Keep in mind that things we would not even notice can scare a bird half to death. A ceiling fan, a new red hat, a hawk flying outside of the window.
One time my African grey was fluttering around in his cage agitated. He just wouldn't settle down. He took me several minutes of scanning the area and moving things around before I figured out the phone cord had been moved. He must of thought it was a snake coming to get him. I put it back down behind some furniture hidden and he immediately calmed down.