STEVENSVILLE - Riding the front edge of an arctic cold front, thousands of geese and other waterfowl descended on the Bitterroot Valley's Lee Metcalf Refuge on Thursday morning.
Refuge officials estimated that close to 8,000 snow and Ross's geese had migrated into the area over the past day.
"This is the largest migration of those two species that we've seen at the refuge in recent memory," said Bob Danley, the refuge's outdoor education coordinator.
Several hundred tundra swans and a handful of trumpeter swans are also using the area, as well as numerous other species of waterfowl.
Danley said the migration is all driven by weather.
"The weather has really set all of this up," he said. "We've had an extended Indian summer and now we're set to get the whammy next week. The geese are an indication that the cold weather is coming our way."
As the wetlands freeze farther north, the birds began their move into the Bitterroot Valley.
The geese are using the wetlands at the refuge just north of Stevensville as a site to roost - and they are foraging green spots on nearby grassland pastures.
"We think they could hang out here for a few days, but there is no guarantee," Danley said. "They could be flying as far south as Hamilton now to forage, but they are likely to continue to use the refuge overnight."
There is good viewing of the unusually large migration from the county road that bisects the refuge.
Anyone making the trip should definitely make sure they roll down their windows and take time to listen.
"It's an amazing sound when there is such a large number of birds in one place," Danley said.
There is no way to know just how long it will last.
When the promised cold blast finally arrives, the birds will be on their way to warmer climes.
"The Germans have a word for it - zungeruhe," Danley said. "The urge to migrate will certainly come."