wingspan. [8] [10] Dwarfing these species, the booted eagle species Haast's eagle (Hieraaetus moorei) of New Zealand, was probably the most massive species ever known in the entire accipitrid family, with females averaging an estimated 10 to 14 kg (22 to 31 lb) and perhaps weighing up to 17 kg (37 lb) and measuring up to about 140 cm (55 in) long, while males weighed an estimated 9 to 12 kg (20 to 26 lb). The Haast's eagle went extinct by the 16th century when human colonizers killed off their primary prey, the moas. [11] [12] Beyond their typically large size, Aquilinae species have few outward shared characteristics as they are a fairly diverse subfamily. Nonetheless, every species shares the feature of their legs being covered in feathers. Only two buteonine hawks share this feature beyond the Aquilinae, in a presumed case of convergent evolution. [1] [13] Many species within the subfamily are colored for camouflage with varying patterns of brown, black, yellowish or white being commonplace, darker colors being favored by forest dwelling varieties and brown to straw coloring common to open country species. A few more brightly colored species (in adult plumage), with striking patterns of chestnut in about four, none more striking than the ornate hawk-eagle (Spizaetus ornatus). [13] Roughly half of booted eagle species have a strikingly different looking juvenile plumage, which can in some species be nearly all white, but even where the differences are subtle between adults and immatures, usually some physical differences are noticeable such as white wing patches in traditional Aquila species, to visually distinguish young from adults. [13] Many species have a notable head-crest, such as Nisaetus and most Spizaetus , with the feature being most extreme in the long-crested eagle (Lophaetus occipitalis). [13] Like most accipitrids, they have large powerful hooked beaks for tearing flesh from their prey, strong legs and powerful talons. Compared to other large raptors, the feet and talons of booted eagle species are often particularly large and powerful relative to their size. The most extreme example seems to be the crowned eagle, which has a hallux-claw (or rear talon) of around 56 mm (2.2 in) about the same sized hallux-claw as the Philippine eagle (Pithecophaga jefferyi) (not part of the Aquilinae), which weighs on average nearly twice as much. [14] [15] The booted eagles also have extremely keen eyesight to enable them to spot potential prey from a distance. [16]

Life histories and range

Golden eagles, like all members of this subfamily, are capable predators of large prey such as foxes but do not disdain carrion either. Aquila chrysaetos 1 (Bohus Cicel).jpg
Golden eagles, like all members of this subfamily, are capable predators of large prey such as foxes but do not disdain carrion either.

Booted eagles are varying in their habitats and habits, being found on every continent inhabited by accipitrids, which includes all continents with the exception of Antarctica. They may inhabit nearly all of the world's terrestrial habitats, with the majority of species being largely forest dwelling, but several preferring all kinds of open habitat from steppe to prairie to tundra as well as most rocky or mountainous areas. By far the widest ranging species of booted eagle is the golden eagle, which is distributed in most of North America (where it is the only species of the subfamily north of Mexico) and much of Eurasia including a majority of Europe, often along most mountainous terrains therein but also other land-based habitats with typically remote semi-open or hilly hunting grounds accessible. [17] So-called "hawk-eagles" are forest dwelling booted eagle types largely represented by Spizaetus (in the neotropics) and Nisaetus (in Asia). Despite many similar features in the two main hawk-eagle genera, they apparently evolved separately for some time and are not closely related. [18] The peak diversity for Aquilinae are in Africa, where nearly half of extant species are known to dwell at least seasonally, exploiting a diversity of different hunting styles, habitats, nesting habits and general body forms. [1] [13] All booted eagle species are opportunistic predators which prey mostly on small vertebrates, often subsisting on a wide range of mammals, birds, reptiles and amphibians as they become locally available or abundant (carrion is also rarely ignored). Species favoring more open habitats tend to hunt most often on the wing, using distance or hugging contours of the ground to surprise prey. Forest dwelling species are more likely to be perch-hunters, watching for prey activity from a high tree perch, but every kind of booted eagle can vary their hunting techniques when necessary. [13] [17] In cases where they become specialists, booted eagles tend to be mammal hunters, such as the considerable dependence of Spanish imperial eagle (Aquila adalberti) on rabbits, of breeding steppe eagle (Aquila nipalensis) on sousliks or Verreaux's eagle (Aquila verreauxii) on hyraxes. [19] [20] [21] Exceptions include the Ayres's hawk-eagle (Hieraaetus ayresii) and, to a lesser extent, the rufous-bellied eagle (Lophotriorchis kienerii), both of which are smallish, swift-flying bird-hunting specialists who dive (falcon-like) on woodland birds while the black eagle (Ictinaetus malaiensis) feeds largely on the contents of birds' nests and squirrel dreys (the only hawk or owl specialized to do so). [13] [22] Most booted eagle species have relatively large feet and talons and can semi-regularly go after prey as large or larger than themselves, even smaller species can occasionally dispatch prey of up to two to three times their own weight. [13] [23] [24] Rare attacks on large prey, such as ungulates, adult monkeys or medium-sized carnivores or other much larger animals, usually involve the larger species of booted eagle, whereas such attacks are exceptionally rare to non-existent in eagles of other lineages. At least four large booted eagles have been known to dispatch prey weighing 30 kg (66 lb) or more. [25] [26] [27] [28]

