Federal wildlife authorities have given new details in the killing of multiple swans in west-central Minnesota, including that the birds were shot and discovered near public land protected for waterfowl.

In mid-January, the U.S. Fish & Wildlife Service (FWS) asked for the public's help in the investigation of the birds' deaths in Stevens County, which occurred between Dec. 16 and 17, according to the agency.

The new details are the number of birds, how they were killed, and the location of their discovery:

Fifteen dead birds were found shot on private property near the intersection of 260th Street and 520th Avenue, near the southwest corner of Lamprecht Waterfowl Production Area.

The swans were a mix of trumpeters and tundras, both of which are protected by state and federal laws.

Minnesota has the highest population of trumpeter swans in the lower 48 states. A survey in the state estimated 65,000 trumpeter adults. While some head to the central U.S., trumpeter swans tend to overwinter in central and southern Minnesota where there is open water and food. Tundras are the most populous swan in North America.

Lamprecht Waterfowl Production Area (WPA) covers 250 acres and is part of Morris Wetland Management District, managed by the FWS. The district has about 250 WPAs over eight counties.

The federal land is protected wetland and grassland habitat for waterfowl and other wildlife. Nearly all of the WPAs in the nation are located in the prairie pothole region that includes Minnesota, Iowa, Montana, and North and South Dakota.

The investigation into the swans' killings continues. Anyone with information should contact FWS agent Andrew Daiber at andrew_daiber@fws.gov.