That’s fine… but then it’s not a matter of being a mesorah on the bird, it’s a matter of the bird having a certain set of properties (just as with a mammal or fish) and any new bird we find with that same set of properties would also be kosher, even if there was no mesorah for it.
Well, actually, the current minhag of ashkenazim according to the rema is to require a mesorah on birds. So no, even if we found another bird with the precise same set of properties (simanim, which are listed in the shulchan aruch), we could not eat it.