Where to find Minnesota’s only salt lake

MARIETTA, MINN. - Tens of thousands of birds look like tiny black and white specks floating on the surface of one of Minnesota’s most mysterious lakes.

Peering through a monocular, Curt Vacek lists off their species: greater white-fronted geese, canvasback ducks, mallards. Often, he spots other birds that don’t reside in Minnesota but migrate through: snow geese, avocets, tundra swans and greater yellowlegs.

What draws them all there? The water in this 320-acre lake straddling the South Dakota border is salty — the saltiest lake between the Atlantic Ocean and Salt Lake City, Utah, according to the Minnesota Ornithologists’ Union.

Officially called Salt Lake, its brackish water draws birds — and bird watchers — that flock to its shores for a birding festival each spring. Nearly 150 species have been counted there in a single weekend, said Vacek, Appleton area wildlife supervisor for the Minnesota Department of Natural Resources.

Birding there has become so popular that this year’s festival, which begins Friday and ends Sunday, was nearly called off because crowds were getting too large.

“Last year, there were too few guides and too many people out there. At one point we had a caravan of 28 [cars] ... It was a logistical nightmare,” said Trey Weaver, of the Ornithologists’ Union, which puts together the festival. “ I knew [we] could not do it ourselves.”

This year, the festival has been revamped with three free buses, an introduction to birding class, a meet-up point at Lac qui Parle State Park (where bird counts will be tallied) and a dinner at the American Legion in Marietta.

Amy Rager, Extension educator for the University of Minnesota’s Master Naturalist program, who coordinated the festival’s changes, expects about 250 people.

“Last year, it was my first year and I was surprised this was here right in my backyard,” she said. “The prairie is just as exciting as the North Shore, you just don’t know it yet.”

For years, Vacek has sought information on how the lake got its salinity. It’s still something of a mystery.

Some scientists believe the salt seeps into the water from deep, underground rock layers; others contend it comes from shallower rock layers, according to a study published in the Geochemical Society in 2018. Still others believe the salt could come from the surrounding topsoil.

Whatever the case, although the lake is only 4 to 5 feet deep, it is an important spot for migrating birds — some seeking respite on their long flight north and others looking to nest in the surrounding foliage.

The Great Plains of Canada, northwest of Minnesota, holds thousands of saline lakes and wetlands. Research shows these bodies of water are vital for bird migration.

Saline bodies of water are major breeding grounds for over 80% of North America’s ducks, according to the study. The amount of salt in the water affects vegetation, waterfowl nesting and the length of birds’ migration stops.

Minnesota’s Salt Lake has about a third of the salinity of the ocean, according to the DNR.

Shorebirds are drawn to the lake’s the mudflats that line the edges when the water recedes, as well as the small shrimp brine that live in the water, which aren’t found anywhere else in Minnesota, Vacek said. Sago pondweed that floats on the surface of the lake is food for the birds, and grebes use it to to nest.

Salt Lake, a prairie basin, dries out about every 20 years and wind blows saline crystals away. That resets the wildlife cycle, Vacek said.

But the lake is overdue for a reset because of years of tiling and wetland drainage, Vacek said. The last time it dried out was in 1982; it was almost completely dry in 1990, Vacek said.

All that water has contributed to the disappearance of the crimson saltflat tiger beetle, which once populated the mudflats. Without a reset, the water may soon become too salty for the brine shrimp living there, and even someday become toxic to migrating shorebirds, Vacek said.

The DNR began permanent protection efforts in 1973, and the lake now sits in the Salt Lake Wildlife Management Area, with the South Dakota side a federal waterfowl protection area.

Mae Peterson, known as “the bird lady of Lac qui Parle County,” helped make sure the area was preserved, said Anthony Hauck, communications manager for Audubon Conservation Ranching, a branch of the National Audubon Society that aims to help declining grassland bird populations.

Peterson banded more than 15,000 birds and saw more than 286 species in her life, with many of the rare sightings at Salt Lake, Hauck said. Her documentation of birds inspired others to start the Salt Lake birding festival 45 years ago, making it the state’s oldest birding festival, Hauck said.

Festival officials are predicting robust bird-watching this weekend. Though all 125 seats available on the buses have been reserved, birders can drive around the lake in their personal vehicles.

“We’re going to have puddles of water all over,” Vacek said, “and those small puddles are what really attract and keep hold some of the birds here to nest.”