Their breeding habitat is open country across western North America, including mountain areas, as far north as Alaska. They nest in pre-existing cavities or in nest boxes. In remote areas, these birds are less affected by competition for natural nesting locations than other bluebirds. Mountain bluebirds are a monogamous breed. The male can be seen singing from bare branches. The singing takes place right at dawn, just when the sun rises. Females usually build the nests themselves. Eggs: pale blue and unmarked, sometimes white. Clutch Size: 4-5 eggs. Young are naked and helpless at hatching and may have some down. Incubation normally last 14 days and the young will take about 21 days before they leave the nest. Both males and females fiercely protect the nest.