Continuity mistake: The cut Melanie gets, after being attacked by the first gull, goes away completely after being treated. There should still be some kind of mark. (00:30:50)
Other mistake: It seems well established that the film takes place over a weekend. However, Melanie drives up on Friday, stays at Annie's apartment that night, goes to Cathy's party the next day, Saturday and stays at Mitch's that night. Nowhere in the movie is it implied that she stays another night and in fact she doesn't. Everything else in the movie after the attack at Mr. Faucet's farm takes place on Sunday and there would be no school in session when the children are attacked.
Continuity mistake: After Mitch puts the logs in the fireplace he runs without jumping over anything to the window behind the desk. Later when we see that spot just before the lights blow out the logs extend all the way to the brown chair without any space in between for him to run through. (01:41:20)
Continuity mistake: The gas station attendant drops the gas hose as the bird hits him and the first spray of gas wets the gravel to the right of it. The next time the hose is seen it's moved closer to the cement below the pump, it's shooting at a different angle and the gravel to the right is dry. (01:24:35)
Continuity mistake: As Melanie and Mitch walk past the side of the restaurant look closely at the windows at the top left of the screen. They have transparent green shades on the rear windows that are pulled down about one-third of the way from the top. In the next shot, when we see the back of the restaurant, no shades are pulled down. (00:26:25)
Continuity mistake: In the wide shot of the party scene as everyone is running into the house a girl in a bright red sweater and white skirt pulls her mother in the blue dress by the hand. In the next shot they've changed positions and are together with the mother's arm around the girl's back. (00:53:00)
Continuity mistake: As Melanie walks around with her flashlight she goes into the kitchen and looks at the lovebirds. This cage has 11 rungs on the side and is not the same one that she walked into the house with when she brought the lovebirds up from San Francisco, which had 19 rungs. (01:46:15)
Continuity mistake: In the shot of Mitch holding the log just before he runs to the window behind the desk, the brown reclining chair that sits by the fireplace has been moved for the camera. We see it there in the scene when Lydia says, "Did you get the windows in the attic Mitch?" and earlier in the movie when Melanie brings the lovebirds in. (01:41:20)