2. Just a Moorhen
When I finally managed to get to Tristan it was not to study the seabirds of Nightingale. I found another excuse. I went to Tristan to solve the mystery of the flightless Tristan da Cunha Moorhen, known locally as Island Cock or sometimes Island Hen.
Superficially there is nothing special about the Tristan Moorhen. It looks just like any other ordinary Moorhen, that we might see in our parks and ponds. Blackish brown, with a row of white specks along the flanks, a yellow and red bill, yellow or greenish legs, and a nervously twitching cocked tail with a few white feathers on the underside. Perhaps it is a little darker than our local Moorhen at home, the legs are stronger and thicker, and the wings are shorter and more rounded. But these small differences do not make it special. The thing that makes it special is that it is, or was, to be found nowhere except on Tristan da Cunha. Whether we say 'is' or 'was' depends on whether we consider the endemic Island Cock extinct or not. There was even a question as to whether it ever existed at all. This was the Great Mystery I was going to solve.
The original Moorhen of Tristan was unable to fly. The wings looked normal but the primaries were too soft, the flight muscles too weak to lift the bird off the ground. Loss of flight ability is a feature often seen in birds on isolated islands The most famous example is the extinct Dodo of Mauritius. In the rail family, to which Coots and Moorhens belong, flightlessness on islands is particularly common. Rails in general are poor flyers. Perhaps this is why they are prone to being blown away from their migration routes when strong winds come from the wrong direction. When they are blown away from the land these lost birds will usually perish at sea unless they accidentally find an island. It is easy to imagine that an involuntary, exhausting flight over thousands of miles of open ocean, would be an extremely traumatic experience for a land bird and that, once safely on an island, they might make a vow never to fly again. However, bird brains do not work like that but there are certainly evolutionary advantages to becoming flightless in the absence of predators. Today, most flightless island species are either already extinct or threatened with extinctiont, due to the arrival of Man and the accompanying goats, pigs, cats and rats. Allegedly the Tristan Moorhen went the way of the Dodo in the nineteenth Century.
The Tristan da Cunha Moorhen was described as a new species to science in 1861. Sir George Grey, Governor of the Cape Colony, donated a fine collection of live animals to the Zoo of the Zoological Society in London. The animals were to be shipped from Cape Town to London under the care of Mr Benstead, the Society’s agent. A few days earlier, a Tristanian girl working in Sir George's household, brought five live Moorhens from her island to Cape Town. They joined the South African collection in the ship’s hold. Unfortunately, their cage was placed a little too close to another cage which held a hungry Jackal. Already before departure the Jackal had killed two Moorhens. Mr Benstead prepared the skins, but, alas, the heads were missing having been eaten by the Jackal. Two other Moorhens died during the long sea voyage. They were put in jars and preserved with alcohol. Eventually number five arrived alive and well in England, where it lived happily for three years in the London Zoo. In 1864 it died and ended up between the camphor balls in a drawer of the British Museum.
In 1861 Doctor Philip Lutley Sclater, Secretary of the Zoological Society, examined the four dead Moorhens and the live one in the Zoo. He concluded these were not ordinary Moorhens, but a new species, as yet undescribed. A scientist describing a new species has to follow strict international rules, based on a system designed by Linnaeus in the mid-eightteenth century. Every species gets two Latin names, the first indicating the Genus, the second the Species. A Genus contains one or more closely related Species. Our Common Moorhen is called Gallinula chloropus - greenlegged little chicken. Sclater found that the Tristan Moorhen looked enough like an ordinary Moorhen (or Gallinule), to be placed in the same Genus Gallinula. In the Species name he wished to reflect the insular origin of the bird. In true Latin this would have become insularis but for reasons unknown Sclater preferred to use the Greek word nesiotis (in his description he adds in parentheses ‘nesiotis = insularis’). So, in full, the scientific name of the Tristan Moorhen became Gallinula nesiotis.
Old reports tell us that Tristan Moorhens tasted delicious. They were not only eaten by Man, but also by the dogs, cats and rats that came to the island with them. Their combined efforts managed to wipe out the species before the end of the nineteenth Century. In 1873 the famous Challenger Expedition called at Tristan da Cunha. The naturalists knew about the Moorhens and wished to see them in the wild. But the islanders told them that Island Cocks were no longer to be found anywhere near the Settlement. The Expedition failed to observe them. In spite of their lack of effort, the negative accounts of the Challenger Expedition caused the Tristan Moorhen to be declared officially extinct by 1873.
All that is left of the Tristan Moorhen is a handfull of bones and two prepared skins - the Type Specimen, and the Co-Type, respectively. The scientific history of the species is an extremely short one: from 1861 until 1873 - just twelve years. An insignificant history of an insignificant brown bird that was doomed to be forgotten.
