The wedge-tailed eagle (Aquila audax), also known as the eaglehawk, 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. 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 and a length of up to .
The wedge-tailed eagle is one of its native continent's most generalised birds of prey. They reside in most habitats present in Australia, ranging from desert and semi-desert to plains to mountainous areas to forest, even sometimes tropical rainforests. Preferred habitats, however, tend towards those that have a fairly varied topography including rocky areas, some open terrain and native woodlots such as Eucalyptus stands.
The wedge-tailed eagle is one of the world's most powerful avian predators. The introduction of the European rabbit (Oryctolagus cuniculus) has been a boon to the wedge-tailed eagle and they hunt these and other invasive species in large volume, although the wedge-tailed eagle otherwise generally lives on marsupials, including many surprisingly large macropods. Additionally, wedge-tailed eagles often eat carrion, especially while young. The species tends to pair for several years, possibly mating for life.
Although historically heavily persecuted by humans through poisoning and shooting, mostly for alleged predation on sheep, wedge-tailed eagles have proved to be exceptionally resilient, and their numbers have quickly rebounded to being similar or even higher numbers than before European colonisation, thanks in part to humans inadvertently providing several food sources, such as rabbits and a large volume of roadkill.
Taxonomy
thumb|left|An adult wedge-tailed eagle at [[Lake Burrumbeet in flight, notably dark and blackish colour]]
thumb|right|A young wedge-tailed eagle perched in [[Birdsville Track with an unusual amount of pale colour showing due likely to moult]]
The species was first described in 1801 by the English ornithologist John Latham, under the binomial name Vultur audax. At one time, the wedge-tailed eagle was classified in it is own monotypical genus Uroaetus, perhaps due to its unique form. The specific scientific name for the species, audax, is derived from the Latin , meaning "bold", indicative of their perceived disposition, perhaps when hunting, although the species is, in general, highly wary, and even timid, around humans. The eagles of the Aquila genus are part of the subfamily Aquilinae, within the larger Accipitridae family. The subfamily is commonly referred to as booted eagles or sometimes as true eagles. Those species may be distinguished from most other accipitrids by the feathering covering their legs, regardless of distribution. With some 39 or so species, the Aquilinae is present on every continent except Antarctica.
The wedge-tailed, Gurney's and Verreaux's eagles form a clade or a species complex with the well-known golden eagle (Aquila chrysaetos), the most widely distributed species in the entire accipitrid family, as well as outwardly dissimilar (smaller and paler-bellied yet also powerful) eagles like the Bonelli's eagle (Aquila fasciata), the African hawk-eagle (Aquila spilogaster) and the Cassin's hawk-eagle (Aquila africanus), the latter three having once been considered members of a different genus.
Beyond the aforementioned species, based on genetic testing, the four other Aquila species, although outwardly similar to golden and wedge-tailed eagles, being large, dark and brownish, with long wings, are thought to form a separate clade, and are paraphyletic from the members of what can be called the golden eagle clade. Other related outliers from outside the Aquila genus, are the small-to-mid-sized Clanga or spotted eagle species, and the widely found and quite small Hieraeetus eagles. One member of the latter genus contains the only other widely found Aquilinae eagle in Australia, the little eagle (Hieraaetus morphnoides). However, the separation of the two subspecies has been called into question, largely because the reported differences in both size and coloration can be attributed to clinal variation, and some of the insular populations may still be at an intermediate stage of subspecific formation.
- A. a. audax (Latham, 1801) – This subspecies resides in the entire continent of Australia as well as in southern New Guinea. It is the typical wedge-tailed eagle as subsequently described.
- A. a. fleayi (Condon & Amadon, 1954) – This race is endemic to Tasmania. The subspecies is named in honour of David Fleay, an Australian naturalist who was the first to propose the difference of the insular race. Furthermore, it has a deep chocolate brown overall colour rather than blackish, with a whitish buff colouring to the nape rather than tawny-rufous feathers there.
