One theme in Daphne’s “The Birds” is a struggle to survive, to live. Nat’s family is one of the first in his area to experience an attack by a large number of birds. First, Nat fights off about half a dozen birds from his room. Later, the birds attack his children in their room, and Nat kills over fifty of the birds, using a blanket as a defense weapon. Following this experience, he determines to protect his family from any further attacks by boarding up the windows and chimneys in his house as has been advised in the news broadcasts. After the second bird attack, he piles up his sills with bodies of dead birds for extra security. He also boards up his kitchen door. He notices that the “birds attack with the flood tide,” so he replenishes his family’s stock of food, fuel, and light from the Triggs’ farm.

Another theme is the role of women in the family. Throughout the story, Nat’s wife is portrayed as a weak person, someone to be taken care of, much like the children. Nat hides various important things from his wife—for instance, the fact that the birds have already broken into the children’s room upstairs, or that the Triggs are dead. Also, he does all the work that involves securing the house against attack from the birds, without any help from her. She mostly concerns herself with cooking, cleaning, and nursing her family’s injuries. This is one reason why Nat seems quite isolated in his fight against the birds toward the end of the story. It seems like it is him alone against the birds. Still, Nat’s family is unified in its struggle for survival, even if some of its members only play small roles in this struggle. Nat comes across as a strong leader and head of the family.

One theme is Daphne DuMaurier's story, "The Birds," is survival of the fittest. Nat Hocken is a survivor. Unlike the Trigg family, Nat instinctively feels that something is wrong with the birds from the very onset of the story. It is simply not usual for birds to attempt to gain entry into houses and attack people. After the first night of the attack by the birds, Nat listens to the news and begins to board up his house; Mr. Trigg does nothing except get ready "to join the shooting match." His plan is to shoot the birds and have fun while he's at it.

However, by the end of the story, the Triggs are dead. They didn't heed the advice of others. Nat protects his family by securing his house and getting the necessary supplies from the Triggs' farm. He and his family are able to survive the bizarre bird attack because he prepared for the worst. He is a survivor.

In "The Birds," one of the most prevalent themes is that of human survival; this is evident through the activities of Nat Hocken. In his efforts to keep his family safe from the birds, for example, Nat develops a number of survival tactics which range from physically battling the birds to maintaining supplies and improving the defenses of his home.

As the story progresses, Du Maurier introduces the theme of isolation. This is best depicted by the silence of the radio after only two broadcasts. These broadcasts are important because they provide the Hocken family with information and help them to feel connected to the rest of the world. The absence of these broadcasts, therefore, leaves the Hockens feeling isolated and totally dependent on themselves, as Nat comments:

“There isn’t going to be any news,” said Nat. “We’ve got to depend upon ourselves.”

Finally, it is also worth noting the theme of outsiders. This is demonstrated through the references to Russia, a country which is blamed by Mrs Trigg for the sudden change in weather. Later, the Russians are also blamed for the birds' attacks on humans. 

For more themes, please see the reference link provided.