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House Finch mystery solved

This male House Finch has an eye disease caused by a bacterium known as Mycoplasma gallisepticum. Photo by Dan Arndt (Creative Commons)

Scientists have reconstructed how a bacterium that affects domestic poultry jumped to wild birds and then morphed to cause a disease that has killed at least half of the House Finches in eastern North America.

The bacterium, known as Mycoplasma gallisepticum (MG), causes respiratory disease and sinusitis in pigeons as well as domestic turkeys and chickens. It turned up in House Finches near Baltimore around 1994. Within two years, it had infected finches in every state east of the Mississippi; by 2004, it had reached the West Coast.

MG causes the eyelid on one or both eyes to become red and swollen; sick finches often linger around bird feeders and are easy targets for predators.

According to Wesley Hochachka, assistant director of Bird Population Studies at the Cornell Lab of Ornithology, and a team of researchers from Cornell, Princeton, Virginia Tech, and North Carolina State universities, MG has jumped repeatedly between poultry and House Finches, but only a single lineage has evolved and persisted in finches. Birds in western states are infected with the same strain that infects eastern finches.

“All the lineages of bacteria that have successfully spread in House Finches can be traced back to a single progenitor,” Hochachka says. “The descendants from this progenitor traveled from east to west across North America and adapted to changing conditions by becoming either more or less virulent.”


The researchers reported their findings in the September issue of Proceedings of the Royal Society B, a journal of the national academy of science in the United Kingdom.

Wildlife rehabilitators stress that the condition caused by MG is treatable; the infection clears rapidly with the administration of appropriate antibiotics. To prevent the spread of the disease, clean your feeders regularly. Use a solution of 10 parts water to 1 part bleach, and make sure you have enough feeders in your yard to prevent overcrowding.

Step-by-step instructions for how to clean your bird feeder.


Learn more about the disease from the Cornell Lab of Ornithology.

Read the abstract

Wesley M. Hochachka, André A. Dhondt, Andrew Dobson, Dana M. Hawley, David H. Ley and Irby J. Lovette, 2013, Multiple host transfers, but only one successful lineage in a continent-spanning emergent pathogen, Proceedings of the Royal Society B, 7 September 2013, vol. 280 no. 1766, doi: 10.1098/rspb.2013.1068. Abstract.

A version of this article appeared in the October 2013 issue of BirdWatching magazine.

Originally Published

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