I've heard of this "hanging" of game birds. From what I've heard you're supposed to leave the guts in. Different strokes for different folks (oh my stomach - be still).
With pheasent, I immediately gut them, or field dress them by sticking a hooked piece of wire up the butt and dragging out the guts. When I get home, or to camp, I cut off the wings, feet, head, and skin them.
With grouse, soon as I collect them, I stand on the wings and pull on the feet. This pulls the guts and head out with the legs and pulls most of the skin and feathers off. I twist off the wings and end up with the breast (the only meat worth collecting with grouse). No knife needed. I carry plastic bags in my pocket to pop the breast into.
Some people think this is bad. "What about the legs - they say." Please. About a teaspoon full of meat per leg - and full of bones and cartilage besides. I don't collect legs unless I intend to get a lot of grouse.
If you must have the leg meat, slit the leg meat and fold it out - butterfly fashion. Fry the leg in hot grease and the tiny bones and cartilage will pop out.
I usually save the feathers and fans from both birds - the only reason I would carry a knife while grouse hunting.
PG