I would like to add one thing: if your male cockatiel decides that the place to display his "male cockatiel behaviors" ison top of somebirdie else's cage, and especially if that somebirdie else happens to be male also, grab him, put him back into his own cage, and go out, quick, and get some plexiglass. Because while those behaviors are sort of cute and funny to us, somebirdie else will be annoyed enough to bite off the cockatiel's little toes for that sort of "indecent proposition"!
Just a bit of unpleasant experience. . .