The mountain bluebird is a cavity nester. They will often compete for nest sites with the western bluebird. At one point their population was in decline because of habitat loss due to an increase in agriculture, however investments in nesting boxes by concerned land owners has helped to increase their numbers. The female builds the nest by herself. She will typically lay 4 to 8 eggs which she will incubate for about 2 weeks. The chicks take about 3 weeks until they fledge. While nesting both male and female will defend the nest.