The rump feathers, while used to determine the sex of a ruffed grouse, are also a vital component of the venerable Carp Crack pattern. The ruff feathers, located on the sides of the necks of both genders, are used to form the collar on the Mustache Ride and Landing Strip patterns, as they are long and wispy, providing lots of movement in the water. They are the ultimate soft hackle for those larger streamer fly patterns.
Regardless of how you obtain a ruffed grouse skin, whether it be a a retail acquisition, roadkill salvage, harvested bird, or a donation from a fellow hunter, consider yourself blessed. The ruffed grouse is the pinnacle prize of keen fly tyers.