Description
thumb|In flight, the wedged tail is clearly visible.
thumb|right|A wedge-tailed eagle foraging on the ground
Wedge-tailed eagles are large birds with a characteristically black appearance, although they can appear tar to charcoal brown, depending on lighting and individual variation. Juveniles tend to be broader winged by comparison. The wingspan is around 2.2 times greater than the bird's total length. The eagle often spreads its deep wing emarginations to reduce drag in high winds. Its nearest rival in Australia for size is some 15 percent smaller linearly and 25 percent lighter in weight. The same average figures for a survey of 126 eagles in 1932 were and , respectively.
According to one guide, the mean body mass of male wedge-tailed eagles is while that of females is listed as , which, if accurate, is one of the most extreme examples of size sexual dimorphism known in any bird of prey. However, another sample showed far less stark size differences, with 29 males weighing an average of and 29 females an average of . However, the Nullarbor Plain eagles appear slightly smaller than wedge-tailed eagle sizes from other surveys, based on body mass and wing chord sizes. Another source claimed an average male weight of and average female body mass of . The mean body mass of males in Tasmania was while that for females was . Among the entire booted eagle subfamily, in addition to the two heavier Aquila, it is outsized in bulk by the martial eagle (Polemaetus bellicosus), while the also long-tailed crowned eagle (Stephanoaetus coronatus) can average of a roughly similar body mass to the wedge-tailed eagle, although the latter is marginally the heavier bird. Among standard measurements, within the nominate subspecies, the wing chord of males may range from while that of the female is from .
Identification
thumb|left|A juvenile in the [[Northern Territory, notable for paler areas on the wing coverts and nape as well as for a browner overall hue]]
Their unique combination of large size, lanky build, long, diamond-shaped tail (though can be round-ended when both central feathers are moulted together), mainly black or rather dark plumage, and long wings seen when soaring or gliding make all ages of the wedge-tailed eagle fairly unmistakable in the majority of their range. Furthermore, the Gurney's eagle has a much paler immature plumage. The Papuan eagle (Harpyopsis novaeguineae), the only other island raptor in New Guinea that approaches the wedge-tailed in size, is a highly distinct and forest-restricted species, being much paler, particularly below, with long, bare legs and different proportions, more like a giant Accipiter with short rounded wings, a long, somewhat rounded tipped tail, and a large, rounded head. Female calls in wedge-tailed eagles are similar but are generally lower and harsher than males.
Offshore, the wedge-tailed eagle may be distributed in several of the larger Australian islands and some of the smaller ones. Those include a majority of the Torres Strait Islands, Albany Island, Pipon Island, the isles of Bathurst Bay, many small isles in Queensland, from Night Island down to the South Cumberland Islands, Fraser Island, Moreton Island, North Stradbroke Island, Montague Island, Kangaroo Island, the Nuyts Archipelago, Groote Eylandt and the Tiwi Islands. In Tasmania, they may be found essentially throughout as well as some isles of the Kent Group, Bass Strait, Flinders Island and Cape Barren Island. In New Guinea, the wedge-tailed eagle is highly range restricted and can be found predominantly in the Trans-Fly savanna and grasslands and the general area around the Western Province, as well as in Indonesia Merauke Regency, with some isolated reports in Western New Guinea, the Bensbach River and the Oriomo River.
Habitat
thumb|right|Wedge-tailed eagles favor varied environments, mostly those with some leafy trees and rocky areas, but can be seen in a great variety of habitats.
The wedge-tailed eagle lives in an extremely wide range of habitats. Assorted habitats known to host wedge-tailed eagles includes open woodland, savanna, heathland, grasslands, desert edge and semi-desert, subalpine forests, montane grasslands and mountain peaks, not-too-dense tropical rainforests, monsoon forests, dwarf conifer forests, some wetlands as well as regularly forays to coastal areas, though normally along the coasts they occur around plains somewhat away from the water. A strong preference was detected for C. cunninghamiana alternatively with several Eucalyptus species was detected in the Australian Capital Territory, sloping ground allowing good access and access to tall, mature trees being paramount to the eagles in the study. Quite often they will be seen soaring over hills, mountains or escarpments as well as over flat plains, especially spinex grassland.
