There are several key themes in Beak of the Finch, but one of the most predominant is the idea of change. Throughout the book, Darwin and his fellow scientists observe how different species of finches on the Galapagos Islands adapt to their changing environments. They watch as some finches evolve longer beaks to reach deep into trees for food, while others develop shorter beaks to crack open hard seeds. This process of natural selection leads Darwin to formulate his theory of evolution by natural selection.
Another important theme in Beak of the Finch is competition. The scientist must constantly compete with other researchers for funding and resources in order to continue their work. They also face competition from developers who want to build resorts on the islands or exploit its natural resources. This creates a tense atmosphere at times, but ultimately drives the scientists to work even harder to understand and protect these unique creatures.