Darwin's Finches, Galapagos

Darwin brought about 30 different finch species back as specimens from his journey on the Beagle (dead and stuffed, I’m afraid, though it is a good image, the bearded naturalist surrounded by 30 noisy finches in his study).

When he examined their beaks, he found that each finch possessed a different one; some were small, some were big, some were long and thin, others wide and thick, and each was suited to the availability of different foodstuffs in their habitat.  Darwin theorized that all the different finches had an ancestor in common and that, over time, they had changed, each species evolving a set of adaptations to help it survive and thrive in its locality. 

One of the most famous of these finches is the woodpecker finch.  These small, greenish-grey finches are some of the only birds in the world to use tools, using small sticks to dig into the soft bark of the scalesia trees, looking for grubs.

Then there’s the vampire finch.  These dark brown and black finches co-operate in gangs to steal the eggs of nesting boobies.  Armed with their razor-sharp beak, one finch will hop on the back of a booby, drawing blood.  As the red blood stains the white feathers, they mass on the poor boobie, drinking, pecking more and drinking the blood.  When the victim can’t take it anymore it flies away, leaving its eggs unguarded.

The vampire finches’ beak is sharp but not sharp enough to pierce the thick, leathery shell of booby eggs.  In response, the finch stands on its beak, using it as leverage for its little legs to push the egg.  Performing this little acrobatic feat, he will push it again and again until it falls somewhere and cracks.  The rich, gooey yolk spills out and the finches feast.

 

The medium ground finch shows evolution in action.  Though this process usually happens gradually over millions of years, these finches have shown great changes in size and beak shape in just a few generations in response to new challenges, especially regarding fitting into the new urban environments found on the island.  From the ground finch, we can observe evolution happening in real-time!  How cool is that?

 

Finally, there’s the warbler.  This little guy is often overlooked, but it is probably the closest relative to the original finch that colonized these islands.  These finches are equipped with thin, needle-like beaks, which they use to pick insect out of cracks in tree bark.

Ecologists use these finches as indicator species.  The health of their populations often reflects the health of their ecosystem as a whole.