Study Surprise: Many Bird Species Exposed to “Eye Disease”
A recent press release from the Cornell Lab of Ornithology explains how the bacteria that causes house finch eye disease is found in many species, and not just feeder birds.
“The results were shocking,” says André Dhondt, director of Bird Population Studies at the Cornell Lab of Ornithology. “More than half the bird species we tested have been exposed to the bacteria responsible for House Finch eye disease.” A paper recently published in the online scientific journal PLOS ONE shows that a bacterial parasite previously thought to infect only a few species of feeder birds is actually infecting a surprisingly wide range of species, though most do not show signs of illness.
“This organism, Mycoplasma gallisepticum, is much more widespread than anyone thought,” Dhondt explains, “although in most species there are no signs of conjunctivitis”
Species testing positive for exposure to the bacteria include feeder favorites such as Black-capped Chickadees, Tufted Titmice, and American Goldfinches. But exposure was also detected in forest species, such as the Wood Thrush.
“That was another surprise,” says Dhondt. “How on earth do Wood Thrushes get infected with mycoplasma? They’re not a feeder bird at all. Everyone has always assumed that feeders play a major role in the transmission of the disease and this study shows that’s not necessarily so.”
Dhondt’s team trapped and tested nearly 2,000 individual birds from 53 species, looking for evidence of current infections (bacterial DNA) or past infections (antibodies) by Mycoplasma gallisepticum. The birds were trapped in and around Ithaca, New York, between January 2007 and June 2010. The diagnostic tests revealed that 27 species of birds were infected by this bacterium. The actual number of species exposed to the bacteria could be even higher than suggested by this study because the test for antibodies is known to produce false negatives.
House Finch eye disease first appeared in North America in 1994 when people watching backyard feeders started seeing birds with swollen, runny eyes. Dhondt says that a strain of the bacteria, usually found in poultry, was able to grow successfully in House Finches. The House Finch lineage of the bacteria has been mutating since it was first detected.
“The organism could mutate into a form that is much more virulent among other bird species and create a new epidemic,” noted Dhondt, who added that while we know that many species of songbirds are exposed to Mycoplasma gallisepticum, we still do not know whether the bacteria in other species of songbirds are identical to that living in House Finches in the same area.
While many species of songbirds can be infected by this bacterium, only House Finches regularly exhibit swollen eyes as a result of infections, and citizen-science participants in the Cornell Lab’s Project FeederWatch are still tracking the occurrence of disease in these finches. The take-home message for people who feed backyard birds remains the same: keep the feeders clean. If you see sick birds, leave them alone, take down the feeders and clean them, being sure to wash your hands thoroughly afterward.
The paper, Diverse Wild Bird Host range of Mycoplasma gallisepticum in eastern North America, is co-authored by André Dhondt, Jonathan C. DeCoste, and Wesley M. Hochachka from the Cornell Lab of Ornithology and David H. Ley, North Carolina State University.
The work described in this paper is part of a larger collaborative research project that has received funding from both the NSF and NIH through their initiative to study the Ecology and Evolution of Infectious Diseases.
15 comments on “Study Surprise: Many Bird Species Exposed to “Eye Disease””
We have read several previous postings from a Florida list-serve (BRDBRAIN) with articles regarding this avian eye disease (sometimes referred to as “avian pox”). We had thought it only affected House Finches, but about 5-6 weeks ago we noticed a Brown Thrasher in our yard in Sarasota, Florida which appears to have this disease on its left eye. On reading this post and the PLOS ONE article, it is disturbing to learn of the many types and large number of birds affected by this disease. We do keep our feeders clean and were surprised when we noticed this thrasher. One afternoon we saw it with another Brown Thrasher which did not have the disease. We have never seen it come directly to any of our feeders and it seems to eat only what falls on the ground below the feeders. We have been watching other backyard birds that also pick up food from the ground (mostly Northern Cardinals and Mourning Doves) and haven’t noticed any of them with any eye disease, at least not yet anyway and we hope it stays that way.
I have kept a feeder during the winter months here in Anchorage, Alaska for years and maintained it through the summer for the first time this year. I have been watching a Steller’s jay with feather loss around the eyes which has progressed to dark encrusted patches. My impulse was to make sure he was well fed to help him heal, but I now see I was only exposing other birds to the infection. These jays tend to winter over here, so I will have to watch for signs in other birds when I re-install the feeder.
