My male Alexandrine parrot's nape band is not coming out clearly

by Sayan Banerjee
(Kolkata,West Bengal,India)

My male alexandrine parrot is approximately 20 months old.He has a clear and prominent black ring around his neck,but he has only 3 or 4 pink feathers on his nape band region.He grew that pink feathers along with the neck ring black feathers 7-8 months I want to know when will his nape feathers completely arrive??????