I would look at the hotspots map in ebird filtered by the month or week. Lots of folks who do big years focus on areas where they can see the most amount of species in a single location, like Tucson, Aleutian Islands, south padre island, you could always reference folks big year itineraries

I think both photos might be Willow Ptarmigan, scalloping on the back, largish bill relative to the head and the habitat, as well. White tailed tend to be more in barren rock areas, and rock are more so in tundra. I think the habitat is probably the biggest indicator.