Wedge-tailed Eagle Australia’s Largest Raptor
Warning, graphic content. They kill Eastern Grey male Kangaroos.
Caution, this article contains descriptions of actual kills and eating the prey.
Two Wedge-tailed Eagles circled a grazing mob of kangaroos, they had selected one young adult male to attack and dived at it. The kangaroo was about 1.2metres tall.
The Eagles separated this one kangaroo from the mob and started repeatedly striking the animal, taking it in turns, climbing to 20 to 30metres and then rapidly diving at the animal, striking at its head with talons and buffeting the head with their wings.
Strikes on the kangaroo were occurring every 15 seconds, with visible wounds to the head and neck, this continued for over 30 minutes, the kangaroo started stumbling, seeming disorientated and losing balance.
Diving attacks by the Eagles were from different directions keeping the kangaroo in the same area, and after another 15 minutes the kangaroo fell. Then the Eagles landed and started to feed, the kangaroo didn’t react, apparently dead.
The smaller bird, probably the male, fed from a large gash in the kangaroo’s neck, both Eagles fed from the carcass for 20 minutes, consuming much of the neck, torso and right leg.
Nestlings in their nearby nest were later seen feeding on fresh kangaroo remains.
These accounts are from a research paper by Fuentes & Olsen (2015).
On another occasion two soaring adult Eagles started attacking one large adult male, about 1.7m tall, which appeared to have difficulty with its bounding gait, possibly it had been hurt in the legs or hips from a car strike.
These Eagles used a similar technique, attacking alternately and repeatedly from height but the first two strikes were head first, using the beak to attack and injure the kangaroo. After this the talons and wings were used and 22 minutes passed before the kangaroo was knocked down, the Eagles landed on the kangaroo and attacked with their beaks and talons.
They flew off when the kangaroo stood up, only to resume their diving attack, the kangaroo fell 13 times before the Eagles finally landed and started to feed. They were joined in the feeding by a fledgling Eagle that had remained in the air during the attack.
The Eagles stayed with the carcass for nearly an hour consuming large amounts of the leg, tail and some of the viscera. They then flew to a tree branch 50m away.
Joeys are also taken. An Eagle dived at a young adult female with a young kangaroo in her pouch, the kangaroo had trouble hopping away and after a short distance forced the joey out of the pouch. Quickly a second Eagle swooped in and immobilized the joey in its talons, while the first Eagle drove the adult female kangaroo away.
Both Eagles then eviscerated the joey and fed for 10 minutes, before one of the Eagles took the carcass back to their nest (Fuentes & Olsen, 2015).
While working in a forested area, I have disturbed a female kangaroo with a large young in her pouch, when the female started to hop away the joey fell out, being almost too big for the pouch, but the mother immediately came back, encouraging the joey to follow (Personal account, Peter Miles).
The Wedge-tailed Eagle Aquila audax is found all over the continent of Australia including Tasmania and the dry desert inland. They favour forests and woodland with tall trees for nesting and observing but also open land for hunting.
Adult Eagles are about 90 to 110cm in length with a wingspan of 2.8m. Older birds develop almost black feathers They are Australia’s largest raptor (Gower, 2012).
On the Fleurieu Peninsula in South Australia, where I do a lot of my environmental work, there are large areas of remnant woodland but also extensive areas cleared for pastoral agriculture. It appears that the Eagles have adapted to the changed landuse to agriculture.
The average Eagle range for a breeding pair is 34 square kilometres, with a range between 18 to 75 sq km. There are known to be 29 territories over the peninsula which has an area of 1500 square kilometres.
Most pairs commenced egg incubation by mid-winter and the young fledged by early-summer. Mostly there was one young fledgling, with two pairs having two young.
In this study 4 Eagles were killed by a new wind farm which was built alongside a tree with a nest, and two were electrocuted at powerline poles.
On the Fleurieu there was general landholder sympathy and no persecution of the Eagles, with most landholders valuing the presence of the large birds. They clean up carrion and take rabbits and foxes.
