Backyard bird and nectar feeders need to be properly filled to avoid getting birds sick. When it comes to birdseed, be sure to store it in a dry place inside an airtight container. If there's any moisture, mold and bacteria can grow. To make sure your birdseed is fresh, give it a good smell; if it smells off, bury it deep inside your compost pile. When it comes to nectar feeders for hummingbirds, take a look at the feeder. If it's cloudy, discolored or has floating particles, it needs to be scrubbed clean and refilled with new nectar. Old nectar can be fatal to birds.