Care and Safety
House Finch Eye Disease
A finch with one eye swollen shut, clinging to a feeder port long after the other birds have left, is the classic presentation. The feeder itself is how it spread.
The short answer
- House finch eye disease is mycoplasmal conjunctivitis, caused by the bacterium Mycoplasma gallisepticum. Look for crusty, swollen, watery or fully closed eyes.
- It hits house finches hardest, with goldfinches and purple finches also affected. Most other feeder birds are largely unaffected.
- Tube feeder ports are the main transmission point, because infected birds press their faces against the plastic and leave the bacterium behind.
- Take feeders down for one to two weeks, disinfect thoroughly, then consider a design with less face to surface contact.
- Affected birds are not blind from the infection itself, but a bird that cannot see well starves or gets caught. Many do not recover.
A house finch with one or both eyes crusted, swollen and weeping, sometimes swollen fully shut, has mycoplasmal conjunctivitis. It is caused by the bacterium Mycoplasma gallisepticum, and it has been part of North American backyard bird feeding since it jumped into wild house finches (Haemorhous mexicanus) in the mid-1990s and spread across the continent.
The birds are usually easy to spot because they behave differently. An affected finch sits at a feeder port far longer than a healthy bird, moves slowly, does not react to your approach, and often stays on the feeder when the rest of the flock scatters. It is trying to feed with limited vision.
What follows is how to recognize it, why tube feeder ports specifically drive transmission, what to do with your feeders, and which design changes actually reduce the risk. There is no home treatment, and that part is not a judgment call.
What the disease looks like#
The signs are concentrated in the face, which distinguishes this from the general lethargy of salmonella at feeders.
| Sign | Detail |
|---|---|
| Swollen eyelids | Red, puffed tissue around one or both eyes |
| Crusting | Dried discharge gluing the lids partly or fully closed |
| Watery discharge | Wet, matted feathers below the eye |
| Cloudy eye surface | The eye looks dull or filmed over |
| Behavior | Sits long at a port, slow to react, stays when the flock flushes |
| Species | Overwhelmingly house finches; also goldfinches and purple finches |
Not every eye problem is this disease. Birds get eye injuries from collisions and fights, and a single bird with one damaged eye and otherwise normal behavior is more likely hurt than infected. What points to mycoplasma is bilateral swelling, crusting rather than a wound, and more than one bird showing it.
One clear case is enough to act on
You do not need a confirmed diagnosis or a second sick bird. Mycoplasma spreads by direct contact at shared surfaces, so an affected finch feeding at your tube today is depositing bacteria that other finches will press their faces into tomorrow. Take the feeders down the day you see it.
Why tube feeders are the transmission point#
The mechanism is unusually specific. Mycoplasma gallisepticum lives in the eye, sinus and respiratory tissue, and it spreads when an infected bird's face touches something another bird's face will touch.
A tube feeder port is exactly that surface. A finch reaching seed through a small opening presses its face and eye region against the plastic collar, then the next bird does the same at the same port a minute later. Finches feed in flocks and take turns at a handful of ports, so a single infected bird can contaminate every port on the feeder in an hour.
This is why house finch eye disease is thought of as a feeder disease in a way that many other bird illnesses are not. The birds would still contact each other in the wild, but not dozens of times an hour at six fixed points.
Nyjer feeders carry the same problem for goldfinches, and mesh socks are worse than tubes because the bird's whole face works into the fabric and the fabric cannot be disinfected.
What to do when you see an affected bird#
- Take down all seed feeders and the bird bath for one to two weeks. A shared water source spreads it too.
- Bag the seed for the trash rather than returning it to storage.
- Rake up spilled seed and hulls below each feeder.
- Scrub, disinfect, rinse and dry every feeder using the full method in how to clean a bird feeder: hot soapy water first, then a 10 minute soak in 1 part household bleach to 9 parts water, then a thorough rinse and complete drying.
- Discard mesh nyjer socks. They cannot be cleaned.
- Wipe the poles, hooks and perches birds land on with the same solution.
- Tell your neighbors. Finch flocks move between yards all day, so a single yard shutting down accomplishes less than a street doing it.
One to two weeks is the standard interval. It is not a magic number; it is long enough for the flock to disperse to other food and for any bacteria left on surfaces to die off. If you are still finding affected birds when you rehang, take everything down again for a longer period.
Why not just leave the feeders up and clean often
Cleaning a feeder every week does nothing about the eight hours of finch traffic between cleanings. The bacterium moves bird to surface to bird within minutes, not weeks. Removing the shared surface entirely, for long enough that the flock breaks up and spreads out, is the only intervention that interrupts the cycle.
