Recently severe weather has been sweeping across the Peach State dropping heavy rain in our backyards. The last front that passed over my home dropped almost three inches of rain in just a few hours. When such an event occurs, you cannot help but wonder if heavy rain dilutes the sugar water in our hummingbird feeders.
Although many hummingbird fanciers are convinced that heavy rainfall can dilute the concentration of sugar in a feeder, I do not know of any studies that corroborate this claim. However, enough people believe this to be the case that some manufacturers of hummingbird feeders offer feeders that are less susceptible to rain flowing into the food reservoirs on their feeders. In an effort to hinder rain draining through feeding portals, some hummingbird fans place a plastic dome over their feeders. Others simply shroud their feeders with plastic plates. Others address the problem by purchasing feeders featuring very small feeding portals. If water pouring into a feeder is a problem, it makes sense to use feeders equipped with small feeding ports.
If you find that hummingbird use of your feeder drops off significantly after heavy rain, this could be an indication that your hummer food is diluted. It has been shown that when given a choice hummingbirds prefer flowers that produce nectar with the a high sugar content. Since that is the case, it is understandable that they would also prefer hummingbird food with at least a 25 percent concentration of sugar.
The best advice I can offer is until we know for sure if rainfall can dilute hummingbird food, if feel your food is diluted, go ahead and replace it.