A Martial eagle on its nest in Tanzania. Polemaetus bellicosus Martial Eagle.JPG
A Martial eagle on its nest in Tanzania.

Booted eagles, like almost all raptorial birds, are strongly territorial and tend to maintain expansive home ranges against conspecifics. [29] Given their need for ample hunting ranges, the territory of most booted eagles tend to be extremely large, with several dozen square kilometers being common. [30] [31] Territories are usually maintained with display flights but vocal displays are known in some of the denser forest dwelling varieties. [13] [32] Nests of Aquilinae tend to be typically large as in most eagles, with ample surface space needed, whether located in trees, rocky formations or on the ground. [13] [32] As is typical in many raptorial birds, pair bonds are strong between males and females and in many booted eagle species, they may mate for life. Primarily females incubate the egg and brood the young, while males usually have the responsibility of food capture. [13] [32] Clutch sizes are usually small in booted eagles, rarely more than 3 eggs are laid, and most parents will manage to produce only one to two fledglings depending on species. In most booted eagles, beyond threats from the outside world, most eggs are laid and hatched at intervals, thus one sibling is usually considerably bigger and often kills its younger siblings. [33] While brood size and fledgling rates are typically low, booted eagles may have even lower productivity due to the long dependence period of the young relying on their parents for food and protection, and some species may only nest every other year. [34]

General status

The black-and-chestnut eagle is one of several endangered booted eagles. Black and chestnut Eagle.jpg
The black-and-chestnut eagle is one of several endangered booted eagles.

Due to their large territories and low productivity, most booted eagle species are sparsely distributed and not infrequently uncommon-to-rare even in regional strongholds where ample habitat remains. Booted eagle species tend to be highly sensitive to human activities, mainly habitat alteration or destruction, human disturbance, collision with man made objects (especially non-insulated electrical pylons and wind turbines), accidental or intentional killing of staple prey species and various forms of persecution by humans. Due mainly to these factors, seven species of booted eagle are currently classified as Vulnerable to extinction by the IUCN. Four little-known forest dwelling species are classified in more severe status as Endangered: the Philippine hawk-eagle (Nisaetus philippensis), Pinsker's hawk-eagle (Nisaetus pinskeri), Javan hawk-eagle (Nisaetus bartelsi) and the black-and-chestnut eagle (Spizaetus isidori). A very different eagle, the steppe eagle, is also considered Endangered despite having been considered one of the most numerous of all eagles after a disastrous, ongoing decline mostly due to electrocutions from dangerous powerlines, poisonings and increasing steppe fires around nests, these killing them off en masse while breeding and migrating. An even more drastic classification of Critically Endangered was given to the Flores hawk-eagle (N. floris). In all five endangered hawk-eagles, near epidemic levels of forest habitat degradation, primarily direct deforestation, has been determined as the primary cause of their declines. [35] [36] [37]

Systematics

The cladogram of the Aquilinae shown below is based on a molecular phylogenetic study of the Accipitridae by Therese Catanach and collaborators that was published in 2024. [38]

Aquilinae

Stephanoaetus – crowned eagle (placement uncertain)

Nisaetus – hawk-eagles (10 species)

Spizaetus – hawk-eagle (4 species)

Lophotriorchis – rufous-bellied eagle

Polemaetus – martial eagle

Lophaetus – long-crested eagle

Ictinaetus – black eagle

Clanga – spotted eagles (3 species)

Hieraaetus – eagles (5 species)

Aquila – eagles (11 species)

