Moldy birdseed and unclean bird feeders can make birds sick.
Homeowners who enjoy feeding birds can takes steps now to help birds stay healthy, according to the Minnesota Department of Natural Resources.
In spring and especially in warm, humid weather, it is common for mold to form on wet birdseed. The mold can cause an avian disease called aspergillosis, which affects the birds' respiratory systems. Salmonella is another disease that affects birds and is associated with unclean feeders. Both diseases can be fatal to birds.
To clean a feeder, use a solution of one part bleach and nine parts water, and scrub the entire surface. Always allow the cleaned feeder to dry out in the sun, as the sunlight will help kill bacteria on the feeder. Hummingbird feeders should be cleaned about every week to 10 days during the summer, to keep the sugar water from producing mold.
Staff from the DNR Nongame Wildlife Program urges bird enthusiasts to also rake or sweep up any fallen seeds and seed hulls under their feeder to prevent moldy conditions from occurring on the ground. Seeds left on the ground can also attract meadow voles, house mice, other rodents, raccoons, deer and even bears.
Keep the feed dry by using a hopper-type feeder or a fly-through feeder, and always scrape out old seed that accumulates in the corners. Tray feeders with a screen bottom will allow seeds to dry out from above and below after a rain shower, but thick layers of seed could still trap moisture, so consider more frequent fillings with less seed.
More information about bird feeding is available at mndnr.gov/birdfeeding. Books about attracting and feeding birds include, "Wild about Birds: The DNR Bird Feeding Guide" and "Landscaping for Wildlife." These books were made possible by donations to the Nongame Wildlife Fund.