Adam Rogers for Wired, "Animals Who Drink and the People Who Cut Them Open":
The first thing Kinde noticed in the birds was damage, bits of bleeding and bruising to the muscles. No surprise—they’d run into buildings. In most of the birds, the liver had also burst, another hallmark of collision. But it was the throat that took Kinde by surprise. Cut open, the esophagus of each was packed with tiny red berries. “And then we go down to the stomach, the gizzard, and it’s engorged, too,” Kinde says. That’s not weird by itself; cedar waxwings are frugivores. They live mostly on fruit. But it started Kinde thinking. “The immediate cause of death in these birds was trauma,” he says. “But why?” Kinde sent samples of the birds’ tissue for the usual tests—heavy metals like mercury and arsenic, organophosphate pesticides, West Nile virus, avian influenza, bacterial infection. And he hit the books. Cedar waxwings sometimes get disoriented because of heat, but only at a certain time of year, so that wasn’t the answer. The fruit, though, was interesting. They were from an invasive ornamental pepper tree that grows clusters of bright red berries, inducing animals like cedar waxwings to eat them and spread the seeds via droppings. When the fruit ripens and animals don’t get to it right away, yeast moves in. Pepper fruit can ferment right on the tree. So next Kinde sent the intestinal contents of one of his birds out for an ethanol screen. He got a major hit—226 parts per million. “It was much, much higher than the amount of alcohol that would make a person intoxicated” Kinde says. Cedar waxwings get anywhere from 85 to 100 percent of their calories from fruit, and the pepper berries seemed to be the only thing available to them. Kinde concluded that the birds were stuffing themselves on fermented berries and trying to fly while intoxicated. Disoriented, they’d fly right into a building. Interesting read; I'm fascinated by nature stuff.