Happened last night, actually. I have two parakeets and at night, I keep their cage covered to keep them warm and block the light out so they can sleep better. They're usually quiet and sleep peacefully through the night. Except for last night. It was around midnight and all of the sudden they started freaking out and flying around the cage, obviously spooked by something. I quickly uncovered the cage so they could see, and they eventually calmed down and settled on their perch again. It reminded me of all those ghost movies I've seen where animals can see/sense demons and shit that humans can't. I'm sure there's a logical explanation for this, like maybe one of them moved in their sleep and startled the other one, but I don't know. It was definitely unsettling because they never usually do this.