In a population of finches in which one group birds has short parrot-like beak and another long narrow what process probably occurred?

Natural selection.

Over time, the birds with the short parrot-like beaks were better able to survive and reproduce in their environment than the birds with the long narrow beaks. This is because the short parrot-like beaks were better suited for eating the seeds that were available in the environment. As a result, the birds with the short parrot-like beaks became more common in the population, while the birds with the long narrow beaks became less common. This process is known as natural selection.