Thoughts in a Haystack

The finches of the Galapagos are much more famous, even being given the general appellation "Darwin's finches," but the mockingbirds were more important. It was the mockingbirds that first started Darwin thinking that species might not be stable:

When he arrived on San Cristobal Island (then known as Chatham), he immediately saw that the mockingbirds were similar to ones he had collected in South America.

The next island he visited was Floreana (known as Charles Island at that time). Darwin was surprised to see the mockingbirds were all noticeably different from those on San Cristobal.

Though the finches were important evidence for his theory later on, Darwin did not even realize that all of them were finches, so diverse they had become, until he had returned to England and his bird specimens were examined by John Gould.

Darwin also avoided the error with the mockingbirds that he made with the finches:

Darwin wrote down these differences and those he saw in mockingbirds in two other islands. Crucially, he noted which mockingbird was from which island, something he didn't do with the finches.

Two of Darwin's specimens have now gone on display at the Natural History Museum in London. Lucky Londoners!
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Link - Posted by John Pieret @ 12:01 AM