Unexpected Behaviour--Wedge-tailed Eagle

Bird behaviour can sometimes surprise you when you least expect it. I had been birding on Goat Bluff, on the South Arm peninsula, on the eastern shore of the Derwent River, and decided to make the short journey to the South Arm neck, really hoping to get to grips with one of the Swamp Harriers which hunt over the marsh there, from time to time. The first thing I noted as I drove along the neck, was the flock of Oystercatchers, mostly Pied with a couple of Sooty, roosting within a metre of the road. Although the tide was in, this isn't the favoured roost site, and I surmised that they had been disturbed, but by what or whom? I drove on. I casually looked toward the stunted trees, growing on the windswept dunes to the South, half expecting to see a Harrier, the treetops being a vantage point they often use to survey the marsh. I did a double take! Instead of the expected Harrier, there was the unmistakable shape of a Wedge-tailed Eagle. Quickly doing a U turn, I pulled to the side of the road to watch and take a photograph, albeit from inside the car, as I felt sure it would fly off if I got out. Having secured a shot, (I've added the image to show it really was a free flying bird!), I got a little bolder and moved the car closer. It lifted off and using the updraft from the dunes, hunted over the area. I watched, just enjoying the moment, as the eagle went about it's business, but a little disappointed in not getting a better shot.
But all was not lost! It returned to the vantage point it had only recently left. Well, over the next 20 minutes or so, I got a little bolder in my approach. Eventually getting ouit of the car and walking up to the tree it was in--and it stayed there! The shots shown here were taken from the sort of distance an eagle or indeed any other bird, would almost certainly normally cause them to take flight. I walked back to my car with the eagle still atop the tree, mulling over why it had behaved so apparently indifferent to my presence. Perhaps it was driven by hunger, or is it a recently rehabilitated bird? I have seen, what I suspect is this bird, hunting over nearby woodland and on to Betsy Island, usually harried by local Forest Ravens. I doubt that I'll ever know the cause, but it's events like this, that make birding so pleasurable.