I was in a forest near Hill City last winter trying out new snowshoes and attempting to spot snowshoe hares before they saw me. It wasn't easy because their white fur blended in perfectly with the snow.
The forest was very still as I snuck along, searching for a hare's black eye in the whiteness. Suddenly the silence was shattered as a brown, feathered rocket blasted from under the snow at my feet and thundered away through the trees. As I tried to regain my wits and slow my racing heart, I realized I had just rousted a ruffed grouse from its snow roost.
Ruffed grouse are more numerous in Minnesota than they are in many other parts of their range. The birds are uniquely adapted to Minnesota winters. They don't have a dense undercoat of feathers to keep them warm, but they compensate by roosting under the snow, where their body temperature can warm the air to above freezing and they aren't exposed to the winter wind. A grouse in a snow burrow uses 30 percent less energy staying warm than one in the open. In very cold weather they might spend up to 90 percent of their time under the snow.
Seeing a grouse enter a snow burrow can be as dramatic as seeing one burst free. A friend saw it once and described it to me.
"The bird was flying through the woods," he said, "when suddenly it folded its wings like it had been shot and plunged into the snow. When I went to investigate it blasted out of the snow again about a yard from the entry point and flew away."
Normally grouse tunnel in about a foot and hollow out a roosting spot. Before leaving the roost to feed in the morning and evening a grouse might poke its head up like a periscope to survey for danger. When all is clear they fly to the nearest tall aspen to rapidly fill up on buds, often leaving wing prints as they leave. They usually return to the safety of a new roost shortly after they eat their fill.
Snow roosts protect grouse from predators as well as from the weather. Winter forests are devoid of substantial cover, so grouse in the open are easy targets for predators. Fishers and owls are just some of the predators that eat grouse if they can catch them.
A chief predator in the winter is the northern goshawk. They come down to northern Minnesota to survive prey shortages in Canada. They perch in tall conifers or fly through the forest and ambush grouse as they search for food. By staying under the snow as much as possible, grouse can avoid most predators.
This winter is shaping up to be a tough one for grouse. The population already is near the low point of its 10-year cyclic fluctuation. Goshawk numbers are very high this year. To top it off, we have very little snow. Grouse need at least 7 inches of snow to roost in.
Grouse normally burrow when the temperature dips below 20 degrees. Without adequate snow, grouse are forced to find shelter elsewhere, including marsh grasses, blown-down trees and conifers. These offer some warmth but little protection from predators.
When we get snow again and you're out trying your new snowshoes, skis or snowmobile, look for the snow burrows of ruffed grouse. But no matter how vigilant you are you're never quite ready for the heart-stopping shock that occurs when the snow erupts at your feet and a grouse thunders away to safety. Take a moment to calm down and appreciate one of the wonders of winter in Minnesota.
(Rick Horton is the forest wildlife biologist for the Ruffed Grouse Society in Minnesota. He lives in Hill City.)
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