Fortunately, very few of us ever see diseased or sick birds at our feeders, but it does cause some concern when you do. Don’t worry, though. As long as you keep your feeders and birdbaths clean, this isn’t something you need to worry about. Even more reassuring is that none of the common diseases of backyard birds are passed on to people directly. For example, West Nile virus—a disease that occurs often in the crow family, including jays and magpies—is carried to people by mosquitoes, not by birds. In order for people to get this disease, a mosquito that has bitten a bird with the virus must then bite a human.
Here are the five most common backyard bird diseases that have been studied extensively at the Cornell Lab of Ornithology in Ithaca, New York. To learn more about these diseases, contact the National Wildlife Health Center.
House Finch Disease
Birds infected with this disease (also called mycoplasmal conjunctivitis) appear to have red, swollen, runny or crusty eyes. While some sick birds recover, many die from starvation, exposure or predation. More recent reports indicate that the condition has also spread to the American goldfinch. As birds flock together at feeders, transmission of the disease becomes more likely.
There are two forms of avian pox. In the more common form, wart-like growths appear on the featherless areas of the body, such as around the eye, base of the bill, the legs and feet. In the second form, plaques develop on the mucous membranes of the mouth, throat, trachea and lungs, resulting in impaired breathing and feeding. The virus can be spread by direct contact with infected birds or contaminated feeders, or by ingestion of contaminated food or water.
This is a fungal disease that affects the respiratory system of birds. External symptoms include difficulty in breathing, emaciation and increased thirst. Birds can also have difficulty walking. When their eyes are infected, there may be a white opacity in one or both eyes, accompanied by a discharge. Sick birds becomes infected by the ingestion or inhalation of mold spores from contaminated foods.
This is a relatively common cause of mortality in feeder birds, but the symptoms are not always obvious. Sick birds may appear thin, fluffed up and depressed and may have pasted vents and swollen eyelids. They are often lethargic and easy to approach. Salmonellosis is primarily transmitted by fecal contamination of food and water by birds.
This disease most commonly affects pigeons, doves and the raptors that feed on them. It is characterized by raised lesions in the mouth, esophagus and crop. Infected birds can contaminate birdbaths with their oral secretions, which can in turn expose many other birds to the disease.
What About Bald Birds?
This is one fairly common sight that’s not caused by disease: The most noticeable, sickly-looking birds are northern cardinals and blue jays whose head feathers have fallen out, exposing bare black skin. Bird diseases aren’t to blame here – instead it’s a parasite. The affected birds usually survive and grow back their head feathers in a few weeks.
Help Fight Bird Diseases
- If you find a diseased bird, it’s best to report it to your state or local wildlife agency. If you are asked to take the bird in for an examination, try to catch it by throwing a light towel over it and placing it in a box with airholes.
- If you find a dead bird, place it in a double plastic bag and into the garbage while wearing gloves.
- If sick birds come to your feeder, minimize the risk of infecting other birds by cleaning the area thoroughly. You may need to take down your feeders for a week or so to encourage the sick birds to leave the area first.