Years ago the sight of Wedge-tailed Eagles soaring over Tamborine Mountain was commonplace.
A huge flying fox colony on the eastern escarpment provided an ideal hunting ground for eagles. Almost daily, a resident pair of eagles would swoop over the colony, catch a flying fox, then fly back to their nest in the gorge. Sometimes other eagles would join them. On one occasion five eagles were observed flying together over the flying fox colony, riding the thermals to great height then dropping down to the treetops – what a spectacular sight that must have been. Extermination as a pest, loss of large nesting trees, reduction of prey and destruction of habitat have reduced the number of Wedge-tailed Eagles but they may still be observed on Tamborine Mountain from time to time.
These impressive birds are Australia’s largest bird of prey and are also among the largest eagles in the world. Females are usually bigger than males; birds may weigh up to 5.3 kgs, be up to 1.04 metres in length and have a wingspan of 2.5 metres. Their colour is sooty black with tawny hackles on their neck, pale brown wing covers and under-tail coverts. Young birds are paler, with feathers darkening as birds mature. The legs are feathered, wings are long and up-swept and the distinctive wedge shape of the tail gives the bird its name.
Wedge-tail Eagles are highly aerial and can soar for hours without a wing-beat; sometimes they may fly at altitudes above 2000m. Their hearing and eyesight are extremely keen and it is believed that their eyesight extends to infrared and ultraviolet range, which enables them to see thermals and to spot prey such as a rabbit, from a distance of 1.5 k
They eat carrion and live prey including birds, lizards and mammals, particularly rabbits and hares. They may hunt singly, in pairs and larger groups. Working together allows them to catch larger animals such as kangaroos, however they can only lift up to 50% of their body weight.
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.
We are very fortunate to be able to observe these magnificent raptors in the wild, lets hope they continue to soar above us for many years to come.