The tawny eagle (Aquila rapax) is a large bird of prey. Like all eagles, it belongs to the family Accipitridae. Its heavily feathered legs mark it as a member of the subfamily Aquilinae, also known as booted eagles. Tawny eagles have an extensive but discontinuous breeding range that constitutes much of the African continent as well as the Indian subcontinent, with rare residency in the southern Middle East. Throughout its range, it favours open dry habitats such as semideserts, deserts steppes, or savanna plains. Despite its preference for arid areas, the species seldom occurs in areas where trees are entirely absent. It is a resident breeder which lays one to three eggs in a stick nest most commonly in the crown of a tree. The tawny eagle is perhaps the most highly opportunistic of all Aquilinae, and often scavenges on carrion or engages in kleptoparasitism towards other carnivorous animals but is also a bold and active predator, often of relatively large and diverse prey. It is estimated that tawny eagles can reach the age of 16 years old.
It is also the national animal of Ghana.
Taxonomy
Dutch naturalist Coenraad Jacob Temminck described the tawny eagle in 1828 from an Indian type specimen. "Tawny eagle" has been designated the official name by the International Ornithologists' Union (IOC). Aquila is Latin for "eagle" while rapax is also Latin for "to grasp", and relates to the word rapacious, i.e. highly predatory. The tawny eagle is a member of the booted eagle subfamily (Aquilinae) within the Accipitridae family. The booted eagle subfamily all have feathers covering their legs and are distributed in every continent that contains accipitrids. However, study of genetics have resulted in several reclassifications. These include the moving of smaller, paler and more forest-dwelling eagles in Aquila, the separation of the unique spotted eagles to the genus Clanga as well as the division of some small eagles to the genus Hieraeetus outside of Aquila. Furthermore, genetic research has further revealed a schism in superficially similar eagles between the tawny eagle and its close relatives and other superficially similar Aquila such as the golden eagle (Aquila chrysaetos) species complex. To date, the tawny eagle species group and golden eagle species group are still contained in the same genus despite the apparent lack of close relation.
thumb|left|A tawny eagle sitting on the ground displaying typical features: a mid-sized eagle with a long neck, well-feathered legs, well-proportioned frame and large bill lacking a deep gape.
The tawny eagle was previously treated as conspecific with the migratory steppe eagle (Aquila nipalensis). These eagles were considered part of the same species as recently as 1991. The steppe and tawny eagles were split based on pronounced differences in morphology and anatomy. The steppe eagle is a larger bird, with a much more pronounced gape, and differs by appearance in its blockier frame, bigger wings and evinces different coloring at all stages of development, despite some morphs of the two eagles superficially resembling one another. Furthermore, the respective species differ in ecology (dietary biology, nesting habits) and are strongly allopatric in their breeding ground distribution. Genetically, the tawny eagle may cluster more closely with the imperial eagle species complex despite the steppe eagle being more sympatric with those northerly Eurasian eagles.
