The ornithologists assertions (dramatic irony)
Irony is used in the diner when the amateur ornithologist smugly rejects Melanie's story about the attack on the school children as impossible for a variety of reasons. Her assertions, which she voices as beyond all doubt, are ironic in that she fails to understand her own situation, though the audience understands it perfectly well. They also point to a larger theme of human assumptions of superiority over nature being put to the test.
Look...Back There...on the Jungle Gym...It's...Dramatic Irony
Irony is an often misunderstood literary device too easily confused with mere sarcasm or coincidence. Dramatic irony is the simple manifestation a character exhibiting behavior that the audience can recognize as inappropriate or disconnected from the reality of the situation because the audience has more information than the character. In this famous scene, the disconnect between Melanie’s calm demeanor and the disquieting activity the audience can see taking place behind her is a demonstration of dramatic irony.
He's not the villain: situational irony early in the film
Early in the film, Melanie walks into Mitch's apartment building to deliver the birds. She gets in the elevator with a strange man, who stares at her as they go up. When she gets off the elevator, he seems to be following her and watching her. Experienced horror or thriller film viewers at the time would have immediately suspected this man to be a villain: he finds himself alone with our vulnerable female star, and acts strangely around her. However, he soon defies our expectations by speaking to her kindly and helping her. This is an example of situational irony, in which something in the film contrasts with the audience's expectations of what is going to happen.
This isn't usual, is it?
After the attack on the birthday party, marking the third attack that Melanie has witnessed, she calmly asks Mitch, "this isn't usual, is it?" This is an excellent example of understatement in the film, a type of verbal irony. Melanie is understating reality here: she knows the events to be in fact highly unusual, and her reactions to each one indicate that she thinks this. As viewers, we too know the situations to be incredibly unusual, menacing, and dangerous, and her casual tone and phrasing drastically underplays the situation.
