Wedge-tailed Eagle
SPECIES Wedge-tailed Eagle
TAXONOMY Aquila audax audax
STATUS Least Concern (Redlist.org); Least Concern NT, QLD (ala.org.au); Endangered; Tasmanian subspecies (ala.org.au)
a.k.a. Australian Wedge-tailed Eagle, Eaglehawk, Mountain Eagle
The Wedge-tailed Eagle is the largest bird of prey in Australia and among the largest in the world. Compared against the top 10 largest, it is ranked 4th. It has often been rivalled against the American Bald Eagle although having many similarities in behaviour, they are a unique species. The Bald Eagle is slightly smaller and heavier than its very distant Australian cousin.
Distribution
There are two recognised subspecies having been separated geographically for 10,000 years:
Wedge-tailed Eagle (Aquila audax audax): Found throughout the mainland and southern New Guinea, recognised by their golden or reddish-brown coloured nape; and,
Tasmanian Wedge-tailed Eagle (Aquila audax fleayi): Found only in Tasmania, recognised by their buff or cream coloured nape.
Habitat
They are found in all natural habitats including open plains, on the edge of forests, and mountains.
Feeding
This bird of prey hunts a variety of animals including mammals, reptiles, and birds. They will seize their prey from both the ground or the forest canopy. If common to the region, rabbits will make up most of their diet. However, they are known to attack animals as large as a kangaroo as they are capable of taking prey several times their own weight. They will also take small possums or birds from their nests in tree hollows. The Wedge-tailed Eagle is also known to hunt cooperatively in pairs or small groups.
Carrion (the decaying flesh of dead animals) is an important food source and relied upon during winter or when a juvenile lacks experience. Groups have been seen sharing the carcass of large animals.
Behaviour
Majestic in manner, the Wedge-tailed Eagle can often be seen soaring high for long periods. It may swoop or be aggressive toward intruders in defense of territory. It has also been seen perched conspicuously on the top of trees, telegraph poles, or rocky outcrops.
They are not usually vocal, but sometimes whistle, yelp, or squeal.
Appearance
Adult Wedge-tailed Eagles are mostly a dark, blackish brown, with feathers that cover their legs resembling a ‘baggy pants’ look all the way to their claws. They have a reddish-brown hackle on the back of their necks with a mottled bank across their upper wing. The undertail coverts and the base of the flight feathers are pale.
Juveniles will have a lighter coloured hackle, which darkens when they reach full maturity at the age of 8 years. The mottled banks across their upper wings are much wider.
Wedge-tailed Eagles possess a distinctive wedge shaped tail, which is how they were named. It can also be described as diamond shaped and it is quite long. Total length ranges from 85 to 105 centimetres. Adult males weigh between 2 to 4 kilograms with adult females weighing up to 5.3 kilograms. Females are larger and heavier in this species.
Wings are relatively narrow and possess deeply notched tips. Total wingspan can range from 180 to 230 centimetres. The wings enable soaring flight, reaching high altitudes and gliding majestically within the air currents. They can get stuck on the ground if they do not have sufficient space and air current to take off. This is one reason why they prefer open grasslands for hunting.
Like many birds of prey they have incredible eyesight, possess massive claws, and have a formidable beak.
Reproduction
Adults are found both alone and in pairs that mate for life. Breeding season varies based on food availability and geographic location. In poor conditions, they may not reproduce at all. However, breeding generally occurs between June and August with a second occurrence in October if the chick does not survive.
Pairs conduct mating rituals of soaring displays that include rolling, touching talons, and deep dives followed by upward swoops. Pairs will also defend their territories against other Wedge-tailed Eagles as their territory may contain a number of nests however usually one is favoured and re-used each year.
Constructed in a large tree or rocky outcrop, the nest consists of a large platform of sticks. It is refurbished annually and can reach up to 2.5 metres across and nearly 4 metres in depth. Some nesting sites have been known to be reused for decades. Nests have been found built on the open ground in barren environments. Both adults will repair the nest, whilst the male will bring fresh lining materials daily.
The clutch can be up to two eggs, with the female primarily responsible for incubation which can take up to 48 days. Once the chicks have hatched, the male will carry out hunting duties to provide for the female and chicks. The female will shred the meal and feed it to the young. Unless conditions are very favourable, usually only the fittest chick will survive and flourish.
Chicks attain flight feathers(fledge) by 95 days. Once able to leave the nest, juveniles remain dependent on their parents for up to another six months. At this juncture they will seek out their own territory reaching sexual maturity by five years old. They will find a mate and begin reproducing by the age of seven. Wedge-tailed Eagles can survive up to 40 years in captivity.
Threats
In the past, populations had been widely persecuted due to the mistaken belief that they primarily preyed on domestic livestock. There may have been an argument at one time, however it is now known that Wedge-tailed Eagles prefer to prey on the abundance of available feral rabbits now present. They also have improved access to hunting due to deforestation, increased available carrion due to drought and vehicular strikes, and legal protection to reduce disturbances to nesting sites. Populations on the mainland are abundant, widespread, and increasing.
However, this is not the case for the Tasmanian subspecies as they are still affected by nesting disturbance from increased human activity. Conservation efforts are focussed on land preservation and the education of farmers. Despite total legal protection of both subspecies; they are still trapped, poisoned, and even shot at.
Updated 5 May 2021