Interestingly, though they are related, the film and the original story have different themes. The film is not a direct adaptation of the original book, which features a family fighting for their life against a murderous invasion of birds, while the movie follows a romantic subplot between previously unconnected individuals.

The main difference between the two, however, is the overarching theme. The book was written in 1952, at the beginning of the Cold War, and is used as an expression of the oppressing tension experienced by people living through that time. There was a feeling that, at any moment, death could swoop in and take everyone around you instantly due to nuclear war. In 1963, when the film came out, the Cold War was still in full force, but naturalism was also taking hold—and the story centers much more on the idea of nature rebelling against the oppression of humanity.

Hitchcock's The Birds was not a direct adaptation of Daphne Du Maurier's short story by the same name. Hitchcock and his screenwriter Evan Hunter really only took the idea of birds attacking humans. Other than that, there are few similarities.

First all, the book was set in the UK and the film was set in the USA. Second, the characters in the book are completely different to the characters in the film. In the story, the main character is a married man called Nat who is doing everything he can to protect his family. The film has two main characters: Melanie Daniels and Mitch Brenner. Neither of them are married, and they serve as the film's primary love interest. In addition, the family unit in the film, represented by Mitch's family, is, in comparison to the short story, very weak. Mitch's mother, Lydia, is possessive, and Mitch's ex fiancée, Suzanne, wallows in self-pity.

The main difference between the two is the characters; the characters in the film adaptation are different than the characters in the short story. 

Also, both take place after World War II but the story's time frame appears to be soon after the end of the Second World War. So it took place sometime after 1945. The film adaptation's time frame is the 1960s. The short story is set in England whereas the film takes place in the US.

Perhaps the biggest difference between the story and the film is that Alfred Hitchcock shot the film in the little village of Bodega Bay, which is just a little bit north of San Francisco, whereas the story by Daphne du Maurier is set in Cornwall, England. The Hitchcock film features American actors Rod Taylor and Tippi Hedren. The short story in a lot more gruesome than the film because the birds in the original story cause vastly more death and destruction than they do in the Hitchcock film.

As the link to "The Birds" on enotes points out, the short story by DuMaurier "presents an unrelenting portrait of terror and a compelling analogy of the atmosphere of fear generated in America and Europe during the Cold War years." Although it concerns a family, it does not have the love story that is central to the Hitchcock film. Also, the film emphasizes nature's unexplained rebellion against humans, suggesting a revenge theme, while the short story, as eNotes points out, was written to depict the horror of the bombing in England during WWII and fear of a nuclear holocaust in the 1950s and 60s.