Because some birds don't like the idea of some random cat making a meal out of them.

She shrieks in return, hardly the same kind that defeaned him earlier but she wants to send out a warning shot of her own. She's hardly a helpless little bird here, and takes advantage of the cat's stumble by gaining some ground and using her own talons to climb up a post that leads to the rafters.

But she doesn't think a little stumble will stop him. Shrieking at him again, Aqua positions herself properly and sends her own powerful gust of wind his way with her own wings. Follow her will you? She'll make sure you can't even reach her.