Galapagos finches discovered by Charles Darwin
Well known by their valuable contribution to Charles Darwin Theory, they are considered the key of the theory, due to their multiple races.
It takes some effort and interest to learn to identify the finches.
What makes Darwin's finches so difficult to identify is the variability of their beaks (which can sometimes be exacerbated by interbreeding) and the fact that the beak of one species may overlap into the range of another.
More information about Darwin's finches
The Ecology and Evolution of the Galapagos Finches