New Scientist:

After overindulging in berries, flocks of cedar waxwings flew drunkenly to their doom. That's the conclusion of a new report in the Journal of Ornithology.

...[T]he downfall of the flocks came from eating too many berries. Lacking a crop – the expandable pouch near the throat used to store food – waxwings stow meals in a distensible oesophagus. "When the fruit stays in the oesophagus, it ferments and produces ethanol," says Kinde.

The waxwings had ingested so many berries that their large livers "could not keep up with the alcohol produced by the fermentation", with ethanol concentration as high as 1000 parts per million. By the time they finished stuffing themselves with berries, they were too drunk to fly safely.