Most dont reccomend a "shoulder bird" even though we all want to let our inner pirate captain come out. My female indian ringneck did the same thing when she was younger, I "grounded" her from the shoulder till i could completely trust her again. I know, different species, but same issues. My cockatiels on the other hand, if I know they have a tendency to bite for any reason, weather it be aggression, or overzealous preening, they dont get on my shoulder, two of my four are trustworthy enough to hang on my shoulder. Personally, I think if blood is being drawn its possibly more of an agression issue than a overzealous issue, and I'd keep the bird(s) that bite off my shoulders till they chill out.
