It’s the time of year when the landscape is laid bare, the ground is impenetrable with frost, and flying insects have faded into memory. As fall slides into winter, resident songbirds like robins and waxwings must switch from their warm weather diets of earthworms and arthropods to the best of what’s left: fruit, and lots of it. As it turns out, this is also the time of year when conditions become ripe for the conversion of fruit sugars into alcohol via natural fermentation.

Studies show that waxwings, whose winter diet is comprised almost exclusively of fruit, metabolize alcohol seven times faster than finches (seed eaters) and three times faster than starlings (omnivores). In addition, a waxwing’s liver constitutes nearly 5 percent of its total body weight, compared to just under 3 percent for starlings and finches. Larger livers and higher rates of alcohol metabolism likely evolved in response to occasional exposure to fermented fruit. For the most part, these adaptations enable waxwings to dine on boozy berries without ill effect. » Continue Reading.