S DARKNESS FELL on Nov. 28, 2016, residents of Butte, Montana, heard the unmistakable honking of some 60,000 snow geese circling the Berkeley Pit, a defunct mine now flooded with toxic water. A snowstorm hit that night after an unusually warm autumn, and the geese, caught on a late journey from Canada to California, were forced out of the sky. They blanketed the surface of the water. Onsite staff tried to frighten them off, but an estimated 3,000 birds died.
