Tassie researchers get rare insight into what makes magnificent wedge-tailed eagles tick
Ernie took four times longer than usual to leave his nest as a fledgling, which has provided Tassie researchers a rare insight into the notoriously shy wedge-tailed eagle. Watch here >>
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It’s a frustration experienced by parents around the globe – an adolescent who just won’t leave home.
But Tasmanian wedge-tailed eagle Ernie took dragging his wings to extremes, when he was recorded staying four times as long as the average eagle on his Maria Island patch.
“We’d never observed behaviour like Ernie’s before, it was very unusual,” said Dr James Pay, an expert in eagles from The University of Tasmania.
Wedge-tailed eagles generally fledge around five months old, leaving their parents territory and establishing their own home elsewhere so they don’t inter-breed with close relatives.
But at 20 months Ernie was still resident in his parents territory, and scientists began to wonder if the general aversion wedge-tailed eagles show for open water was stronger than previously documented.
Despite a distance of only 4km from Maria Island to mainland Tasmania, the open water was proving too great for Ernie.
A number of times he started out on the journey across the water, before turning back for home.
“During this time the other eagles in his tracking cohort – 25 other youngsters – were flying thousands of kilometres, while he’s bouncing around and around Maria.” Dr Pay said.
Despite decades of research no-one yet knows how many wedge-tailed eagles are alive in Tasmania, but they remain firmly on the endangered animal list, facing a multitude of threats including motor vehicle crashes, power lines, poisons, and competition for habitat.
Tasmanian wedge-tails are markedly shy compared to their mainland counterparts, said Dr Pay, which makes studying them tricky for scientists.
“Working out what they need when you can’t see them, they’re flying up high, alone, they’re quite cryptic, that’s where tracking comes in.”
UTAS scientists use GPS trackers to monitor the birds, but even tagging a Wedge-tailed is an ordeal, with scientists having to climb huge trees and then abseil down on the bird from above.
Video footage of their efforts show nests strewn with baby possum bodies, and the eagle itself lying deep and flat in the nest in an attempt to hide.
But the efforts are worth it, Dr Pay said. Birds at the top of the food chain such as eagles are vital to the stability of the ecosystem, and even Ernie’s reluctance to leave home has provided researchers with important findings.
“If they’re not leaving home, that means their parents aren’t having another chick – so the breeding rate overall could be lower than previously thought,” said Dr Pay.
Elsewhere in Australia GPS tracking is being used to try and demonstrate to rural farmers that raptors are not preying on stock, with long-running studies finding only 1% of lamb deaths are attributable to Wedge-Tails.
“[It] helps give us a better understanding of how the eagles survive and, particularly for an eagle that has been probably the most persecuted worldwide, how they’re managing to survive and cope with that sort of treatment,” Mr Falkenberg told ABC South Australia.
“Wedge-tails aren’t the killers that they’re perhaps perceived to be and that wedge-tailed eagles can provide a fantastic service in getting rid of vermin and cleaning up properties.”
Ernie has now started travelling around Tasmania, and has developed a fondness for the Tasman Peninsula. With their shy and reclusive nature, the Tasmanian sub-species of Wedge-Tailed eagles need all the help they can get, says Dr Pay.
“We are observing that the Tasmanian sub-species is definitely much more sensitive to disturbance than those throughout the rest of Australia and New Guinea,” said Pay.
“And that’s important to respect that when we’re trying to save them.”
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