Grouse research leaves unanswered questions about Pennsylvania's state bird

October 15, 2004

University Park, Pa. -- After about three decades of joint ruffed grouse research on a Centre County game land, wildlife scientists in Penn State's College of Agricultural Sciences and the Pennsylvania Game Commission agree on one thing: They have learned a lot about Pennsylvania's state bird, but there is still much they don't know.

Such as what, exactly, causes the dramatic and well-documented population cycles of the popular game bird -- when they go from plentiful to rare in the span of a decade or so, and then their numbers bounce back. That question, which has confounded hunters and wildlife experts for decades, is particularly vexing in 2004, a year after two of the worst Pennsylvania grouse-hunting seasons in memory. The outlook for this fall's season looks only marginally better.

"We have been studying grouse and grouse habitat for about 30 years on State Game Land 176, about five miles northwest of State College," says Duane Diefenbach, an adjunct associate professor of wildlife. "Habitat studies, of necessity, are of long duration and we're not done yet."

Better known as "the Barrens," State Game Land 176 once was owned by millionaire Andrew Carnegie and iron ore was mined there long ago. It now is owned by the Game Commission and consists of 2,800 acres of intensely managed forested habitat. The tract was closed to grouse hunting at the end of the 1988-89 hunting seasons to avoid interference with research. The purpose of the research on the Barrens is to document how grouse populations respond to intensive forest management. Grouse numbers are monitored by recording flushes in the same places fall and spring, and drumming surveys during the breeding season.

"We have learned so much about grouse at the Barrens," says Bill Palmer, a game bird biologist with the Pennsylvania Game Commission widely considered to be the foremost grouse expert in the state. "What fascinates me the most is that even though we have not allowed hunting there for 15 years or so, the grouse population in the Barrens has pretty well mirrored the statewide average. With better habitat out there, we have many times the number of grouse -- but it very much mimics the statewide cycles."

Continued habitat loss across Pennsylvania has Palmer worried that the current down cycle in grouse populations might persist. "The last two years of grouse hunting have been terrible, Palmer says "Grouse hunting has been bad before, but it comes back as the number of birds increases. The scary thing now is habitat trends -- our forests, like our hunters, are aging. The percentage of our forests in the seedling and sapling stage is just 11 percent. It was 21.6 in the late 1970s. In the last 25 years, we have lost about 1 million acres of early successional forest habitat that grouse need."

As grouse numbers have fallen in recent years, hunting pressure has dropped off. "What happens is that folks lose interest when hunting is poor," Palmer says, noting that he keeps in touch with "cooperating grouse hunters" who annually keep a diary of their time in the field. Last year, he heard from 370 cooperators, who reported that instead of spending the normal 10,000 to 12,000 hours hunting, they logged just 7,500 hours.

"The bottom line was that the flushing rate of 1.05 grouse per hour was the lowest recorded since 1976," he says. "This year I predict the population will be up 10 to 15 percent. I don't like to predict flushing rates, but it might be up to 1.2 per hour this fall. In 2002, the flushing rate was 1.17, and in 2001 it was 1.51 flushes per hour. The average over the past 39 years has been 1.44 flushes per hour. At the peak of a grouse population cycle, the rate was 1.74 in 1994 and 1995."

So what might cause grouse population cycles? Diefenbach and Palmer are candid about not being sure. "Nobody is certain," Palmer says. "We think it is a combination of factors such as disease, habitat, predation and perhaps extreme weather conditions."

"In the birds northern range, grouse population declines often follow declines of snowshoe hare populations," says Diefenbach, who has been a serious grouse hunter since he was a child, trailing along behind his dad in the New England woods. "Predators such as great horned owls and goshawks switched to preying on grouse. In Europe, researchers have dosed ptarmigans (a relative of the ruffed grouse) with antibiotics, killing parasites and stabilizing populations. It's not a simple question. Our work at the Barrens has shown that with the proper habitat conditions and cutting rotations, you can increase densities but you can't stop the population cycles."

And Diefenbach points out that research done at the Barrens shows that it is not just timber cutting that helps grouse thrive. "It is the type and manner of timber harvesting that matters to grouse numbers," he says. "Proper forest management gives more consideration to how you cut, what you cut and where you cut. It's about a lot more than just cutting trees."

Palmer agrees. "Without more habitat, the future for grouse in Pennsylvania doesn't look bright," he says. "But having said that, I really think the hunting will come back. You hear a lot of gloom and doom these days about grouse, but in '94 and '95, we had great hunting. Ten years ago we had some of the best grouse hunting we ever had, and we might get back to that."

(Media Contacts)

Last Updated March 19, 2009