ImageGenusLiving Species
Crowned Eagle (Stephanoaetus coronatus), at Ndumo Nature Reserve, KwaZulu-Natal, South Africa (28842574882).jpg Stephanoaetus Sclater, 1922
ELJA.jpg Nisaetus Hodgson, 1836
Spizaetus melanoleucas - Flickr - Dick Culbert.jpg Spizaetus Vieillot, 1816
Rufous-bellied-hawk-eagle2.JPG LophotriorchisSharpe, 1874
Martial eagle (Polemaetus bellicosus).jpg PolemaetusHeine, 1890
Long-crested eagle (Lophaetus occipitalis) Uganda.jpg Lophaetus Kaup, 1847
Black eagle.jpg IctinaetusBlyth, 1843
Greater spotted eagle.jpg Clanga Adamowicz, 1858
Booted Eagle Hieraaetus pennatus by Dr. Raju Kasambe DSCN2245 (1).jpg Hieraaetus Kaup, 1844
Aquila fasciata (Wadi Hinna, Oman).jpg Aquila Brisson, 1760

Related Research Articles

<span class="mw-page-title-main">Eagle</span> Large carnivore bird

Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. True eagles comprise the genus Aquila. Most of the 68 species of eagles are from Eurasia and Africa. Outside this area, just 14 species can be found—two in North America, nine in Central and South America, and three in Australia.

<span class="mw-page-title-main">Accipitridae</span> Family of birds of prey

The Accipitridae is one of the three families within the order Accipitriformes, and is a family of small to large birds of prey with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a few feeding on fruit. The Accipitridae have a cosmopolitan distribution, being found on all the world's continents and a number of oceanic island groups. Some species are migratory. The family contains 255 species which are divided into 70 genera.

<span class="mw-page-title-main">Golden eagle</span> Species of eagle

The golden eagle is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known birds of prey in the Northern Hemisphere. These birds are dark brown, with lighter golden-brown plumage on their napes. Immature eagles of this species typically have white on the tail and often have white markings on the wings. Golden eagles use their agility and speed combined with powerful feet and large, sharp talons to hunt a variety of prey, mainly hares, rabbits, and marmots and other ground squirrels. Golden eagles maintain home ranges or territories that may be as large as 200 km2 (77 sq mi). They build large nests in cliffs and other high places to which they may return for several breeding years. Most breeding activities take place in the spring; they are monogamous and may remain together for several years or possibly for life. Females lay up to four eggs, and then incubate them for six weeks. Typically, one or two young survive to fledge in about three months. These juvenile golden eagles usually attain full independence in the fall, after which they wander widely until establishing a territory for themselves in four to five years.

<span class="mw-page-title-main">Wedge-tailed eagle</span> Bird of prey within the genus Aquila

The wedge-tailed eagle is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. Adults of the species have long, broad wings, fully feathered legs, an unmistakable wedge-shaped tail, an elongated upper mandible, a strong beak and powerful feet. The wedge-tailed eagle is one of 12 species of large, predominantly dark-coloured booted eagles in the genus Aquila found worldwide. Genetic research has clearly indicated that the wedge-tailed eagle is fairly closely related to other, generally large members of the Aquila genus. A large brown-to-black bird of prey, it has a maximum reported wingspan of 2.84 m and a length of up to 1.06 m.

<span class="mw-page-title-main">Booted eagle</span> Species of bird

The booted eagle is a medium-sized mostly migratory bird of prey with a wide distribution in the Palearctic and southern Asia, wintering in the tropics of Africa and Asia, with a small, disjunct breeding population in south-western Africa. Like all eagles, it belongs to the family Accipitridae.

<span class="mw-page-title-main">Buteoninae</span> Subfamily of birds

The Buteoninae are a subfamily of birds of prey which consists of medium to large, broad-winged species.

<span class="mw-page-title-main">Changeable hawk-eagle</span> Crested hawk-eagle (Nisaetus cirrhatus) from South and Southeast Asia

The changeable hawk-eagle(Nisaetus cirrhatus) or crested hawk-eagle is a large bird of prey species of the family Accipitridae. More informal or antiquated English common names include the marsh hawk-eagle or Indian crested hawk-eagle. It is a member of the subfamily Aquilinae, with signature feathers, absent in tropical raptors from outside this subfamily, covering the tarsus. It was formerly placed in the genus Spizaetus, but studies pointed to the group being paraphyletic resulting in the Old World members being placed in Nisaetus and separated from the New World species. It is a typical “hawk-eagle” in that it is an agile forest-dwelling predator and like many such eagles readily varies its prey selection between birds, mammals or reptiles as well as other vertebrates. Among the members of its genus, the changeable hawk-eagle stands out as the most widely distributed, adaptable and abundant species. Individuals show a wide range of variation in plumage from pale to dark, varying with moult and age giving rise to the name "changeable".

