The Beak of the Finch: A Story of Evolution in Our Time

Rosemary and Peter Grant and those assisting them have spend twenty years on Daphne Major, an island in the Galapagos studying natural selection. They recognize each individual bird on the island, when there are four hundred at the time of the author's visit, or when there are over a thousand. They have observed about twenty generations of finches -- continuously.
Jonathan Weiner follows these scientists as they watch Darwin's finches and come up with a new understanding of life itself.