Hello Exile,
All feeders should be thoroughly cleaned at least once a month, but popular feeders may need to be cleaned much more frequently depending on how many birds use them and how much seed is consumed. I personally take the non-toxic approach and use the following steps which I would elsewhere on the internet:
Fungi such as Aspergillus fumigatus, a fungus which causes respiratory infections in birds, can grow on the feeders.
Here is a non-toxic solution and technique to make this chore easier and safe for the birds.
If you are enthusiastic about bird feeding and operate more than a couple of feeders, cleaning them on a rotating schedule will prevent having to clean them all at once–a potentially burdensome task.
Obtain a tub big enough to hold your birdfeeder(s), a scrub brush, outdoor hose, gloves, scent-free liquid soap or detergent, and white distilled vinegar.
Place your feeder in the tub outdoors, fill it it with warm water and a squirt of liquid soap or detergent. Wearing gloves, scrub the parts of the feeder you can reach, and rinse thoroughly with a hose. Empty the tub and fill it with clean water and 4 cups of vinegar.
Let the feeder soak for 1 hour. Rinse thoroughly.
Kind Regards
Stephen