Well, the question was because, some of them (not all) have both an ocular ring (a circle around the eye which has no feathers) and something like a mask (darker grey feathers around a dark ocular ring and a darker cere).
This male has a light ocular ring but no mask: http://animal-world.com/encyclo/birds/p ... Parrot.php
This male has a dark ocular ring and the 'mask' I was talking about:
http://www.animalphotos.me/bird6/bird6-redb.htm





