Here's why:
* He lacked the knowledge: Darwin wasn't a specialist in bird classification. He wasn't even a professional biologist at the time of his voyage.
* Similarities were striking: The finches shared many physical similarities, leading him to believe they were closely related.
* Gradual change: Darwin's observations on the finches, along with other animals and plants, led him to the idea of gradual evolution. He realized that species could change over time, and the finches were likely variations within a single ancestral species.
It was only after he returned to England and consulted with experts, particularly John Gould, who was a leading ornithologist, that Darwin realized the finches were indeed different species. This was a pivotal moment in his development of the theory of evolution by natural selection.
