Hole in the tongue

[Cregg]

My citron crested cockatoo has a hole in center of her tongue. I'm told it's normal, but am curious about the origins/purpose of it.
Any comments are appreciated.

 

[Pedro]

Cregg, thought this link would explain it all.

Avian Anatomy

 

[Cregg]

Thanks Pedro. But as thorough as that site is, it doesn't address the hole in the tongue. Makes me wonder if it's abnormal.