Sometimes my gals are like that and I just don’t see what they are seeing!From the tilt of her head I'd say she saw something that made her wary. The Buckeyes are afraid of snakes and have done this twice for one (a big one and a small one) and even for frogs but it's been really hard to find / see what they're calling about. When they were young they did it for anything that moved that they'd never seen before.