In the deserts of the Lake Eyre basin, they are often seen in gibber plains along treed watercourses and drainage basins, here often concentrated around Eucalyptus in stony creek beds. In the sandy desert areas of Western Australia, wedge-tailed eagles were once reasonably common but have largely vacated the region after the macropod prey they live off of there were all but hunted to extinction. Wedge-tailed eagles commonly occur from sea level up to about with seemingly no preference based on altitudinal level. One of the few habitat types considered to be strongly avoided by wedge-tailed eagles are areas intensively settled or cultivated areas. During the intense heat of the middle part of the day, it often soars high in the air, circling up on the thermal currents that rise from the ground below.
The wedge-tailed eagle is largely sedentary as expected of a raptor dwelling in the subtropics, although they also dwell in the tropics (far northern Australia and New Guinea) as well as in the temperate zone (Tasmania). The small New Guinea population is apparently indistinguishable from the mainland race and so possibly result of recent colonization, although no records exist of migrating wedge-tailed eagles islands past the Torres Straits. Due to their tendency for wandering, some authors class the wedge-tailed eagles as a "partial or irruptive migrant". However, while they are arguably irruptive, it does not fit the mould of a true migrant well since under normal circumstances adults are rather sedentary unless environmental changes force them to move.
The wedge-tailed eagle is the only bird that has a reputation for not infrequently attacking hang gliders and paragliders, although other eagles including the golden eagle have also been recorded to behave thusly. Based on the response the eagles show to the gliders, they presumably are defending their territory and treating the perceived intruder like another eagle. Cases are recorded of the birds damaging the fabric of these gliders with their talons as well as some other parts of the gliding apparatus, but not the humans themselves, has been reported. They have also been reported to attack and destroy unmanned aerial vehicles used for mining survey operations in Australia.
The presence of a wedge-tailed eagle often causes panic among smaller birds and, as a result, aggressive species such as magpies (one of the most vulnerable types of passerine to eagle attacks), butcherbirds, wagtails, monarch flycatchers, lapwings, and miners as well as smaller birds of prey, including both accipitrids and falcons, any of which may aggressively mob eagles (see video). Multiple species may join the kerfuffle and mob them, especially while the eagles perched, often engaging in noisy calling, presumably meant to disorient the predator, and occasionally in physical attacks against the eagle, typically focused where the big, relatively lumbering eagles could not grasp the attacking birds. The wedge-tailed eagle usually does not engage its tormentors but sometimes rolls in the air to present talons whether perched or not. Sometimes wedge-tailed eagles appear to fight but this and other behaviours, especially between young eagles, may be interpreted as playful.
