A strange bird-like humanoid race found in the alien forests. They seem docile enough to let human researchers observe them up close.
They are intelligent and have their own cultures and all, they just speak a different language.

It’s unknown why they go through this process. Researchers speculate that they do it for mating purposes but then some Gavians become all male groups. The transformation is also permanent.

It seems this ability really was for mating purposes since the old times but now that they became an intelligent species, it’s something they do voluntarily and is part of their culture.

Fun fact : while clownfish are known for changing from male to female, did you know that multiple kinds of fish can also do the other way around?
The Asian sheepshead wrasse or the Kobudai change from female to permanently male. They become very handsome (drastic transformation) and fights the older male for dominance! How cool is that?