The display is unmistakable in northern woods: a soft thumping that accelerates from a few beats into a blur over about eight to ten seconds. The male stands upright on a raised log or rock, braces his tail, and cups his wings forward and back with enormous force.
The mechanism was long misunderstood. High-speed film established that the wings never touch the log or the bird's body. The rapid stroke creates a brief low-pressure region, and air rushing to fill it produces the pulse, essentially a small acoustic shock repeated in an accelerating series. The result is very low in pitch, which is why it carries a long way through forest and is often felt as much as heard.
The grouse's other reliance is winter forage. Ruffed grouse depend heavily on aspen flower buds, and they burrow into deep soft snow to roost, which is why late winters with icy crusts rather than powder can be hard on populations.