>If you are in Sydney, there are no rabbits running around suburbs and the rats do well to stay out of sight. Are you suggesting that the local cats will search out rabbits and rats instead of try and hunt the local birds (which I have seen cats do)?

The rats are there. Humans can't without them. Cats, like all other predators go for the easy target first and do overwhelmingly hunt rats/mice ("small vertebrates" :), insects. And if a cat would catch an ill or stupid bird - it is a favor for the bird's species that some predator is required to perform, and due to the human presence the natural predators are unavailable. For example, about who is damaging the bird population - here in the Bay Area in the few small spots without development i regularly see Asian people gathering wild birds eggs. They just clean it up, taking it all. The local newspapers, of course, are from time to time actively discussing how cats are damaging the birds population. To try to "help" the birds, at one park here they even eliminated the ferals - and were surprised that [the morons should have read history of the other such cases before doing it], the immediately grown population of rats destroyed the rest of the eggs that humans hadn't, and the bird population was completely decimated.

For thousands of years free roaming cats protected humans from rats and everybody around humans from humans' rats. That is the evolutionary machinery that brought a cat to live with humans - the easy availability of a fat rat. And by the way, nutritional value wise the rats/mice are much better than birds. Have you seen "Living with Wolves" btw?

>All the introduced species need to be controlled

yep. The most damaging introduced species - humans - needs to be controlled for other species to have a chance for survival. Until that happens, the poor cats and wolves and the others will be scapegoated for human stupidity, greed, hypocrisy...

The article you linked forgot to mention that in natural steady conditions, without human intervention, the presence of foxes and cats never eliminates the "small mammals" population - instead due to natural predator/prey relationship (which exhibit well known cyclic patterns through the years - which includes described in the article cycle step of increasing prey population with decreasing predator population (which in turn leads to increased predator population, which in turn leads to decreased prey population which in turn leads to decreased predator and so on... ) the "small mammals" population is kept healthy and naturally evolves ... well, until human intervene