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.