Sick Birds and Bird Diseases

Birds infected with House Finch eye disease (also called Mycoplasmal conjunctivitis) have red, swollen, runny, or crusty eyes. In extreme cases the eyes become swollen shut and the bird becomes blind. House Finch eye disease is caused by the bacterium Mycoplasma gallisepticum. This bacterium has long been known as a pathogen of domestic turkeys and chickens, but it has been observed in House Finches since 1994. The disease has affected several other species, including American Goldfinch, Evening Grosbeak, and Purple Finch. Learn more about House Finch eye disease.

Two forms of avian pox exist. In the more common form, wart-like growths appear on the featherless areas of the body, such as around the eye, the base of the bill, and on the legs and feet. In the second form, plaques develop on the mucous membrane of the mouth, throat, trachea, and lungs, resulting in impaired breathing and difficulty feeding.

Avian pox can be caused by several strains of the pox virus and has been reported in at least 60 species of birds, including turkeys, hawks, owls, and sparrows. The virus can be spread by direct contact with infected birds or contaminated surfaces (e.g., feeders) or by ingestion of contaminated food or water.

Avian influenza is an influenza virus that occurs naturally in wild aquatic birds, including ducks, geese, and gulls. Mild forms of avian influenza (known as low pathogenic avian influenza, or LPAI) are routinely found in wild birds and don’t cause serious illness. From time to time, a mild strain changes through mutation or mixing with other flu viruses into a more severe type of the virus (highly pathogenic avian influenza, or HPAI). These HPAI can wreak havoc on wild bird populations. Symptoms of avian influenza vary depending on the strain of virus and bird species. Learn more about any current HPAI outbreaks on the Cornell Lab’s website.

Salmonellosis is caused by bacteria belonging to the genus Salmonella. It is a common cause of mortality in feeder birds, but the symptoms are not always obvious. Sick birds may appear thin or fat and fluffed up and may have swollen eyelids. They are often lethargic and easy to approach. Some infected birds may show no outward symptoms but are carriers of the disease and can spread the infection to other birds.

Salmonellosis is primarily transmitted by fecal contamination of food and water by sick birds, though it also can be transmitted by bird-to-bird contact. Occasionally, outbreaks of the disease cause significant mortality in certain species including Pine Siskin, Redpoll, and American Goldfinch.

Learn more about salmonellosis on the Cornell College of Veterinary Medicine website, including a PDF fact sheet you can download.