The Beak of the Finch by Jonathan Weiner

Author:Jonathan Weiner [Weiner, Jonathan]
Language: eng
Format: epub
ISBN: 978-1-101-87296-3
Publisher: Knopf Doubleday Publishing Group
Published: 2014-05-13T16:00:00+00:00

EVEN THOUGH HIS THINKING about evolution was formed by what he had seen in the Galápagos, Darwin never quite understood how much species are like islands. The momentum of his long argument sometimes made him sweep past and ignore the distinctiveness of species, and talk as if all the categories of life run smoothly together. “I look at the term species as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other,” Darwin writes in the Origin, as if species were just as arbitrary a convention as varieties, which are merely “less distinct and more fluctuating forms.”

It is true that the thirteen species of Galápagos finches are things of the passing moment, like the bodies of the individual birds that make up each species, like the islands that are their home, and like the very planet that is the home of all these islands. But one of the most significant facts about bodies, islands, and planets is that while they last, they are real, distinct, and separate. True species are as real as bodies, islands, or planets, though what holds them apart is not as uniform or as obvious to the eye. Even now, even with hybrids flourishing triumphantly on Daphne Major, most of the finches on the island seldom interbreed.

Clearly song is part of the finches’ secret. But song is not everything. If it were, the cactus finch that sings a fortis song would be able to mate with a fortis female, and the broadcasts of the loudspeakers that Laurene and Peter arranged on Daphne and other islands would have had an effect on both male and female finches. The males often attacked the speakers, but the females acted completely uninterested. In almost five hundred trials, only three females ever came over to the speakers.

To find out what was missing for the females, Peter and Laurene set up two speakers 10 meters apart on the lava and placed a stuffed male decoy on top of each one. Now the females were more interested. They hopped over to investigate each speaker. They came closer to a male decoy of their own species than a male of another, and spent more time near it. They also spent more time with a male from their island than a male from another.

Obviously the females are looking for something more than song. So are males, since when females approach a singing male, the females do not sing, yet the male decides somehow whether the female is one of his own species, a bird of his feather, worth the trouble and expense of courting.

The word species comes from the Latin verb specere, to see. Linnaeus used the word to mean groups of animals and plants that look distinctly different to the eye. After screening each other with songs, Darwin’s finches must do their taxonomy as Linnaeus did. They must tell one another apart by eye.

To find out what the birds are looking for, Laurene Ratcliffe and Peter Grant performed a slightly ghoulish series of experiments.

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