I guess since Ziggy came first, he seems to have taken Ozzie under his wing....so to speak! LOL! They seem to be good cage mates yet once in awhile Ziggy will bite (not hard) at Ozzie's nose! I have no idea what that's all about but I keep a close eye on those two. We have yet to hear much more than a peep out of Ozzie yet and that's once maybe every other day.
As long as Ziggy isn't injuring Ozzie or drawing blood I'd say it's normal harmless bickering behaviour. Even my bonded pair do this to each other sometimes (such as when Honey wants Henry to preen him but he doesn't do it to her liking and they lock beaks for a second, only gently though). Since Ozzie is a baby and is new to your household it's expected for him to be quiet, just wait for his personality to come out once he gets more comfortable and settled and he'll be chattering away, I'm sure!