So, hoping someone can impart a little insight into what is required in order to summon your chocobo to fight by your side.

I have 50 Gysahl Greens in my inventory, and I can ride around on my chocobo just fine. However, when I try to use a Gysahl Green, I get a red message on my screen that says "Action not yet learned".

Is there a particular/special quest I need to finish? Is there a particular/special item I need? Do I need to be a particular rank with my Grand Company? I can't seem to find any information on this on these boards, or via a Google search. And all the npc's involved with getting the chocobo in the first place, have nothing to add/say about any prerequisite for summoning it, other then using the whistle in to unlock the chocobo in the mount area of the Actions & Traits screen.

Any help would be greatly appreciated.