My zebra finch finally stopped biting completely!!!
I literally cried. After about 10 days of patient work, Ruby finally took a bath without freaking out today. I know it sounds small but if you've been through the bonding process with a nervous bird you know how HUGE this is. Never give up, it's so worth it.
My parrotlet did this too! Turned out it was because of hormonal season — spring is brutal. Once I addressed that, everything went back to normal.
I've had birds for 15 years and I've seen this many times. In my experience it usually comes down to a subtle environmental change you might not even notice.
So what I ended up doing was leaving the radio or TV on when I'm out — background noise helps. Within a few days there was a noticeable improvement. Definitely worth trying.
Anyone near Hamilton should check out the bird section at Pet Valu — surprisingly good for the area.