So I can scratch THAT off my to-do list.
After lunch today, I cleaned our seed feeders with vinegar and water (one part vinegar to four parts water). It needed to be done. Plus, I'd read a press release on the subject, "Wildlife experts urge safety, cleanliness for bird feeders." Yesterday, I chatted with ornithologist Cliff Shackelford (who wrote the release) about another topic, and we briefly discussed bird feeders. Needless to say, now James and I (okay, mostly me) are thinking of taking down our sunflower feeder for the summer months. (Read the release for more info.)
Back to feeder cleaning solutions, Wild Birds Unlimited recommends "using one part liquid chlorine household bleach in nine parts of tepid water (a 10 percent solution) to disinfect. Make enough solution to immerse an empty, cleaned feeder completely for two to three minutes. Allow to air dry. Once or twice a month should do, but weekly cleaning may be needed if you notice sick birds at your feeders."
Bottom line: All bird feeders, including hummingbird feeders, must be kept clean to protect bird health.