Hi All,
I think I have found answer on my question, here is it (http://www.avianweb.com/PBFD.html):
Feather Plucker or PBFD? Young chicks are not likely to pluck; so this would not apply to chicks. However, if an adult bird develops bald spots, you might consider either possibility. You can distinguish between PBFD and normal feather plucking by looking at where the feathers are being lost. If they are missing from the head and crest - an area they cannot get to with their beak to pluck - then it is likely to be Psittacine Beak and Feather Disease.
A Bird Suffering from PBFD ...
is likely to show the characteristic abnormal feather and beak growth
might have feathers that look like stubbles and are obviously deformed
is likely to have short ‘clubbed’ feathers
may develop curly feathers
may have feather shafts that often break, or you might see narrowing or pinching of the shafts (this condition worsens with each molt and your bird will usually become progressively balder due to inactivity of its feather follicles).
may have a beak that is deformed, especially the upper beak, and often overgrown; the beak usually splits or breaks