Hi simtom and a warm welcome to you from all the Staff and Moderators. I took the guide Birds of Australia (a Photographic Guide) by Iain Campbell, Sam Woods and Nick Leseberg, which served me quite well, though a bit bulky. There are a couple of phone apps.
I think there may be guides for different parts of Australia if you're not travelling the whole country. It may help if you ask in the
Information Wanted forum and let them know which states you will be visiting as I think there are guides for the individual states as well.
I'm sure you will enjoy it here and I look forward to hearing your news.