Perhaps more than at any time in history, Minnesota ruffed grouse hunters don’t know what to expect when they decamp to the woods on Saturday, opening day of the “ruffie” season.

That’s because in the past 10 years or so the correlation between the spring drumming counts of these birds (which this spring were unchanged from 2018) and their fall population has weakened so much that the drumming survey is no longer considered a reliable predictor of fall grouse numbers.

Department of Natural Resources (DNR) grouse researchers are attempting to dissect this disconnect, and with the help of hunters are expanding a study this fall to determine whether West Nile virus is killing young grouse during the summer, before hunters can encounter them in October, November and December.

Yet another DNR study just starting might in future years replace drumming counts as a fall grouse population predictor. DNR researcher Charlotte Roy in May initiated the project, asking forestry workers and others who spend a lot of time in the state’s North Woods to document grouse broods they saw this summer.

Such diary-keeping, patterned after similar efforts in Pennsylvania, might also shed light on if, and when, young grouse disappear in summer.

“We’re hoping as we get more brood survey data in coming years that we can do better forecasting of the fall grouse population,’’ Roy said. “The brood survey isn’t intended to replace our spring drumming counts, because they provide a different piece of information about the long-term trend of the grouse breeding population.’’

In addition to forestry workers, DNR nongame and wildlife department employees were among people tasked to keep brood diaries this summer, as were employees of the Red Lake and Leech Lake bands of Chippewa.

Diaries that Roy has received so far haven’t been tabulated. Her best advice to hunters, she said, is to stay mobile this fall, because bird numbers could vary widely across the state’s north country.