Searchresult 'Sulphur-crested Cockatoo'
Fred Van Gessel, Birds Australia/ Australian Museu: Birds in Backyards is a research, education and conservation program
Oswaldo Cortes: xeno-canto, the community database of shared bird sounds from the whole world.
The birdsongs are available online in different formats. In order to listen to them, you will need the appropriate software and browser plug-ins. I recommend Winamp Media Player and the VLC Media Player, both of which can be downloaded for free.