Some people refer to the dusky grouse as mountain chickens because they weigh about 3.5 to 4 lbs fully mature. And are about the size of a chicken. In bad weather and depending on the snow depth they will not come off of the roost.
Seriously, it was likely a turkey. There is only one turkey sized ground nesting bird in north america...and that is a turkey.
The next smallest bird would be a grouse, likely blue grouse.
The next smallest upland bird would be a sage grouse, a good size male will weigh in at about 7.5 lbs.