In cycles lasting roughly 10 years, grouse populations undergo dramatic and inexplicable fluctuations, independent of weather or habitat conditions. After the population reaches a peak, numbers drop during the next several years before beginning to climb again. One explanation for the decline, postulated by the late University of Minnesota grouse guru Gordon Guillion: Male aspen build up an unpalatable chemical to prevent being eaten when grouse numbers get too great. Another theory, by University of Wisconsin research scientists Don Rusch and Lloyd Keith: Periodic invasions of goshawks and great-horned owls (driven south due to cyclical declines in Canadian snowshoe hare populations) cause grouse numbers to plummet.
Whatever the reason for decline, Minnesota's ruffed grouse population now appears to be on the upswing. This past spring's statewide average drumming count went up 20 percent from last year, to its highest level since 2001.
One sour note in southeastern Minnesota: Drumming counts remain well below the long-term average for that region. Oak forests there are less likely to be clear-cut, which means fewer early successional forests.
Elsewhere in the state's grouse range, however, the grouse population appears poised to take advantage of abundant habitat in the next several years. Steve Merchant, DNR forest wildlife program coordinator, says the next population peak could be one of the "super highs" that occur roughly every 20 years, such as in the early 1950s, 1970s, and 1990s.
"We won't know for sure until around 2010," Merchant says, "but when you look at all the grouse habitat we've got out there and the fact that grouse numbers are climbing again, this is a real exciting time to be a grouse hunter in Minnesota."