I saw this exact thing a couple of months ago not so far from Arhnem. (I thought it might be a crane, but it was moving very fast... so I could be mistaken.)<p>This bird was diving at about 30-45 degrees from fairly high, and it suddenly inverted, stayed inverted for a second or so, and then righted itself. It was moving very fast, and you could actually hear the sound (and the changes of sound) of the air as it was moving through it.<p>There were no other airborne birds of that size that I could see anywhere near it, so I initially thought it was dying or otherwise out of control. But then it descended below view, and I never heard a thump.<p>I searched for inverted bird flight immediately after and learned that there are a number of observed cases where birds may do that. One theory is that they sometimes do it because they enjoy it. Other theories of course involve chasing prey, observing things, showing off, etc. But I like the idea that a bird might just be having fun. I mean, if I could fly, I think I would screw around all the time just because I could. After all, children will just run around wildly just because they can run.