Darwin's finches (also known as the Galápagos finches) are a group of about 18 species of passerine birds. They are well known for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or tribe Geospizini. They belong to the tanager family and are not closely related to the true finches. The closest known relative of the Galápagos finches is the South American "Tiaris obscurus". They were first collected by Charles Darwin on the Galápagos Islands during the second voyage of the "Beagle". Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands.