It's been an extremely wet spring and moisture can create some messy conditions at your bird feeders. Wet food can clump in feeders. It can also create an environment for mold to grow.
Mold can be very unhealthy for birds and it is therefore important to keep feeders clean from mold throughout the year. If you see mold growing on your feeders or bird food, throw the food in the trash and clean your feeders with a solution of 10 parts water and one part bleach. Rinse the feeders thoroughly and make sure they are completely dry before putting them back out.
Bird food that falls on the ground can also turn moldy in wet weather. Be sure to rake up fallen foods and toss them out periodically as well.
