Alfred Hitchcock's works tend to be divided into beautifully plotted (mostly romantic) mysteries and thrillers which depend more on scares than ideas, and viewer response to them tends to be divided along similar lines. My taste runs more to the mysteries, and so may be somewhat skewed when it comes to THE BIRDS which may well be Hitchcock's second most famous thriller after PSYCHO, and as such normal critical standards may well be suspended.
No, as beautifully set as this film is, very little in the plot or dialogue makes a lot of sense, and the special effects, while outstanding for 1963, don't bear close examination in 2021, but Hitchcock knew how to structure a thrill (1973's THE EXORCIST learned from Hitchcock and THE BIRDS that the greatest way to heighten horror is to deny that it is possible or let the threat build S L O W L Y as in the crows gathering on the school "monkey bars") so that most of the scares still hold up. Tippi Hedren is no Ingrid Bergman or Grace Kelly as an actual actress, but she is just what Hitchcock wants as the beautiful victim he can surround with excellent actors to flesh out his situations.
The bottom line is that the film's greatest weakness, the non-ending and failure to explain the attacks, may not matter to fans. Thrills don't depend on logic . . . or even that the original short story the film was based on was inspired by an actual massed bird attack on a crowd in Boston in the 1840's. We're far more aware of ecological concerns today than when the film was released in 1963, bit while it may not add much to the practical discussion, it certainly feels timely in a macabre sense.
My two stars are for the movie as a film for ALL audiences. Fans of mindless thrillers would probably give it four or even five if possible.