Charles Darwin’s trip to the Galapagos Islands significantly influenced his thinking and paved the way for his theory of evolution. Since the 1970s, Princeton biologists Peter and Rosemary Grant have been studying Darwin’s Finches and now claim that they’ve witnessed evolutionary change because of competition first hand.

The ground finch, Geospiza fortis, is a medium-sized bird that lives on the small island, Daphne Major. In 1977, after a drought caused the small seeds they normally ate to become scarce, the finches evolved larger beaks that allowed them to crack and eat the larger seeds.

In the 1980s, a new finch species, G. magnirostris appeared.

Fast forward to 2003-04 when another drought occurred. Like in 1977, the seeds the birds normally ate became scarce. Because the G. magnirostris had a larger, heavier beak, they had a much easier time eating the larger seeds that remained.

The G. fortis were forced to try to get by eating the smaller seeds. Those finches with smaller, more dextrous bills had the advantage and by the following year, the G. fortis had a significantly smaller beak - around 5% on average.

Since the major difference between this drought and the one in 1977 is the presence of a second species competing for seeds, the Grants conclude that G. fortis evolved a smaller beak in order to escape this competition.

This change to evade competition, known as character displacement, has been inferred many times when competitors are more different where they co-occur than where they live apart. This is the first time, though, that the entire process has been observed from start to finish.

Source: New Scientist (subscription)