Difference Between Cockatoo And Parrot How Can I See The Difference Between A Male/female Young Corella?

How can I see the difference between a male/female young Corella? - difference between cockatoo and parrot

I googled etc, but without success so far. A short-billed Corella girl fell from the nest while taking flying lessons. They are members and it gives a verbal response from them.
In other parrots, cockatoos and one of the Galahs difference in eye color: brown black = male = female.
This boy has a gray-blue ring (IRIS) and I think about 6 weeks and repeaters heavenly parents for food. I accepted this task, and who "loves food (specialty) I give him baby parrots. Every day is a special bird tray, stand, and conversations with parents. Several times a day, I call "flying hours, and I notice that grows much stronger in the starting blocks. Hopefully soon follow their parents on the run.
I like it but know how to find what he was a boy or a girl?