This is the Idaho State Bird (also Nevada), a male Mountain Bluebird (Sialia currucoides). Appropriately, this was taken in Idaho near Henrys Lake. They are insect eaters and cavity nesters. As much as 80% of their diet is insects and they often use abandoned woodpecker nests as habitat.
The Mountain Bluebirds’ favorite habitat is the fringe areas of forested mountains and has been observed in areas as high as 11,000 feet in Idaho (Burleigh 1972). This one was taken at about 6800′ near the continental divide about 2 miles from the forest edge. They also return to the same nesting sites for years.
For years now birding enthusiasts have worked with private, state and federal landowners to provide nesting boxes for this and other cavity-nesting species. You’ve probably seen them attached to trees, telephone poles and fence posts as you travel around.