Different worlds, it seems.
Most hunters out west don't even "hunt" grouse. We just pick them off as targets of opportunity, on our way back to camp during other hunting seasons. (I'm sure human population density is a factor in grouse habits and habitat.)
If you're in grouse country here, it isn't uncommon to flush them every few minutes - and that's not counting the birds that sit tight, and let you walk past.
Ruffed and Duskies like the trees, and usually just sit in the shadows of some low pine bows without flushing. Even if they do flush, they don't go very far. On average, I'd say they only go 15 to 20 feet, before ducking into some thick brush or under another tree. And, they'll sit there, letting you close the distance again.
One of my brothers has killed more with clubs (tree branches), than he has with a firearm. Generally, the shots we take are on birds we just happen to notice before we get close.
The various species of Sage grouse are a bit different, and will often flush in groups of 3-5 .... at distances ranging from 25 feet to just as you step on them. They're bigger, slower targets, that aren't hard to shoot on the wing; since they tend not to fly directly away from the shooter, but in sort of an increasing-radius arc. But, that usually isn't necessary. They often give themselves away by taking a few steps, then pausing before reassessing the threat and taking flight. That pause gives a hunter the opportunity to knock them over on the ground.
Just for the record - I've never been good at spotting stationary grouse. They have to be REALLY obvious, or moving, for me to see them. I have a lot of respect for the guys that can pick out the tiny little grouse eyeballs in the shadows, at 50 yards.
We do seem to have it easier, out here.
During the '98 deer hunt one of my brothers filled his tag early. For the rest of the hunt, he carried a shotgun. On one particular hike back to camp, we ignored all of the grouse we saw (not wanting to carry them), until we came across a large group we couldn't pass up in the middle of the trail. They were lined up like Rockettes.
Less than 30 feet and 7 rounds later, we had 13 grouse for dinner. And only two of them made it off the trail before they died.
It wasn't really an unusual encounter, other than the way they were lined up.
"Such is the strange way that man works -- first he virtually destroys a species and then does everything in his power to restore it."