Feeder designs that reduce face contact#
When you rehang, the design change is worth making. The goal is less pressing of faces against a fixed surface that many birds share.
| Design | Face contact | Comment |
|---|---|---|
| Mesh nyjer sock | Very high | Whole face works into fabric; cannot be disinfected |
| Small-port nyjer tube | High | Bird presses into the port collar to reach seed |
| Standard sunflower tube | High | The classic transmission point |
| Tube with a wider port opening | Moderate | Bird reaches in rather than pressing against the rim |
| Hopper feeder | Lower | Bird stands on a sill and takes seed from an open trough |
| Platform or tray feeder | Lowest for faces | But birds stand in the food, which raises the fecal route |
There is no design that is safe on every axis. Open trays reduce eye to plastic contact but let droppings fall directly into the seed, which is the transmission route for salmonella. The practical compromise for a yard with a heavy finch flock is more feeders, spaced further apart, holding less seed each, cleaned more often. Spacing guidance is in how many feeders and how far apart.
Metal port collars help slightly for a different reason: smooth metal is easier to disinfect than scratched, chewed plastic, and scratched plastic holds organic residue that shields bacteria from bleach.
Do not treat wild birds#
This comes up every time and the answer does not change. Do not catch the bird to wipe its eyes, do not buy poultry antibiotics, and above all do not put medication in the feeder or the water.
Dosing a wild flock delivers uncontrolled amounts to birds that may not be infected, does not clear the infection reliably in birds that are, and contributes to antibiotic resistance in a bacterium that also matters to commercial poultry. It is also unlawful in many circumstances, because most native songbirds are federally protected and possession requires a permit.
If a finch is so badly affected that it cannot feed or fly, the right call is a licensed wildlife rehabilitator, reached through your state wildlife agency or a local Audubon chapter. The full triage sequence is in there is a sick bird at my feeder.
Report what you see
Project FeederWatch has tracked house finch eye disease through volunteer feeder observations since the outbreak began, and that reporting is how the spread was mapped in the first place. If you already count birds, note the affected ones. It costs you nothing and the data is genuinely used.
What to expect afterward#
House finch eye disease is now endemic across most of the continent rather than a single passing epidemic. Local flare-ups come and go, often peaking in late fall and winter when finches concentrate at feeders. Seeing it once does not mean your yard is permanently compromised.
Populations have adapted somewhat over the decades since the outbreak began, and severity varies year to year and place to place. What has not changed is the mechanism: crowded birds at shared ports. Any season where you have a large house finch or purple finch flock is a season to clean more often than you think you need to.
A finch-safe setup#
- Two or three smaller feeders spread at least 10 feet (3 m) apart rather than one busy tube.
- Ports with metal collars, on a feeder that dismantles without tools.
- Enough seed for three or four days, not a full week, so nothing sits and spoils.
- A weekly clean during finch-heavy months, using the schedule logic in how often to clean bird feeders.
- No mesh socks if you have had eye disease in the yard.
- A bird bath scrubbed and refilled every day or two, not topped up.
- Feeders positioned so ground-feeding birds are not standing in the fallout, which is also the fix for seed mess and hulls.
If you want the finches without the tube, the feeding approach that works best for them is set out in how to attract house and purple finches.
Frequently asked questions#
What causes house finch eye disease?
A bacterium called Mycoplasma gallisepticum, which was already known as a poultry pathogen before it appeared in wild house finches in the eastern United States in the mid-1990s. It spread west across the continent over the following years and is now found in house finch populations across much of North America. The disease it causes is properly called mycoplasmal conjunctivitis.
Can house finch eye disease spread to other birds?
American goldfinches and purple finches are regularly affected, and the bacterium has been recorded in a number of other species. House finches remain by far the most commonly and most severely affected bird at feeders. Chickadees, titmice, nuthatches and woodpeckers are not typical victims.
Should I take my feeders down if I see a finch with swollen eyes?
Yes, take them down for one to two weeks, clean and disinfect everything, and rake up the spilled seed underneath. This breaks the cycle of birds repeatedly contaminating the same feeding ports. If you are seeing several affected birds, leave the feeders down longer and consider whether your feeder design is concentrating face contact.
Can house finch eye disease infect humans?
There is no evidence that Mycoplasma gallisepticum causes disease in people. It is a serious pathogen of poultry, so anyone who keeps chickens or turkeys should treat contaminated feeders as a real risk to the flock. Wear gloves and wash your hands when cleaning feeders regardless, because other feeder organisms including salmonella do infect people.
Do birds recover from house finch eye disease?
Some do. Birds with mild infections can clear them and survive, and the bacterium does not kill directly. The usual cause of death is indirect: a bird that cannot see well fails to find food, cannot avoid a hawk or a cat, and does not last long in winter. Severely affected birds rarely survive in the wild.
Can I treat a finch with eye disease myself?
No. Do not attempt to catch, medicate or put antibiotics in the feeder. Dosing wild birds is ineffective, illegal in many contexts, and helps drive antibiotic resistance. If a bird is clearly unable to function, contact a licensed wildlife rehabilitator through your state wildlife agency and follow their advice.