Mountain Bluebirds are one of the most recognized birds around Craters of the Moon's Loop Road. Males are a bright sky blue while the females have dull gray bodies with blue wings. The only bluebird normally found above 5000 feet in elevation the Mountain Bluebird is common throughout the northern portions of Craters of the Moon. Like other blue colored birds they have no pigments in the feathers. The microscopic structure of the feathers reflects sunlight in the same way that molecules of air in the sky make the sky look blue. Just like the sky looks gray on a cloudy day so bluebirds appear to "fade" when clouds hide the sun.
During the summer months they feed primarily on insects. During the spring and early summer, look for them feeding on tent caterpillars on shrubs. Like robins and other thrushes they will eat berries and small fruits when available. This flexibility allows them to migrate north earlier than most birds and their arrival in March is a sure sign the winter is beginning to release its snowy grip on Craters. They can be found here from early March when large flocks begin migrating through until early October when migratory flocks are again seen on the way south for the winter.
All bluebirds nest in cavities such as old woodpecker holes and rotted out areas in trees. All three species of bluebirds in North America have declined as forests have been cleared and dead trees cut down for firewood, safety, or aesthetic reasons. Natural tree cavities have never been abundant so bluebirds are competitive and are aggressive toward other bluebirds.
Why are they are so common at Craters? Research in the 1980s found that Mountain Bluebirds were most abundant in the lava fields at Craters of the Moon and around the volcanoes in the Cascade Mountains. As it turns out bluebirds don't have to nest in trees. Any hole or closed in space that is the right size and with an entrance the right size of about 1 ½ to 2 inches can be used. The lava fields at Craters of the Moon have an abundance of crevices and pockets that are just the right size for nesting bluebirds. This means that the availability of roosting and nesting sites does not limit the number of bluebirds as it does in most of North America. What limits the number of bluebirds here is the availability of insects to eat and their willingness to tolerate each other. This adds up to bluebirds being one the most commonly seen birds at Craters of the Moon. When driving the Loop Road or walking a trail watch for a flash of blue against the black lava as a Mountain Bluebird flies by.