- A. r. rapax; distributed in Africa from the southern Democratic Republic of the Congo and central Kenya to all points southwards. Adult often of this nominate subspecies are often relatively more strongly rufous in colour than other races and are sometimes dark streaked below. Meanwhile, the juvenile tends to be light rufous. wing chord lengths in this race have been measured at in males and in females. The tail length of both sexes in A. r. rapax measures with a tarsus length of . Body mass can range roughly from in overall samples of at least 36 eagles. This race is described to appear "neater" than the nominate subspecies, possibly due to this race often occurring in even more desert-like conditions than the other races and thus having more compact feathering. It is when compared to the nominate, often duller and browner above, showing less of a rufous tinge. Meanwhile, individual pale morph of A. r. belisarius often a shade or two darker than pale nominate but not consistently so. Although said to be slightly larger, measurement data shows this subspecies to of broadly very similar size to the nominate race. In males, the wing chord is and, in females, the wing chord is . Sometimes A. r. vindhiana is suggested as full species. This subspecies averages darker than either other race and usually is lacking in warmer rufous tone. In general, it is somewhat more similar in hue to the steppe eagle. In males, the wing chord reportedly averages about and in females, it averages . The bill and head are strong and bold, the body well-proportioned and feet are powerful while the countenance is quite fierce-looking. Most adults are usually a general grey-brown or rufous-tawny color, with occasional pale spotting visible at close quarters on the nape and belly, coverts uniformly toned as the body. Adult plumage is obtained between the 4th and 5th years of life. As is typical in birds of prey, the female tawny eagle is larger than the male, though relatively modestly so and a difference between the sexes is typically up to 15%. A typical length for a tawny eagle is considered about . Wingspans can measure from . Weight can range in fully grown birds from . Average weights were reported in one study as in 5 males and in 5 females. Another small sample of African males, sample size four, averaged while three females averaged . In all standard measurements combined, the wing chord can vary from , the tail from and the tarsus from . The culmen length of Kenyan tawny eagles was measured at , averaging , while the gape width is on average, ranging from . The hallux-claw, the enlarged rear talon often used as a killing instrument on accipitrids, can measure from , averaging in one sample and in another. The talon size is not especially large for a booted eagle and is proportionately similar in size to those of steppe eagles and eastern imperial eagles (Aquila heliaca).
One source that can especially engender potential confusion in its wintering range is the formerly conspecific steppe eagle. The steppe is larger with a shorter neck, relatively longer and narrower wings, a more massive beak, particularly via the exceptional depth of the gape (although in flight can appear smaller headed due its less protruding neck) and has a longer and rounder tail. Furthermore, steppe eagles tends to have much bolder and widely spaced barring on the wings than tawny eagles and more distinct dark trailing wing edges and paler throats.
Beyond steppe eagles, comparisons to various other groups of sympatric booted eagles may be made. Compared to the spotted eagles, the tawny eagle's tail is longer, the bill more prominent, the wings usually less squared-off in flight, the neck longer and the overall look rangier, despite these species being of often similar size. In contrast to the imperial eagles, the wings of the tawny eagle are broader and have less even trailing edges, the bill is slightly less prominent, and the wings are more likely to be held slightly upwards, while the body size is smaller. When compared to the golden eagle species complex, of which only the golden and the Verreaux's eagle (Aquila verreauxii) are usually relevant (although three dissimilar and sympatric pale-bellied eagles, of a size with tawny eagles or smaller, are found as part of this evolutionary chain), the tawny eagle is considerably smaller, its wings do not taper as much nor are they as likely to be held in a strong dihedral, and proportionately, the bill is notably longer and the tail is rather shorter. The likewise migratory lesser spotted eagle (Clanga pomarina) is smaller than the tawny eagle and more compact with a distinct white U above the tail. The young chick tawny eagle chips initially but once its feathers emerge, it tends to beg with a loud call, i.e. we-yik, wee-yik. The north African population is scarce. In Morocco, they are heavily depleted with a few populations left in some regions such as Tarfaya, Tan-Tan and Souss-Massa. They are likely extirpated from Tunisia, where they were once frequent. In West Africa, some tawny eagles occur in Gambia, Togo, Nigeria and (though possibly not breeding) in Ivory Coast and Ghana. In east Africa and central Africa, the tawny eagle is found in central and eastern Democratic Republic of the Congo and throughout the drier portions of Uganda and in the entire nations of Kenya, Tanzania, Zambia (quite often residing in the Luangwa valley and the Chambeshi drainage), Malawi and Mozambique. In east Africa, it is considered perhaps the most widely distributed and regularly sighted brown eagle. In southern Africa, the tawny eagle is found throughout Zimbabwe (now often rare apart from Matabeleland and Chipinga Uplands), Botswana (still regular in Okavango Delta) and some areas of Namibia, southern and western Angola (Cuando Cubango, Cunene, Huíla Namibe, to Malanje), Eswatini, Lesotho and northern and central parts of South Africa, i.e. mainly north of the Orange River but sometimes down to the Cape Province. The tawny eagle may be extinct as a breeder in Eswatini where it was last confirmed to have bred in 2001.
thumb|A tawny eagle perched in [[Rajasthan in India.]]
