One bird that is sometimes mistaken for a mountain bluebird is the indigo bunting. Although similar is size and color the indigo bunting does not have the lighter colored breast of the mountain bluebird. The indigo bunting also has a thinker beak which is light in color compared with the thin black beak of the mountain bluebird.
While I was birding at Fort Snelling State Park on the 7th of June I heard a bird singing somewhere down the trail. The song of the indigo bunting varies by location, and I am not very good at identifying birds by their song, so I was not really sure what type of bird that it was.
So I followed the sound down the trail and found this indigo bunting perched in the open singing. He let me get a few pics before he disappeared into the foliage.
An interesting fact that I found out when I was reading up on indigo buntings is that during migration they typically travel at night, using the stars as a guide. I am guessing that they do this because their blue coloration is a lot more noticeable in the day time then it is at night. It does make it harder to get pictures though when they are traveling at night.