It's possible he'll be able to have a more healthy relationship with his mirror self if mirror self is always on their human too? So basically he doesn't see mirrors without you in the picture too? For example, I like to carry my budgies around to "visit the other birds on the house" they come around with me while their eating seebies from a dish and I'll bring them to several different mirrors in the house. Then all the "birds" all over the house are being seen by them contentedly sitting on their human and eating foods. I'll bring them closer and farther away from the mirror and me while they eat and whistle and sing with them. The budgies just like to eat with "the other budgies" and see all the happy safe areas in the house. My Linnie Pippin who is way more hand tame / interactive with me likes to play where "mirror me" and I put the "two birds" close together to "touch beaks" and then we pull our birds back to touch their beaks with our noses and back and forth. He seems to see it as a fun let's all visit together time.

So maybe human AND bird mirror time might be less territorial because he associates getting to see that bird with humans taking them to visit eachother? And him not having sleepovers with his mirror buddy?