<gallery widths="200px" heights="155px">
File:Wedge-tailed Eagle dayboro.ogv|In flight, 'mobbed' by Australian magpie, Dayboro, SE Queensland
File:Wedge-tailed Eagle sam95.ogg|Samsonvale, SE Queensland, Australia
</gallery>
Dietary biology
thumb|A wedge-tailed eagle standing on [[roadkill carcass of kangaroo in the Pilbara region of Western Australia]]
thumb|[[Cannibalism|Cannibalizing a wedge-tailed eagle roadkill, killed when itself was feeding on a kangaroo roadkill]]
The wedge-tailed eagle is one of the world's most powerful avian predators. Prey is usually grabbed via a pounce or snatch during a gliding flight or a tail-chase from low quartering or transect flights. Prey is not infrequently spotted from a soaring flight and they may undertake a long, slanting stoop towards it. Sometimes, an eagle may pull brushtail possums and other mammals from tree cavities, as well as young birds from a nest. They've been known to follow wildfires to search for fleeing animals or alternately tractors and other farm equipment for the same purpose. Regardless of prey size and season, tandem hunts, mainly by breeding adult pairs or sometimes loosely associated young eagles, are not uncommon. When hunting domesticated prey, they've been seen to land near livestock mothers to intimidate them and separate their young, so they can attack the latter. Carrion is a major diet item, also; wedge-tails can spot the activity of ravens around a carcass from a great distance, and glide down to appropriate it. Carrion consumption is recorded in all season and contexts, although generally non-breeding birds are more likely to scavenge and young wedge-tailed eagles, even more so shortly post-dispersal, are thought to be far more likely to scavenge on carrion than adults generally. Wedge-tailed eagles are often seen by the roadside in rural Australia, feeding on animals that have been killed in collisions with vehicles. The importance of carrion relative to live prey has not been greatly studied but away from human development, especially roads, carrion is less likely to be encountered and eagles of all ages must presumably hunt to survive. In general, Australian accipitrids of many species not infrequently come to carrion and they along with large passerines like Corvus species and currawongs probably fulfill the niche that vultures do in other continents to some extent, albeit with considerably less specialization.
Prey spectrum
<gallery widths="200px" heights="155px">
Pogona vitticeps (32494027291).jpg|Regular wedge-tailed eagle prey can vary in size down to small lizards such as bearded dragons, their favourite variety of reptilian prey.
CSIRO ScienceImage 1147 European rabbit.jpg|The introduction of rabbits to Australia has been greatly harmful to the Australian environs but a boon to opportunistic wedge-tailed eagles, which often take them in great numbers.
Large Eastern Grey male kangaroo (9645655070).jpg|Regular prey can range up to the size of large adult kangaroos such as eastern grey kangaroos, usually attacked in hunting pairs.
Galahs.jpg|A diversity of birds may be taken with medium-sized, common birds such as galahs taken relatively frequently due to the conspicuousness.
</gallery>
The wedge-tailed eagle is a dietary generalist, opportunistically capturing a wide range of prey species. The wedge-tailed eagles tends to prefer smallish to fairly large mammals as prey. In a small study from Armidale, New South Wales, it was estimated that mean prey weight was . It only ranks behind the crowned eagle and harpy eagle and rivals the martial eagle as the eagle likely to attack the largest prey on average.
Mammals
Introduced mammals
While the introduction of invasive species to Australia has been generally having a negative to devastating effect on native animals and ecosystems, the wedge-tailed eagle is one of a few native species to largely benefit from these introductions. This is especially due to the introduction of the European rabbit, which were deliberately introduced repeatedly (abortively in 1859 and then via a concerted effect from 1937 to 1950), largely so the wealthy could hunt them. The wedge-tailed eagles quickly took to the rabbits as prey along with another introduced leporid, the European hare (Lepus europaeus).
One Canberra study found that 98.5% of the rabbits taken were adults. However, other studies estimated the mean weights of rabbits taken by wedge-tailed eagles as variously from or "usually over ", infrequently reported to , size of the rabbits being perhaps limited the poorly-suited soil and environs of the Australian wilderness. Meanwhile, the European hare is neither as widely established nor as prolifically taken as rabbits by wedge-tailed eagles but are by no means neglected and a substantial meal. Ultimately, the rabbit population may have more than halved and locally have been some 90% reduced. In the region of Broken Hill, White Cliffs and Cunnamulla, rabbits have gone down from accounting for 56–69% of the diet to 16–31% of it.
thumb|right|Wedge-tailed eagles are disproportionately likely to be seen eating [[carrion of roadkills (killed by cars). In the wild they often capture live prey. They often tolerate sharing carrion with other scavengers, such as ravens, despite them being prey species as well.]]
Much more controversial at one time than hunting introduced rabbits and hares is the wedge-tailed eagle's occasional tendency to feed on and sometimes kill domesticated livestock animals. The predation of wedge-tailed eagles on young farm animals has been the primary historic driver for the persecution of the species. However, in no known study have domestic livestock been known to be primary prey. Additionally, feral cats, mainly juveniles, can be part of their prey.
