Darwin Mockers on the Galapagos

My father died last month. During our last visit, I told him that France and I would shortly be heading to the Galapagos, which he had never been able to visit. He reminded us he had a copy of The Voyage of the Beagle. Just two months before, I had read to him the introductory chapter from his prized second edition copy of The Origin of the Species. Even if at the end it was all about family, I think we both loved that our last conversation was about Darwin and books.

Our trip to the Galapagos was therefore not just a visit to a new ecoregion, the Galapagos Islands Scrubland Mosaic (NT1307), but a pilgrimage to Darwin’s memory on behalf of my father, an evolutionary biologist. It was on his 1835 visit to the Galapagos that Charles Darwin started to put together his theory of natural selection as a driving force of evolution. Darwin’s writing and thinking changed our understanding of the world. Evolution and natural selection shape all the forms of life that we can now package into areas called ecoregions.

As a biologist and an ecoregion birder, I assumed I would write this blog about the 16 species of “Darwin finches” (recent studies have actually shown they are tanagers and not finches) on the Galapagos, all endemic to this ecoregion (one other species in this group occurs on Cocos Island off Costa Rica). True that their beak differences are interesting and their different behaviors are fascinating, but to identify and photograph, they are a pretty monotonous set of similar blackish birds! In fact, by the end of our trip, I had my own doubts about species limits between them as one “species” seems to just merge into the next.

So instead let me focus on a second much less known group of birds on the Galapagos that show the same island-to-island differences as the Darwin finches – the four species of Galapagos mockingbirds. In fact, it was thinking about the mockingbirds from the Galapagos when the farthing first dropped for Darwin, that here was a prime example of evolution by natural selection. It was only later that the finches supplanted them as the poster chicks of adaptive radiation.

In an earlier blog from the Southeastern Mixed Forests, I wrote that the favorite bird of Thomas Jefferson, well before Darwin’s time, was the “mock bird”, the Northern Mockingbird. Great thinkers are attracted to the same birds! Darwin called them “mocking-thrushes”. He wrote, speaking of his “ahaa” moment, that “My attention was first thoroughly aroused by comparing together the numerous specimens, shot by myself and several other parties on board, of the mocking-thrushes, when, to my astonishment, I discovered that all those from Charles Island [now Floreana] belonged to one species (Mimus trifasciatus); all from Albemarle Island [Isabela] to M. parvulus; and all from James [Santiago] and Chatham [San Cristóbal] Islands…belonged to M. melanotis.”

France and I did a 6-day trip around the islands, with a great group of fellow passengers and guides. We managed to see the two mockingbird species above. If many of the Darwin finches are a bit on the dull side and the inter-island differences rather obscure, one would have to say the same for the mockingbirds! Here are photos of a few other Galapagos specialties.

 

 

Darwin’s epiphany about natural selection has been verified and demonstrated in countless ways over the last two centuries. Such a dramatically different way of explaining the natural world understandably had its doubters at the time. But it is sad to note that even today, the mockers are still there. The current US Administration is rife with creationists, leaving little room for evolving mockingbirds!

My father is turning over in his grave.