One motif that recurs throughout “The Birds” is fire. The onslaught of the birds is associated with the change of seasons from autumn to winter, and their attack corresponds with the cold snap. Nat blames both the frost and the birds' madness on the menacing east wind. In contrast, stability and normalcy are represented by fire, which staves off the cold and the darkness.
At the start of the story, when Nat hears a cry from his children's bedroom and goes to check on them, he lights a candle, but a draft from the door blows it out before he reaches them. Nat is forced to battle the invading birds in darkness. The first major invasion of the birds into the Hockens' home is marked by a flame being extinguished. After the birds' systematic attack on mankind begins, the kitchen hearth becomes the stronghold of the cottage. Nat tells his children that sleeping in the kitchen will be "cozy," but he thinks to himself that "they would be safe because of the fire." Keeping up the fire in the chimney is a practical concern, since it provides necessary heat while also blocking the birds' entry. In Nat's mind, it acquires an almost ritual significance:
[The birds' invading] could not happen again, not if the fire was kept burning day and night.
It haunts his dreams when he forgets to light it. When he wakes up and the birds are forcing entry, he lights the fire despite the risk of the chimney catching fire, killing the birds in the chimney. Nat finds the danger of setting the house on fire less frightening than the danger of the birds, despite fire's destructive capacity. If fire is relatively domesticated by mankind, the birds are totally unpredictable and uncontrollable. But as time goes on, Nat's faith in humanity's capacity to survive falters. Just as the wireless radio loses its power to impart authority and keep the Hockens safe, the hearth fire and all the rest of Nat's safety measures seem increasingly meaningless. Arguably the most "civilized" use of fire, purely for pleasure and not survival, is cigarettes, which have also become a scarcity; Nat has only two left in his pack. At first, he sets one aside "for a rainy day," but the next day, after the reality of the situation has fully set in, Nat tells his wife he'll smoke the last cigarette after all. Implicitly, it seems unlikely that the Hockens will survive to the next rainy day:
He reached for it, switched on the silent wireless. He threw the empty packet on the fire and watched it burn.
In the final sentence of the story, the wireless and the cigarette packet, both market goods and thus signifiers of human exchange and progress, are defunct. The last image is the hearth fire consuming the cigarette box. The fire still creates a circle of safety, but now its symbolism is more ambiguous; rather than ending by stressing its warmth, du Maurier stresses its capacity for destruction.