Berkeley Pit bird management has been 99% effective Itâs been an unusually warm winter that has caused the appearance of waterfowl over the Berkeley Pit to dip a little below average. By: Kaitlyn Aguiles and last updated 2021-01-18 21:10:43-05 BUTTE â Itâs been an unusually warm winter that has caused the appearance of waterfowl over the Berkeley Pit to dip a little below average. Montana Resources Vice president of environmental affairs Mark Thompson said they're waiting on more birds that are unusually staying up north this time in winter "There are still quite a large number of Canada geese and mallard ducks still to the north of us in the Missouri drainage and its tributaries so weâre keeping a close eye on those if a cold front were to move in that may tend to push them south, weâre keeping a good eye on that," Thompson said.