Native mammals
Presumably, the primary native prey of wedge-tailed eagles is marsupials, particularly macropods, which is also in accord with studies involving places where rabbits have declined or never occurred. Many wallabies, kangaroos, and associated animals are included in the diet, with over 50 marsupials known to be in the species' prey spectrum. When selecting marsupials, wedge-tailed eagles tend to ignore smaller species and focus on larger-sized ones.
A video surveillance study at the nest determined that seemingly freshly killed, albeit usually quite young macropods were delivered to nests near Broken Hill.
Wedge-tailed eagles have been recorded attacking eastern grey kangaroos weighing over . Furthermore, an adult female western grey kangaroo was witnessed to be killed "in a few minutes" by a hunting pair of wedge-tailed eagles, and the eagles are considered a serious predator of the western grey. In some unusual cases, wedge-tailed eagle hunting parties can form whilst hunting red kangaroos, sometimes including up to 15 eagles (more loose, opportunistic aggregations than well-organized groups), but usually only a pair is sufficient to kill such prey. Other marsupials are by no means neglected. Other notable marsupials known to fall prey to wedge-tailed eagles include adults of the following: koalas (Phascolarctos cinereus), quokkas (Setonix brachyurus), eastern (Dasyurus viverrinus), western (Dasyurus geoffroii) and tiger quolls (Dasyurus maculatus), Tasmanian devils (Sarcophilus harrisii), bilbies, numbats (Myrmecobius fasciatus), common wombats (Vombatus ursinus), southern greater gliders (Petauroides volans) and potoroos.
With relative infrequency, other classes of mammals, beyond leporids and marsupials, may be taken opportunistically by wedge-tailed eagles. Occasionally, an eagle may take a monotreme including both the platypus (Ornithorhynchus anatinus) and the short-beaked echidna (Tachyglossus aculeatus). Several species of rat are readily taken and even the house mouse (Mus musculus), likely the smallest mammalian prey known for wedge-tailed eagles at around in weight. Beyond sheep, pigs, and infrequently young goats (Capra hircus), other ungulate prey, entirely introduced by man into the Australasian region, is eaten exclusively as carrion so far as is known, including cattle (Bos taurus - despite claims that eagles have killed young calves, which is possible, they have only ever been witnessed feeding on afterbirths and not harming calves), Javan rusa (Rusa timorensis) in New Guinea, sambar deer (Rusa unicolor) in northern Victoria and water buffalo (Bubalus bubalis) in the Northern Territory. In one instance, a young girl was apparently subject to a brief attack by a wedge-tailed eagle, in what was likely an attempted act of predation, near her rural home but the attack was abandoned by the eagle. It has been noted that some different species of large eagles are thought to occasionally attack children as prey though, among extant species, only the crowned eagle and martial eagle, both in Africa, are thought to have successfully carried out rare acts of predation on human children.
Birds
thumb|A wedge-tailed eagle feeding
thumb|A raven [[Mobbing (animal behavior)|mobbing a wedge-tailed eagle, the latter being an opportunistic predator of many birds]]
Birds take a clearly secondary position to mammals when importance and especially prey weight are concerned; however, the wedge-tailed eagle shows some fondness for avian prey.
On Kangaroo Island, Australian and little ravens together constituted 19% of the diet. Peculiarly, one study found that among a large sample of 1826 prey items in the Northern Territory that the most often identified prey species was the tiny budgerigar (Melopsittacus undulatus), at one of the smallest avian prey species for this eagle.
