5/22/12 By Cecilia Brey (#3) LE-2 Darwin’s Finches

Who was Darwin? A British scientist born to a wealthy family on 12 February 1809 in Shrewsbury, England. Darwin‘s theory of evolution, and his book, Origin of Species, have changed the way we look at the natural world. His theory involves species evolving over time in order to adapt to their environment. This process involved natural selection, which meant the species who are most adapted to their environment are the most likely to survive and reproduce.

Voyage of the Beagle A 5-year-long (1831-1836) voyage that began when Darwin was 22. The ship traveled along the South American coast, and Darwin was able to explore many of South America’s islands, including the Galapagos. The crew’s job was to map the area, but Darwin used the opportunity to study the plants and animals living there.

The Galapagos Islands An archipelago that lies atop the equator about 600 miles off the west coast of South America. Home to many endemic species. That means that these species’ habitats are found in only one particular area. An example includes the Galapagos Tortoise.

Location

Darwin’s Discoveries Darwin discovered that many of the species on the Galapagos were found nowhere else on Earth. Also, he marveled on how well the species adapted to their environment. Darwin noticed that many of the species on finches on the island had different, specialized traits. Darwin believed these birds evolved from a common ancestor and developed specialized traits over time.

Finch Beak Comparative Chart

Seed Eaters This includes the sharp-beaked, small, medium, and large ground finches. Their beaks are broad and designed for crushing, so it is easy for them to crack open seeds. The small and medium ground finches have smaller beaks to eat small seeds, and large finches have broader beaks for eating large seeds that the small finches cannot eat.

Seed Eaters

Insect Eaters The warbler, woodpecker, and small and large insectivorous tree inches eat primarily insects. They have sharp beaks that are ideal for grasping and catching insects in midair. The woodpecker finch has a special beak that can drill holes into trees to look for insects.

Insect Eaters

Fruit Eaters The vegetarian tree finch is the only finch that feeds primarily on fruit. They have short beaks that resemble a parrot’s, which are ideal for eating fruit.

Cactus Eaters The cactus ground finch is the only finch that feeds on cactus. They feed on the flowers of Opuntia cactus, and they even nest in the cacti. They have long beaks that curve downward.

Blood Eaters The vampire finch is similar in appearance to the sharp-beaked ground finch and it is known for drinking the blood and eating eggs of other birds. It has a very long, sharp beak that is used to puncture birds’ flesh.

Woodpecker Finch Beak is long and pointed and is used for probing and finding insects and grubs in tree bark. Sometimes, they use tools like cactus spines or twigs to obtain food. Grayish-olive color, beak goes from pink to black as the bird matures.

Warbler Finch Beak is short, thin, and used for probing and eating insects. Dull, olive-gray feathers. Both sexes look the same.

Large Ground Finch Large ground finches are the largest of the island’s finches (hence the name). They have large, broad beaks, which are ideal for eating seeds. Males are completely black and females are golden-streaked.

Competition? The small and large ground finch both eat seeds and live in the same habitats, so it is likely than the two species would compete with each other. If something happens to reduce the number of available seeds, the small ground finch may have an advantage because it also feeds on parasites that live on the tortoises and iguanas.