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.
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.
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?
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.