Not only does it stop using its tail to attack, but it also drops the tail's axe the first time you chop it(or maybe it's random and I was lucky like that?).
Pretty simple fight if you keep your shield up and strafe around behind them. Oh, and if you finish the first one off as quickly as possible before its fire-breathing cousin joins in.
I didn't didn't know you could chop of the first bell gargoyle's tail. It looks like he stops flying after that. Nice