When Melanie is lying unconscious after the birds attack her, Mitch gives her some brandy to 'alleviate' the pain. However, in no way should he be giving her this because any liquids given to an unconscious person could cause them to choke, and they should especially not be given any alcohol.
At the end of the movie when Mitch gets in Melanie's car to take it out from the garage, he closes the window of the car. After a minute when he gets of the car in front of the garage the window is open.
While in the car when the crows attack the school, Melanie's left hand is by her head when she beeps the horn. In the next shot, her hand is on the steering wheel while beeping the horn, the next shot her hand is by her head again.
When the gull attacks Melanie, at the 24th minute, we see Mitch jumping from the pontoon twice: once from Melanie's point of view, then a second time from the pontoon. And Mitch's attitude is clearly not the same in the two shots.
When Melanie arrives for dinner with Mitch and his family, the driver's seat of her car is clearly set further back than the rest of the front seats. When she leaves, she gets into the car and we see the driver's seat is now perfectly aligned with the rest of the seats.
Annie and Melanie open the door to Annie's house when a seagull hits it. As the door opens houses are clearly visible across the road, after they look up again from the dead bird the view is now the bay with no houses at all.
When Melanie Daniels is sneaking up Mitch's dock to deliver the lovebirds, she looks over at the barn he's in, the sky has a complete gray cloud cover. Seconds later, she looks at the barn, not a cloud in the blue sky.
While chatting, Annie leans against Melanie's car after they have just met. Melanie thanks Annie and speeds off. In the next shot and while Melanie has clearly left, Annie seems to just having left her prop and stands on her feet again. Also the car sound can be heard in a distance.
At Cathy's birthday party, when Mitchell and Danielle climb the small hillock to chat, Mitchell is holding a bottle of colored liquid, probably whiskey. After the camera angle changes, when they approach the top, same bottle now has some clear liquid.
When Melanie is approaching Mitch's house in the boat, and even while she's walking down his dock after leaving the love birds, his car is parked pointing directly out of the garage. But after she paddles away and he walks from the barn to the house, and for the remainder of the scene, the car is parked at an angle to the garage.
Melanie is able to deliver the lovebirds by piloting a boat to the Brenner's dock. At Cathy's party the next day, we see from the top of the hill that the dock is not accessible by water (water level too low).
When Melanie is calling her father from the restaurant, her left hand is holding the phone wire. In the next shot, her hand is still holding the phone wire but she has a much looser grip on it and her hand is closer to the phone.
When Melanie goes upstairs with the flashlight, there's a close shot of the brass doorknob as she arrives there. Two reflections of light sources are visible on the knob, when there should be only one from the flashlight.
During the scene where the red haired girl falls, she breaks her glasses, however her face was too close to the ground for the glasses to shatter so badly. The cracks on both lenses are also thick white star burst patterns showing they had been already smashed by something like a hammer, and even if the glasses had genuinely smashed from landing on the ground, the damage would not be identical to both lenses seeing as how they landed at an angle, only one lens would have sustained the most damage and left one side still in tact. The glasses were broken before they were even dropped.