Cornell Lab of Ornithology

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WINTER 1998/VOLUME 12, NUMER 1

House Finch Disease Survey
Become A Member

House Finch Eye Disease
Heads Steadily West
By André A. Dhondt

Please cite this Page as:
Dhondt, A.A.  1998. House Finch Eye Disease Heads Steadily West.  Birdscope, Volume 12, Number 1:  11-12.

What will happen next with the eye infection
epidemic in House Finches?

Since January 1994, when House Finches with symptoms of an eye disease were first observed at feeders in Washington, D.C., the disease has spread rapidly through the eastern House Finch population. Mycoplasmal conjunctivitis, as the disease is commonly known, is caused by Mycoplasma gallisepticum, a parasitic bacterium previously known to infect only poultry.

The map at right shows that by November 1994, the epidemic had spread mainly north, covering a triangular region between Virginia, southern Ontario, and southern New Hampshire. By November 1995, the disease had spread farther south and southwest, reaching Georgia in the South, Illinois in the Midwest, and Quebec in the North. A year later, it had moved west into Missouri, Iowa, and Minnesota (although the range retracted somewhat in the North). By March 1997, the final line presented on this map, mycoplasmal conjunctivitis had reached the Dakotas and had also been reported in Texas.

Our survey does not track the epidemic well in the Great Plains, because few House Finches have been reported there, and we have few participants in that area.

Because the introduced eastern House Finches have now expanded far enough west to come into contact with the original western House Finch population, it is quite possible that the western birds will also become infected and that Mycoplasma gallisepticum will eventually cover the entire North American House Finch range. Will it? If so, at what rate will the epidemic continue to expand? Will House Finch numbers also decrease in the West?

The map below, based on approximately 28,000 data forms submitted by close to 3,500 participants, is a spectacular example of the power of citizen science. Within months after this new disease was discovered, our volunteer collaborators were reporting data, and they continue to do so three years later.

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Tracking an Epidemic

The map above is the result of complex analyses carried out by Roger Slothower, the Lab's Geographic Information System scientist.  The black dot represents the approximate location where the conjunctivitis in House Finches was first observed in January 1994.

  Using only reports from participants who sent data for at least 16 different months, Roger calculated the approximate extent of the epidemic each November:  The stippled area shows the distribution of conjunctivitis in November 1994, the dotted line delineates the limit of  conjunctivitis in November 1995, and the dashed line represents the limit of conjunctivitis in November  1996.  The solid line uses data from all reports and delineates the full extent of the epidemic known in March 1997.  The crosses are locations with reports of the eye disease that are farther than 200 kilometers away from any other disease report in that month.

These data bring us to our next question of study.  Will Mycoplasma gallisepticum spread farther west and infect the western House Finches?

Because we now know more about the disease, and because the survey is entering a new stage, we are changing the House Finch Disease Survey somewhat. Online FeederWatch participants can participate by submitting electronic House Finch Disease Surveys when they submit their biweekly FeederWatch counts. See http://birds.cornell.edu/HOFI/HOFIdisease.htm for online instructions.

Paper-based FeederWatchers need to request data forms. If you are not yet a participant, call (607) 254-2440 or send e-mail to birdeducation@cornell.edu to sign up. Or, send in the postcard from your FeederWatch kit. This survey is free to FeederWatchers. If you are already a House Finch Disease Survey participant, request new data forms well before you run out. Thanks for your help!

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