Why does the Galapagos island finch's beak change?

The Galapagos island finch's beak changes primarily due to natural selection in response to environmental conditions and food availability. During periods of drought, for example, birds with larger, stronger beaks are better equipped to crack open tough seeds, leading to an increase in their population. Conversely, when softer seeds are more abundant, birds with smaller beaks may thrive. This adaptive evolution illustrates how species can rapidly change in response to their habitats.