Continuity mistake: After the birds break the window, Mitch tries to close the shutter and they peck at his left hand bloodying it up. In the next shot as he finally gets the shutter closed there's no blood on his hands. After this he ties the window shut with the cord from the lamp and the blood on his hands is back again.
Continuity mistake: Mitch runs up and opens Annie's door in order to get Cathy from the house. The door is not wide open when they walk away. When Mitch walks back and puts his coat over Annie's body even though no one went near it, the door has been opened as far as possible and is now flush with the wall behind it on the right.