Periodic population crashes have been noted in grouse. Predators may also have a significant effect- hawks, owls, foxes and coyotes. The most vulnerable are eggs and subadults that havn't learned how to avoid predators. Their abundance is determined more on weather and food supply. Major crashes of dense populations follow a sequence of hard winters with cold rainy spring.
Predation tends to dampen the cycle somewhat, skimming off the peaks.
10 year cycles noted. Reasons not clear, but may include bad weather, predators and intraspeficic competition. A life equation for ruffed grouse is difficult to show, because the populations are in a state of increase or decrease, very seldom stable. Remember, the natural mortality may end up higher or lower than this, resulting in an increased or decreased population. Birds not harvested in the fall are likely to die during the winter.