Additionally, wedge-tailed eagles may take Australian brush turkeys (Alectura lathami) and malleefowl (Leipoa ocellata), quail, pigeons and doves, frogmouths and owlet-nightjars, cuckoos, buttonquails, stilts, lapwings, plains-wanderers (Pedionomus torquatus), thick-knees, gulls, petrels, cormorants, herons, ibises and spoonbills, cranes, other birds of prey, kingfishers, honeyeaters, quail-thrushes, whistlers, monarch flycatchers, mudnesters, artamids, true thrushes, grass warblers, starlings and pipits. The smallest avian prey attributed to wedge-tailed eagles is the zebra finch (Taeniopygia guttata). Two estimates estimated the typical body mass of emus attacked were merely , respectively, against an average of for adult emu. Some of Australia's largest flying birds are also included in the wedge-tailed eagle's prey spectrum. An unusually close feeding association with a very large bird is with the Australian bustard (Ardeotis australis) in northwestern Queensland, where bustards were found to account for 13.4% of the pellet contents and 23% of prey biomass. That study calculated the mean weight of bustards taken as , indicating that the eagles were selectively predating the much larger male bustards. The most preferred reptilian prey by far is bearded dragons. In Western Australia, shingleback skink (Tiliqua rugosa) and somewhat smaller western blue-tongued skink (Tiliqua occipitalis) collectively comprised about 7.5% of the diet. Even lace monitors (Varanus varius), which weighs on average adults, can be a prey for this powerful eagle. Contrarily, lizards down to the size of a pygmy spiny-tailed skink (Egernia depressa) and a thorny devil (Moloch horridus) may be taken.
Beyond lizards, wedge-tailed eagles seldom seem to hunt other types of reptiles. Eastern long-necked turtle (Chelodina longicollis) have been claimed as prey in one report although any other confirmed cases of predation on turtles by this species are not known. Predation on frogs or other amphibians is almost unheard of for wedge-tailed eagles, however, based on toxicity reports in eagles, they may consume invasive cane toads (Rhinella marina) from time to time. Similarly rare in the species' diet is fish, although common carp (Cyprinus carpio) and western blue groper (Achoerodus gouldii) have been documented as prey. The wedge-tailed eagle has the ability to exploit a more catholic variation of both prey and habitat since it exists with relatively fewer competing species. However, the white-bellied sea eagle clearly does not shy away from contentious border disputes with wedge-tailed eagles and the two species can often be seen be seen readily attacking each other, occasionally in talon grappling and sometimes cartwheeling attacks on one another. Clearly, there is ample partitioning between the wedge-tailed and white-bellied sea eagles, the latter adapted to mostly open wetlands and coasts and, while also a dietary generalist, they tend to derive most of their diet from fish, water birds and other wetland-dwelling prey, and they seldom compete directly for prey such as mammals with wedge-tailed eagles. When it comes to carrion, wedge-tailed eagles tend to dominate other predators, especially most birds, with most kites, other assorted raptors and some large passerine birds, mainly Corvus species and butcherbirds, coming to dead animals including roadkills. However, heavier terrestrial meat-eaters can hold their own at times against wedge-tailed eagles, namely red foxes, dingos, monitor lizards and Tasmanian devils, despite all these species sometimes turning up as prey of these eagles as well. Wedge-tailed eagles will opportunistically prey on other birds of prey. They share this aptitude with other large eagles in different parts of the world such as golden eagles, although such acts are relatively infrequent, it is clear that the wedge-tailed eagle is considered a primary threat by many raptors based on witnessed attacks by eagles on them and the mobbing behaviour of other raptors. Among the other birds of prey known to occasionally fall prey to these eagles are little eagles, collared sparrowhawks (Accipiter cirrocephalus), grey goshawks, brown goshawks (Accipiter fasciatus), Pacific bazas (Aviceda subcristata), black-breasted buzzards, peregrine falcons (Falco peregrinus), Australian hobbies (Falco longipennis), black falcons (Falco subniger), brown falcons and Nankeen kestrels (Falco cenchroides).