Out of Africa, the species may possibly be found in the southwestern part of the Arabian Peninsula, i.e. in Yemen and extreme southwestern Saudi Arabia in the Tihamah and 'Asir Regions, but few to none confirmed breeding events have been reported in the last few decades. The tawny eagle is considered a rare vagrant in Israel, though some are verified, other reports of them often turn out to be misidentified steppe eagles. They are also known as a rare vagrant in Oman. In Asia, the tawny eagle exists in isolation in southeastern Iran (as in Arabia, verified recent breeding is not known) and somewhat more continuously in eastern Pakistan (often in the Indus valley), much of north and peninsular India, eastward scarcely through southern Nepal and Assam. Though Nepali tawny eagles are rarely recorded, it is thought that the species still resides there in lowland semi-deserts. The Indian range is from Punjab through the Indo-Gangetic Plain and western Bengal, northeastern Bihar, the Deccan Plateau with range continuing down to Andhra Pradesh, Karnataka and (mainly north-central) Tamil Nadu. Records of vagrating tawny eagles turning up in Myanmar, northern Vietnam and Thailand are thought to have been likely misidentified steppe eagles or are based on now unidentifiable specimens. A small handful of vagrants have been verified to turn up in Sri Lanka (the only known appearance by an Aquila eagle there). Old reports of vagrancy, probably in need of confirmation, are known also from Afghanistan. In southern Africa, thornveld is often the preferred habitat with the tawny eagles mostly preferring stands of Acacia. Despite similar climates, within the miombo woodland, the tawny eagle tends to be more scarce. This reliance on some rainfall is probably key to habitat quality and resulting prey populations to some extent, but also to the availability of nesting sites.
Behaviour
thumb|A tawny eagle in flight.
The tawny eagle, quite unlike the steppe eagle, is largely sedentary and non-migratory. However, in Africa it is at times considered to be fairly nomadic and can engage in some seasonal movements. In west Africa, A. r. belisarius rather regularly travels shorter distance to damp woodlands during October through November, returning north in April, and perhaps at least at times, migrates into Kalahari region of Botswana and may vagrate to southern South Africa. Sometimes, tawny eagles seem to ping semi-regularly between Ethiopia and west Africa. From the Indian range, individuals vagrate not infrequently to nearby Bangladesh, most likely as juveniles post-dispersal wanderings, but reports of the species wandering into southeast Asia such as Thailand are now considered likely apocryphal. Generally, in areas such as southern Africa, tawny eagles usually seldom seem to leave their established breeding territories and juvenile eagles generally wander no more than several dozen kilometres from their original nest. A bird banded as a nestling in Esigodini was recovered quite nearby at Fort Rixon more than two years later. While non-breeding steppe eagles are often slightly social and flock at opportunistic feeding sources, the tawny eagle is usually considered solitary. Small groups or aggregations are known to occur in Africa as well near concentrated foods and even communal roost have been reported in trees, power pylons or on the ground.
Feeding
thumb|left|With a [[black-backed jackal, road traffic victim in Ethiopia.]]
The tawny eagle is unique as an Aquila eagle in the lack of apparent specialization in its feeding behaviour. Nocturnal animals such as genets and springhares have been preyed upon by tawny eagles in areas where there was no possibility they were killed by traffic at night. In addition to other observations have been made where tawny eagles drink and bathe at night, some nocturnal subsistence behaviour by this species has been inferred but no irrefutable evidence has been brought forth either. Semi-regular attendance at grassfires in India, presumably in order to capture displaced creatures, has been reported. Reportedly, most prey the tawny eagle will take alive will weigh not less than and not more than , however live prey has been revealed to be regularly more variable than even that estimate represents.
