I was really surprised by this too. At Taronga they're considered dangerous animals i.e. potential to cause fatalities. I asked the keeper when he came out of the exhibit if the bird had been hand-reared, and he replied it had not. He went on to say that individual cassos have different personalities, and some of them are quite docile. He went on to say that hand-reared birds tended to be more aggressive when adults while parent-reared were often more placid, but hastened to point out that either way they are reared you will still got docile ones, and you still get psychotic nightmarish ones.
Although I haven't worked with cassos, having been in the industry and associated with keepers and zoos all over the world for more than 40 years, I know many things we assume or have heard are not always correct, and that keepers have a much better idea about their charges than people who don't work with those animals.