Occasionally owls are also included in the prey spectrum when an opportunity arises, including barn owls (Tyto javanica), southern boobooks (Ninox boobook) and even powerful owls (Ninox strenua). Wedge-tailed eagles are apex predators and have no well-documented predators, although presumably they have some nest predators, likely including ravens and currawongs, especially when displaced by human disturbance from their nests. Most of the large falcons, including peregrine, brown and black falcons, and at times large owls nest in unused or abandoned wedge-tailed eagle nests.
Allopreening occurs occasionally between pairs but is seldom observed, although at times has been considered a "regular" part of the courtship process. Mating tends to occur on a bare branch or dead tree in the nest area, and may continue into the nestling period. Contrary to old accounts, the species does not mate in flight. Aerial displays may go on for a while normally early in the breeding season, between 3 months and 3 weeks prior to egg laying. Territorial aggression can extend towards hang gliders and aircraft, advances noisily, bill open and talons extended until flying just above and behind or slightly ahead of pilot then swoops repeatedly after making contact with the hang-glider. Not far from that in Mutawintji National Park density was around a pair per . At Fowlers Gap, there were 9–10 pairs per . In the Fleurieu Peninsula in South Australia during the early to mid 2000s, there was a pair per , active nest sites were apart, while the average home range around the nest is roughly. In the Perth area, it was projected that the mean home range was about .
Nests
thumb|right|Nest in a [[Flindersia maculosa|leopardwood tree at Mutawintji National Park]]
Both sexes may participate in building the nest but the female takes the greater share, often standing in the middle and building outwards.
Good sized nests can weigh well over . Occasionally they may nest in dwarf trees at as low as . Additionally they have been known to nest on power pylons and telegraph poles.
Other smaller animals may nest among the sticks at the base of active wedge-tailed eagle nests such as finches, pardalotes and even possums (which more so than the small birds are presumably vulnerable to the eagles if caught in the open), perhaps gaining some protection from the presence of the eagles. Other species, such as Pacific black ducks (Anas superciliosa), falcons and owls, may also benefit by utilizing unused nests for their own breeding purposes, although typically only the falcons usually use them with relative regularity. The female lays multi-egg clutches by some 3 days or so apart. Each egg normally weighs about , the equivalent to about three chicken eggs or about 3% of the female eagle's body weight, 10% when the clutch number is 3, which is typical for an Aquila eagle but a small percentage relative to smaller raptors. However, the male will incubate at times as well, at least up to an hour at a time. Sufficient environmental conditions can largely reduce sibling aggression. Potential predators such as goannas are struck when found to be approaching the nest, although the eagles usually abandon the nest when a human approaches. Repeated intrusions and noisy disturbances may have a net negative effect such as on Tasmanian wedge-tailed eagles, as these factors often lead to nest failure. Most recoveries in one banding study were distributed under from their original banding site, mostly as fledgling age juveniles, but some meandered up to away. In a further study in New South Wales at Burrendong Dam, from 1993 to 2003, 15 pairs produced an average of one fledgling per territory but 1998 due to drought conditions, the rate was only 0.4 chick per territory. Within Kinchega National Park, however, the rate of 0.99 young per pair was fairly consistent regardless of climatic conditions. 0.73 fledglings were produced pair per year in south-west Western Australia. During periods of drought in Western Australia, some wedge-tailed eagles may forgo breeding for up to four years. Higher annual rainfall in Western Australia, higher in mesic than arid areas, made a big difference in pair productivity, with 12% of arid zone pairs producing young, or 0.13 fledglings per pair, a very low productivity, while the mesic zone 69% of pairs produced fledglings, or 0.77 fledglings per pair. As of that analysis, Birdlife considers the overall population of wedge-tailed eagles to be "possibly increasing". Although wedge-tailed eagles are often scarcer than those large distribution suggests, their total distribution covers more than 10.5 million square kilometres and the population is quite likely within hundreds of thousands. Steel-jawed rabbit traps were set around carcasses and Heligoland traps could sometimes trap several eagles at once, beyond sustained shooting and poisoning efforts. Despite such stunningly high rates of persecution, the wedge-tailed eagle was remarkably resilient to the haphazard persecution inflicted by humans in a way many other Australian wildlife, especially the regionally endemic mammals, and even other eagles elsewhere often are not.
