When I checked in on the most recent tracking data yesterday and found Wallu's transmitter showed no movement for 3 days, I was worried. This has in the past meant the transmitter's owner has died, and I dreaded to think of Wallu, our longest-tracked eagle, having lost his life. Given we have just moved into the 'new eagle year', and territorial behaviour will be heightening as the breeding season approaches, it would not be surprising to find a resident adult male killed by a usurper. It was at this time of year, 3 years ago, that our adult female Gidgee was ousted from her home range and later died.
Fortunately, however, this story does not have such an ending! I rang the Matuwa homestead and was delighted to talk to the current caretakers, John and Gail Grenville, who kindly offered to assist by investigating further. I later received an incomplete voice-to-text message on my phone, which said:
"Hi Simon,
We found the tracker lying on the ground but no..."
This was enough info for me to realise what had happened, and that Wallu was not dead, and I rang Matuwa back instantly for more news. When John and Gail reached the GPS coordinates shown on my tracking map, they found his PTT on its side with one part of the harness frayed, causing it to dismount. This is a very interesting discovery, as this initial harness design was a 'permanent' mount, unlike the method used now which is made with a weak link, and I expected it may have lasted much longer. It appears the heat and harsh conditions in the arid zone (along with some encouragement from big, hooked beak!), caused the harness to weaken and eventually break on one of the main straps. So after 3 years and 10 months, the end of an era has arrived, and Wallu is wild and free again! We will check on him later this year during our eagle research trip during the breeding season (Wallu is still identifiable from his leg band), and possibly even catch him to give him a health assessment. Thanks so much to John and Gail for their wonderful help! More updates soon!
nice post
ReplyDeleteGreat work and I hope it results in some concrete actions that will improve the survival rates for these magnificent and ecologically important birds.
ReplyDeleteWhat research have you done into the possible side-effects on the eagles physiology of the implanted tracking devices and the actual satellite signals? I would expect the birds own electrical/magnetic system would be impacted leading to central nervous and endocrine disruption at least.
It's a delicate balance in scientific research isn't it - the good that may come from future findings and the possible negative impacts on the species we are trying to help.
All the best,
Susan
Hi Susan,
DeleteThe tracking devices are not implanted but attached to the bird using a backpack harness. There is no evidence that tagged birds' central nervous systems are impacted by these transmitters, which have been used on thousands of raptors around the globe for over 2 decades.
Thanks for your comment.
Regards,
Simon