<span class="mw-page-title-main">Mountain hawk-eagle</span> Species of bird

The mountain hawk-eagle or Hodgson's hawk-eagle, is a large bird of prey native to Asia. The latter name is in reference to the naturalist, Brian Houghton Hodgson, who described the species after collecting one himself in the Himalayas. A less widely recognized common English name is the feather-toed eagle. Like all eagles, it is in the family Accipitridae. Its feathered tarsus marks this species as a member of the subfamily Aquilinae. It is a confirmed breeding species in the northern part of the Indian subcontinent, from India, Nepal through Bangladesh to Thailand, Taiwan, Vietnam and Japan, although its distribution could be wider still as breeding species. Like other Asian hawk-eagles, this species was earlier treated under the genera of Spizaetus but genetic studies have shown this group to be paraphyletic, resulting in the Old World members being placed in Nisaetus and separated from the New World species. As is typical of hawk-eagles, the mountain hawk-eagle is a forest dwelling opportunistic predator who readily varies its prey selection between birds, mammals and reptiles along with other vertebrates. Although classified currently as a least-concern species due its persistence over a rather wide distribution, this species is often quite rare and scarce and seems to be decreasing, especially in response to large-scale habitat degradation and deforestation.

<span class="mw-page-title-main">Rufous-bellied eagle</span> Species of bird

The rufous-bellied eagle or rufous-bellied hawk-eagle is a bird of prey in the family Accipitridae that is found in the forested regions of tropical Asia. Relatively small for eagles and contrastingly patterned like a falcon, this species was earlier placed in the genus Hieraaetus and sometimes also in the genus Aquila but thought to be distinctive enough to belong to a separate genus.

<span class="mw-page-title-main">Bonelli's eagle</span> Large bird of prey

Bonelli's eagle is a large bird of prey. The common name of the bird commemorates the Italian ornithologist and collector Franco Andrea Bonelli. Bonelli is credited with gathering the type specimen, most likely from an exploration of Sardinia. Some antiquated texts also refer to this species as the crestless hawk-eagle. Like all eagles, Bonelli's eagle belongs to the family Accipitridae. Its feathered legs marked it as member of the Aquilinae or booted eagle subfamily. This species breeds from Southern Europe, Africa on the montane perimeter of the Sahara Desert, and across the Indian Subcontinent to Indonesia. In Eurasia, this species may be found as far west as Portugal and as far east as southeastern China and Thailand. It is usually a resident breeder. Bonelli's eagle is often found in hilly or mountainous habitats, with rocky walls or crags, from sea level to 1,500 m (4,900 ft). Habitats are often open to wooded land and can occur in arid to semi-moist climate. This eagle, though it can be considered partially opportunistic, is something of a specialist predator of certain birds and mammals, especially rabbits, galliforms and pigeons. On evidence, when staple prey populations decline or are locally scarce, Bonelli's eagle switch to being an opportunistic predator of a wide variety of birds. Despite its persistence over a large range and its continued classification as a least concern species by the IUCN, Bonelli's eagle has declined precipitously in various parts of its range, including almost all of its European distribution, and may face potential local extinction. The species' declines are due to widespread habitat destruction, electrocution from electricity pylons as well as persistent persecution.

<span class="mw-page-title-main">Verreaux's eagle</span> Species of bird

Verreaux's eagle is a large, mostly African, bird of prey. It is also called the black eagle, especially in southern Africa, not to be confused with the black eagle of south and southeast Asia. The Verreaux's eagle lives in hilly and mountainous regions of southern and eastern Africa, and very locally in the Middle East.

<i>Aquila</i> (bird) Genus of birds

Aquila is the genus of true eagles. The genus name is Latin for "eagle", possibly derived from aquilus, "dark in colour". It is often united with the sea eagles, buteos, and other more heavyset Accipitridae, but more recently they appear to be less distinct from the slenderer accipitrine hawks than previously believed. Eagles are not a natural group but denote essentially any bird of prey large enough to hunt sizeable vertebrate prey.

