The state bird of Idaho is the mountain bluebird, a type of songbird considered quite common in western North America. The mountain bluebird is most often found in the Rocky Mountains, and has also been designated the state bird of Nevada. These birds, scientifically named Sialia arctcia, can also sometimes be found in eastern and midwestern North America, as well as in Alaska. They typically grow to a length of about 7 inches (17.8 centimeters), and generally weigh no more than 1.1 ounces (30 grams). Males are generally azure blue in appearance, while females are mostly grey with blue feathers on the tail on wings, and juveniles of the species are generally comparable in appearance to the adults, but with less striking plumage.
The Idaho state legislature declared the mountain bluebird the state bird of Idaho during its 21st legislative session on 29 February 1931. The state bird of Idaho is only one of the state's designated bird symbols. The state also has adopted the peregrine falcon as its official state raptor.
These bluebirds typically feed mostly on insects. They have been known to feed on grasshoppers, beetles, bees, wasps, ants, and stinkbugs, among others. They are believed to derive as much as 92 percent of their diet from insects. The rest of the mountain bluebird's diet typically consists of berries and seeds, including grapes, hackberry seeds, and sumac seeds.
Little is known about the nest-building habits of the state bird of Idaho, because these birds often take advantage of the nesting boxes they are offered. They have been known to take over deserted woodpecker nests, and have also been seen nesting in naturally occurring declivities. They are believed to prefer nesting in aspen, pinyon, and fir trees, at heights of between 12 and 35 feet (3.65 to 10.67 meters) above the ground.
It is believed that the female of the species alone builds the nest, while the male may simply go through the motions of helping. Male mountain bluebirds have been observed to drop any nesting materials they have gathered before they're able to make it back to the nest. Sometimes, they fail to gather any nesting material at all, but appear to be pretending to gather it.
The mountain bluebird is most often found in open ranch lands and forests, often near the boundaries of the forest. They typically summer in the northern Rockies and Alaska, but can often be found outside of their normal ranges during the winter. The state bird of Idaho has been found as far south as Mexico. They have also been known to expand sufficiently far towards the East Coast of North America to encroach upon the territory of the eastern bluebird.