The opening of the story contains symbolism. Du Maurier uses the opening of the story to indicate a theory of correspondence, a connection between the weather and impending dramatic elements in the story:
On December the third, the wind changed overnight, and it was winter. Until then the autumn had been mellow, soft. The leaves had lingered on the trees, golden-red, and the hedgerows were still green. The earth was rich where the plow had turned it.
The change in season is almost symbolic regarding the change that Nat and others will experience very soon. The birds themselves occupy symbolic importance. Naturally, they are predatory in the context of the story, but in her descriptions, Du Maurier uses them to indicate the challenges that human beings face:
...there are more birds about than usual; I’ve noticed it too. And daring, some of them, taking no notice of the tractor. One or two gulls came so close to my head this afternoon I thought they’d knock my cap off! As it was, I could scarcely see what I was doing when they were overhead and I had the sun in my eyes. I have a notion the weather will change. It will be a hard winter. That’s why the birds are restless.
The "restless" condition of the birds is symbolic of what is going to happen as the narrative develops.
Nat's initial defense of his children is also described in an interesting way. Du Maurier describes flailing, trying to use anything to defend his children from the birds' attack: "He seized a blanket from the nearest bed and, using it as a weapon, flung it to right and left about him in the air." The symbolism of a blanket, an object of nurturing and comfort, having to be used as a means of defense is significant. The chaos that the bird end up causing is significant. After the first attack, Nat goes to the kitchen, visibly shaken by what he has experienced in defending his children: "The sight of the kitchen reassured him. The cups and saucers, neatly stacked upon the dresser, the table and chairs, his wife’s roll of knitting on her basket chair, the children’s toys in a corner cupboard." This is symbolic because Du Maurier constructs the kitchen as a realm of safety and security, a domain in which all is well. Such a construction is in stark contrast to what is to come. In each of these situations, symbolism is used the heighten the tension between the human beings and the birds. In doing so, Du Maurier uses objects like the kitchen, the blanket, and weather to enhance the increasingly helplessness that Nat and the humans face against the birds.