MINNEAPOLIS (WCCO) – There’s something about Rice Lake National Wildlife Refuge that ducks really seem to like.

For the second time this month, National Weather Service radars picked up a massive flock Thursday over the refuge, which is just south of McGregor, in north-central Minnesota.

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Officials at the refuge told forecasters that almost 900,000 ducks were in the air that morning as a waterfowl survey was underway.

Last week, radar also picked up the signal from a massive flock (about 600,000 ducks) over Rice Lake. However, meteorologists first suspected it could have been the plume of a wildfire.

When the weather service called the refuge out of caution, they learned that a waterfowl survey had been underway. Indeed, refuge officials later told them at some years close to a million ducks are counted over Rice Lake.

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Why does the refuge attract so many for ducks?

“It’s all about wild rice,” said Walt Ford, the refuge manager, explaining that the ducks feed on the rice as they make their long migration south.

He says that Thursday’s survey spotted an estimated 896,000 ducks over the lake, most of them ring-necked ducks. The record for ducks surveyed was set in 1994, when more a million were seen over Rice Lake.

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According to the U.S. Geological Survey, it’s not uncommon for flying animals to appear on radar. Bats, birds, and swarming insets all ping the radar in various places across the country.