Violence
Violence is one of the book's primary themes. The narrator is disturbed by the way in which the Greggs take pleasure in killing animals. She is upset by the sight of a dead deer that they have shot and this reaction triggers her use of magic on them. Later, the Greggs are transformed into ducks and are subsequently threatened with their own guns. They beg for their lives and the mother duck says it is funny that they are no longer fond of hunting when they are the ones being hunted. She asks why they should be spared when they killed her children. The serious point the book makes about violence is that it always causes serious harm. When the Greggs hunt at the beginning of the book, they do so for sport and enjoyment, not recognizing, or being concerned with, the fact that they are murdering animals.
Animal Rights and Environmentalism
Animal Rights and Environmentalism is one of the book's other central themes. The narrator loves nature and has a special appreciation for the countryside around her. She is upset when the people in her village participate in activities like hunting because they are being disrespectful to this part of the world that she cherishes. The magic that she uses on the Gregg family transforms them into birds and forces them to understand that ducks, as living beings, are worthy of respect and consideration, and shouldn't simply be killed for sport. This respect for the lives of animals, in turn, feeds into a broader respect for nature and the world around them.
The narrator is pleased with the change of heart she observes in the Greggs in the aftermath of this realization. She sees that they have found a way to live in harmony with nature and be respectful to it, instead of taking advantage of it.
Morality
Morality is another key theme in the book. When the Greggs are transformed into ducks, they are threatened by the ducks who take over their home. They brandish the Greggs' guns at them and prepare to shoot them. The Greggs beg for their lives, as Mrs. Gregg asks them not to kill her family, as her boys are just children. The mother duck points out the contradiction in her request, as she is asking for a level of empathy that her dead children did not receive from the Greggs when they killed them. This moment explores the morality of hunting, as mother duck reframes the Greggs’ actions as murder as opposed to sport. The narrator intuitively understands this moral code and attempts to make the Greggs see it from her perspective.
Childhood
Childhood is also a major theme of the book. The narrator is a young girl and is frequently at odds with the adults around her. Her teacher is rude to her when she misspells a word. The Greggs do not respect her impassioned defense of animals. However, what becomes apparent by the story's end is that the narrator actually has the strongest, purest sense of morality, as she understands the plight of the deer and ducks. She is more in tune with the natural world than the adults around her. In this way, Dahl reveals how children instinctively understand important things about empathy that adults often overlook.
Harmony
Harmony is another important theme in the book. At the end of the story, the narrator travels to the Greggs' farm to see that they have changed completely. They change their last name to Egg and are seen feeding the birds on their property. Instead of expressing a need to harm or control the nature around them, they instead have found a way to coexist. In this way, the narrator is pleased to find that the Greggs (now Eggs) have joined her in appreciating and being kind to their animal neighbors.
Power
Power is also a theme in the book. The Greggs control the natural world around them with the use of their guns. However, after being transformed into ducks, they lose their ability to exert this control. The ducks they previously hunted, now grown human-size, take both their guns and their home. The situation completely reverses when the ducks threaten the humans with guns, as they now have all of the power and the humans are completely at their mercy. After being put in this frightening position, they vow to never hurt another animal again. The ducks then destroy their guns. They learn their lesson because their loss of power forces them to see how they have been terrorizing the natural world around them.
Magic
Magic is one of the book's main themes. The narrator recognizes that she possesses extraordinary magical powers, but is equally aware that she cannot control them. She says that she has an emotional response to something and the power is simply released from her finger. Her transformation of the Greggs teaches them an important moral about being kind to animals. However, her effect on her teacher, while humorous to the other students, concerns her. She is worried about not being able to manage her powers. This is indicative of both her young age and her slow process of learning to control her impulses.
