Why Children and Birds, Mr Hitchcock?

I have chosen Alfred Hitchcock’s “The Birds” (1963). The scene in my mind was the gathering of birds in the school yard while children were singing in their class. Melanie was sitting in the garden in her soft green suit, which she acted in throughout the film. I first watched the movie as a child in late 1960’s and I never forgot how much I was scared watching it. I have always felt that the scenario was unfair to both children and birds.