A preliminary trial satellite tracking has been completed. Small tracking units were fitted to the tail feathers of two wedge-tailed eagles. The first was a young female recovered from the Southern Highlands and the other bird a mature male from the Casino region. The units are approx 20grams in mass and are attached to the base of the tail feathers.
Initially, these trackers were meant for two masked owls. However, although the tracking units only weigh 20grams (which is far less than the 5% of body mass recommended by the ethics approval process) they were deemed unsuitable to be fitted to the base of the tail feathers. For owls, there are two conclusions, this size tracker requires a harness fitted between the wings or the requirement to use far lighter tracking units. Fortunately, there were two wedge-tailed eagles ready for release – perfect candidates to trial these trackers.
Trackers only communicate with satellites at predetermined times and in this case they were already set for nocturnal activity, i.e., owls, so not ideal for the eagles. Time did not permit the units to be returned the suppliers in New Zealand for reprogramming. Also, the trackers need a clear line of sight to satellites to achieve a proper signal (and hence accurate location). Often birds nest in heavy cover of trees so a signal is not always possible.
There were a few anxious days when the only data location for the older male was stationary on the edge of an escarpment. Had the bird after so much care and extensive rehabilitation simply flew off to perish?
Later, when new location points were downloaded from the satellite data (and after a ground search) it became clear that the bird was simply roosting high on the cliff face tucked away from the path of the satellite.
The younger female, in general, seemed not venture too far from her release point. There was partial expectation that the older male might orientate himself, then head for the Casino region but this proved not to be the case. His behaviour was fascinating in that he would stay for roughly a week on the Wollondilly (possibly hunting rabbits) then in one day fly to the Nowra area to spend a week on the Shoalhaven River, before heading west again.
Early results are very preliminary and subject to much further research and analysis of the data. Battery life of the units is an issue and being investigated with the suppliers. However, they confirm that birds do survive in the wild after lengthy rehabilitation which certainly is great news.
Data and information about released bird behaviour are crucial to understanding more about this iconic Australian raptor, so please donate to the satellite tracking project via our supporters page.