everytime i look my birds, it seems that they bite themselves all the time (not all the time but at times). even though they bite the tail too! is it normal for my birds too do that all then time or is there something wrong with them? but funny thing is that after while is thay they puff themselves up and shake xD.

dont worry: D their probably just preening themselves (gromming and maintaining their feathers)

Its normal thats how birds groom themselves

experince

They are probably preening themselves (taking care of their feathers).