We hunted bunnies back East in Southern Ontario by stomping brush piles. Cotton-tail rabbits would flush & we'd shoot them with shotguns, 20, 16 or 12 gauge, depending on the person.

Out West here, we stalk very slowly through the bush with our muzzleloading rifles & spot snowshoe hares sitting in the sun, usually beside a birch tree.(white bark) We'd look for that little black eyeball, perfectly round and a not natural shape. Once we caught on, we'd see them before they'd "flush" and shoot them in the head. Head-shots only count. That way, any calibre was good to go. I preferred my .69, using 35gr. 2F- a go-pow load. I could head the head bones breaking, separate from the pow of the shot. My springer would retrieve the bunnies than managed to get down into the willow bushes under the snow. She would get tied though, and try to ride on the backs of our snowshoes. She was a little 30 pounder- a runt, throw-back to the co cocker family, but fantastic hunting dog for ducks and grouse.
Best hunting in this manner was in March, with us having to use snowshoes due to the 6 to 8 feet of remaining snow covering up the willow bushes.