Some birds become completely phobic when you try to put it on - even if you go super super slow - my Senegal refuses it - I take him outside in a small portable cage instead. I've also tried a harness (Aviator) with a crimson belly conure - no go either. I tried acclimating the senegal when he was very very young (just weaned) - it didn't make any difference - he got so freaked out with the harness going over his head that I thought he would choke himself before I managed to get it off him - scary stuff (this senegal is not phobic about anything else).