[Well, seeing as Aether does meow at cats... he's gotta moo at the cow.]

[And when he gets a moo in response, he brings a hand to his chin and nods, as if understanding the intricacies of geo cow language.]

Hmm... maybe he just doesn't have much to say? I have a friend in Mondstadt who can summon a talking raven named Oz with her vision, so I thought he might be something similar.