Often the species is less intentionally harmed via human disturbance via land development particularly intensifying agricultural and modern settlements, which can in turn lead to clearing of mature trees, disturbances at the nest and decline of native prey species, all of which have a net negative effect on the wedge-tailed eagles. Eggshell thickness was not significantly decreased by the use of DDT likely due likely to the largely mammal-based diet of the species, whereas raptors which consume birds or fish are disproportionately effected by DDT. On occasion, the species is still subject to illegal shootings and poisonings, however persecution of the species is significantly less prevalent in recent decades. Within the Fleurieu Peninsula, some 1.74 eagles on average are claimed by wind farm turbine collisions. Surprising resilience even to drought was found recently in the wedge-tailed eagles in the Australian Capital Territory where pair occupancy remained consistent through drought for wedge-tailed eagles but not for little eagles, but this is may have more to do with the wedge-tails more successful uncoupling from a dependence on declining rabbits as prey than the little eagle. Of 84 eagle deaths or debilitating injuries, 52% were attributable to collisions or electrocutions, 15.5% due to persecution, 11% due to natural causes and 15% were due to unknown causes. With the island's population numbering quite low and likely continuing its declining, as evidenced by slow replacement of lost pair members, the subspecies is listed as state-endangered. Furthermore, surveys contrasting 1977–1981 with 1998–2001 data found a decline of around 28% in the island's reported number of eagles.
Studies indicate that Tasmanian eagles mostly nest in emergent trees in old-growth native forest exposed to early morning sun and sheltered from prevailing strong winds and cold spring winds, given the more temperate climate there relative to most points in mainland Australia. The subspecies requires forest areas greater than in which to breed and is very prone to desert its nest when disturbed. Furthermore, of 109 eagle carcasses recovered in Tasmania, all of them had trace levels of lead in their livers or femurs with at least part of the exposure likely from lead ammunition. In addition, like all eagles, Tasmanian wedge-tailed eagles are vulnerable to electrocutions, and collisions with vehicles, overhead wires, and fences and poisonings, largely via illegal killings by poachers of Tasmanian devils and forest ravens (Corvus tasmanicus).
In protected areas, protocols are in place to protect Tasmanian eagle nests and protect them by creating an obligatory nest reserve of at least 10 ha and forestry operation have been restricted during the breeding season to outside a buffer zone of , extending further to if the proposed work is in the line-of-sight of the nesting eagles. About 20% of known pairs are outside protected areas and on private land, so are largely outside the strict legal protection the subspecies has on governmental forest land. The wedge-tailed eagle is also a symbol of the Australian Defence Force, featuring prominently on the ADF Flag, and the Royal Australian Air Force and Australian Air Force Cadets both use a wedge-tailed eagle on their badges. The Royal Australian Air Force has named its airborne early warning and control aircraft after the bird, the Boeing E-7 Wedgetail.
Early in 1967, the Australian Army 2nd Cavalry Regiment received its new badge, a wedge-tailed eagle swooping, carrying a lance-bearing the motto "Courage" in its talons. The regiment's mascot is a wedge-tailed eagle named "Courage". Since its formation, there have been two, Courage I and Courage II. In 1997, while on flight training with his handlers, Corporal Courage II refused to cooperate and flew away, not being found for two days following an extensive search. He was charged with being AWOL and reduced to the rank of trooper. He was promoted back to corporal in 1998.
The West Coast Eagles, an AFL football club from Western Australia, uses a stylised wedge-tailed eagle as their club emblem. In recent years, they have had a real-life wedge-tailed eagle named "Auzzie" perform tricks before matches.
References
External links
- – educational profile covering identification, behaviour, conservation and ecology