House Finch Eye Disease
Potentially Lethal and Spreading to Other Bird Species
Caused by a pathogen common in turkeys and chickens, this contagious disease has killed millions of birds in North American. Scientists need help monitoring its spread.
Based on data from the National Audubon’s Year 2000 Christmas Bird Count, researchers at the Cornell Lab of Ornithology determined that between 180-300 million house finches died from mycoplasmal conjunctivitis, a bacterial disease commonly known as house finch disease, or house finch eye disease.
Though primarily a respiratory illness, the most noticeable symptom of mycoplasmal conjunctivitis is red, swollen eyes that may be runny or crusted over. The bird may be so infected that it is totally blind and unable to care for itself. Bird watchers may also notice that infected birds are lethargic, do not fly off with the flock, and do not feed. The infection is probably very uncomfortable as diseased birds are often seen repeatedly wiping their faces on branches and feeders.
Spread across the continent
This contagious disease was first identified in house finch populations in Maryland and Virginia in 1993. According to an article by David Ley, in the September 2005 issue of Journal of Wildlife Diseases, house finch disease spread throughout the eastern range of the bird (from Quebec to Florida) in only three years. By 2004 the epidemic had spread across the continent to the Pacific coast.
Spreading to other species
Initially reported only in house finch populations, the disease has recently been reported in other members of the finch (fringillidae) family, such as goldfinches, purple finches, evening grosbeaks, pine grosbeaks, dark-eyed juncos and house sparrows, and some non-finch species such as blue jays, and black-capped chickadees.
Disease Milder in Other Species and Western House Finches
Though the disease has spread across North America and to other species, the die-off is not as dramatic as it was among the eastern populations. According to Audubon, this may be because eastern house finch populations are not native to the Atlantic coast. The birds originally came from the southwest. They were introduced in the east in during the 1940’s by pet shop owners who released them when new laws made it illegal to sell wild birds. Since a relatively small number of birds were released, inevitable inbreeding occurred resulting in a limited gene pool which may have made the birds more susceptible to disease.
Disease being Tracked
Volunteer observers have been helping The Cornell Lab of Ornithology track the spread of house finch disease since the mid-90’s. Anyone in the US or Canada with a backyard bird feeder is invited to participate. Information on how to identify finches, what symptoms to look for, and how to report observations can be found on the Cornell Lab web site, House Finch Disease Survey.
Participating in the survey takes only a few minutes on a semi-regular basis over the course of a year. Participation is free, and participants receive a year’s subscription to Birdscope, the Cornell Lab’s informative newsletter.
The Lab encourages participation, even if the birdwatcher has never seen a sick bird at the feeder. By studying observations of both healthy and diseased birds from thousands of birdwatchers across North America, the researchers can piece together a picture of the prevalence and geographic range of this and other avian diseases.