Out of the southern and eastern areas of Africa, less quantitative analysis has been undertaken into the feeding habits of tawny eagles, even around nests. What is known of their prey elsewhere is mainly from wide-ranging surveys, secondary accounts and photographs. Otherwise, the prey incidentally reported in India is extremely varied, including even the hindlegs of a jungle cat (Felis chaus) (but this may have been scavenged). Tawny eagles may hunt a couple dozen species of rodent from different parts of the range, ranging in size from the Natal multimammate mouse (Mastomys natalensis) to the South African springhare (Pedestes capensis). Rock hyrax (Procavia capensis) and yellow-spotted rock hyrax (Heterohyrax brucei) are occasionally preyed upon by tawny eagles. The tawny eagle may be one of the most accomplished predators of mongoose, many food studies reflecting relatively high numbers of them and they appear to be one of the most feared predators at meerkat (Suricata suricatta) colonies. In the Karoo, the local tawny eagles reportedly live mostly off of mongooses, either meerkats or yellow mongooses. Similarly small or slightly larger carnivores like striped polecats (Ictonyx striatus) and genets are not infrequently prey for tawny eagles as well. Various monkeys may be eaten, although not infrequently as carrion, tawny eagles may too in seldom cases attack juveniles of monkeys such as Patas monkeys (Erythrocebus patas), grivets (Chlorocebus aethiops) and vervet monkeys (Chlorocebus pygerythrus) up to the size of juveniles of several species of baboon. However, unlike with larger eagles, the troops of certain baboons do not seem to regard tawny eagles as a threat based on their behavioural responses. While most ungulate prey other than dik-diks is probably largely scavenged as carrion or stolen from other predators, the small calves of ungulates such as Thomson's gazelle (Eudorcas thomsonii) are sometimes apparently killed by tawny eagles. A general picture appears to emerge that tawny eagles quite often takes relatively large mammalian prey, surprisingly often creatures weighing up to such as hares, dik-diks, the young of other antelopes, hyraxes and so on.
thumb|left|A tawny eagle is mobbed by a [[blacksmith lapwing; these eagles are a potential menace to many different kinds of birds.]]
While mammals prey varies from rodents to hares, mongooses and small antelopes, the diversity and size range of bird taken may be even more impressive and more than 120 avian prey species have been reported in the prey spectrum. gamebirds, especially francolins and guineafowl, mostly medium-sized species of bustard and hornbill and numerous water birds from small coursers, lapwings, rails and grebes to large flamingoes, storks and herons both small and large. Further impressive water bird prey includes reportedly spur-winged goose (Plectropterus gambensis), which weighs about twice as much as tawny eagle. More minor avian prey includes nightjars, coucals, sandgrouse, swifts, bee-eaters, kingfishers, rollers, wood hoopoes, turacos, parrots and several passerines. One small passerine the tawny eagle may routinely hunt is the super-abundant red-billed quelea (Quelea quelea). Near poultry farms, tawny eagles can take to not infrequently lifting free-range chickens (Gallus gallus domesticus) and other poultry, especially when the eagles must feed their young, thus in turn potentially drawing ire of local farmers.
Various snakes are taken opportunistically by tawny eagles and they can be quite bold about hunting venomous snakes. In southern Africa and Kenya the following snakes have been identified in the foods of tawny eagles: Egyptian sand boa (Eryx colubrinus), young African rock python (Python sebae), speckled sand racer (Psammophis punctulatus), rufous beaked snake (Rhamphiophis oxyrhynchus), black-necked spitting cobra (Naja nigricollis), black mamba (Dendroaspis polylepis), boomslang (Dispholidus typus) and puff adder (Bitis arietans). They also hunt lizards not infrequently given the chance, usually favoring fairly large species but capable of taking those ranging from geckos to rock monitors (Varanus albigularis). More minor prey have included turtles, frogs and toads and fish. A tawny eagle in southern Africa was seen to wade into shallow water and successfully pull out a largish catfish. Tawny eagles can also take communal nesting and swarming insects fairly frequently. These are generally termites, which can attract several of these eagles especially amongst non-breeding eagles and young ones. When visiting termites, the tawny eagles commonly eat alates and may, with an unusual lack of aggression, share the food source with several other birds of prey, including as many as a half dozen conspecifics. At times, tawny eagles can also be attracted to swarms of grasshoppers. In one case, a tawny eagle was seen consuming the fruit of an Adansonia tree, an unusual instance of frugivory which is very rare in accipitrids other than one unusual species: the palm-nut vulture (Gypohierax angolensis).
