In the opening paragraphs of "The Birds," Nat notices that the winter is so far quite different than that of previous years. The birds are more "restless," for example, and appear to be unsatisfied, even when they feed. In addition, there are more birds than usual, a fact which is supported by the observations of the farmer, Mr Trigg.
After the attack on Nat's house, Du Maurier describes the cold ground and how it has the "hard, black look of frost." This, perhaps, foreshadows Nat's attempt to bury the dead birds which have attacked his family. The ground is too hard to dig, however, and Nat is forced to take the birds to the beach. While he is there, he sees the gulls riding the waves and realises that the birds will return to attack his home. He must now take action to safeguard his home so that his family is protected.