At a former open pit copper mine filled with billions of gallons of toxic water, sirens and loud pops from propane cannons echo off the granite walls to scare away birds so they don’t land. After several thousand migrating snow geese perished in the Berkeley Pit’s acidic, metal-laden waters in 2016, its owners deployed a sophisticated arsenal to frighten away flocks, including lasers, drones, fireworks and remote-controlled boats. Montana Resources already had been hazing incoming birds with spotlights and rifle shots into the water — and a spokesman says those existing deterrents likely helped the company avoid a penalty or...