House Finch Eye Disease (5 Frequently Asked Questions)

Sometime around 1940, little birds known as House Finches were transported from their native homes in the des­erts and grasslands of west­ern North America to New York City, where they were sold in pet shops under the name “Hollywood Finches.” This bustling illegal bird trade was eventually shut down when a concerned birdwatcher saw what was happening and reported it to the Audubon Society.

house finch eye disease

To avoid being busted by federal wildlife officials, a couple of pet shop owners released their trafficked House Finches into the wild. Because of the brutal New York winters, some of the birds that were released ended up dying. But a small group of about 50 finches survived and spread to surrounding states.

The eastern House Finch population expanded rapidly from there, and within three decades, these plucky little birds were so widespread that they became one of the most common songbirds in the United States.

And that’s when their real trouble began. 

How Did House Finch Eye Disease Start?

In 1994, the volunteers working for Cornell Lab of Ornithology’s Project FeederWatch started seeing reports of sick House Finches from birdwatchers in Washington D.C., and Maryland.  Project FeederWatch is an annual survey operated by the Cornell Lab of Ornithology and Birds Canada. Survey data comes from backyard birdwatchers and other citizen scientists who submit information about the types of birds they see in their communities.

house finch eye disease

The 1994 reports described House Finches with swollen eyes and odd feeder behavior. Scientists conducted lab tests and determined that the House Finches were experiencing conjunctivitis caused by the bacteria Mycoplasma gallisepticum. At one time, this bacterium, also known as M. gallisepticum, only affected domesticated poultry, like chicken and turkeys. But somehow, avian mycoplasmosis had evolved and started causing infection in songbirds like House Finches.

This new infection, called Mycoplasmal conjunctivitis, House Finch conjunctivitis, or House Finch eye disease, spread rapidly throughout the eastern House Finch population. In less than one year, it was in Ontario to the north, Virginia to the south, and Ohio to the west. From there, it has since spread throughout most of the House Finch range.

Which Birds Get House Finch Eye Disease?

House Finch eye disease primarily affects House Finches, but it has also been seen in other songbird species, including the American Goldfinch, Evening Grosbeak, House Sparrow, Pine Grosbeak, and Purple Finch.

What Does House Finch Eye Disease Look Like?

house finch eye disease

Not every bird with House Finch eye disease will look the same, but most birds will exhibit one or more clinical symptoms. The most common symptoms include ocular and nasal discharge, swollen eyelids, and swollen conjunctiva. Conjunctiva is a thin mucous membrane on the front of the eyeball and the inner surface of the eyelids.

As the disease progresses, crusts can form around the eyes, and the eyes can even swell shut. Birds may lose weight or have a ruffled, mangy appearance. They may also try to get relief by rubbing their eyes against branches, feeders, or other objects.

What Happens to Birds with House Finch Eye Disease?

Some birds with House Finch eye disease will recover and go on to live normal lives, but others may not be so lucky. Birds who have trouble seeing have trouble flying. They can also have trouble finding feeders, foraging for food, or evading predators. In extreme circumstances, birds can die from starvation or exposure.

Can House Finch Eye Disease Be Prevented?

House Finch eye disease is spread through bird-to-bird contact and surfaces contaminated with feces and ocular discharge. Some researchers believe it can also be passed in the air through respiratory droplets. House Finch eye disease cannot be transmitted to humans or non-avian pets (like cats or dogs).

Initially, some organizations suggested that birdwatchers temporarily stop feeding sick birds to prevent the spread of the disease. However, it is now believed that doing so could make the problem worse since sick birds will travel to other feeding stations in other backyards and take the disease with them.

According to many organizations, including the Cornell Lab of Ornithology and the National Audubon Society, the best way to prevent the spread of House Finch eye disease, as well as other infectious diseases, is to regularly wash bird feeders and bird baths with soapy water and a ten percent bleach solution (made with 9 parts water and one part bleach). It is also a good idea to use feeders with non-porous surfaces because they are easy to wash.

This post was written by Anna Champagne. You can learn more about her at Champagne Outdoors.

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5 Comments

  1. Avian conjuctivitis and avian salmonellosis are 2 feeder-driven epizootic disease that are highly transmissable from bird to bird and result in significant mortality rates in backyard birds every season of the year. Keeping feeders clean and sanitized is important, but the existence of these avian diseases proves that birds can be sickened by bacteria-laced droppings they’re exposed to in between cleanings. And, the birds most often afflicted by these highly transmissable avian diseases and pathogens are the finches you noted in your article, which are among backyard birder’s favorite birds. Backyard birding is a lot like fishing, and it’s fun. But, to say the least, it is not without it’s continous serious health threats to garden birds. Birds gather in mass at feeders making the threat of the spread of disease even worse across species.

  2. Thank you for the informative article, Lady Anna. It’s sad to see another species and wildlife ecosystem suffering due to inappropriate human interaction.

    I moved here to Emery County, Utah a few months ago, and discovered a love for birdwatching. There is a large and healthy population of House Finches here. I don’t even have to leave my apartment—they visit the two black locust trees just outside my bedroom window every day(as well as several other species).

    They are beautiful little birds, with sweet songs. I can understand why they would be viewed as profitable in the pet market. Sadly, it almost never works out well for the species or ecosystem involved when when animals are intentionally or unintentionally thrown into a new location. 😔

  3. It’s sad to see another tragic wildlife issue resulting from humans doing their usual. I just moved to this area(Emery County, Utah) a few months ago, and discovered a love for birdwatching.

    There is a large and healthy population of House Finches here. I don’t even have to leave my apartment to watch them—they visit the two black locust trees outside my bedroom window every day. They are such beautiful little birds, with sweet songs. I can understand why they would be viewed as profitable by pet sellers. But it rarely works out well for wildlife ecosystems when new species are intentionally or unintentionally thrown in.

    Thank you for the informative article, Lady Anna.

  4. Just another feeder-driven epizootic disease that is easily spread from bird to bird when they are exposed to feeder surfaces that are covered in bacteria-laced droppings. As you mentioned, it has been documented that other finches, besides house finches are affected by the disease. Birds gather in mass at feeders, especially finches, and when they’re exposed to contaminated droppings on feeder surfaces by being able to perch directly on them this opens the door wide for these diseases like Conjunctivitis and Salmonellosis to spread like wildfire in their populations. Keeping feeders clean and periodically sanitized is important, but it’s no silver bullet when birds are exposed to bacteria-laced droppings on feeder surfaces in between cleanings.