 White granulated sugar is the best sweetener to use in hummingbird feeders.A ratio of 1 part sugar to 4 parts water, or 25% concentration, is a common recipe, although hummingbirds will defend feeders more aggressively when sugar content is at 35%, indicating preference for nectar with higher sweetness and sugar content.Organic and "raw" sugars contain iron, which can be harmful, and brown sugar agave syrup, molasses and artificial sweeteners also should not be used.