Sucking your finger.

[Ozii]

Whenever Peaches goes onto here back, you rub her belling, and she grabs your other hand, and sucks on the finger, why is that, as that is what she is doing often, even when she is not on her back. Is there a reason? could she have been taken from her mother to early?

[Zanizaila]

Perhaps. But birds don't "suck" as mammals do, since they don't have lips and no mammaries.
So a bird having been taken to early and showing baby-behaviors would rather do things like begging from a spoon, wanting warm and moist food and eating like a chick (bobbing head up and down when swallowing).

[liz]

Birds have better sencers in their tongues. He is tasting you, smelling and feeling the texture of your skin as well as heat from your body. He is being personal.