47. End of the quest


In 2002 my freezer defrosted. Dineke and I were on holiday in the USA and our daughter was going to use our house for a couple of days. She found the electricity down, probably as a result of a recent thunderstorm which had happened before, and the freezer thawed. Fortunately, it was in a shed outside, otherwise the stench would have permeated every corner of the house. The contents were, of course, lost, except for my two Tristan Moorhens, which I had kept there for almost ten years by this time. They looked, although probably inedible now, still good enough for the skins to be prepared. I took them to the Zoological Museum in Amsterdam, where the skins were indeed successfully prepared. We looked at the stomach contents but found nothing identifiable. No eggshell fragments in any case. I took the skinned bodies back home to re-freeze, but decided that they would be safer in the freezer at my institute.

            I also decided that I had waited long enough for the DNA results from the samples Michael Swales collected in 1993. Not a word from him or from Gary Nunn, who would do the analysis. Gary had been completely absorbed by albatross-DNA, which had become his specialty. He is one of the people responsible for splitting up Wandering Albatross populations accross the world into separate (hardly distinguishable) species, and splitting the Yellow-nosed Albatrosses into an Atlantic and an Indian Ocean species. Meanwhile, my institute had also started to embrace DNA-analysis for various purposes, so now I could just ask a colleage to do the job. He was very enthusiastic at first, but after a few months he told me he could not find the additional funds needed or a student do do the actual work. So I went back to Amsterdam, where I had donated my skins. Same response. Enthusiasm first, then a few months silence, and finally the message that they could not fit it into their programme. Next I tried Wageningen University, with the same results. Now I had been shopping around for more than three years.

            Finally, in 2005 there came a solution. I saw a publication of a newly established institute: the Ancient DNA Laboratory at the University of Leiden specialised in analysing DNA samples from old museum specimens. This paper was about the landsnails of the genus Balea. These tiny snails, only a few millimeter in length, occur in continental Europe, The British Isles, Iceland, the Azores, and... Tristan da Cunha! DNA-analysis revealed that Balea snails from Europe reached the Azores, probably sticking to the feathers of migratory birds, and developed there into two endemic species, one of which was later transported to Madeira, and from there back to Europe, where it now lives side by side with the ancestral species. From the Azores, one species managed to reach Tristan, most likely again with the aid of birds. The authors of this paper thought of long distance migrants like waders, which often accidentally reach islands in the South Atlantic, but in my view Skuas could also be a likely vector. Skuas, originally birds of the far north, managed to reach the Antarctic, through trans-equatorial migration (we see Siberian Pomarine Skuas in the South Atlantic), and establish new species there, one of which later moved back to the North Atlantic, to become the Great Skua of Iceland.

            In Tristan da Cunha the Balea snails split up into at least eight different species, all endemic to the group, some endemic to only one island, others occurring on two, three, or all four islands, including Gough, indicating that transport by birds must have been a relatively common thing.

            I contacted the first author of this interesting paper, professor Edi Gittenberger, and he told me that his study of the land snails of Tristan was greatly stimulated by reading my book on the Moorhen. And, yes, he would be delighted to adopt my Moorhens as a case. So my two corpses moved to Leiden. The museum had plenty of skins from Gough to use, so now we only needed DNA from the type specimen in the British Museum to complete the study. DNA from old bird specimens is usually taken from feathers, which often have tissue remains inside the root of the shaft, especially in feathers which were still growing when the bird was killed. When the skins are treated with arsenic body feathers yield no good DNA. The best results come from flight feathers. But no museum curator in his right mind would allow such a feather to be pulled from a type specimen. Gittenberger and his co-workers had developed another technique. They would drill a miniscule hole in the sole of the foot, to reach untainted tissue, and take a minute sample there, leaving only an almost invisible little hole in the foot. They conferred with their colleagues in Tring, and got them sufficiently interested in the project to obtain permission to take a foot tissue sample from the type specimen of the Tristan Moorhen. So there we go!

            First, the DNA of the type specimen differed significantly from the DNA extracted from birds from Gough. Secondly, DNA from both Tristan and Gough seemed to be more different from ordinary Common Moorhens from the Americas than from Eurasia and Africa. Because of the prevailing winds all endemic land birds of Tristan and Gough had been thought to originate from South American relatives. It now seems that the Moorhens came from Africa, and not from South America. Thirdly, the DNA from my corpses was identical to DNA from Gough. That leaves us two firm conclusions. One: the Tristan Moorhen did exist, and differed from the Gough Moorhen (I already had sufficient proof from my early eyewitness accounts, but this genetic confirmation is nice, of course). Two: alas, alas, the present day Island Cocks on Tristan are not survivors from the original stock, but are descendants from the birds that Mister Swales put there (shouldn't 'ave dunnit).

            Amazingly, the genetic distance between Tristan and Gough Moorhens seemed to be slightly larger than the distance between Gough moorhens and ordinary Common Moorhens from Africa. Also, this distance was in the same order of magnitude as the difference between various subspecies of Common Moorhens throughout the world. This suggests that the birds from Tristan and Gough should be seen as one single species, Gallinua nesiotis, with two subspecies, Gallinula nesiotis nesiotis (extinct) on Tristan, and Gallinula nesiotis comeri on Gough. End of story, end of my 40-year quest. The results were published in an online scientific journal (Groenenberg et al. 2008).

            Interesting personal detail: of the hundreds of papers I have written or co-authored, only the very first and the very last deal with the Moorhens of Tristan da Cunha. This has a symbolic value as if the Moorhen embraces all the other things I have done in my life, like a pair of bookends.

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