I’ve always been told that grouse switch to Aspen buds as cold winter moves in and the ground freezes up. This string over at Upland Journal proves that that’s not the whole story. Some bird’s diets are a bit more diverse.
The bird was shot in late December. Check out the content of it’s crop (and just how full that crop is) to see what it has been eating.
I think that green, leafy stuff is Toothed Wood Fern.