Continuity mistake: After they talk about the apartment Melanie wants to use the phone. As she walks through the door Annie looks up at the birds flying and we see the top of her porch and a bare tree. This is wrong, as earlier in this scene when Melanie walks up to the door there are a lot of plants hanging down from the roof of the porch.
Continuity mistake: In the scene when Melanie is taking tea to Lydia, Lydia's hair changes between shots. When she is resting on her back you can see sections of hair are down by her neck. When she leans forward, her hair is all up on her head. This changes back when she's lying down again. Lydia's hair changes in consecutive shots, during other scenes as well.
Continuity mistake: When the birds attack the town, two horses gallop down the street, dropping crates of vegetables. In a later shot the crates are more broken and the vegetables are more spread out and are in a much different position than when they were in the earlier shot of when they were dropped.
Continuity mistake: When we first see the table with the food on it the sandwiches in the middle are piled up in interlocking stacks of three with one more pile of three or four sandwiches rising in the center. When we see the sandwiches again up close as Mitch brings the little girl into the house, they are neatly stacked above each other though not interlocking as before and the middle pile is not there.
Continuity mistake: As Melanie and Mitch walk down the hill Annie and Cathy are standing in the middle of the yard with two other children between them and the lounge chair. In the next shot as we see Lydia carrying the cake, the two children disappear and Annie and Cathy have moved to the left closer to the door.