Mountain Bluebird (Sialia currucoides)
https://ebird.org/checklist/S132004023
https://macaulaylibrary.org/asset/550536341
https://macaulaylibrary.org/asset/550536361
When I first saw this I thought it was a chipmunk. But when I got closer I decided it was probably a ground squirrel. It’s flanks were also reddish and it had a striped back.