Central and eastern Alaska, western and central Canada and western USA. Non-breeding south to south-western and south-central USA and western and central Mexico.
 
Population
Estimated population is 5,200,000 (2010).
Mountain Bluebird (Sialia) [XC254429]
by Paul Driver from Blue Bell Campground, Custer State Park, South Dakota, United States (call)
Mountain Bluebird (Sialia currucoides) [XC420507]
by Bobby Wilcox from Ely, White Pine County, Nevada, United States (call)
Subspecies
No subspecies.
Has been suggested that specific name currucoides inapplicable, and that name arctica is required. Occasionally hybridizes with Eastern Bluebird (Sialia sialis).