Eagles tracked for the first time
For the first time, says AGS-funded ornithologist Simon Cherriman, our largest bird of prey has successfully been tracked
WHEN YOU HAVE a wedge-tailed eagle under your arm, it’s important to keep hold of its legs. With skin-tearing talons and feet equipped with several tonnes of crushing power, they are formidable weapons.
Having just fitted a satellite transmitter to one of these birds for the first time, I placed it on the ground, pinning its wings with one hand and gripping its legs firmly with the other. Then I released my grip and hopped back to watch it take off.
It had taken me several years to get to this point. Wedgies are powerful predators and adept flyers. Although they are one of the better-studied raptors in Australia, sophisticated GPS/satellite-tracking technology – which has been used globally to follow bird movements – had never been used to study them before.
Eagles are perfect subjects for long-term studies because they can carry large tracking devices (platform terminal transmitters or PTTs) attached with special harnesses.
However, to attach a PTT, I first needed to catch a wild wedgie. In 2012 I sought advice from retired eagle experts Michael Ridpath and Michael Brooker, who gave me insights into the trapping methods used during their research in the 1970s.
Wedgies need a stretch of flat ground to use as a runway to get airborne. So, in order to catch them, we lured them with carrion into chook-pen-like traps under their favourite perch trees. The idea was that, once inside, the lack of space would prevent them from getting airborne once more.
In June 2013 I headed to my remote study area in the Murchison region of WA, and built and baited two such traps. The stage was set.
The following day, my heart thumped as we approached the first trap. A flurry of wing-beats blurred the scene and an eagle promptly took off. Then I saw a second eagle inside the trap. Finally, this was the moment I had been waiting for. A boyhood dream had become reality.
The eagle was an adult male, which I named Wallu, after the local Martu word for eagle. It took 40 minutes for me to fit the PTT and measure Wallu, then I removed the falconry hood (used to calm him during handling) and released him.
As I stood back and watched, Wallu raced forward and launched into the air, soaring down the dirt track like a 747 taking off.
The next day, we captured an adult female. I fitted her with a GPS tracker and named her Gidjee. Four months later, I found myself clinging to the side of Gidjee’s nest, face to face with her healthy nine-week-old daughter, Kuyurnpa.
I fitted this young female with my third PTT, and then placed her back. A week later, she was ready to fledge, and take me, via a satellite connection, along for the ride. Since then Kuyurnpa has revealed that wedgies can fly at altitudes of 3000m.