The blue grosbeak is a fairly large, chunky, finchlike bird with a very large, thick, triangular bill. Adult male upperparts are dark blue, with two broad rusty wing bars. The bill is large and conical, with the lower bill reflecting silvery pale blue. Underparts are dark blue. Male may appear almost black unless the sunlight reflects off the plumage. Female is rusty tan on head, back, and solid (unstreaked) underparts, with two buffy or rusty wing bars, narrower than those of the male. Rump is pale blue. Song, often sung from a prominent perch, is a melodious series of guttural warbles that rise and fall in pitch. Call is a loud, sharp chink.
Similar species: The closely related indigo bunting looks similar and can also appear blackish in some lighting, but it is more sparrowlike: much smaller, with a smaller bill. Adult males lack rusty wing bars. Indigo buntings are abundant and easily seen statewide, while blue grosbeaks are rare to uncommon in many parts of Missouri. The eastern bluebird (Missouri’s state bird) is a type of thrush, with a much thinner bill; both sexes have orangish breast and white belly. When they look blackish in poor light, blue grosbeaks can be confused with brown-headed cowbirds, which are about the same size and are found in similar habitats; remember that cowbirds have narrow, blackbird-type bills; they also lack wing bars and do not share the grosbeak’s tail-twitching habit. The blue grosbeak’s closest relative, the lazuli bunting, is very rarely seen in western Missouri, usually in spring. Male lazuli buntings are smaller (the size of an indigo bunting) and have an orangish breast and white belly, similar to the eastern bluebird.
Length: 6¾ inches.
Statewide; summer numbers are greatest in the southern two-thirds of the state. Rare to uncommon in the northern third of Missouri and in the Mississippi Lowlands.
Habitat and Conservation
Not abundant anywhere, and usually not easy to locate, blue grosbeaks live in shrubby places: tangles, old fields reverting back to woods, prairies, hedgerows, and shrubby pastures. In the Ozarks, the blue grosbeak’s harsh bubbling song can commonly be heard from thickets, grasslands with shrubby draws, old fields, and forest edges. Many people hear them singing or calling first, or catch a glimpse of a fairly large blue bird with a heavy silverish bill as it flies between bushes and small trees.
Blue grosbeaks forage on the ground or in their beloved shrubby tangles for insects, seeds, and fruits. As with many birds, insects make a large percentage of the diet during breeding season, when the growing young require plenty of protein. Once the young have grown, the diet includes more seeds and fruits. If you have plenty of bushy cover, blue grosbeaks may visit your backyard birdfeeder.
A summer resident, uncommon in southern Missouri except for the Bootheel, and rare in northern Missouri. Apparently blue grosbeaks are fairly uncommon and not very abundant everywhere they occur. They are most associated with the southern United States and Great Plains. Their range expanded northward when American settlers converted forestlands into croplands, with their mix of open and brushy places.
Present in Missouri May through mid-September. In spring, males arrive first; females do most of the nest building. The cup nests are made from a wide variety of materials from twigs and rootlets to pieces of fabric, string, and paper, shedded snakeskins, and more. Nests are usually positioned low in shrubs among briars and other dense vegetation, usually near open areas such as roadsides and old fields. Clutches comprise 3–5 eggs, which are incubated 12–13 days. After hatching, the young remain in the nest another 9–10 days. There can be 2 broods a year. The winter range extends from Mexico and the Bahamas south to Panama; blue grosbeaks in the eastern United States fly over the Gulf of Mexico to reach Central American wintering grounds. A blue grosbeak can live to be at least 7 years old.
In the early 20th century, “economic ornithologists” carefully studied the diets of birds. Blue grosbeaks were found to eat large quantities of crop-damaging insects, such as grasshoppers, weevils, and cutworms. Though they also eat some grain crops after breeding season, their help in dispatching insect pests easily outweighed the cost of seeds they ate as they prepared to migrate south again.
Brown-headed cowbirds live in many of the same kinds of habitats as blue grosbeaks. Cowbirds are nest parasites: instead of building their own nests, they deposit their eggs into the nests of other birds, which unwittingly rear the cowbird young, often at the expense of their own young’s survival. Blue grosbeaks are heavily parasitized by cowbirds.