This 9 March 2015 video from Britain says about itself:
Bird Feeding Hygiene – Keeping your bird feeders clean
A video … describing how to keep the bird feeders and feeding areas in your garden clean.
From the Cornell Lab of Ornithology in the USA:
The Best Way to Clean Your Feeders—According to Science
Feeding birds is fun, but it comes with the risk of spreading disease—that’s why Project FeederWatch recommends cleaning feeders regularly. Researchers looked into the best cleaning regime and found that dilute bleach is a key ingredient.
Get the full details here.