House Finches with weird-looking eyes are probably afflicted with mycoplasmal conjunctivitis, also known as House Finch Eye Disease. And despite the name, other birds may also become infected with this disease—often other small songbirds like goldfinch or Purple Finch. It is caused by a bacteria called Mycoplasma gallisepticum, a species known to cause respiratory infections in chickens and turkeys.
In early fall, the prevalence of this infection increases dramatically, and sick birds may appear at feeders. From 1994–2008 the Cornell Lab conducted a citizen-science study of House Finch Eye Disease. You can read about what we learned, the disease’s causes and symptoms, and find useful links on Project FeederWatch’s House Finch Eye Disease page. You can also participate in Project Feeder Watch to help track sick finches.
The disease is passed from bird to bird, which means that transmission may happen at bird feeders because they are places where birds congregate. There is also some evidence that feeders can play a direct role in disease transmission, picking up the disease from feeders, so to to be safe, if you notice sick birds, we recommend that you take down your feeders and clean them. To clean your feeder, take it apart and use a dishwasher on a hot setting or hand wash either with soap and boiling water or with a dilute bleach solution (no more than 1 part bleach to 9 parts water). Rinse thoroughly and allow to dry before refilling. Let them dry completely and then re-hang them. Also, rake the ground beneath your feeders to remove old seed and bird droppings.
If more than one bird gets sick from this or any other illness, it’s not a bad idea to close down your feeding station for a couple of weeks to at least encourage the flock to disperse, to minimize the risk of other birds catching it.
Read more in our Living Bird article, House Finch Eye Disease: Outbreak, Then Understanding.
You may also want to contact a local wildlife vet or wildlife rehabililtator for help with sick birds.
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