What group of birds is known for adaptive radiation on the Galápagos Islands?

The group of birds known for adaptive radiation on the Galápagos Islands is Darwin's finches. Their close relatives diversified from an ancestral population into species with different beaks, diets, and ecological roles.

Darwin’s finches are a group of about 18 passerine bird species found mainly in the Galápagos, with the Cocos finch living on Cocos Island. Despite their common name, they are not true finches; they belong to the tanager family. Their shared ancestor is thought to have reached the islands from mainland South America more than a million years ago.

Natural selection shaped beaks suited to particular foods. Ground finches have sturdy bills for seeds, cactus finches use longer bills to feed on cactus flowers and seeds, and warbler-finches specialize in insects. These differences illustrate adaptive radiation: one ancestral lineage rapidly diversifies as populations exploit different niches.

Charles Darwin collected Galápagos birds during the second voyage of HMS Beagle, but ornithologist John Gould later recognized that his specimens represented a distinctive related group. Long-term studies by Peter and Rosemary Grant have documented beak changes in response to drought and food availability.