Wedge-tailed Eagle (Aquila audax)

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Aquila audax | [authority] Latham, 1801 | [UK] Wedge-tailed Eagle | [FR] Aigle d’Australie | [DE] Keilschwanz-Adler | [ES] Aguila audaz | [NL] Wigstaartarend

Subspecies

Genus

Physical charateristics

The Wedge-tailed Eagle is a large brown eagle with long-feathered legs and a diamond or wedge shaped tail. The tail shape is prominent when seen soaring. It flies with slow powerful wing beats, and soars and circles at great heights. A slender eagle, it has large wings and a very distinctive wedge-shape tail, and it soars to great heights. They are spectacular fliers, using the large tail as a rudder to make awkward turns. As they fly so high they are able to see quarry from a long way off, stooping to lose height at some distance then coming in very fast and close to the ground, using the long tail to make quick turns around or over obstacles as they approach.

Range

Australasia : Australia, South New Guinea. The Wedge-tailed Eagle is a bird of Australia only. Individuals occasionally appear in New Guinea, but this is generally accidentally, and it does not form part of their normal range.

Habitat

The Wedge-tailed Eagle is found from sea level to alpine regions in the mountains, but prefers wooded and forested land and open country, generally avoiding rainforest and coastal heaths. Eagles can be seen perched on trees or poles or soaring overhead to altitudes of up to 2000 m. Wedge-tailed Eagles build their nest in a prominent location with a good view of the surrounding countryside. It may be built in either a live or dead tree, but usually the tallest one in the territory. In some parts of Australia, where tall trees are absent, small trees, shrubs, cliff faces or even the ground may be used. The density of active nests depends on the abundance of prey and other resources. In most years, nests are usually 2.5 km – 4 km apart. If conditions are particularly good, the distances apart may be less than 1 km because the birds require smaller areas to find sufficient food.

Reproduction

Wedge-tailed Eagles mate for life and are monogamous, although they will find another mate if their existing mate dies. The pair engages in spectacular aerobatic displays as well as spending hours preening each other. The male and female share the duties of nest building, incubation and feeding of the young. Wedge-tailed Eagles build nests in large tall tree (live or dead) which give them a good vantage point to observe the surrounding countryside. The nests are used for many years and may be 1.8 metres across, 3 metres deep and weigh up to 400kg, although the part utilised is a relatively shallow cup lined with twigs and leaves. The density of active of nests depends on the abundance of prey, and range from 1 – 4 km apart. Surrounding the nest site is a large home range where the pair hunts. Although the pair defends their nest site vigorously, they do not defend their home range and this area usually overlaps with other birds. Breeding takes place between April and September. 1-3 eggs are laid at intervals and after 42-45 days incubation; a white downy chick emerges. The chicks stay in the nest for 5 weeks and then spend a further 11 weeks with the parents after which they disperse (up to 850km in 7-8 months). Often only one chick survives, usually the oldest and largest. Eagles may live 19-20 years.

Feeding habits

Wedge-tailed Eagles eat both live prey and carrion. Their diet reflects the available prey, but the most important live items are rabbits and hares. Rabbits usually comprise about 30-70% of the diet, but may comprise up to 92%. The introduction of the calicivirus has resulted in the decline of rabbits in many parts of Australia. It is not yet known how this will affect the Wedge-tailed Eagle. Other food items include lizards, birds (weighing over 100 g) and mammals (usually weighing over 500 g). Wedge-tailed Eagles will kill lambs, but these make up only a small percentage of their total prey. Carrion is a major food source; roadkills and other carcasses are readily eaten. Many of the reports of predation on lambs result from birds scavenging already dead animals. Up to 20 birds may attend a carcass, although only two or three feed at any one time. Wedge-tailed Eagles may hunt singly, in pairs or in larger groups. Working together, a group of eagles can attack and kill animals as large as adult kangaroos. This explains the scientific name of the Wedge-tailed Eagle which means ‘bold eagle’. Under ideal conditions, an eagle can lift about 50% of its body weight. Often, eagles may cache food items on a branch near the nest area.

Video Wedge-tailed Eagle

httpv://www.youtube.com/watch?v=UHs6bgppBHU

copyright: Josep del Hoyo

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Migration

Sedentary, young may disperse up to 800 km of the breeding site after the first year.

Distribution map