Here is some information prepared by the National Audubon Science – Audubon At Home staff.
Cleaning birdfeeders and birdbaths is a crucial practice in preventing the spread of disease between birds. Recently, scientists noted that the spread of Trichomonad protozoan parasites, which cause a disease termed , was on the rise especially among mourning dove and band‐tailed pigeon populations in the West.
You may have a disease problem at your feeders if you notice that some birds are less alert or active, they feed less or cower on a feeder. They may also be reluctant to fly, and their feathers may appear disheveled. Birds afflicted with Trichomoniasis typically develop sores in their mouths and throats. Unable to swallow, they drop food or water contaminated with Trichomonads (which can live for up to five days in food and several hours in water) that other birds then consume, thus spreading the disease.
With the concern over this and other diseases, including Salmonellosis, Aspergillosis, and Avian Pox, which are easily transmitted at birdfeeders and birdbaths, the National Audubon Society recommends paying diligent attention to cleanliness in pursuit of responsible and rewarding bird feeding practices.
Disinfect Your Feeder and Birdbath
To keep pathogens at bay, immerse your seed feeder or birdbath in a nine to one water‐bleach (non‐chlorine) solution, rinsing it thoroughly, one to two times per month . In the presence of outbreaks, disinfect twice as often.
Empty Birdbath Everyday
Brush or wipe it clean and rinse, then refill the birdbath with fresh water.
Discard Old Seed & Hulls
When you clean your feeder, get rid of the old seed. Rake or sweep up any uneaten hulls on the ground. In winter, scraping off a few inches of snow will suffice. For busier stations, seed trays may be used to catch jettisoned hulls and seed.
If possible, provide more than one feeder and spread them out. Crowding only expedites the spread of disease, so give the birds variety and plenty of room.
Clean Hummingbird Feeders
In addition to the information provided above in the 6 Steps, another alternative is to wash hummingbird feeders with a solution of one part white vinegar to four parts water about once a week. If your feeder has become dirty, try adding some grains of dry rice to the vinegar solution and shake vigorously. The grains act as a good abrasive. Rinse your feeder well with warm water three times before refilling with sugar solution.