Ummm--I think the native peoples of the Sierra got a majority of their calories from acorn mush. That involves a lot of work in gathering the nuts, husking, grinding, pouring boiling water over the meal to leach out the poison tannin, then cooking it.

http://roundvalleyschools.org/pages/...%20Culture.pdf

I think manzanita berries are full of "bitter" instead of calories--I think the natives just used them for tea.

I did chow down constantly on blackberries when touring at lower elevations in the Cascade-Sierra, but saved a lot of time by bringing Ramen and pasta. Don't forget the wild grapes in late summer. Crayfish in creeks are easy to catch, and delicious too.
I also gathered pine nuts from the "Digger" pines, but that's just because they were delicious. I probably spent more calories extracting and cracking them than I took in.