In 1888 a new Moorhen was discovered, by George Comer, second mate of the American whaler Francys Alleyn, when they were killing seals at Gough Island. Like the Tristan Moorhen it looked very much like an ordinary Moorhen, with a cocked tail white underneath, white flecks on the flanks, and yellow legs. Comer called the birds 'Mountain Cocks', and said:
"They cannot fly and use their wings to help them in running... They are quite plentiful and can be caught by hand. Could not get on a table three feet high. The bushes grow on the island up to about 2000 feet, and these birds are found as far up as the bushes grow... Tip of bill bright yellow, scarlet between the eyes. Legs and feet yellow, with reddish spots."
Comer took six birds on board alive, four of which quickly died. Two reached America alive and were kept there for a while, tethered by a rope-yarn, but eventually they escaped. The skins of the four dead ones ended up on the desk of scientist J.A. Allen, who described them as a new species in 1892. He found the weak wings too different from those of the Common Moorhen to place the bird in the same Genus so he designed a new Genus name, Porphyriornis. The Species name, he derived from Comer. So the full name of the Gough Moorhen became Porphyriornis comeri. Allen also studied the thirty year old skin of Sclater’s Type Specimen, finding it so similar to his Gough Moorhen that he had to place the two species in the same Genus. Thus, he rechristened the Tristan Moorhen and called it Porphyriornis nesiotis.
Gough Moorhens never became extinct, and are still to be found all over the island. Specimens have been taken regularly, both alive and dead. Live Gough moorhens could be seen in the London Zoo, where they bred happily for many years. In England Gough Moorhens have escaped and are now running wild, interbreeding with the closely related Common Moorhen. The Gough Moorhen is a thriving species currently not threatened with extinction.
In 1970, Gisela Eber, a German biologist, studied the zoogeography of the Moorhens of the world. The Common Moorhen is a cosmopolitan species, to be found in almost every continent, and on many oceanic islands. When comparing populations, carefully measuring skins in museums, one can analyse differences and resemblances and thus form an idea about the history of the species’ distribution, and its geographical origin.
Digging her way through the ornithological literature, searching for remote Moorhen populations, Gisela inevitably came accros the Moorhens of Tristan and Gough. She also studied skins of both species in the British Museum, where, at that time, she only could find one single skin of the Tristan Moorhen. She concluded that there was no difference between the two species and that the differences between the descriptions of Sclater and Allen all fell within the individual variation in a longer series of skins from Gough Island. Thus, she combined the two forms as one single species. She also disagreed with Allen that abberant wings justified a separate Genus status. She brought the Tristan/Gough moorhen back to Gallinula, where all ordinary Moorhens are to be found.
Finally, Gisela reasoned that is was extremely unlikely that a single species, colonising two seperate islands, and evolving into flightlessness on both, would not diverge through chance processes and under the pressure of markedly different climatic contitions (Gough being much colder and wetter than Tristan). From an evolutionary viewpoint this might even be considered an impossibility. When she found that the Tristan Moorhen only ‘existed’ from 1861 to 1873, just yielding the one specimen she could find, and that it was followed up by the Gough Moorhen in 1892, her conclusion was logical: The single specimen allegedly from Tristan, must in reality have come from Gough, and in all probability was mislabelled. It was not at all unlikely that people who collected specimens on Gough Island, would label them as ‘found near Tristan da Cunha.’
Gisela Eber was not the first scientist to cast doubt on the validity of the Tristan Moorhen as a species that really existed. In 1949 two South African marine biologists visited Tristan to investigate the possibility of starting a viable fishery for Tristan Rock Lobsters (which has been in South African hands ever since). They were also keen ornithologists, and published an extensive paper on the ornithology of Tristan da Cunha. Their opinion on the Moorhens was that is was questionable, at the least, whether the Tristan Moorhen ever existed in reality. But it was Eber who took the firm decision on this issue. She concluded that the Tristan Moorhen was simply a mistake.
The scientific name of the Island Cock has been moved to Gough Island. The Gough moorhen should now be called Gallinula nesiotis – Sclater’s name, and not comeri, because the name nesiotis was given earlier. The rules in nomenclature are very strict. With this move the Tristan Moorhen was totally annihilated. It had been reduced to an administrative error.
The Tristan Moorhen was officially 'discovered' as a new species in 1861, but it had been seen by many non-scientific people long before that. Eber, and the scientists who successively believed her, did not know that. But I knew. So I made it my life work, my personal Odyssey, to rehabilitate the Tristan Moorhen, to put it back in history.