I reckon Cassowaries are pretty fierce. They are from Australia and so have to be.
I love those.
I was at the local zoo once and one of them, who had the three largest feathers of its wings clipped barely short of bleeding to prevent flight, not that they really fly or whatever, jumped/flew up and landed on the seven foot high fence on its breast and stole/nicked/grabbed my kid's bag of popcorn. He then proceeded to protect all his bounty from the others in the "environmental cage" who all ran over to get some.
My son thought it was amazing and felt that he had gotten something from the zoo that many do not get to experience.
That big-assed, beautiful bird would not allow the other birds in his environment to have any of the popcorn until a certain female wandered over rather slowly, huffed at all the other birds and flipped her tail toward her benefactor.
I do not think the "thief" ever ate any of his bounty; he did it all for her. He protected her food while she ate and ate, then, when she was done, she turned and huffed at him and went back to the shade of her tree.
Very interesting, almost mammalian, behavior from a fairly large, kind of scary bird. Did I mention those sumbitches can fucking jump? Their wings are not much bigger than my hands, but they still use them to guide their "jump/flights."
Once I was near an emu pen, against the fence taking pics of a family of three chicks interacting when a large adult emu grabbed my camera. I had a big long lens on it and the bird could not hold on to the lens with its beak, so it grabbed the camera by the camera strap, with my neck still in the strap and tried to take off. I was on the other side of the fence and there was no way I was going to let go of my six thousand dollar camera system.
Fortunately, as I as reaching over the fence and had the bird by the throat and yelling for some assistance, one of the caretakers emerged and started bitchin' like hell at me, then realized that I had the bird in one hand and my camera strap in the other and the bird was about to drag me over the fence, since my feet were about a foot off the ground.
She just started using one of those "clicker things" and the emu just let go of everything and turned to her.
Kind of an anti-climactic ending, but I was not done fighting for my camera, when the caretaker came over and "shut the bird down" with that training clicker thingy.