Here's some background information about Bluebirds!
There are actually three different species of bluebirds -- the Western Bluebird (Sialia mexicana), the Mountain Bluebird (Sialia currucoides), and the Eastern Bluebird (Sialia sialis). Although the three species are similar, their looks and behaviors differ slightly, and they're found in different regions. One easy way to tell the species apart is by color. The Western Bluebird has a "ring" of blue or gray around its neck; the Eastern bluebird has orange around its neck; and the Mountain Bluebird has no orange on it at all.
Bluebirds live in open spaces with small amounts of trees and shrubs. They prefer prairies and meadows over dense forests. They are generally found in North America; each of the 3 species has a different range, though they tend to overlap. Western Bluebirds are found West of the Rocky Mountains, Eastern Bluebirds are found between the Eastern half of North America and the Rocky Mountains, and Mountain Bluebirds are found between the Rocky Mountains and the Pacific coast.
Most of a bluebird's diet is made up of insects such as grasshoppers, crickets, and beetles. They also eat a small amount of fruit and wild berries, especially in winter when the cold kills off insects. The amount of wild fruit available as a food source in winter often decides whether or not a bluebird will migrate.