In addition, the storm flattened crops, broke windows and damaged roofs and vehicles in the region, according to a press release from Montana Fish, Wildlife & Parks.
Agency wildlife biologist Justin Paugh estimated 20 percent to 30 percent of the waterfowl and wetland birds at the Big Lake Wildlife Management Area were killed or injured.
"Of the birds that still are alive, Paugh estimated that five percent of ducks on the lake and 30 percent to 40 percent of living pelicans and cormorants show some sign of injury or impaired movement – mostly broken wings and broken wing feathers," the wildlife agency release said.
The Washington Post reported that the National Weather Service issued a severe thunderstorm warning for Molt just before 6:30 p.m. on Aug. 11, predicting hail and gusty winds. The storm dumped 3-inch hail and lashed the area with more than 70 mph winds.
"This isn't uncommon for us, but it normally happens in June," NWS meteorologist Shawn Palmquist told the Post.
"June is when we have lower freezing levels and can get hail. August is typically more a wind month," Palmquist said.
The preserve features a shallow lake and wetland used for nesting by dozens of species, including Canada geese, double-crested cormorants, gulls, ducks and pelicans.
Paugh said wildlife officials are concerned that the dead birds and the injured ones could increase the possibility for disease among the remaining bird populations.
"On a positive note, the lake is still covered in waterfowl that are alive and healthy. Life will go on," Paugh said.