On November 28, an incoming snowstorm pushed a swirl of 25,000 snow geese into the vicinity of Butte, Montana, reports the Associated Press. That’s about five times as many geese as the city sees in a whole year. And in many places, such a large flock of the bright white birds with black-tipped wings would be exciting. But for employees at the Berkeley Pit, a 700-acre gaping hole filled with contaminated water, the incoming geese were a nightmare.
That’s because the Superfund site is death trap for the birds, a 900-foot-deep, highly acidic former open pit copper mine contaminated with heavy metals like cadmium, arsenic and cobalt. About 10,000 of the birds landed on the water, one of the only bodies of open water in the area, since their typical stopping point at Freezout Lake was frozen, reports Susan Dunlap at Montana Standard. Employees worked through the night using noise and flashing lights to chase the geese away. The next morning, the AP reports, employees had scared off 90 percent of the geese. But not before many of the birds succumbed to the red-colored toxic stew. Officials are still tallying the death toll and the AP says they expect the tally to be at least four digits.
Mark Thompson, environmental affairs manager for mine company Montana Resources, which manages the site, tells the AP the employees “did incredible things to save a lot of birds and they really put their heart and soul behind it. They did everything they could think of.”
It’s not the first time geese have perished at the site. Ben Guarino at The Washington Post reports that in 1995, the carcasses of 342 snow geese were collected from the Berkeley pit, which ceased activity in 1982. Though Atlantic Richfield Company initially denied the water was to blame, instead claiming the birds ate tainted grain, later necropsies showed that the digestive tract of the geese were covered by sores and blisters caused by the acidic water.
The site is too large to construct a netting system or other permanent goose-deterrence device, so the company began a project of hazing the birds away from the contaminated water, using rifles shots to scare off incoming flocks and large loudspeakers blaring the noises of predators. Those efforts seemed to work. According to Dunlap, though 22,000 birds visited the mine between 1996 and 2001, only 75 deaths were reported. Guarino reports that 14 birds died in the pit between 2010 and 2013. The size of the flock this time around, however, simply overwhelmed the deterrence system.
Twenty of the dead birds have been collected for study, and if the companies managing the mine are found negligent, the EPA will issue fines. But Thompson argues that the incident was caused by a perfect storm of events—increases in snow goose numbers in recent years combined with a late migration after a warm fall and then sudden snowstorm created a unique condition.
“I can’t underscore enough how many birds were in the Butte area that night,” Thompson tells the AP. “Numbers beyond anything we’ve ever experienced in our 21 years of monitoring by several orders of magnitude.”
While snow geese overwinter in the Mississippi delta and in some coastal areas, they are a rare sight for most Americans. They bypass much of the country on high-altitude migratory flights from Mexico to Canada, stopping in huge groups to refuel. It’s believed that changes in farming techniques in the last 20 years have produced more waste-grain for the birds to feed on, causing their numbers to boom from three million individuals in the 1970s to about 15 million today.