Darwin's finches are a group of about fifteen species of passerine birds. They often are classified as the subfamily Geospizinae. It is still not clear to which bird family they belong, but they are not related to the true finches. They were first collected by Charles Darwin on the Galapagos Islands during the second voyage of the Beagle. All are found only on the Galapagos Islands, except the Cocos finch from Cocos Island. Darwin's finches are examples of adaptive radiation and divergent evolution.
Therefore, the correct answer is option D.