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Eagle eye on endangered bird

Meet the zoologist who gets more text messages from wedge-tailed eagles than humans

Ping. It’s another text message to Dr James Pay’s phone. This time, it’s from Wyatt, a fine feathered friend soaring above Mount Field National Park.

Since James first moved to Tasmania five years ago, he jokes that he has received more text messages from eagles than humans.

The birds are sending regular updates on their whereabouts, courtesy of a GPS tracker they carry on their backs.

This high-tech University of Tasmania research project is shedding light on Australia’s largest bird of prey, the endangered Tasmanian wedge-tailed eagle, known colloquially as wedgies.

Birds with a presence

Before James became acquainted with Australia’s largest carnivorous bird for his PhD, he was studying small birds in the Pyrenees mountains in France.

A childhood fascination with dinosaurs morphed into a love of their avian descendants.

“I grew up loving animals and I think many people gravitate towards birds because they are very visible in the environment and often make a lot of noise, which makes them easier to observe.”

Wedgies certainly have a presence; they are a metre in length with wingspans of up to 2.3 metres.

Despite their formidable size, the apex predator is endangered. Numerous eagles are injured or killed each year from various causes, including collisions with powerlines, wind turbines and cars. They are also shy breeders, who will abandon their nest if humans come too close.

Solar-powered backpacks

James is most interested in juvenile wedgies.

“A lot of the eagles we find injured or dead in Tasmania are younger birds, so we want to find out more about their behaviour to see how we can encourage their survival.

“To do this we need to understand where they travel in the first years of life and identify what habitats they need, so we used GPS tracking to see where the birds go and what they do.”

Weighing around 65g, the devices are fitted “like little backpacks”. Powered by solar energy, they will continue to transmit birds’ movements for up to five years.

Head for heights

Fitting the trackers requires perfect timing, a head for heights and a strong grip.

“We put them on the young birds in the nest, just before they fledge, as this is when the adult birds are less sensitive to disturbance,” he said.

Wedgies like to build their nests in the biggest trees available, with some up to 80 metres high (that’s slightly taller than the Wrest Point Hotel Casino).

One person scales the tree to the nest, places the eagle chick in a secure bag and lowers it down to the ground.

“I’m usually at the bottom where I put the GPS tracker on the chick,” James said.

“When I say ‘chick’ people think of a cute fluffy bird, but, physically, they are almost a fully-grown eagle.”

After a quick snack, usually store-bought wallaby mince, the chick is sent back up to the nest.

Updated every six seconds

The moment the wedgie takes flight, the GPS starts sending information back to James and the team.

“We get sent 3D dots via text message that tell us where and how high the birds have been over time. It’s a similar concept to tracking movement with Google maps.”

“During my PhD, we were receiving fixes from the tracking devices every 15 minutes, but since then it has been updated to once every six seconds, which is amazing because you can see exactly what the bird is doing.”

Dr Pay fits a solar-powered backpack to a young eagle. Credit Simon Cherriman.

When the birds’ colour-coded dots are joined and overlaid on a map of Tasmania, they look like “science spaghetti”.

But this isn’t a case of simply throwing spaghetti at the wall. The studies are gaining valuable information about which habitats are important to the birds during different behaviours, their survival rates at different points in their life and their biology.

“After they leave their nest, young wedge-tailed eagles stay in their parents’ territory where they are looked after and learn how to be an eagle. However, we didn’t know how long the young birds ‘stay at home’ like this with mum and dad.

“Much like humans, we discovered that the young birds are staying with their parents far longer than expected.”

For instance, one wedgie, named Willow, stayed in the nest for 20 months, five times longer than expected. 

Around Tasmania in eight hours

The high-tech tracking is also allowing them to study another behaviour known as dispersal, where the immature birds travel long distances across Tasmania after leaving their parents.

“Eagles can fly without expending much energy by using thermal soaring, using rising pockets of warm air to gain height effortlessly.”

Data from one of their birds, Malu, shows him shooting up to 600m above ground in eight minutes, gaining height at up to 2.1 metres per second.

Wyatt the wedgie flew almost 250km around Tasmania in eight hours using the same energy-efficient form of travel.

Some of their nest cameras shed light on the birds’ dining habits.

“Eagles vomit up all the indigestible parts of their food in a pellet. We find all sorts of things in them, like echidna quills!”

Measures to protect

While James and the team are still digesting all the information from their high-tech research, they have already gained valuable insights into the habitats that are important to eagles at different life stages.

Like humans, when the birds are young, they stay close to their parents. Gradually they spread their wings, leaving their parents' territory to fly longer distances.   

By understanding where wedgies wander and when, it’s hoped that we can put measures in place to protect the places that are important to them and ensure that these endangered avian giants don’t go the way of their prehistoric ancestors.