This paper examines how the disease commonly known as “House Finch eye disease” affects species other than the House Finch.  The disease is also known as conjunctivitis, and is caused by the bacterium Mycoplasma gallisepticum.   Symptoms of the disease include swollen, crusty eyes – victims frequently become blind and die.  Between 1994 and 1998, participants in Project FeederWatch and the House Finch Disease Survey recorded conjunctivitis in 31 species other than the House Finch.   Most of these cases (75%) were observed in just three species: American Goldfinch, Purple Finch and House Sparrow.  American Goldfinch were more than 7 times as likely to contract the disease in areas where infected House Finch were reported than in areas where only healthy House Finch were found.  Similarly, if infected House Finch populations were in the area, the likelihood of infection was 2.9 times higher in Purple Finches, and 2.4 times higher in House Sparrows.  While nearly 20% of survey locations reported sick House Finch, less than 2% of locations reported sick individuals of the other three species.   The disease is likely transmitted from House Finches to other “secondary host” species via contaminated surfaces at bird feeders, or through direct competition with infected House Finches at feeding stations.  However, at the current levels of infection, the disease is unlikely to significantly impact populations of American Goldfinch, Purple Finch, or House Sparrow.

Barry Hartup and George Kollias of the Cornell College of Veterinary Medicine, and Andre Dhondt, Keila Sydenstricker and Wesley Hochachka of the Cornell Lab of Ornithology, wrote this article.   It was published in the Journal of Wildlife Diseases in 2001.