Wingshooters in Minnesota, Wisconsin and Michigan waited a year for test results they hoped would determine whether West Nile virus is killing the states’ ruffed grouse. The answer? Maybe, maybe not.

What is certain, Minnesota Department of Natural Resources (DNR) researchers say, is that at least some grouse across the three states are being exposed to the virus, meaning a fraction of killed grouse submitted last year by hunters carried antibodies consistent with West Nile exposure.

However, no Minnesota birds showed evidence of the virus in their hearts, indicating, the researchers say, the birds weren’t sick when they died.

“The study tells us that some birds that have been exposed to West Nile virus are surviving — both juvenile and adults — and they are not sick when harvested in the fall,” Charlotte Roy, DNR grouse project leader, said in an agency news release.

“But this study does not tell us about birds that may have died from the disease over the summer.”

The last point is key because in Minnesota, spring ruffed grouse population drumming counts in the past decade have not correlated as closely as they once did to hunters’ fall harvests. Researchers suspect something is killing young grouse particularly during the summer, and because West Nile has shown up elsewhere in ruffed grouse, including in Pennsylvania, the collaborative study was begun by Minnesota, Wisconsin and Michigan.

Among 273 samples submitted by Minnesota hunters last year, 34 (12.5%) had antibodies consistent with West Nile exposure. But unlike in Wisconsin and Michigan, the virus wasn’t found in any of the Minnesota birds’ hearts, meaning, as Roy said, they weren’t sick when they were killed.

The virus was considerably more prevalent in Wisconsin grouse (29% of tested samples) and slightly more common among tested Michigan grouse (13%). In Wisconsin, two of 235 grouse showed evidence of the virus in their hearts, and in Michigan, four of 213 did.

West Nile is carried by infected mosquitoes and can affect people and animals. Not everyone who is bitten contracts the virus, the DNR stressed, and transmission has not occurred to people who eat affected animals.

The three states’ study is continuing this fall. More information, including how hunters can submit samples of birds they harvest, is online at https://tinyurl.com/y5tlhkg9.