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PRINCETON — Just before sunrise Wednesday, it was quiet in the marshy area at Sherburne National Wildlife Refuge where sandhill cranes congregated for the night.

As the cloudy sky started to lighten, the still of the morning transitioned to a whirring cacophony of trumpeting, rattling and honking as the cranes awoke. Some took flight to go scour nearby fields for corn left over from the fall harvest.

Despite the near-freezing temperatures and icy wetlands, about 10,000 cranes roosted overnight at the refuge, which is a popular stop on the birds' migration from Canada to Florida and other southern states. That number was far less than what spotters saw last week when a record-breaking 29,300 cranes roosted at the refuge — the highest number since the last record count of nearly 15,000 in 2019.

"It's a powerful sight to see that many birds in one place," said Cody Carlstrom, wildlife biologist at the refuge. "They're such an iconic species. They're practically prehistoric."

Sandhill cranes are one of the oldest bird species in the world. They stand about five feet tall with gray plumage and a red crown on their head. Even more distinctive than their leggy bodies and broad wings are their high-pitched rattle calls.

The sandhill cranes at Sherburne National Wildlife Refuge are eastern population cranes. The midcontinent population, which can be hunted due to their higher numbers, are a different breeding population and are known to congregate in Nebraska in the spring.

Carlstrom estimates there are only about 100,000 eastern population cranes compared to about 600,000 midcontinent population cranes. But 100,000 is a mighty improvement from a century ago when cranes were nearly hunted to extinction. Hunting was outlawed by the federal Migratory Bird Treaty Act of 1918.

"They're a really good success story," said Bruce Galer of Elk River, who is a member of the nonprofit Friends of the Sherburne National Wildlife Refuge, a group of about 600 volunteers that support the refuge financially and through volunteer work.

Galer and Princeton resident Dean Kleinhans participated in the Nov. 8 count, when nearly 30,000 birds were tallied flying from their gathering spot in the 1,500-acre marshy area called the St. Francis Pool. It's the area Carlstrom calls a "smorgasbord of migratory birds" because it's a safe place for swans, geese, American coots and other birds to gather and roost.

"Fifteen years ago, we were glad to have 1,000 of them out there," said Kleinhans, who started volunteering at the refuge in the 1990s. Last week, he counted 6,600 just in his section of the marsh.

The 30,700-acre refuge, which is southwest of Princeton and north of Big Lake, was established in 1965 at the urging of local conservationists and hunters who wanted to restore wildlife in the St. Francis River basin. Carlstrom said fewer than 100 cranes staged at the refuge in 1992. By the mid-2000s, peak staging numbers were about 3,000, and numbers have steadily increased over the last decade.

Every October, refuge staff and volunteers carry out a weekly count. Those participating are trained to watch specific sections to avoid an overcount. On Oct. 11, they counted about 6,000 cranes. By Tuesday, they counted about 17,000. Carlstrom said weather dictates the cranes' ability to find food — amphibians, fish, insects, seeds and corn — so they generally fly out when temperatures drop and the snow flies.

Carlstrom said U.S. Fish and Wildlife Service staff are unsure why the refuge set a record this year.

"There's no real smoking gun answer," he said. "But as cranes begin migration, they fly in large flocks and they go to the places they know have the resources they are looking for. They became familiar with the refuge and return year after year."

Friends of the Sherburne National Wildlife Refuge also helps organize early-morning tours in the early fall for members of the public who want to see the cranes up close. People can also generally see cranes from roads near the northern edge of the refuge or in farm fields north of the refuge in October and November. Cranes fly throughout the day, but a two-hour window around sunrise is the best time to visit, says Carlstrom.

It's something everyone should experience, Kleinhans said.

"It's kind of like skydiving. You don't know anything about it unless you've done it once," he said. "Your sensory experiences are overloaded in a way you can't anticipate. You're hearing the combination of all those birds. You can hear their wings flapping. There are just so many sensory gems."