Q. I know ruffed grouse populations follow a fairly predictable 10-year cycle of peaks and valleys. Someone recently told me the down years result because ruffed grouse hens lay fewer eggs during those years. Is that true?
A. I also have seen the cycle of ups and downs with ruffed grouse populations and have written about it on occasion, but I’ve never heard anyone say the trend results from hens laying fewer eggs.
Nor have the experts I asked.
“I’m not aware of any data that look at that,” said Charlotte Roy, grouse project leader for the Minnesota Department of Natural Resources.
Instead, she said, most of the recent research into grouse population cycles focuses on climate effect and makes a strong case for climate as a factor.
“I was rather amazed at how well it seemed to explain things—especially given it’s been such a mystery for so long,” Roy said. “It makes sense from a lot of different angles that climate would be a key driver in that cycling.”
Ted Dick, forest game bird coordinator for the DNR and a biologist for the Ruffed Grouse Society, said hadn’t heard the “hens lay fewer eggs” explanation, either.
“I don’t know if you can say it’s way off, but I haven’t heard it summarized down to that aspect,” Dick said.
Ruffed grouse rely on snow both for thermal cover and to hide from predators, and birds likely enter nesting season in poorer condition after winters with marginal snow, Dick said. That could affect hatch rates or chick survival.
“Part of the issue could be they’re less fit and more stressed with fewer reserves, but I haven’t heard it measured that succinctly,” he said.