Those large groups form up when the weather comes in and promptly break down again when it clears. I usually find many small groups spread out between the larger groups, even in the middle of a storm. Heavy weather gets them moving and forming into the large groups and makes them easier to find. Once the weather clears, you'll find small groups all over the place on their normal wintering grounds. If it's a cold, wet winter, they'll usually be a little further down the drainages, but not that far from their summer and especially their normal winter grounds. Hang out near the property boundaries and you'll catch them moving back and forth, even during late season bluebird weather. That's how and where I got my cow this past Sunday.
