The centerpiece of evolutionary
biology in the Galapagos are the 13 species of Darwin's finches.
The finches are small, drab birds that differ from one another
primarily by their beak shape and, therefore, the ecological
niche in which they live. They represent a group of very closely
species at the point at which they are still in the process
of diverging away from each other. The finches were far too
complex for Darwin to understand - indeed, their history is
still in the process of being unravelled, but he observed that
with this birds, it was as if a single pair reached the island
and then they evolved into the various types which he saw. The
birds in the slides below are the small, medium and large ground
finches, the cactus finch, the large cactus finch, and the warbler
finch. The differences in plumage are sex and age related: mature
males are black (except for the warbler finch).