During a relatively unproductive banding day on 15 August 2011, I caught this juvenal Chipping Sparrow that suffered from a bad pox infection. Avian pox is a virus that affects many different species of birds. The virus is commonly seen in songbirds. This slow-developing disease comes in three strains (fowl, pigeon, and canary pox virus).
Mosquitos carry the virus, which is also transmitted by contact with other infected birds and by contaminated food or water, particularly at bird feeders. Two forms of the disease exist. The first causes warty growths around eyes, beaks, feet, and unfeathered skin. The second causes growths in the respiratory system. Birds with either form of pox are often weak and starving. This Chipping Sparrow, with its crusty warts and yellowish fluid around its nostrils, appears to show symptoms of both forms of avian pox.
Birds, particularly Wild Turkeys and Bald Eagles, suffer significant mortality from pox. Birds can survive, as apparently did an American Crow reported by The Minnesota Birdnerd blog site. Survivors acquire at least limited immunity from the disease. No treatment is known for avian pox in wild birds. Washing infected areas with antiviral drugs often just spreads the disease. Birds can be saved by wildlife rehabilitation units, but require supportive care and protection from secondary infections. Bird feeding areas should be decontaminated with 10% bleach. Removing infected birds may reduce transmission of the disease but is illegal. Mosquito control is also a possible remedy. Fortunately humans are not known to be susceptible to avian pox infections. People who handle birds should take precautions to avoid spreading the disease between captive birds. This information was gleaned from the National Wildlife Health Center and the Michigan Department of Natural Resources.