Hi Kennedy. I'm aware from the bird watching forum here on Dave's that House Sparrows are really problematic to other bird species in North America, especially Bluebirds. To your knowledge, are any of our native Australian birds a target?
Margaret, I am not aware of any problems for other bird species caused by House Sparrows in Australia.
On the whole they have become birds of towns and of farmland, but they practically never venture into the natural bush.
European starlings are similar in this regard, except that they do compete for nesting sites with several Australian parrots.
It is the Common Blackbird that is the bigger problem as they do like the bush as well as farms and gardens and as well as competing with native birds, are major spreaders of seed from berry bearing plants and contribute greatly to the spread of weeds.