I have to say most of Bill Brysons books are like that, I loved his notes from a small country, very funny. As for the Casawary, it is I believe one of only a few birds believed to be a danger to a full grown man! Oz is a bit like that though, it has some stunning animals but an awfull lot of them will hurt you in one way or another, they even have an Octopus that is very small but if it bites you it will cause you to go into a paralytic shock, your lungs and hart will stop and then you die. They have some of the worlds most deadly snakes, spiders and even the Dingo has been known to kill, add on to that all the things in the water that will kill you like Sharks, Crocs, Octopus, stingray, shellfish and Jellyfish and you'd sometimes think it is a risk just to go outside!
It is however a lovely place and the waters sometime team with fish, the sun mostly shines and the locals are friendly so it is a great place to visit.
All the best.
Mike