Keep It Clean
Cleanliness is the most important aspect in attracting hummingbirds. They will quickly abandon a neglected feeder for a cleaner alternative.
Depending on the outside temperature, nectar can spoil in as little as 2-5 days, causing fermentation and mold growth.
Keep feeders shaded in extremely warm temperatures. Offer nectar only in quantities that can be consumed within a few days. Wash the feeder every time you take it down for a refill. To clean, use a mix of hot, soapy water. Scrub stubborn spots with a feeder mop or similar. Rinse thoroughly before refilling.