How the Bohemian waxwing gets drunk off fruit
The Bohemian waxwing gets its name from the wide-ranging movement of winter flocks, playing off the nomadic behavior of the gypsies of Bohemia. As the species flies south for winter, the birds wander in search of their favorite berries, especially rowan berries. They stay until the food runs out and then move on again. When fruits are more scarce, they'll move farther south than usual in what is called an irruption. The largest irruption recorded in Europe happened in the winter of 2004-2005, when more than half a million waxwings were counted in Germany alone.
Because the source of their food varies in abundance and the birds can't be quite sure when or where their next meal will be, they feast when they can, sometimes eating double their own weight in berries each day. One bird was recorded eating between 600-1,000 cotoneaster berries in six hours! They pluck fruits from the trees and sometimes eat fallen fruits from the ground. With this binging behavior comes consequences. While the birds can metabolize the alcohol produced by fermenting fruit better than humans, they can still become intoxicated. Instances have been recorded of some waxwings "drinking" themselves to death by eating more fermenting berries than their bodies can handle, and they die from ruptured livers or from flying drunkenly into objects like buildings or fences.