Have you ever wondered why the birds attacked the people in 'Master of Suspense' Alfred Hitchcock's movie The Birds? Hitchcock, a pioneer and master of psychological thriller, left cinema-goers terrified by his movie The Birds, in which the life of a couple in love in a small Northern California town turns upside down as birds of all kinds suddenly begin to attack people there in increasing numbers and with increasing viciousness.

For years people have wondered whether our feathered friends can actually turn into vicious killing machines. And finally the mystery seems to have been solved by Sibel Bargu, an oceanographic researcher at Louisiana State University in Baton Rouge. Bargu, an ardent fan of Hitchcock's movies, was left deeply impressed by The Birds when he was a child and took it upon himself to crack the mystery behind whether it was possible for birds to actually attack humans.

Hitchcock's movie was based on a short story of the same title written in 1952 by Daphne Du Maurier, but it is said that Hitchcock also showed interest in a real-life event that happened in the year 1961, in Monterey, Calif. People living in the Monterey Bay area reported huge flocks of seabirds which, without any possible explanation, rammed themselves against their houses. The incident, which left the residents rattled, took place two years before the release of the film. However, no one could understand why the birds behaved like that and Hitchcock never explained the reason behind the bird attack in his film.

Bargu now has a scientific explanation. I am pretty convinced that the birds were poisoned, Bargu told USA Today.

His conclusion came after the scientists examined the stomach contents of the dead birds that left the trail of terror in 1961. Examination of the stomachs of the animals revealed toxic algae, which cause amnesia, disorientation and seizures, on three-quarters of the plankton the birds ate.

Bargu explained that, in the 1960s, there had been a housing boom and some toxic agents could have leaked out from the septic tanks in construction sites. This could have caused the algae to become toxic and, the toxin passed on to the birds. No wonder the birds were so frenzied and freaky.

However, solving the mystery does not rob from The Birds the honor of being the one of the best thriller movies of all time. Though the film's special effects did not win the Academy Award (the winner that year was Cleopatra), it is said that Hitchcock had put in quite an effort to recreate the scene of attack, using CG (computer graphics), assembling mechanical birds and even training hundreds of real birds.

Check out below several impressive scenes from the thriller movie.