Tasmania’s magnificent wedge-tailed eagle is a sub-species of the wedge-tailed eagle of mainland Australia. Having been isolated for 10,000 years from their mainland counterparts, Tasmanian wedge-tailed eagles are an endemic subspecies. It is Tasmania’s largest bird of prey.
Tasmanian Wedge-tailed Eagle (Aquila audax fleayi)
by Carol Haberle
Brown-black to almost black when mature, the Tasmanian wedge-tailed eagle’s feathers are edged in a lighter brown. It has a long, wedge shaped tail and feathered legs. A very large bird, when fully grown will stand over a metre tall, weighing up to 5 kilograms and with a wing span up to 2.2 metres. The only difference in plumage between the sexes is that an adult female is usually slightly lighter in colour than her mate. Females can weigh between 4.2 – 5.3kg, while the male weighs 3.2 – 4.0kg.
Found in open plains, forests and mountains, the wedge-tailed eagles are very effective hunters. The eagles catch and kill their prey using their long and powerful talons. It is a magical sight to see one soaring high in the sky as it hunts its prey, then with speed plummets to the ground for its capture. Their diet consists of rabbits, hares, wallabies, possums, lizards and carrion. Carrion is a major food source for the eagles, roadkill and other carcasses are often eaten.
Although sometimes found from sea level to alpine regions in the mountains, the wedge-tailed eagle prefers wooded or forested land and open country, though most often avoids rainforest and coastal heathland. Eagles are often seen perched on trees or soaring overhead at altitudes of up to 2,000m. Eyries (nests) are built in a prominent location with a good view of the surrounding countryside. They will build them in either live or dead trees, often in old growth forest, and usually choose the tallest tree in their territory. Occasionally eagles will nest on cliff faces. Often reused for years, the eyrie is large and built of dead sticks and bark. The male and female wedge-tailed eagle share in the duties of eyrie building, incubation (sitting on the eggs) and feeding of the young.
Wedge-tailed eagles are monogamous (the practice or condition of having a single sexual partner during a period of time), and studies show they will mate with one partner for life. In the event one bird of a pair is killed, the survivor will find a new mate. Breeding pairs are very territorial, they live in one area throughout the year and will defend the territory around their eyrie sites from other wedge-tailed eagles. Around their territories are large home regions where the birds hunt for prey, though they do not defend this region.
Quite often two or more pairs will have home ranges overlapping, and share the region. The average home range can be up to 10 hectares in size. Territories have up to five alternative nests, most of the time constructed within 200m of each other. One of these nests is usually favoured for breeding. When not breeding, the pair visits nests to eat prey, perch or renovate these nests. Eyries consist of a bunch of large dead sticks with a shallow depression on top which is lined with fresh twigs, leaves and bark.
Birds and The Breeding Season
Wedge-tailed eagles are very shy nesters, with their breeding season being August to January. The birds will often desert their nests, especially if disturbed by land clearing early in the breeding season. The female can lay 1-3 eggs (though usually only one egg is layed per year, and less than half of the territories produce an egg at all), but often only one chick is raised. A breeding pair of eagles need over 10 ha of surrounding forest especially uphill of their nest tree. The eggs are white, measuring 73 mm x 59 mm with reddish brown spots and blotches. If producing more than one egg, the eggs are laid at intervals of two to four days, while incubation starts with the laying of the first egg. The eggs are incubated by both parents for 42-48 days. Even with the intervals between laying, the eggs do not hatch simultaneously. The first chick hatches larger than the second, which in turn is larger than the third. Chicks when hatched are covered with a white down, and fed by the parents for the first five weeks, after which the chicks can then recognise pieces of food and will feed off the floor of the eagles nest.
The first feathers begin to grow at two weeks of age. If threatened by predators, the young chicks will lie flat in the eyrie and will defend themselves if needed. The adult wedge-tailed eagles rarely defend their young. Survival rates of the chicks depend on many factors including local conditions, amount of prey available and the amount of disturbance. In a good year, and if conditions are perfect, two chicks may fledge in an eyrie. Due to the differences in size, the oldest and largest chick has the best chance of survival. The chicks can remain in the nest for up to 90 days. The young remain near the nest for several weeks after fledging (leaving the nest) and for at least three months after leaving the nest they will depend on their parents for food. The young may sometimes accompany their parents until the next breeding season. To witness these magnificent birds of prey taking their young out on the first flight provides truly awe inspiring moments, the adults can be clearly heard ‘talking’ to the young one as it flies in circular movements, while the adults occasionally ‘criss-cross’ beneath their young one while guiding it safely.
Tasmanian Threatened Species
The wedge-tailed eagle is listed as endangered under the Tasmanian Threatened Species Protection Act 1995, and is also included in the Federal list as an endangered subspecies for several reasons. The number of breeding pairs and the breeding success rate is quite low, with less than 150 pairs successfully breeding each year in Tasmania. Death from unnatural causes remains high. Major threats to the wedge tailed eagle include habitat loss, nest disturbance, collisions and electrocutions with power-lines and through the shooting, trapping and poisoning by some farmers who blame them for loss of stock.
Juvenile birds are the most at risk, due to the fact they are still learning to hunt for themselves and are more likely to scavenge on dead lambs. With awareness, attitudes are changing and it is now recognised that lambing losses to eagles are only small, more often than not involving sick lambs. Many farmers are now developing better ways to deal with eagles during lambing, such as throwing the juveniles a few dead rabbits at this time. The Tasmanian wedge-tailed eagle has been subject to Recovery Plans since 1992. Actions include increasing public awareness of the wedge-tailed eagle’s plight, educating the public about the eagle’s importance and consulting with farmers to protect nest sites and reduce disturbances near nests during breeding.
In closing I would like to extend a sincere thank you to photographer friend, Brett Chatwin, for helping me out with photos for this article and allowing them to be published here by Think Tasmania. Visit and follow Chatwin Photography on Facebook. It is strictly prohibited to copy, alter, display, reproduce or redistribute (in whole or part) these images in any way, shape or form without written permission of the photographer. Under copyright laws this is strictly prohibited.
Remaining photos strictly ©Carol Haberle, H&H Photography.
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