In September 2016 two wedge-tailed eagles that had been found injured and subsequently nursed back to health at HigherGround Raptors were ready to be released to the wild to fend for themselves. But would they survive after their time in captivity? Would they be fit enough to find their own food? Where would they go? Can the immense effort and resource that goes into rehabilitating raptors (or for that matter, any wild animal) be justified? These are the questions that every carer asks when they are about to release their rehabilitated charges.
To try to answer these questions, Australian Raptor Care and Conservation Inc set up a research program using satellite trackers to follow the movements of rehabilitated raptors (birds of prey) after their release to the wild. With generous grants from Wreceived funding from Wingecarribee Shire Council, Wildlife Rescue South Coast and National Geographic two tags to be attached to the birds and to communicate with specific passing satellites were purchased and the necessary permits obtained.
The two eagles were to be the first subjects of the program. The first eagle (WTE 009) was a recently-fledged juvenile, probably a female, who had been found lonely and isolated on a knoll in southern NSW. She was not injured, but was in very poor condition with damaged feathers and was severely emaciated. With specialised care, and after two moults, she recovered, put on weight, regained her energy and made best use of HigherGround Raptors’ circular flight aviary to attain a high level of fitness.
The second eagle (WTE 016) was an older male who had been found trapped by the leg in a legal dog trap in northern NSW. X-ray examination by a veterinarian showed that the bird had a long-standing fracture of one leg that was, however, healing satisfactorily and did not need any specialised surgery. Like the first eagle, 016 was placed under specialised care and over several months regained weight and condition. He was considered ready for release at the same time as 009. As he had been in care for a few months and would have lost his territory during that time, and considering the unsafe environment due to the continuing wild dog trapping in the area, it was decided to release him in the same location as the young female eagle.
Both birds were taken to the Southern Highlands Veterinary Centre where the trackers were attached. The birds were anaesthetised and the trackers were attached to the top of the two central tail feathers, using suture material and strong glue. The trackers weighed well below the 5% of the birds’ body weight that is considered the maximum for such attachments. The two birds were taken back to the aviary where they were placed in soft release cages to fully recover and where they could constantly be observed by CCTV for any discomfort caused by the trackers. Once they had recovered, both birds seemed to tolerate the trackers attached to their tails very well and paid them no attention. Everything went well, so they were released into the wild the next day by simply opening the cage door.
The tracker on 009 began transmitting immediately and continued to do so for 70 days. During that time, the eagle stayed in the general vicinity of her point of release, moving within a radius of approximately 25 km. Almost every day recorded a movement so we knew that she survived and apparently thrived up to the time her transmissions stopped. (The battery life of the transmitters is limited, although in this case, we would have hoped for longer transmission).
Unlike his companion, 016 gave us initial cause for concern! Following an early contact, the satellite failed to pick up any transmissions for the next two days and we feared the worst. A desperate search over difficult terrain failed to find him. But then, three days later, there was a transmission! (We think that he had holed up in some dense trees whilst he got himself together and that the dense foliage had prevented contact with the satellite). After that, he kept transmitting for 68 days. During this time, he apparently established two preferred areas for roosting (the trackers were set to transmit at roosting time): one near the coast on the Shoalhaven River and the other in the hilly area of Canyonleigh. His last transmission was from Canyonleigh. But the story didn’t end there. Just before Christmas one of the researchers, whose phone number was on the tracker, received a call from a farmer who had found the tracker attached to a fallen feather beside a dead kangaroo on his farm North of Crookwell. Our bird was heading West!
This was ARCC’s first experience with tracking rehabilitated raptors but we learnt several things. Firstly, that wedge-tailed eagles, at least, have a good chance of survival post-release. Secondly, that the level of fitness they attained in the circular flight aviary was sufficient to ensure their survival. We also learned not to panic if a tracked bird goes off the air for a period after release: some of them seem to need time to gather their thoughts before launching into the rest of their lives. All this is good news for the carers who dedicate their energy and resources to rescuing these kings of the sky.
Where to now? ARCC is currently licensed to track another eight raptors and subject to availability of funds (the trackers cost over $2500 and are not likely to be recovered) we plan to track more wedge-tailed eagles and, using lighter trackers, some other raptor species as well. Watch this space! If you’d like to help us out with funds, please click the ARCC PayPal contribution button – every contribution is gratefully received!