The ending of 'The Birds' is both mysterious and thought - provoking. After the intense and harrowing experiences of being attacked by the birds, Melanie, Mitch, and the others are able to get into a car and start to drive away. The birds that were once so aggressive have become quiet. Hitchcock deliberately left this ending open - ended. It could be that the birds' aggression was a short - lived phenomenon, or it could be that they were simply following some instinctual pattern that had run its course. This ending also serves to heighten the sense of dread and the unknown. We are left with the characters, and by extension, the audience, still in a state of fear and uncertainty as they leave the scene of the attacks, not knowing if the birds could resume their attacks at any time in the future.
Hell House isn't based on real events. It's more of a fictional construct designed to capture people's attention and stimulate their imaginations. Sometimes, fictional stories like this can seem realistic, but they're not true.