Eastern bluebirds are small birds with short, slender beaks and short legs. They are brightly colored, with a blue upper body, red breast, and white belly. Males have wing and tail feathers that are blue with black or gray shafts and tips. Females look similar to males, but are usually duller in color and are slightly larger.
Adult eastern bluebirds weigh 27 to 34 grams. They are about 18 cm long from the tip of their beak to the end of their tail.
Young bluebirds are grayish in color. They have speckled breasts and their wings have blue tips. As they become adults, the blue color becomes much more obvious, and speckles on their breast disappear. (Terres, 1980)
Eastern Bluebirds are native to the Nearctic region. They are found east of the Rocky Mountains from southern Canada to the Gulf states and into Mexico and Honduras. Humans have introduced these bluebirds to Cuba. (Terres, 1980)
Eastern bluebirds prefer open land with scattered trees for perching, nesting, and feeding. They are often seen in parks, gardens, hedges, and other areas that provide perches. They are also commonly found sitting on fences and utility wires. (Terres, 1980)
Eastern bluebirds are usually monogamous (one male mates with one female). Occasionally, one male will mate with two females. Sometimes, young bluebirds from one brood will stay near the nest to help their parents raise a second brood. However, this is not very common. Helpers are much more common among western bluebirds. (Gowaty and Plissner, 1998)
Eastern bluebirds mate in spring and summer. A mature female will typically raise two broods each season. Females do most of the nest building over about 10 days. The nests are cup-shaped, and lined with soft grass. They are built in abandoned woodpecker holes or other cavities that provide protection (usually several feet above ground). Each female lays 3 to 7 (on average 4 or 5) light-blue eggs. The female then incubates the eggs, which means that she sits on them to keep them warm until they hatch. The eggs hatch 13 to 16 days after being laid. The chicks are altricial (helpless) when they hatch. The female broods the chicks to keep them warm, and both parents feed them insects. The fledglings leave the nest 15 to 20 days after hatching. Several studies have shown that some young stay around the nest to help their parents care for a second clutch. Young bluebirds may begin mating when they are one year old. (North American Bluebird Society, 1999; Tveten, 1993)
The young are altricial, meaning they cannot care for themselves upon hatching. Both parents cooperate in raising the young. The female broods the chicks for up to 7 days after hatching. Both parents feed the chicks while they are in the nest and for about three weeks after they have left the nest. The chicks are fed mainly insects. (Gowaty and Plissner, 1998)
Eastern bluebirds can live up to 6 to 10 years. The oldest known wild individual lived 10 years and 5 months. However, most mortality occurs in the first year of life, making average lifespans much shorter than this.
Eastern bluebirds are very social. At times they gather in flocks of 100 hundred or more birds. However, they are territorial as well. They defend a territory around their nest during the breeding season, and a feeding territory in the winter.
Eastern bluebirds are partially migratory. They fly south when food becomes scarce or when temperatures and other environmental conditions become harsh. When hunting, eastern bluebirds often fly from their perch to the ground to catch an insect or other piece of food.
Home ranges of eastern bluebirds range from 1.1 ha (during the breeding season) to 120.8 ha (during winter). (Gowaty and Plissner, 1998)
Eastern bluebirds communicate mostly through sounds. They have different songs for mating, territoriality, and other purposes. The most common call of the bluebird sounds like -chir wi- or -chur lee-. When repeated several times, the call sounds like the words -truly- and -purity-. Eastern bluebirds also use body signals to communicate. (Terres, 1980; Tveten, 1993)
Eastern bluebirds eat a variety of foods depending on the season. In summer months, eastern bluebirds consume mostly beetles (order Coleoptera), crickets, caterpillars, grasshoppers, and other insects. A United States Biological Survey study of 855 eastern bluebirds found that the bluebird diet was 68% insects. During the fall and winter seasons, when insects are less common, eastern bluebirds eat fruits and plants, including blackberries, honeysuckle, dogwood, red cedar, and wild grapes.
Eastern bluebirds drink water from ponds, streams and birdbaths. They appear to prefer running water versus standing water. (North American Bluebird Society, 1999; USGS Northern Prairie Wildlife Research Center, 1999)
Eastern chipmunks and flying squirrels prey on eastern bluebird eggs and nestlings. House sparrows, European starlings, American kestrels black rat snakes, black racers, fire ants, domestic cats, black bears, and raccoons are predators of adults and chicks.
When approached by a predator, male eastern bluebirds make a song-like warning cry. If a male is not present, a female will begin to sing, hoping to attract a protective male back to the territory. Both males and females will also flick their wings and warble when predators are nearby. (Gowaty and Plissner, 1998)
Eastern bluebirds affect communities of the insects they eat. They also provide habitat for many species of parasites, including mites, lice and blowflies.
We do not know of any way that eastern bluebirds harm humans.
Eastern bluebirds may help to control insect populations.
The future of eastern bluebirds has been of concern to conservation agencies. Populations of eastern bluebirds have shrunk over the last few decades (in some places by as much as 90%). However, populations have been growing recently.
Eastern bluebirds are somewhat protected throughout their range. Two reasons why bluebird populations have declined are habitat destruction and competition. Much of the eastern bluebird's habitat has been turned into farmland or commercial property. This has greatly reduced the food and shelter available to bluebirds. Eastern bluebirds also have to compete with the more aggressive, introduced species, house sparrows and European starlings, for food and nesting sites.
The most effective measure that has been implemented to protect eastern bluebirds has been the introduction of nest boxes in good nesting habitat. These boxes are relatively easy to make and maintain. They have been quite successful in providing nesting places for eastern bluebirds.
Eastern bluebirds are listed as a species of "least concern" by the IUCN. They are not protected under CITES or the U.S. Endangered Species Act. There are about 10,000,000 eastern bluebirds in North and Central America. (North American Bluebird Society, 1999; Terres, 1980; Tveten, 1993)
Eastern Bluebirds are the state bird of both New York and Missouri.
Tanya Dewey (editor), Animal Diversity Web.
Kari Kirschbaum (editor), Animal Diversity Web.
Kate Fimbel (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.
Gowaty, P., J. Plissner. 1998. Eastern Bluebird (Sialis sialis). Pp. 1-32 in A Poole, F Gill, eds. The Birds of North America, Vol. 381. Philadelphia, PA: The Birds of North America, Inc.
North American Bluebird Society, 1999. "Fact Sheet: Getting Started with Bluebirds" (On-line). Accessed December 1, 1999 at http://www.nabluebirdsociety.org/start.htm.
Robbins, C., B. Bruun, H. Zim.. 1983. A Field Guide to the Birds fo North America. New York: Golden Books.
Terres, J. 1980. The Audubon Society: Encyclopedia of North American Birds. New York: Alfred A. Knopf.
Tveten, J. 1993. Birds of Texas. Fredricksburg, TX: Shearer Publications.
USGS Northern Prairie Wildlife Research Center, 1999. "Eastern Bluebird (Sialia sialis)" (On-line). Accessed December 4, 1999 at http://www.npwrc.usgs.gov/resource/birds/eastblue/eastblue.htm.