You may not realize it, but that backyard hummingbird feeder filled with sugar water is a natural experiment in fermentation — yeast settle in and turn some of the sugar into alcohol.
The same is true of nectar-filled flowers, which are an ideal gathering place for yeast — a type of fungus — and for bacteria that metabolize sugar and produce ethanol.
To University of California, Berkeley biologist Robert Dudley, this raises a host of questions. How much alcohol do hummingbirds consume in their daily quest for sustenance? Are they attracted to alcohol or repelled by it? Since alcohol is a natural byproduct of the sugary fruit and floral nectar that plants produce, is ethanol an inevitable part of the diet of hummingbirds and many other animals?