Bird Feeder Sanitation

Diseases such as salmonella and conjunctivitis are spread through overcrowding and poor sanitation at bird feeders. The Fish and Wildlife Service recommends the following feeder sanitation protocol to prevent disease:

• Diseases like salmonella can grow in moldy, wet seed and bird droppings in your trays and on the ground below. Move feeders (just a foot or so) each season to allow the ground underneath to assimilate the seed debris and bird droppings.
• Keeping your feeders clean should not be a major undertaking. The degree of maintenance required is directly related to the types of birds you want to attract. A thistle feeder for goldfinches should be cleaned about once a month depending on how often it rains. Feeding hummingbirds requires cleaning at least weekly, preferably two or three times a week. Sunflower and suet feeders may be cleaned monthly.
• Feeders made of plastic, ceramic and glass are easy to clean. Wash them in a bucket of hot, soapy water fortified with a capful or two of chlorine bleach, then run through a dishwasher. Use this regimen with wood feeders, but substitute another disinfectant for bleach so wood won't fade.

You can read more at the US Fish & Wildlife website.