Carrion
thumb|A tawny eagle perched amongst [[white-backed vultures, with which they are often obligated to share carrion in Africa.]]
Although the tawny eagle does hunt for food, it also relies extensively on carrion as a food source. The tawny eagle shares its carrion food sources almost invariably with vultures and usually with several other scavengers such as jackals and hyenas. Other birds that frequently also attend carrion are bateleurs, many other eagles (including steppe eagles) and marabou storks (Leptoptilos crumenifer). The producer-scrounger theory predicts that vultures rely on eagles for information on carcasses. Due to their smaller size, eagles, i.e. tawny eagles and bateleurs, are able to begin foraging earlier in the morning and are thus more likely to locate a carcass first. At large carcasses, there is a hierarchical social structure based on the size of the scavenger. Similar scavenger hierarchies have been reported elsewhere as well. Tawny eagles do tend to be dominant over bateleur at carcasses, however. Usually, the larger the group is of griffon vultures, the less likely the tawny eagle is to get to feed. Semi-predaceous and aggressively disposed vultures, like white-headed vultures (Trigonoceps occipitalis) in Africa and red-headed vultures (Sacrogyps calvus) in India as well as the lappet-faced and cinereous vultures, tend to have little tolerance for tawny eagles, with the latter unlikely to approach until these aggressive vultures have had their fill. On the contrary, though, at times white-headed vultures and tawny eagles have been observed peaceably sharing roadkills in some instances.
Kleptoparasitism
thumb|A tawny eagle perched with a young [[bateleur. The ecology of these species is often broadly similar but the tawny eagle usually dominates the bateleur in food competition.]]
The tawny eagle steals food from other raptors in addition to catching its own prey and coming to previously dead food sources. At times the tawny eagle is considered "fearless" in their piratical attacks and is certain to engage in them more frequently than almost any other member of the booted eagle clan or perhaps even birds of prey. Generally, tawny eagles will surprise other birds of prey with a dashing stoop and yank away the prey item in a manner of seconds; they will seldom completely land if the prey item is intercepted on the ground so they can take off with the plundered item quickly. Other raptors known to be attacked for piracy in well-known and often repeated instances have included dark chanting goshawks (Melierax metabates), bateleurs, lanner falcons (Falco biarmicus) and even the imposing martial eagles (Polemaetus bellicosus) and Verreaux's eagles, the latter eagles having appeared to offer surprisingly little to no contest the tawny eagle's piracy despite their great strength and formidable talons. Carnivorous birds that are not traditionally considered raptorial birds, such as marabou storks and southern ground hornbills (Bucorvus leadbeateri), are also occasionally kleptoparasitized by tawny eagles. Interspecific piracy may be most frequent on bateleur despite that species being similarly sized and powered as the tawny eagle. While 5 displacements of tawny eagles by bateleur were reported in a study on their interactions, 26 instances of tawny eagles displacing bateleurs were described, clearly far more. Several smaller birds of prey were observed to be repeatedly robbed of their catches at a red-billed quelea colony, including queleas crippled but not killed by lanner falcons, although some of the maimed queleas were contested by jackals as well. African fish eagles and Pallas's fish eagles (Haliaeetus leucoryphus) in India both seem to take precedence over tawny eagles at shared feeding sources such as carrion sites and water bird nesting colonies. As aforementioned, a bateleur can succeed in seldom instances in pirating tawny eagles. Even much smaller birds such as house crows (Corvus splendens) have been seen to successfully rob a tawny eagle of its prey.
