One of the themes in The Beak of the Finch by Jonathan Weiner is the evolution of species. The author follows two scientists and the strategies they take in studying the theory of natural selection. They analyze finches at Daphne Major. According to the author, the scientists find out that evolution takes place all the time, not periodically.

Another theme that is highlighted in the book is scientific observation. For instance, the two scientists observe and study Darwin’s finches. The birds’ beaks reveal important information about evolution. Also, the author reveals information regarding other animals that are being observed for understanding evolution. These include fruit flies and moths.

The theory of natural selection is another theme addressed in the book. For instance, Weiner discusses how bacteria are now resistant to antibiotics. He discusses the impact of global warming on evolution—it has resulted in changes in both plants and animals. The writer also mentions how cactus finches destroy the plants they depend on for survival to get nectar faster than other birds.