Not Hitchock.
Daphne Du Maurier. She also wrote “Rebecca”
Yep. It started as a short story by du Maurier.
That story gave Hitchcock the idea for the movie. (AFAIK)
“The Birds” appeared “Spellbinders in Suspense”, one of the short story compilations under Hitchcock’s name in the late 60s, long after the movie. Roald Dahl’s “Man from the South” was also in it, IIRC.
Recently I’ve watched some of the Alfred Hitchcock Presents dramatizations, and I’ve been surprised at how many of the old mystery and horror stories made it to Alfred Hitchcock Presents. Including “A Man from the South”, and another Roald Dahl, “Lamb to the Slaughter”, about a woman who conks her husband dead with a frozen roast lamb, then feeds it to the cops who show up to investigate.
She was also the wife of Lieutenant General Frederick Browning, father of the British Airborne forces, portrayed by Dirk Bogarde in "A Bridge Too Far."