Blue Grosbeak, Passerina caerulea
Blue Grosbeaks are somewhat secretive but can be found across Tennessee during the summer months. They arrive by the end of April and depart by the end of September, and occur in brushy fields, and hedgerows adjoining grasslands and croplands.
Interestingly, they only started nesting in Tennessee in 1945, and had spread across the state by the mid-1960s. The reasons for this dramatic range expansion are unknown.
Blue Grosbeaks are migratory birds and range across most of the southern half of the United States into Mexico and Central America. The winter range includes southern Mexico, Central America, and the Caribbean.
Description: The male and female are very different in appearance, but share the large cone-shaped bill. The male is deep blue with two large rusty-brown wing-bars; the female is mostly brown with two buffy-brown wing-bars.
Juveniles (August-March) resemble the female; males in their first summer (March-September) have a plumage that is intermediate between that of the adult female and adult male, with variable amounts of blue mixed with brown.
Weight: 0.98 oz
Voice: The song is a series of variable rich warbled notes and phrases, typically quiet in tone. The call is a soft metallic chink.
- The Indigo Bunting male and female are similar to the male and female Blue Grosbeak, but are much smaller, have smaller bills, and no wing-bars.
- Eastern Bluebirds have a reddish chest, a white belly, and a thin bill.
- Female and juvenile Brown-headed Cowbirds lack wing-bars and may be streaked on the breast.
Habitat: Blue Grosbeaks can be found in early successional habitats such as brushy pastures and abandoned fields with numerous shrubs and saplings, also hedgerows adjoining hayfields and fields of small grains, and recent clearcuts.
Diet: Insects, other invertebrates, and seeds.
Nesting and reproduction: Nest building begins in late May. Blue Grosbeaks commonly produce two broods per year.
Clutch Size: Usually 3 or 4 eggs, with a range of 2 to 5 eggs.
Incubation: Incubation is done only by the female, and lasts for 11 to 12 days.
Fledging: Both parents feed the young, which leave the nest in 9 to 13 days.
Nest: The nest is a compact cup made of twigs, bark, rootlets, and lined with finer material. The outer shell usually contains pieces of snake skin, paper or plastic. It is usually well concealed in shrubs or vine tangles along forest edge or roadsides. Tennessee nest heights range from just over one foot to 9 feet, with an average of about 3 feet above the ground.
Status in Tennessee: The Blue Grosbeak is a fairly common summer resident across Tennessee, arriving by the end of April and departing by late September. The population in Tennessee is still increasing at a significant rate.
- The first record of a Blue Grosbeak in Tennessee was in Memphis in 1929. Few observations followed until a small breeding population was discovered in 1945 in McNairy County. The first Blue Grosbeak in Knox County was found in 1948, in the Nashville area in 1950, and near Chattanooga in 1953. By the mid-1960s Blue Grosbeaks were established throughout the state. The reason for this sudden increase is unknown as apparently suitable habitat had long been available.
- Most Blue Grosbeaks nesting in the eastern United States probably migrate across the Caribbean, as individuals are regularly sighted on Caribbean islands during spring and fall migration.
Best places to see in Tennessee: Blue Grosbeaks can be found across the state except at the highest elevations, from the end of April to late September. They occupy early successional habitats such as brushy pastures, abandoned fields with numerous shrubs and saplings, hedgerows adjoining hayfields and fields of small grains, and recent clearcuts.
Ingold, J. L. 1993. Blue Grosbeak (Passerina caerulea), The Birds of North America, No. 79 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
Nicholson, C. P. 1997. Atlas of Breeding Birds of Tennessee. Univ. of Tennessee Press, Knoxville.
Sibley, D. A. 2000. The Sibley Guide to Birds. A. A. Knopf, New York, NY.