Why can’t the Galapagos Island cormorant fly?

There is a bird species of cormorant on the Galápagos Islands that cannot fly. It is the only cormorant species in the world that has lost its ability to fly. Why?

Emus and ostriches cannot fly. They are very large birds. The Galápagos Islands cormorant is not a very large bird.

Scientists have found the genes that are present in birds, mammals and most animals, that may have the answer. The genes are called C. elegans.

The genes affect bone growth. In birds, a mutation (change) of the genes cause a weaker breastbone and smaller wings, which are not effective for flying. Scientists think that the mutation of the genes in Galápagos Islands cormorants occurred about two million years ago.

Galapagos Island cormorant

Galápagos Islands cormorant

Other flightless birds, such as ostriches and kiwis, do not have close relatives among flying birds, because their split from flying birds occurred 50 million years ago or more. However, the Galápagos cormorants are closely related to the common birds, the neo-tropical cormorants and the double-crested cormorants.

Alejandro Burga, a scientist, and Leonid Kruglyak, the chairman of human genetics, at the University of California, Los Angeles (UCLA), analyzed the DNA of the Galápagos Islands comorants and other cormorants with his colleagues. Patricia Parker, a behavioral ecologist at the University of Missouri in St. Louis, studies bird diseases in the Galápagos Islands, and she provided tissue samples for DNA of the flightless cormorants. “She had in her freezer over 200 samples of this bird,” Dr. Burga said.

When the UCLA researchers analyzed the DNA they found a gene called Cux1 and some other genes that were involved in the growth of cilia. Cilia is whip-like structures on the surface of cells that help the movement of single-celled animals. But in birds and humans cilia functions like antennas that pick up biochemical signals for bone growth.

Mutations in Cux1 in humans can cause terrible diseases, called ciliopathies. In cormorants, however, mutations in Cux1 seems to prematurely stop bone growth in the wings, resulting in the loss of flight.

This study doesn’t prove that the scientists have the right genes, but it may be further supporting evidence of the work that British scientist Charles Darwin (1809-1882) conducted when he visited the Galápagos Islands on his explorations across the world from 1831-1836 in his ship, the Beagle.

Charles Darwin did not mention the Galápagos cormorants in his 1839 book called ‘’Journal of Researches’’ which was published in 1905 as “The Voyage of the Beagle.” Darwin may never have seen the flightless cormorants on the Galápagos Islands, because they are found on only two islands in the Galápagos.

This study was published in Science on 1 June 2017.

 

 

Photographer: Caroline Duffie Judy

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