Excellent responses from all ... very much appreciated.
Even though he is sometimes reluctant to come off of my shoulder from time to time (and likes to land there uninvited every so often!) I still feel comfortable both physically and with the 'relationship'.
While I do respect the academic/behavioral authors, the real-life perspectives from the thread (kudos to Buffy for 'outing' her self ) are exactly why I joined the forum.
I like to think I am pretty good at taking in a lot of info and sifting it for value and perspective - the responses have been invaluable in that.
In short I plan (yes it's another plan!) is to allow Mort shoulder privileges but monitor his attitude and behavior ... he is a very cuddle bird and likes to plan his head into my neck (particularly good for head rubbing if I haven't shaved apparently) and I wouldn't want to lose that link. I think I will work on getting him to step down from my shoulder even if it is just for a couple of minutes so that he (hopefully) gets that his human perch is not a right!
Again thanks for the views and have a good Xmas - hope you and the birds get nice things from Santa