https://www.allaboutbirds.org/news/analysis-do-bird-feeders-help-or-hurt-birds/
by Bren Lundborg, Wildlife Keeper
Bird feeding is a popular and enjoyable winter pastime for many people, bringing birds in close for easy viewing. While it is widely practiced and can even help biologists monitor populations through programs such as Project FeederWatch (https://feederwatch.org/), there are some potential negative side effects of feeding birds. However, these can be minimized by good feeder cleaning practices and keeping a close eye on the birds at your feeders.
The Importance of Cleaning
There are four avian diseases that tend to be common at bird feeders: Salmonellosis, Avian Pox, Finch Eye Disease, and Trichomoniasis. All can be transmitted by direct contact or by contaminated food or feeders. A major reason these diseases may be more prevalent at feeders is that the close contact between birds gathered at feeders makes transmission easier. If you do see a sick bird, you should remove all food and clean your feeders with a 10% bleach solution. You should also keep your feeders down for at least a week to allow the birds to disperse; remember, birds do not need feeders to survive the winter, so leaving contaminated feeders up actually lessens their chances of surviving. It is also good practice to clean all feeders at least once a week even if you don’t see any sick birds.
What To Look For
The four diseases mentioned above have varying symptoms, but there are some things to keep in mind that may be general indicators of sick birds:
- A ruffled, fluffed out, lethargic appearance. This is especially true if a bird is in an exposed location and tucking its head under its wing: all songbirds are prey species and unless they are in a protected roost where you probably won’t see them, they should look alert and aware of their surroundings.
- Allowing people to approach. While some birds such as chickadees may learn to fly down and eat from people’s hands, most wild birds are not nearly this comfortable around people and in normal circumstances will not allow people to approach closely. If a bird is on the ground and allows you to walk right up to it or touch it, then it is probably sick or injured.
- Obvious signs of disease. Symptoms such as red swollen eyes, discharge around the eyes or beak, or blood on the body are likely indicators of sickness or injury, in which case a bird probably needs help.
If you do see a sick bird at your feeders, call your local avian rehabilitator or a veterinarian for advice–Do not try to care for it yourself! It is illegal to care for wildlife without a license, and some diseases could potentially be transmitted to people or pets. Additionally, many of these diseases require lab work to diagnose and treat correctly. If it is ill enough that you can walk right up to it, you can gently pick it up with latex gloves or a towel and place it in a box in a warm, dark, quiet place until you can get it to a rehabilitator. It is best to wash your hands after handling a sick bird and avoid bothering it as much as possible, as stress will make illness and injuries worse. If you are unsure whether you should handle a bird, call a rehabilitator or veterinarian first to get advice.
Common Feeder Diseases
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| Salmonellosis in a songbird. (Lafeber) |
Salmonellosis. Salmonellosis is a disease caused by the Salmonella bacteria, of which there are many species and strains that can cause none to severe illness. It is more common among flocking species such as Goldfinches, Redpolls and Pine Siskins, but any bird can be affected. One study in Norway found that over 60% of dead songbirds found at feeders had died of systemic Salmonella infections. Birds affected by Salmonella may not have obvious signs, but symptoms such as lethargy, a thin or fluffed out appearance, and red swollen eyelids may be seen. Salmonella is mainly transmitted by fecal contamination of food, but it can also be transmitted from direct contact between birds. Salmonella can also be transmitted to people, so wearing gloves and washing hands is strongly recommended for anyone handling a bird with these symptoms.
Avian Pox. Avian pox is caused by several strains of pox virus (unrelated to chickenpox that affects humans) and affects a wide number of species. Most commonly, wart-like growths can be seen on unfeathered parts of the body such as the legs and around the beak and eyes, although it can appear on wings and other areas as well. There is also a more severe form of infection that can affect the oral cavity and respiratory system, causing breathing difficulty and trouble feeding. Although pox infections are often not lethal on their own, difficulty seeing or eating caused by the lesions can lead to death. Pox viruses are transmitted by direct contact or by contact with contaminated food or objects, as well as mosquitoes in the summertime.
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| House Finch with Finch Eye Disease (Cornell) |
House Finch Eye Disease. Originally a disease of domestic poultry, Finch Eye Disease, or Mycoplasmal conjunctivitis, jumped to House Finches back in the 1990’s. It is caused by the bacteria Mycoplasma gallisepticum. While it is most common in House Finches, it affects other species such as Purple Finches, Goldfinches, and several related grosbeak species. Though it has been shown that other species such as Chickadees and Titmice have been exposed to it, so far it does not seem to cause disease in them. Birds affected by Mycoplasma often have red, swollen and crusty or runny eyes. This leads to difficulty finding food and makes them easy targets for predators. Mycoplasma is also spread by direct contact or contaminated objects. For more information on the history of House Finch Eye disease and the role that citizen science can play in monitoring diseases and wildlife health, read this article: https://feederwatch.org/learn/house-finch-eye-disease/.
Trichomoniasis. Trichomoniasis is caused by a single celled parasite Trichomonas gallinae which mainly infects the upper gastrointestinal tract of birds, causing white plaques that can obstruct the throat and trachea. It is very common in doves and pigeons, with many adults carrying the parasite asymptomatically. However, when it is transmitted to other birds via contaminated food or water it can cause more severe disease. Raptors such as Cooper’s Hawks are also often affected after preying upon doves and pigeons; this is more common in urban environments. Birds with trichomoniasis may not have obvious external signs, but are often weak and lethargic from malnutrition. They will sometimes have some discharge around the beak or nares in severe infections. Trichomonas often do not survive long outside the host, but can survive for up to 5 days in moist grain, and up to several hours in water.
More information about these and other avian diseases can be found here: https://www.northeastwildlife.org/disease-fact-sheets. You can also call the VINS Rehabilitation hotline at 802-359-5001 x 212, for information about these diseases or any other questions you have about potentially sick or injured birds.