<i>Spizaetus</i> Genus of birds

Spizaetus is the typical hawk-eagle birds of prey genus found in the tropics of the Americas. It was however used to indicate a group of tropical eagles that included species occurring in southern and southeastern Asia and one representative of this genus in the rainforests of West Africa. The Old World species have been separated into the genus Nisaetus. Several species have a prominent head crest. These are medium to large-sized raptors, most being between 55 and 75 cm long, and tend to be long-tailed and slender.

<i>Hieraaetus</i> Genus of birds

The genus Hieraaetus, sometimes known as small eagles or hawk-eagles, denotes a group of smallish eagles usually placed in the accipitrid subfamilies Buteoninae or Aquilinae.

<span class="mw-page-title-main">Ayres's hawk-eagle</span> Species of bird

Ayres's hawk-eagle, also referred to as Ayres' eagle, is a medium-sized bird of prey in the family Accipitridae. It is native to African woodlands. Its name honors South African ornithologist Thomas Ayres.

<span class="mw-page-title-main">Pygmy eagle</span> Species of bird

The pygmy eagle or New Guinea hawk-eagle is a bird of prey found in New Guinea. Its natural habitats are primarily subtropical or tropical moist lowland forest and subtropical or tropical moist montane forest. It is the smallest species of eagle.

<span class="mw-page-title-main">Cassin's hawk-eagle</span> Species of bird

Cassin's hawk-eagle or Cassin's eagle, is a relatively small eagle in the family Accipitridae. Its feathered legs mark it as member of the Aquilinae or booted eagle subfamily. A forest-dependent species, it occurs in primary rainforests across western, central and (marginally) eastern Africa where it preys on birds and tree squirrels. It was named after John Cassin who first described it in 1865. Due to widespread habitat destruction, its populations are steadily declining but have not yet warranted upgrading its status from Least Concern.

Buteogallus borrasi is a species of giant buteonine hawk which went extinct in the early Holocene. Formerly endemic to Cuba, this huge bird of prey probably fed on Pleistocene megafauna. Little is known about its appearance and ecology, so no common name has been given.

Booted eagles are eagles that have fully feathered tarsi. That is, their legs are covered with feathers down to the feet. Most other accipitrids have bare lower legs, scaled rather than feathered.

<span class="mw-page-title-main">Crowned eagle</span> Species of bird

The crowned eagle, also known as the African crowned eagle or the crowned hawk-eagle, is a large bird of prey found in sub-Saharan Africa; in Southern Africa, it is restricted to more easterly areas. Its preferred habitats are principally riparian woodlands and various forests. The crowned eagle is the only extant member of the genus Stephanoaetus. A second species, the Malagasy crowned eagle, went extinct after early humans settled on Madagascar.

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  30. ↑ Bosch, R., Real, J., Tinto, A., Zozaya, E. L., & Castell, C. (2010). Home‐ranges and patterns of spatial use in territorial Bonelli’s Eagles Aquila fasciata. Ibis, 152(1), 105-117.
  31. ↑ Bergo, G. (1987). Territorial behaviour of Golden Eagles in western Norway. British Birds, 80, 361-376.
  32. 1 2 3 Brown, L., & Amadon, D. (1968). Eagles, hawks and falcons of the world (Vol. 2, p. 445). London: Country Life Books.
  33. ↑ Simmons, R. (1988). Offspring quality and the evolution of cainism. Ibis 130 (3): 339–357.
  34. ↑ Brown, L. 1976. Eagles of the World. David and Charles, ISBN   0360003184.
  35. ↑ Collaerts, P., Collaerts, E., Verbelen, P., & Trainor, C. R. (2011). Discovery of the Critically Endangered Flores Hawk Eagle Nisaetus floris on Alor island, Indonesia. BirdingASIA 19 (2013): 48–51.
  36. ↑ Tingay, R. E., & Katzner, T. E. (Eds.). (2010). The eagle watchers: Observing and conserving raptors around the world. Cornell University Press.
  37. ↑ Meyburg, B. U. (1986). Threatened and near-threatened diurnal birds of prey of the world. Birds of Prey Bull, 3(1), 12.
  38. ↑ Catanach, T.A.; Halley, M.R.; Pirro, S. (2024). "Enigmas no longer: using ultraconserved elements to place several unusual hawk taxa and address the non-monophyly of the genus Accipiter (Accipitriformes: Accipitridae)". Biological Journal of the Linnean Society: blae028. doi:10.1093/biolinnean/blae028.


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