Nature Essays

Darwin's Medium Ground Finch ( Geospiza fortis)

The Medium Ground Finch is endemic to the Galapagos. Darwin, in the years of his exploration, noticed the differences in the Galapagos finches. These differences between species are in the size and shape of their beaks. Otherwise, their appearance is similar. They are sparrow-size about, 5-6 inches and dark brown, gray or black. Some Finch eat seeds and others insects. The Ground Finches eat ticks they remove with their crushing beaks from tortoises and iguanas. The Sharp Beaked Ground Finch is known as the "Vampire Finch." It jumps on the back of Booby Birds, feeding on their blood. Woodpecker and Mangrove Finch use small twigs and cactus spines as tools. They pick out the insect larva stored in dead tree branches.

The beaks of each finch fit their specific diet and have even evolved in current times. During the Galapagos drought, smaller seeds were produced and so the Finches' beaks were reduced in a measurable size in just a few decades.