AWOL:
I am a little puzzled that it isn't reading -1 (empty buffer), but I don't have a Mega, so can't try it.
I do, and it does read -1 when empty. I don't know why he was not getting the "funny y".
edit: I do if the OP did not have the tx/rx lines connected the other way. That would leave the Serial1 rx line floating.