Large population of house finches at backyard feeders exhibit signs of diseased eyes or infection which indicate partial or complete blindness. The have difficulty flying and trying to land. The location is East Texas in the town of Nacogdoches.
We have been viewing birds at our backyard feeders for 10 or more years. The bird behavior re: eye disease in finches. House Finches in particular are scrappy birds. They peck at the eyes of anything that is near them. They also feed on the ground under bushes that other birds roost in. They also feed from compost piles. If you test for bacteria in all these areas you will find it is present. The most common birds that feed with the House Finches is Chickadees and Gold Finches. We haven’t seen the eye disease in these birds here in Victoria but have seen them pecked at by the House Finches. Perhaps this is why they also get the eye disease.
We have only one tray feeder. The finches don’t feed from it. The other feeders we have are dispenser types or in the case of Niger Seed we use a wire mesh feeder, the birds don’t mess on the seed with these types. We have noticed that all birds that feed at all our feeders are quite precise. They don’t contact the feeder surface, any contaminated seed would be from the mouth of other feeding birds. We are certain washing our feeders unless they show signs of contamination is not necessary.
We are sure the eye disease has been around for thousands of years just like Pink Eye in humans (spread in the same manner) and the increased observance of the eye disease is most likely because sick birds stay around where food is easily available given their disability. This is natural selection and normal. In our area there is no shortage of House Finches.
Your research adds validity to what we have observed. We spend an average of 20 hours per week observing bird behaviour in our back yard over the past 10 years. We are constantly formulizing different scenarios for bird behavior. Quite a few don’t fit with published data.
Thanks, Ray & Connie.
I haven’t seen any rose breasted nut hatches in a year. Wondering where they went? I live in Ann Arbor, Michigan
What has happened to the Rosebreasted nuthatches in Lower Michigan? I haven’t seen any for almost a year. Are they in trouble, or am I doing something different that I’m not aware of, as far as feeding.
I feed suet to several different types of wood peckers, nut hatches & tufted titmouse’s.love to watch them in the morning while drinking coffee. All different types of birds try to eat it but can’t hang on to the tree. Bill McKinley
We have quite a few Brown Thrashers that come to feed from our suet feeder (hanging 12 feet above ground, cleaned regularly) and one seems to have this problem.
I put a picture of it on my e-bird observation
I live about 25 minutes north of Seattle, WA and photographed a Steller Jay (Cyanocitta stelleri) today that has very swollen eyes and missing feathers around them on both sides. Does anyone know if this disease has been seen in jays here? Where is the best place to submit a photo? Thanks!
Hi Renee, I’m not sure if we have any data on jays with House Finch eye disease, but there are also some other diseases with similar symptoms. If you’re a participant in FeederWatch, the best place to submit your photo is in our Sick Birds gallery, which can be found at the bottom on Your Data homepage. If you’re not a FeederWatch participant, you can submit the photo to our Participant Photos Gallery, where you can submit as a guest. You are also welcome to email us about this at feederwatch.org.
I have been observing birds for years but this is the first winter I have set up feeders which are only about 5′ from my window. I try to follow guidelines about feeder hygiene. The birds are so close it is easy to spot eye disease. In the past month I have seen with disease: one Purple Finch, two Gold Finch (unilateral), and one Cardinal (unilateral).
These diseased birds are nearly daily visitors. The Cardinal’s has progressed from just closure to a visible slit beneath which is red tissue. Otherwise he appears healthy. One of the affected Goldfinch went from lethargy to near normal function.
I will attempt photos but the screen distorts the image.
I have seen a brown thrasher with swollen yellow bumps between both eyes and the beak. What could it be? We live in eastern NC.
An additional 2 brown thrashers with this condition, which we suspect is avian pox, were reported to me by a bird enthusiast in Farmville, NC (also in the coastal plain). The number of reports in this species on this blog and elsewhere seems concerning.
I have a brown thrasher that will eat suet out of my hand- certainly not normal behavior. When feeding it, I noticed its swollen eye. I’m in Georgia (where the brown thrasher is our state bird.)