Though rather uncommon in most areas, blue grosbeaks breed across the southern half of the U.S. and northward along the Atlantic Coast, through the Great Plains (including eastern Colorado) and across the Intermountain West. They favor brushy fields, especially near riparian woodlands, where they feed on insects, seeds and berries; grasshoppers are among their favored prey.
Adult males, similar to but larger than male indigo buntings, are identified by their royal-blue plumage, heavy bill and chestnut colored wingbars; they often sing from fenceposts or the top of saplings, wagging and spreading their tail in the process. Females are rather nondescript, brownish birds but have pale blue feathers at the base of their tail; yearling males sport a mix of blue and brown plumage.
The nests of blue grosbeaks, frequently parasitized by brown cowbirds, are generally placed in shrubs or small trees and are lined with a variety of vegetation, human trash and snake skins. Despite cowbird parasitization, the population of blue grosbeaks appears to be stable in most regions and, as noted above, their summer range continues to expand northward. Come September, these open country residents head for Mexico, Central America and the Caribbean.
