One hundred and eighty-five years ago today His Majesty’s Ship Beagle weighed anchor in what is now known as Tagus Cove. She had arrived in the early evening of 30 September and Charles Darwin had spent the day ashore exploring the remarkable volcanic landscape of the island of Albemarle in the west of the Galapagos; there he also saw his first Land Iguanas.
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| Flightless Cormorant Drying its short, sparse wing feathers |
The waters and shoreline of Tagus Cove on the west coast of what Ecuador renamed Isabela was, when we were there in 2012 a good place to see Flightless Cormorants along with Galapagos Penguins, other birds and the ubiquitous Marine Iguana. Many tourists, even wildlife groups, do not see the cormorants because they live only on the northern half Isabela and the adjacent island of Fernandina (Narborough in Darwin’s day) to the west, and the shorter tours do not go to the landings where tourists are permitted on the west coast of Isabela.
The Flightless Cormorant is the largest cormorant and as can be seen from the photographs and video I made to show just this species, the wings are short with the feathers also reduced in size and number. It is very easy to see how flightlessness could have developed relatively recently; food inshore is abundant; there were no land predators until the arrival of feral dogs and cats; long feathery wings inhibit progress beneath the water. Under these circumstances, flight and the adaptations that go with flight would de disadvantageous. In Tagus Cove we were able to see two sea birds, one, a penguin, which became flightless over 50 million years ago, that uses its wings as flippers to ‘fly’ underwater, the other, a cormorant, which had a flying ancestor 2 million years ago, that uses its feet for propulsion.
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| For comparison, a Great Cormorant (Phalacrocorax carbo) João Manuel Lemos Lima on Wikimedia |
It is not surprising that the Flightless Cormorant attracted the attention of comparative anatomists in the 19th and early 20th centuries, and now lends itself to genomic studies that try to determine the changes entailed by flightlessness, that, of course extend beyond the wing itself, in simple structural terms, to the size of the keel of the breastbone and the size of the muscles powering flight. Hans Gadow described the basic differences in 1902. In 1915 there followed a detailed description of the bones of the Flightless Cormorant in the Australian ornithological journal, Emu. It was written by an American surgeon and osteologist who appears to have been, even by the standards of the time, an odious character. Robert Wilson Shufeldt (1850-1934) achieved notoriety over his behaviour towards his second wife, the grand-daughter of John James Audubon. The whole story of how it all came to a judgement by the Supreme Court of the U.S.A. is described here. He also the author of books that promoted anti-black racial policies in that country. There is no doubt that in 2020’s parlance he would be ‘cancelled’. However, he came to the conclusion that the Flightless Cormorant really was that, a cormorant sharing common ancestry with other living cormorants. He implied that the special genus erected for this one species, Nannopterum, was unnecessary. That conclusion, based on comparative morphology, was supported around a hundred years later by molecular phylogenetic analyses, such that our bird is usually now called Phalacrocorax harrisi. It shares a common ancestry with two extant species of the mainland americas, Double-crested Cormorant, P. auritus and the Neotropic Cormorant, P. brasilianus.
The Flightless Cormorant is found within 200 metres of the shore. Even the populations from Isabela and Fernandina, only 5 km apart at their nearest, are genetically distinct, so there is little mixing between populations, even along the shores of Isabela.
Like many of the animals of the Galapagos, Flightless Cormorants are fearless. None of us noticed for a while that one jumped onto the back of our inflatable panga and sat there ignoring the human passengers. The only reason I do not have a photograph is that it sat too near for the camera to focus. We can hardly be surprised that as recounted in my last post, Lord Moyne caught one and brought it back to London Zoo in 1932.
The population is said to fluctuate, like that of the Marine Iguana, with the El Niño-
Southern Oscillation. Once classified as ‘Endangered’, it is, with more recent estimates of population, classified by IUCN as ‘Vulnerable’. The survival of such a bird with a limited range in a specific and special habitat depends, of course, on avoiding an environmental catastrophe. If that catastrophe were to happen then we really would be in trouble.
Burga A, Wang W, Ben-David E, Wolf PC, Ramey, AM, Verdugo C., Lyons K, Parker PG, Kruglyak L. 2017. A genetic signature of the evolution of loss of flight in the Galapagos cormorant. Science 356 DOI: 10.1126/science.aal3345
Duffie CV, Glenn TC, Vargas FH, Parker PG. 2009. Genetic structure within and between island populations of the flightless cormorant (Phalacrocorax harrisi). Molecular Ecology 18, 2103-2111. https://doi.org/10.1111/j.1365-294X.2009.04179.x
Kennedy M, Valle CA, Spencer HG. 2009. The phylogenetic position of the Galápagos Cormorant. Molecular Phylogenetics and Evolution 53, 94-98. doi:10.1016/j.ympev.2009.06.002
Shufeldt RW. 1915. Comparative Osteology of Harris’s Flightless Cormorant (Nannopterum harrisi). Emu 15, 86-114.
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