The Eagles main threat is habitat destruction which is removal of native forests and large trees which they use for nesting (Dennis, 2006).
Previously, as far back as 1892, Wedge-tailed Eagles were actively shot and poisoned by sheep farmers mistakenly believing they took lambs. Between 1958 and 1967 a government bounty system resulted in at least 120,000 Eagle deaths in the states of Western Australia and Queensland, indeed in WA Eagles were declared as vermin. Fortunately, these attitudes have changed and the Eagle has been found not to take many lambs (Knobel, 2015).
Lambs make up part of the Eagles diet in some parts of WA but not many are taken compared to the number of normally occurring all causes neonatal lamb deaths (Brooker & Ridpath, 1980).
The lambs Eagles are seen with are likely to be carrion. As a sheep farmer once told me, “If you’re going to have sheep, you’re going to have dead ones.”
Wedge-tailed Eagles are protected now under each State Government legislation and their habitats are protected by Native Vegetation protection legislation.
Wedge-tailed Eagles do feed on introduced wild rabbits Oryctolagus cuniculus, and some concern was felt about the survival of Eagles after the release of the biological control agent Rabbit Haemorrhagic Disease Virus, the Calicivirus, which was so effective in reducing rabbit numbers, up to 90% reduction.
Observations have shown that the Eagles aren’t dependent on rabbits as a food source for survival, instead more kangaroos, reptiles and birds are eaten. Rabbits cause degradation of environments and as their numbers decline, native species numbers increase (Olsen, et al., 2014).
Lead poisoning through contamination from incidental consumption of lead ammunition in carcasses is a problem worldwide and found to be the case in Tasmanian Wedge-tailed Eagles.
Lead was detected in the liver and femur in all of the over 100 Eagle carcasses collected between 1996 and 2018. Lead causes gastrointestinal stasis, impaired mobility and lowered sensorial ability resulting in mortality. Measures should be introduced to deter the use of lead-based ammunition (Pay, et al., 2021).
Many developments have been made in the use of alternatives to lead ammunition, such as steel, copper and tungsten.
There is scientific disagreement about which were the dominant predators in Australia in the past, mammals or reptiles, with birds not included, but observations suggest that the Wedge-tailed Eagles may be among the dominant predators (Fuentes & Olsen, 2015).
References:
Brooker, M. G., & Ridpath, M. G. (1980). The diet of the wedge-tailed eagle, Aquila audax, in Western Australia. Wildlife research, 7(3), 433–452.
Dennis, T. E. (2006). Status and distribution of the Wedge-tailed Eagle on the Fleurieu Peninsula, South Australia, in 2005. South Australian Ornithologist, 35(1/2), 38.
Fuentes, E., & Olsen, J. (2015). Observations of the killing of large macropods by Wedge-tailed Eagles ‘Aquila audax’. Australian Field Ornithology, 32(3), 160–166.
Gower, P. (2012). Fleurieu Birds. (1st ed.). Stepney, South Australia.: Axiom Publishing. Book.
Knobel, J. (2015). The conservation status of the Wedge-tailed Eagle in Australian law and thoughts on the value of early legal intervention in the conservation of a species. De Jure Law Journal, 48(2), 293–311.
Olsen, J., Cooke, B., Trost, S., & Judge, D. (2014). Is wedge-tailed eagle, Aquila audax, survival and breeding success closely linked to the abundance of European rabbits, Oryctolagus cuniculus? Wildlife Research, 41(2), 95–105.
Pay, J. M., Katzner, T. E., Hawkins, C. E., Koch, A. J., Wiersma, J. M., Brown, W. E., … & Cameron, E. Z. (2021). High Frequency of Lead Exposure in the Population of an Endangered Australian Top Predator, the Tasmanian Wedge‐Tailed Eagle (Aquila audax fleayi). Environmental toxicology and chemistry, 40(1), 219–230.
Rowe, E. L., & Brinsley, R. F. (2018). Breeding productivity of the Wedge-tailed Eagle Aquila audax on the Fleurieu Peninsula, South Australia in 2017. Corella 42, 86, 90.
