Katie Hunt, CNN
On the Galapagos Islands, a ground finch that usually munched on small, soft seeds was forced, during a drought, to eat harder, larger ones. Within the space of a few generations, the bird evolved a larger but shorter beak better suited to cracking large seeds.
The Galapagos medium ground finch (Geospiza fortis). Gabrielle Therin-Weise/Photographer’s Choice RF/Getty Images
The ground finch is one of at least 15 species of Galapagos finch descended from a common ancestor that flew in one fateful day about 2 million years ago, perhaps blown off course from South or Central America. Another finch uses twigs or cactus spines to dislodge and snack on insects, while another, nicknamed the vampire finch, has evolved an especially sharp beak that allows it to peck at seabirds and feed on their blood.
“A bunch of species all descended from the single ancestor have proliferated so there are many species now. And they’re all doing different things,” said Dolph Schluter, a professor of zoology at the University of British Columbia in Canada, who began studying the finches in the late 1970s. “For the most part, they are exploiting the environment in different ways. There are big beaks and small beaks. There are sharp beaks and dull ones.”…