Mockingbirds, not finches, set Darwin on the road to evolution. - New exhibition at the Natural History museum

For the past several decades, the Galapagos finches have been widely regarded as Darwin's inspiration. However, historians familiar with Darwin's notes know the Galapagos mockingbirds were the true catalyst for Darwin's ideas on transmutation - the change of one species into another.

Two of Darwin's mockingbirds, perhaps the most important specimens he ever collected, will go on display for the first time ever in the Darwin exhibition, which opens to the public on Friday 14 November at the Natural History Museum in London. These Floreana and San Cristobal mockingbirds are the individuals from which the two species, both now endangered in the wild, were first described.

Towards the end of his five-year voyage on the Beagle, Darwin worked hard collecting specimens in the Galapagos, starting on San Cristobal Island. Among the birds he observed and collected was a mockingbird, which he immediately recognised as similar to ones he had already collected in South America. On Floreana, the next Galapagos island visited by the Beagle, Darwin noticed and collected a different mockingbird. He wasn't expecting to see much variety in one bird species on the separate islands, but to his surprise, the mockingbirds on Floreana were all noticeably and consistently different from those on San Cristobal. It was while he was on Floreana that the interim governor told him the giant tortoises, too, were recognizably different on each island. After that, Darwin collected mockingbirds from the other two islands he visited and was careful to note from which island each bird came (something he didn't do for the finches). The differences were not between single specimens but between all specimens on each island.

Evolution idea
Later, as Darwin examined his collection on the voyage home, the differences between the mockingbirds on the different islands led him to question, as he described it, ‘the stability of species'. This eventually led him to the idea of evolution, though he didn't use that word until many years later.

Jo Cooper, bird curator at the Natural History Museum, said ‘What's fantastic about these two birds is that visitors will be able to see for themselves the crucial differences that Darwin saw and perhaps be inspired.'

Remarkable differences
Randal Keynes, Charles Darwin's great-great-grandson said ‘Darwin's first sightings of the Galapagos mockingbirds were to prove historic. He later noted in The Voyage of the Beagle that the small difference between the mockingbirds on the two islands was a "most remarkable fact in the distribution of organic beings". Darwin had come to understand that species can change and this ultimately led to our present understanding of life on Earth.'

Floreana mockingbird - only 200 left alive
The Floreana mockingbird is one of the rarest birds in the world and is at risk of extinction. The species is already extinct on its home island of Floreana. Only 200 individuals still survive on two small, nearby satellite islands - Gardner-by-Floreana and Champion.

In support of an international effort to reintroduce the bird to Floreana, the bird group at the Natural History Museum at Tring has provided access to the collection it cares for to allow DNA sampling of two historic specimens. The two birds sampled are the Floreana mockingbird, collected by Charles Darwin, (one of the specimens on display in the exhibition) and another specimen collected by Robert FitzRoy, captain of HMS Beagle.

DNA tests
Independent parallel analyses have yielded promising preliminary results. Analysis of the historic DNA has been carried out by Karen James from the Natural History Museum's Botany Department and Paquita Hoeck and Lukas Keller at the University of Zurich. They are leading the conservation-genetic study of the Floreana mockingbird. Results suggest a strategy for reintroduction, involving birds from the two satellite populations, with the ultimate aim of restoring the Floreana mockingbird to the home island where Darwin first discovered it.

Discover the man and the revolutionary theory that changed our understanding of the world and our place within it at Darwin, an exhibition celebrating Charles Darwin's ideas and their impact, giving new insight into the achievements of this brilliant observer of nature.

The exhibition is a highlight of Darwin200, a national programme of events celebrating Charles Darwin's ideas, impact and influence around the two hundredth anniversary of his birth. www.darwin200.org