Bullockornis was obviously a large flightless bird. In the days in which these giant birds ruled the land there were still not very large mammals and the non-avian dinosaurs were long gone. Therefore these largest of flightless birds were the largest animals that were running about terrestrially. The groups of Bullockornis that were living in the Australian Outback were nearly twice the size of the average emu and were capable of chasing down and eating anything that they wanted to eat. This could have included enormous fruit, if there was any; the bill of Bullockornis would have been quite capable of breaking open even the toughest modern coconuts. In the realm of possible carnivorous diet items nothing would be too tough. Bones could be crushed by a bill of that size and strength; the shearing ability would have been fantastic as well. As of now we know almost nothing about the body of the birds, however the best proxy was living at the same time on different continents, so educated guesses can be made with what we assume is great accuracy.