Daphne Du Maurier's short story The Birds was a reaction to the fears faced by the British and others in the years following World War II, which saw England heavily bombed by Germany, and the emergence of a new threat of attack by the Soviet Union. Du Maurier's story, in short, is a parable. The author had survived the German bombing and rocket attacks and now, when the world should have experienced a period of peace, the specter of Russian bombers and missiles was seemingly growing. Stalin was still alive and in power in the Soviet Union when Du Maurier wrote The Birds, and the murderer of tens of millions of his own people and conqueror of Eastern Europe presented a particularly threatening presence.
Whether Du Maurier was warning against the threat of the Soviet Union or satirizing it is uncertain, but the former is more likely the case given her personal experiences of war. Her narrative is almost "Churchillian" in its warning against complacency (Winston Churchill had warned against the rise of Nazi Germany to no avail and now the former prime minister and statesman, once more cast into the wilderness, was similarly warning against the Soviet threat). Read, for instance, the following passage from The Birds for evidence of such a conclusion:
"Various incidents were recounted, the suspected reason of cold and hunger stated again, and warnings to householders repeated. The announcer’s voice was smooth and suave. Nat had the impression that this man, in particular, treated the whole business as he would an elaborate joke. There would be others like him, hundreds of them, who did not know what it was to struggle in darkness with a flock of birds. There would be parties tonight in London, like the ones they gave on election nights. People standing about, shouting and laughing, getting drunk. 'Come and watch the birds!'"
The story's protagonist, Nat Hocken, views the bizarre and threatening behavior of the birds far more seriously than many others in his native England. His is a lone voice amidst the jubilation he monitors from the more urban and urbane environs of London. That the story ends on a decidedly dismal note can be interpreted in one of two ways: as a warning against complacency in the face of a new threat, or as a warning against mankind's unquenchable thirst for new means of destruction (i.e., nuclear weapons, new to the world's arsenals). The Birds ends with Nat contemplating his imminent demise, and it is in this final scene that the author provides her most compelling evidence that her story was intended, after all, as a warning more against nuclear weapons than against a threat from afar:
"Nat listened to the tearing sound of splintering wood and wondered how many million years of memory were stored in those little brains, behind the stabbing beaks, the piercing eyes, now giving them this instinct to destroy mankind with all the deft precision of machines."
That passage -- "instinct to destroy mankind with all the deft precision of machines" -- certainly lends weight to those who interpret The Birds as a warning against nuclear weapons.