flapping wings in the house?

The other day, I thought there was something flapping in the house. I was not sure about this but thought I heard some wings flapping and some scurrying. i must say I got panicky. I could not see anything. But, I kept thinking something was there. About to dive on me or bite Tulia. there was nothing as it turns out. But, that night, I heard a rustling, threw pillows over my head but it was just a doggy pick up bag that was blowing about. I felt so stupid. Tulia slept calmly through it all. If a bird or a bat or any other creature had been here, I am sure she would have been more animated!