do u mean the crest on his head??? as far as i know its a sign he's on high alert...unsure of whats happening around him....i may be wrong so wait to see if anyone else agrees before u worry....is his neck stretch too?? little mikey does that when he hears a loud noise or sees something move fast he is unsure of.....it could be the budgies are scaring him by their fast movements and noise....im not sure how long you should leave him to see if he calms down...again wait and see what someone else with more experience says....if he doesn't settle and get used to it can you put the budgies in a different room?