To passersby, it looks like an empty, overgrown field in the suburbs, closely monitored by corrections officers from the neighboring county workhouse.

But the St. Paul Audubon Society says the 77-acre, Ramsey County-owned parcel in Maplewood now being eyed for an affordable housing development is a rare urban grassland teeming with nesting migratory songbirds including the Henslow's sparrow, which is on the state's endangered species list. Audubon members, joined by the nonprofit Friends of the Mississippi River and the Legacy of Nature Alliance, are imploring county leaders to save the grassland and incorporate it into Battle Creek Regional Park.

The property is poised to become yet another battleground between conservationists and county leaders, who are searching their own land holdings for sites where they can build desperately needed affordable housing.

"We can't make the mistake of responding to our housing crisis by worsening our environmental crisis," said Colleen O'Connor Toberman, river corridor program director with Friends of the Mississippi River.

More than 80 Audubon and conservation proponents have written the county requesting that the entire site, now under the auspices of the county's Corrections Department, be preserved to accommodate grassland birds that require large areas to nest.

The parcel borders Battle Creek Regional Park on two sides and until recently, county maps showed the grassland site as possible future parkland. County leaders switched it to a potential development site in the past two years, according to Audubon members.

"We are fully in support of meeting the needs for affordable housing," said Audubon member and longtime St. Paul resident John Zakelj. "That's where the county needs to be smart about how they do this, though — where to put the housing and what to preserve."

So far, county leaders have faced opposition at nearly every site they're studying for housing development including the grassland site, Ponds at Battle Creek golf course — also in Maplewood — and the shuttered Boys Totem Town juvenile detention campus on St. Paul's East Side.

Ramsey County Board Chairwoman Toni Carter said no decisions have been made about any of the three sites and that county leaders are listening to all sides, including conservation groups and affordable housing advocates.

"We all want to be able to live, breathe, be healthy and safe," Carter said. "There are a lot of competing priorities for us to balance. ... We are slowing down to be sure we have the ear, the attention and support in our community."

As part of that slowdown, this spring the county hired outside firm Midwest Natural Resources to complete natural resource inventories at the grassland property and the nearby Ponds golf course.

That report will be presented to the County Board later this year, but avian biologists completing the survey posted preliminary reports on eBird, an online bird observation database. They identified more than three dozen birds species on the site, including the Henslow's sparrow

The sparrow, described by the Minnesota Department of Natural Resources as an "inconspicuous, secretive bird" with a quiet, two-syllable song, declined by more than 68% between 1966 and the early 1990s.

According to the eBird posting, Midwest Natural Resources also identified at least five species that the DNR classifies as in "greatest conservation need." They include the grasshopper sparrow, the Eastern meadowlark and the bobolink, all of which have plummeted in population since 1966.

Bob Dunlap, a zoologist with the DNR, said the grassland parcel is a well-known spot for birders, who hover on the trails around the edge of property in hopes of seeing or hearing one of the songbirds.

"If these birds are here regularly, that is something special," Dunlap said.

Dunlap said he isn't taking a position on the future of the property, but said loss of grassland habitat is a major reason for the birds' declining numbers. A federal program where private landowners are paid to leave grassland habitat has helped some bird populations to rebound, but only partly.

"We know the populations are not back to what they were," Dunlap said. "A lot of these lands are not permanently protected."

Julian Sellers, a member of St. Paul Audubon's Conservation Committee, said the group is hoping to help county leaders and community members fully understand what's at stake.

"The state of Minnesota has lost more than 98% of its pre-European settlement grasslands," Sellers said. "Many people, if they drive by this 77 acres, they just think it's an empty space — unused land."

Grasslands don't receive the same protections as wetlands, so it's easy to plow them up for development and farming, Sellers said. The National Audubon Society has identified grassland bird species as among the most imperiled in the United States, he said.

Maplewood Mayor Marylee Abrams said she is listening closely to the Audubon Society and the Friends group. The city exercises considerable control over future development at both the grassland and Ponds golf course sites because it oversees zoning.

"Both of these properties are beautiful," Abrams said. "It is rather unusual to have this type of undeveloped property in the community."

Abrams has already come out in opposition to redeveloping the 88-acre golf course. She said the results of the ecological inventory will strongly influence her and the city's position on the future of the grassland site.

Audubon members acknowledge that the Henslow's sparrow's endangered status doesn't bar the county from development, though county leaders must wait until the end of the sparrow's nesting season to dig up the site.

On a sunny weekday morning, Sellers and Zakelj, also recently named president of the Friends of Maplewood Nature group, walked the grassland site with the county's permission. In an about hour's time, they identified and photographed a Henslow's sparrow, several pairs of bobolinks, savannah sparrows, goldfinches, nesting bluebirds and a juvenile red-tailed hawk.

Zakelj said he empathizes with county leaders. He immigrated to the United States from Slovenia as a child, and said he knows his father struggled to find housing for them.

"These are really tough decisions," he said.

Shannon Prather • 651-925-5037