How big can a little bird get?

Yesterday I stopped by to groom two little greencheek conures.  Baily and Dude seem to know when I'm coming. They act totally out of character and become quite agitated and uncooperative.  They have their own room completely outfitted for their enjoyment.  Their mom had the task of cajoling them one at a time to come down from their cage top and get toweled.  (Not their favorite scenario!)  You should have seen how puffed up and fluffle headed they became!  They acted like little lions trying to be big and bad.  Of course, it all ended well and I was able to trim their little "fishhook" nails. They then headed straight to their window where they watch me through the screen as I left.  Even there they puffed up and acted macho.  Two tough little characters!