Interspecific predatory relationship
thumb|left|A tawny eagle in India flies with two [[black kites.]]
The tawny eagle occurrence in Africa and the Indian subcontinent places it in arguably two of the most competitive environments for birds of prey in the world. One stark difference from virtually any other known eagle is the tawny eagle's nesting habits. That is that this eagle nests almost invariably on the top of the canopy of a tree, rather than a main trunk or large sturdy branch of trees (or on cliffs or, in steppe eagles, the ground). The nesting location of tawny eagles runs more parallel to those of vultures.
Opportunistically, the tawny eagle may prey upon smaller birds of prey but this is fairly infrequent and the capture of raptorial birds has thus far been seldom reported. A hungry or food-gathering male tawny eagle may infrequently plunder the nests of other raptorial birds. Diurnal birds of prey known to be preyed upon by tawny eagle in Africa have included black-winged kites, hooded vultures, pale chanting goshawks (Melierax canorus) and African pygmy falcons (Polihierax semitorquatus). The fresh remains of a secretarybird were found in one tawny eagle nest in Africa but, if the eagles killed the bird rather than scavenged it, this would need confirmation.
Breeding biology
Pairing and Territories
The tawny eagle often seems to pair for life. Like most birds of prey, they are quite territorial towards conspecifics. Undulating sky dances are sometimes performed too by males with a series of descents and upward swoops on partially close wings, accompanied by calling. However, instances of this seem to be rare. In India, the breeding season is usually November to May, but occasionally can vary from any time from October to August. Trees are usually selected that have prickly branches, presumably for protection. In India, intervals were more prolonged when the habitat was less optimal. Cases of eggs being laid in southern Africa in July and August may be cases of replacement clutches. Showing the variation in India, in Punjab, Uttar Pradesh and Bihar, tawny eagles are mainly laying eggs in January while in Kutch and Jaisalmer, the young are already leaving the nests. At around 5 weeks, the eaglet adopts anti-predator behaviours, some laying prone while a novel animal approaches while others adopt a truculent threat posture with feathers raised, gape opened, wings poised to slap and talons barred for slashing. This is and other studies support that rainfall is key to productive success in tawny eagles of this area, with far more two egg clutches rather than one egg ones (which usually failed) and less confined breeding periods in years that had greater rainfall.
thumb|left|An unusually light juvenile tawny eagle from India.
Status
Conservation
The tawny eagle still occupies a large range. During close study of the tawny and martial eagle in central Namibia, a precipitous decline was detected in both, with a tawny eagle population that was once regionally numbered about 19 pairs down to 2 known pairs. The once seemingly innumerous population of this species within Kgalagadi Transfrontier Park was known by the 1990s to be down to merely 40 known pairs. Roadside counts conducted in Mali, Niger and Burkina Faso show that although the majority of raptor species are in drastic population decline, only the tawny eagle and snake eagles are surviving outside of protected areas. In India, the tawny eagle was once considered "our commonest eagle" Poisoning events are far from restricted to Botswana and are thought to be a direct factor in the reduction of tawny eagles as well even in the protected areas of Kruger National Park. In central Namibia, all 5 of the juvenile tawny eagles that were radio-tagged were poisoned by strychnine baits, completely decimating all recruitment of the species in the area.
Further threats to tawny eagles include habitat loss and land-use changes such as intensified cattle grazing, firewood collection and sale and the charcoal industry. Raptor populations are reliant on seasonal rainfall events which influence the survival of prey populations. Electrocutions and collision risks associated with overhead power lines remain a constant threat to large eagles and vultures. Furthermore, the powerline nesting raptors were found to be a significant source of line faulting in the area, causing substantial financial issues. Occasionally, tawny eagles are also killed by flying into various manmade objects such as reservoirs or are killed by automobiles and are at risk at wind turbines in India. The overarching threat to any raptor population is human population increase which causes competition for habitat and food resources. Also, clearly, the banning of poison baits and the mitigation of dangerous powerlines in eagle-utilized areas is key for the survival of the tawny eagles.