Galapagos Islands birdlife and evolution - Darwin´s Finches

The Galapagos Islands is home to 13 species of finch, belonging to 4 genera. These finches all evolved from a single species similar to the Blue-Black Grassquit Finch Volatina Jacarina commonly found along the Pacific Coast of South America. Once in the Galapagos Islands the finches adapted to their habitat and the size and shape of their bills reflect their specializations.

Vegetarian Finch and Ground Finch all have crushing bills while Tree Finch have a grasping bill and Cactus Finch, Warbler Finch and Woodpecker Finch have probing bills.

All of Darwin 's Finches are sparrow sized and similar in appearance with gray, brown, black or olive feathers. They have short rounded wings and a rounded tail that often appears cocked to one side. Most male finch mature to a solid black color, while the females mature to a drab grayish color. Exceptions are made for the Vegetarian and Tree Finches the males never become completely black rather they have a black head, neck and upper breast. Warbler, Woodpecker and Mangrove Finches have more of an olive color.

The finch vary by what they eat some eating seeds and others insects. The Ground Finches eat ticks they remove with their crushing beaks from Tortoises, Land Iguanas and Marine Iguanas and kick eggs into rocks to feed upon their contents. On Isla Wolf the Sharp Beaked Ground Finch is known as the "Vampire Finch" as it jumps on the backs of Masked Boobies and Red-Footed Boobies pecking at their flesh and feeding on their blood. Woodpecker and Mangrove Finch use small twigs and cactus spines as tools to dine on the larva stored in dead tree branches.

Though they have adapted to allow for specialized feeding most finches are generalized eaters. The specialization developed allowing the birds to survive during the dry season or times of drought when little food is available. Then these specialized tools allow the birds to better compete for food sources with other birds and animals.

There are 13 species of Darwin finch in the Galapagos Islands:

Ground Finches    
Small Ground Finch "Geospiza fuliginosa"
Medium Ground Finch "fortis"
Large Ground Finch "magnirostris"
Sharp-beaked ground Finch "difficilis"

Cactus Finches
Cactus Ground Finch  "scandens"
Large Cactus Ground Finch  "conirostris"
Vegetarian Finch "Platyspiza crassirostris"

Tree Finches    
Small Tree Finch "Camarhynchus parvulus"
Medium Tree Finch  "pauper"
Large Tree Finch  "psittacula"

Other Finches
Woodpecker Finch "Cactospiza pallidus"
Mangrove Finch  "heliobates"
Warbler Finch "Certhidea olivacea"