There are never enough scientific studies on parrots in my mind anyway. There is so much still unknown about them . In the last 15-20 years(?) There has been progress, increased interest and studies..
This is one on feather destruction behavior
This is one on feather destruction behavior
An association between feather damaging behavior and corticosterone metabolite excretion in captive African grey parrots (Psittacus erithacus)
African grey parrots (Psittacus erithacus) are kept as pets and are frequently hand-reared. It has been observed that hand-reared African grey parrots may develop behavioral disorders such as feather damaging behavior (FDB). It is well known that chronic ...
www.ncbi.nlm.nih.gov