Blue Grosbeak - Field Marks

By early April, many neotropical migrants have begun to arrive along the Gulf Coast of the United States. Having spent the winter in Central America, the Blue Grosbeak is migrating north to its breeding range, which extends over much of the southern half of the United States.

Blue Grosbeak
Guiraca caerulea

The husky warbling song of the Blue Grosbeak is a common sound in summer around thickets and hedgerows in the southern states. Often the bird hides in those thickets; sometimes it perches up in the open, looking like an overgrown Indigo Bunting, flicking and spreading its tail in a nervous action. During migration and in winter in the tropics, Blue Grosbeaks may gather in flocks to feed in open weedy fields.

Field Marks
Male: Deep dull blue, with a thick bill, two broad tan wing bars. Often flips tail. Immature male, a mixture of brown and blue. Female: About size of Cowbird; warm brown, lighter below, with two tan wing bars; rump tinged with blue.

6-7 1/2" (15-19 cm)

Similar Species
Indigo Bunting is smaller, lacks the wing bars.

A rapid warbling song, short phrases rising and falling; suggests Purple Finch, House Finch, or Orchard Oriole, but slower and more guttural. Note, a sharp chink.

Central United States to Costa Rica. Winters Mexico to Panama.

Blue Grosbeak - Range Map

Eastern birds probably migrate across Gulf of Mexico, while those farther west travel south overland. Strays appear north of breeding range in both spring and fall.

Brush, roadsides, streamside thickets. Breeds in dense low growth in semi-open country, including woodland edges, brushy fields, young second-growth woods, hedgerows. In the Southwest, most common near water, in streamside thickets and mesquite groves. Outside the breeding season, often in open weedy fields. Native forms in Central America inhabit dry tropical forest and edges of other woods.

Diet: Mostly insects and seeds. Eats many insects, especially in summer, including grasshoppers, beetles, caterpillars, cicadas, praying mantises, and others, also spiders and snails. Also eats many seeds (may be majority of diet at some seasons), including those of weeds and grass, also waste grain.

Behavior: Forages mostly on the ground, also in low vegetation. Picks up items from ground and from plants; will hover while taking insects from foliage, and will make short flights to catch insects in midair. Except when nesting, often forages in flocks.

Male sings to defend nesting territory. Nesting activity may last late in summer in some areas.

Nest: Placed low in shrubs, trees, or vines, usually 3-10' above the ground, rarely up to 25' high. Nest (built by female) is compact open cup of twigs, weeds, rootlets, leaves, strips of bark; often adds odd materials such as snakeskin or pieces of paper, string, or rags. Nest lined with fine grass, rootlets, animal hair.

Eggs: 3-5, usually 4. Pale blue to bluish white, usually unmarked, rarely with brown spots. Incubation is by female only, 11-12 days. Male may feed female during incubation. Cowbirds often lay eggs in nests of this species.

Young: Nestlings are fed mostly by the female. Young leave the nest about 9-10 days after hatching. Male may feed young more after they fledge, especially if female is starting second nest.

Has been expanding breeding range toward the north in recent decades. Surveys suggest that overall population is stable or even increasing slightly.

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